Highlight(yellow) - 9.3: The
Acidity and the pH > Page 348 · Location 4694
So what this tells us is, if this data sample is truly representative,
when we measure TA we could say that there is a probability of 95
percent that the pH would be between pHmin and pHmax, and there will be
a difference of 0.68 in pH units between the two values. For example,
with a TA of 7 g/ L (or 0.7 percent) as malic acid, this will tell us
that the pH should be between 3.11 and 3.79, with a probability of 95
percent.
Highlight(yellow) - 9.3: The
Acidity and the pH > Page 348 · Location 4698
Unfortunately, in practice this is not very useful, because it could not
help us in the dosage of the SO2 required to protect the
cider. With our example and a pH of 3.11 (the minimum value), a very
small dose of SO2
is required, while at a pH of 3.79 a dose near the maximum is required.
The standard deviation is too large, and in consequence the graph and
equations cannot be used to dose the sulfite and skip the pH
measurement.
Highlight(yellow) - 9.3: The
Acidity and the pH > Page 348 · Location 4701
Now, if we look at it the other way around, let’s say we have a juice
sample for which we have measured a pH of 3.6. Could this be any help in
blending this cider?
Highlight(yellow) - 9.3: The
Acidity and the pH > Page 348 · Location 4704
Again, this is way too wide to be of any practical use,
Highlight(yellow) - 9.3: The
Acidity and the pH > Page 348 · Location 4706
This analysis confirms that both a pH and a TA measurement of acidity
are necessary in cider making. These two measures each have their own
use, and one cannot be substituted for the other.
Highlight(yellow) - 9.3: The
Acidity and the pH > Page 348 · Location 4707
On a more positive note, this graph may be helpful to double-check the
acidity measurements. If we take both measurements (pH and TA) and plot
this point on the graph, then see that the point is quite far from the
mean line, we might take the measurements a second time to be sure they
are accurate.
Highlight(yellow) - Chapter 10:
The Tannins, or Phenolic Substances > Page 350 · Location 4711
What we call tannin in the context of cider (and also of wine) is in
fact a group of phenolic substances that have two important properties:
Astringency, which provokes an effect of shrinkage of body tissues,
followed by a dry sensation in the mouth. This results from the binding
of the lubrication proteins of the saliva with the tannins, resulting in
a decrease of the quantity of lubricant in the mouth and a rough
sandpaper sensation. We also talk about puckering mouthfeel. This
property (in a moderate amount) is a much-sought-after characteristic of
some classic red wines such as Bordeaux or Chianti. Bitterness, one of
the basic tastes our taste buds recognize. Highly bitter substances are
generally considered of acrid and unpleasant taste. However, a slight
bitterness may be rather pleasant and, in a drink, is thirst-quenching,
as in some quality beers that are well hopped and in tonic water (where
bitterness is given by quinine).
Highlight(yellow) - Chapter 10:
The Tannins, or Phenolic Substances > Page 350 · Location 4720
In fact, the tannins really are compounds called procyanidins, which are
responsible for the bitterness and astringency in fruit. These molecules
may be of varying length, the shorter types being bitter, while the
longer types are rather astringent. Depending on the apple variety,
there may be more or less of the shorter or of the longer types, hence
giving the corresponding character to the juice.
Highlight(yellow) - Chapter 10:
The Tannins, or Phenolic Substances > Page 351 · Location 4723
In cider a moderate amount of tannins adds to the complexity and
gustatory persistence. Tannins give body and consistency to cider, and
when the pleasant sensation lasts for a sufficiently long time we may
say of such a cider that it has a “long mouthfeel.” Tannins also add to
the color of the cider. In contrast, an insufficient level of tannins
may render the cider insipid or uninteresting.
Highlight(yellow) - Chapter 10:
The Tannins, or Phenolic Substances > Page 351 · Location 4726
Most of the tannin in cider comes from the apples, and the concentration
varies greatly with the variety. Table apples generally contain very
little tannin. Cooking apples contain a bit more, and some crabs have an
appreciable quantity. But it is among the special cider apples from some
cider-making regions of England and France that we find most of the
high-tannin varieties.
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The Tannins, or Phenolic Substances > Page 351 · Location 4729
The use of wooden barrels for the fermentation and maturation of cider
also adds to the tannin content,
Highlight(yellow) - Chapter 10:
The Tannins, or Phenolic Substances > Page 351 · Location 4733
maceration of the pulp between milling and pressing will induce some
oxidation of the tannins, darkening the juice and the resulting cider.
And in general the faster the extraction of the juice, the paler the
juice and the cider will be.
Highlight(yellow) - Chapter 10:
The Tannins, or Phenolic Substances > Page 352 · Location 4740
More and more high-tannin apple varieties are now being grown in
commercial quantities:
Highlight(yellow) - Chapter 10:
The Tannins, or Phenolic Substances > Page 352 · Location 4742
newly discovered varieties are exhibiting higher tannin levels and other
good attributes.
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The Tannins, or Phenolic Substances > Page 352 · Location 4743
the addition of these varieties in a blend improves the quality of the
cider, especially its body or “structure.”
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The Tannins, or Phenolic Substances > Page 352 · Location 4746
Even professional cider makers do not generally undertake to measure
tannins, as this is better left to a well-equipped laboratory.
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The Tannins, or Phenolic Substances > Page 352 · Location 4747
There are two main tests to measure the tannin content in a juice or
cider (note that the same tests are used for wine): The Lowenthal
method, also called the permanganate index or titration method, was used
at the Long Ashton Research Station. The result of this titration, total
tannins, is usually expressed as tannic acid equivalent, either in
percent, parts per million, or grams per liter. The Folin-Ciocalteu
index is now the standard method in the wine industry. It is based on a
colorimetric reaction and requires the use of special equipment to
analyze the optical density of a sample. The result of this test is
expressed as a concentration of gallic acid equivalent.
Highlight(yellow) - Chapter 10:
The Tannins, or Phenolic Substances > Page 353 · Location 4756
we may express the total tannin content either in tannic acid or gallic
acid equivalent
Highlight(yellow) - Chapter 10:
The Tannins, or Phenolic Substances > Page 353 · Location 4759
In the absence of a test, a cider maker may have a fairly good idea of
the tannin content by tasting the juice or cider, since the two main
effects of tannins, bitterness and astringency, are very easily
detectable by tasting. With a little bit of practice, you can evaluate
if a sample has low, medium, or high tannin concentration. Besides,
tasting allows a further discrimination between hard tannins, which are
rather bitter, and soft tannins, which are more astringent. For
practical purposes in cider making, we will use the following values for
tannin concentration in apples: Low tannin: less than 1.5 g/ L of tannic
acid equivalent. Sample is mild, with almost no noticeable bitterness or
astringency. Medium tannin: between 1.5 and 2.5 g/ L. Some mild
bitterness or astringency is perceived, generally at a pleasant level.
High tannin: over 2.5 g/ L. Sample is very bitter and/ or astringent,
mouth-puckering, unpleasant. Apples with such a high tannin level would
generally be considered “spitters.” The ideal concentration for a cider
that would be rich in tannins, typical of the West Country in England or
the north of France, would be around 2 to 2.5 g/ L. Most of the ciders
from other producing regions would be around 1 g/ L or below.
Highlight(yellow) - Chapter 11:
The Nitrogenous Substances > Page 355 · Location 4777
First, nitrogenous compounds are essential to life and, in particular,
to the growth of apple trees. Nitrogen is one of the important
constituents of compost, manure, and other fertilizers used in
agriculture. In a well-fertilized orchard, the apple trees are vigorous
in part due to a plentiful supply of nitrogen,
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The Nitrogenous Substances > Page 355 · Location 4779
It is interesting to note that nitrogen is also the main constituent of
air, but most plants can’t absorb it easily in gaseous form, and it is
essentially from the soil that apple trees extract the nitrogen required
for their growth.
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The Nitrogenous Substances > Page 356 · Location 4781
Second, a part of those nitrogenous matters that contributed to the
growth and productivity of our apple tree will end up in the apples
themselves. Some studies have in effect shown that the juice of apples
from fertilized trees contains more nitrogen than juice from
unfertilized trees,
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The Nitrogenous Substances > Page 356 · Location 4786
The main nitrogenous substances in apples are proteins, soluble
nitrogen, amino acids, and a few others in lesser proportions
Highlight(yellow) - Chapter 11:
The Nitrogenous Substances > Page 356 · Location 4787
Of these, proteins account for a sizable portion (in the order of 20
percent) of the total nitrogen, and these can’t be used by the yeasts.
Highlight(yellow) - Chapter 11:
The Nitrogenous Substances > Page 356 · Location 4788
What yeasts need to grow and multiply are amino acids, ammonium salts,
and thiamin (vitamin B1). If these compounds are abundant in the must,
the fermentation will be rapid and complete. And if this kind of rapid
fermentation is the goal, as it is, for example, in the industrial
production of cider, these substances will be routinely added (such a
mixture is often called yeast nutrients).
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The Nitrogenous Substances > Page 356 · Location 4791
On the other hand, if the must contains insufficient quantities of
nitrogenous materials, the fermentation will be slow and may even stop
before completion.
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The Nitrogenous Substances > Page 356 · Location 4792
The cider maker who seeks quality prefers a slow fermentation. In
effect, this permits the complex flavors and aromas to develop
themselves and allows the acids and tannins to smoothen, all of which
enhance the cider. To maximize the quality of the cider, then, it may be
necessary to compromise the productivity of the orchard by adopting
cultural practices that reduce the nitrogen content in apples,
Highlight(yellow) - Chapter 11:
The Nitrogenous Substances > Page 356 · Location 4795
The measurement of the amount of the nitrogenous matters in a must may
be done by formol titration (also called formol index),
Highlight(yellow) - Chapter 11:
The Nitrogenous Substances > Page 357 · Location 4797
Nowadays there are many variants of this test and many ways to express
its result. It is notably used in the wine industry, and a complete
description of the procedure may be found in any reference book on wine
analysis. While formol titration is a relatively simple procedure for a
well-equipped lab, it is quite challenging for a hobbyist to find the
required reagents and do it accurately. In the context of wine and cider
making, the result of the formol titration would give the
yeast-assimilable nitrogen (YAN) or the easily assimilable nitrogen
(EAN) in milligrams of N per liter (mg/ L), which are equivalent to ppm
(1 ppm = 1 mg/ L). Typical values for a cider must would be: 50 mg/ L,
for a must that is poor in nitrogen and thus would have a fermentation
that is very slow and possibly incomplete 80 to 120 mg/ L, the range of
most cider-apple juices and about right for a good, slow to
medium-speed, complete fermentation 120 to 150 mg/ L, for a must rich to
very rich in nitrogen 300 mg/ L, a very high value seen in juice from
fertilized young dwarf trees—not recommended for making a high-quality
cider
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The Nitrogenous Substances > Page 357 · Location 4806
As a side note, the YAN from wine-grape juices is naturally much higher
than the values considered normal for apple juices.
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The Nitrogenous Substances > Page 357 · Location 4807
Another way to measure the nitrogen is by the Kjeldahl method, which is
considered the most accurate test but gives a result as total nitrogen,
a value that includes some nitrogen that is not assimilable by the
yeast.
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The Nitrogenous Substances > Page 358 · Location 4814
Without such test results, most hobbyists can get an idea of the
nitrogen content in the must by observing the following points: The
nitrogen content will vary with the apple variety. Such information may
be obtained by observing the speed of fermentation of single-variety
musts. In particular, early-maturing varieties contain much more
nitrogen, and their juices ferment very quickly. And in general we may
observe that the latest-maturing varieties are the ones that ferment the
slowest, thus indicating that these varieties contain less nitrogen.
Highlight(yellow) - Chapter 11:
The Nitrogenous Substances > Page 358 · Location 4819
Apples from old trees of low vigor will be smaller and contain less
nitrogen and amino acids than those from young and vigorous trees. The
big, handsome apples from commercial orchards contain more nitrogen. I
have also observed that apples that are dead ripe or slightly overripe
at the moment of pressing yield a juice that will ferment more slowly.
This may be explained by the fact that as the maturation proceeds, the
soluble nitrogen compounds (i.e., the YAN) are used to synthesize
proteins that are not assimilable by yeasts (Smock and Neubert, 1950),
without changing the total nitrogen content.
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The Nitrogenous Substances > Page 359 · Location 4825
In summary, for the apples to have a low content in yeast-assimilable
nitrogenous substances and thus promote a slow fermentation for a
high-quality cider, choose apples of late-maturing varieties, from trees
that are older and have little vigor, growing in an unfertilized
orchard, and press them at the latest possible date, when they have
started to become soft or are slightly overripe.
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The Nitrogenous Substances > Page 359 · Location 4827
As a final word, a technique called keeving, routinely used in France
for traditional cider, is being used more and more in the hobbyist
cider-maker community. Keeving (or défécation in French) enables the
cider maker to reduce the quantity of nitrogenous matters in the must
before the start of the fermentation. After a successful keeve, it is
also possible to control the speed of fermentation and to effectively
stop it by lack of nutrients while there is still some residual sugar.
Highlight(yellow) - Chapter 12:
The Pectic Substances > Page 360 · Location 4837
Apple juice contains a small quantity of pectin—or, more precisely,
pectic substances—usually in the range of 0.1 to 1 percent, or 1 to 10
g/ L. These carbohydrate derivatives (polysaccharides) influence certain
aspects of cider making,
Highlight(yellow) - Chapter 12:
The Pectic Substances > Page 360 · Location 4840
they are in part responsible for fruit firmness and the facility with
which the fruit yields up its juice; they are responsible for the
formation of the chapeau brun (brown cap) in the keeving process
(section 15.1); they can cause pectic gels and pectic hazes, which are
defects of the cider and can be rather annoying (chapter 16).
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The Pectic Substances > Page 361 · Location 4847
Within the group of pectic substances are: protopectin, parent pectic
substances that are water-insoluble. These protopectins most notably
occur in cell walls of plants and give some firmness to fruits. pectinic
acids and pectic acids, forms of polygalacturonic acids that are
water-soluble. The difference between the two comes from the presence or
absence of methyl-ester groups in the molecule. Pectic acids do not have
such groups and are said to be demethylated or deesterified, while
pectinic acids do contain a proportion of methyl-ester groups.
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The Pectic Substances > Page 361 · Location 4852
Pectins as used in the kitchen are esterified pectinic acids that have
the property of forming gels with sugar and acid, as in fruit jellies,
for example. In general, pectic substances are degraded by pectolytic
enzymes called pectinase. This name, in fact, is a general term for a
group of specialized enzymes that work to break the pectic molecules.
Among the most important of these enzymes are: protopectinase, which
transforms protopectins into pectinic acids; pectinesterase (PE), also
often called pectin methyl-esterase (PME), which strips the methyl-ester
groups from the pectinic acids to transform them into demethylated
pectic acids; polygalacturonase (PG), which depolymerizes the
demethylated pectic acid and cuts it up into small soluble bits of
simple galacturonic acid; and pectin lyase (PL), which works in a fairly
similar fashion as PG. All these enzymes work together to degrade the
pectin and eliminate its sticky effect. They exist naturally in plant
tissues and are also produced in large quantities for the food industry.
After harvest, during apple storage, the protopectins within cell walls
are naturally broken down into soluble pectinic acids. During that
process, the apples get softer.
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The Pectic Substances > Page 362 · Location 4864
the concentration of soluble pectic substances may easily triple during
that period. Later, as the apples become overripe and mealy, the soluble
pectins are degraded into nonpectic substances.
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The Pectic Substances > Page 362 · Location 4866
As a practical effect, then, if the apples are pressed while very firm
soon after harvest, they will have a maximum level of protopectins and a
minimum level of soluble pectinic acids. Since the protopectins are
water insoluble, they will precipitate with the lees without causing
trouble. On the other hand, if the apples are pressed fully ripe or
slightly overripe, the juice will have a maximal level of soluble pectin
and thus may be more at risk of developing pectic haze or gel. Such
fresh juices will also have more viscosity, making the pressing more
difficult and the juice yield lower.
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The Pectic Substances > Page 363 · Location 4878
In cider making we generally prefer to completely degrade the pectic
substances right at the start of the process so that they won’t cause
problems later on. For this, we use commercially available pectinase,
sold in all wine-making supply stores. These are, in fact, mixtures of
pectolytic enzymes, which usually include PME, PG, and PL, and sometimes
others. Note that there exist different pectinase blends that are
optimized for a certain usage. In particular, we may find in a
wine-making supply store a general purpose fruit pectinase or a
grape-optimized blend. Other blends, optimized for apples or pears, may
be somewhat difficult to find but are more efficient for cider-making
applications. There are three pectic enzyme treatments that may be done
on the must before fermentation: Simple pectinase addition. This is the
simplest treatment. It consists of adding pectinase to the must after
pressing and before doing the yeast-culture inoculation. The enzyme does
its work degrading the pectin during the fermentation. Pectinase
addition is like taking out insurance against pectic troubles that could
happen later. The procedure for doing this was given in chapter 1.
Debourbage, or depectinization. This takes things one step further. It
starts as a simple pectinase addition, to which a fining agent such as
Cold Mix Sparkolloid may be added to help the juice to clear. We then
let the enzyme do its work before the start of the fermentation. After
the pectinase is added to the must, it is left to stand for a few days:
it should clear more or less quickly depending on the temperature, and a
sediment will deposit on the bottom of the container. Most pectinases
don’t work well at low temperatures and need to be around 60 ° F (15 °
C) to be active. The risk to this method is having a natural
fermentation start within this period, but if you have also sulfited the
must, the chances for this are slim. The cleared must is racked into a
new vessel, and the yeast culture may then be added. This
pre-fermentation clarification is routinely done by many commercial
cideries. It allows us to start the fermentation with a clean
pectin-free must, which will facilitate the clearing of the cider once
it is done. Keeving. This is another type of pre-fermentation
clarification process. Done traditionally in France and to a lesser
degree in England, it enables us to obtain a cider that retains some
natural sweetness. In this case we don’t use a pectinase, which is a
mixture of different enzymes, but only one type, the PME, which in
combination with calcium produces the chapeau brun (brown cap). The
juice under this cap is very clear and purged from all the pectin and
impurities. This clear juice is racked into another vessel, and the
fermentation then proceeds. I discuss this procedure further in the
article on sweetness in cider, section 15.1.
Part V: Fermentation and Beyond
Highlight(yellow) - Chapter 13:
Blending > Page 366 · Location 4917
In this article I examine techniques that permit us to predict some
characteristics of a cider obtained from a blend of different varieties
of apples. Note that there are different methods and times to blend:
Highlight(yellow) - Chapter 13:
Blending > Page 366 · Location 4919
Blending of juices before starting the fermentation. This approach is
most suitable when many varieties of apples are grown. One or more
blends may be prepared from each pressing session with apples that ripen
during the same season.
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Blending > Page 366 · Location 4921
Blending “as it goes” (i.e., during the primary fermentation). This
would generally be practiced by a cider maker who makes just one batch
of cider every year: he or she would have one large fermentation vessel,
start the fermentation with the earlier pressings, and add more juice to
the fermenting cider as more pressing sessions are completed, ending
when the latest-maturing apples are finally pressed.
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Blending > Page 367 · Location 4924
Blending of ciders after the fermentation is completed. This case is
better adapted when only a few apple varieties are grown and do not come
to maturity at the same moment. Each variety may then be fermented
individually and the blend done once all these batches are fully
fermented.
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Blending > Page 367 · Location 4927
It is also possible to prepare some blends before the fermentation and
to make a second blending once the fermentation is completed. This is
often done in commercial cideries. For hobbyists, the blending of juices
before fermentation is the most recommended approach.
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Blending > Page 367 · Location 4929
Caution: When you use low-acidity apples, in particular if you are
considering fermenting them as a single-variety cider, remember not to
ferment one batch that would have too high a pH because of the risks of
spoilage. In all cases the pH needs to be 3.8 or lower, which should be
attained by either blending with higher-acidity apples or adding acid.
Highlight(yellow) - Chapter 13:
Blending > Page 367 · Location 4935
So let’s first see what factors go into making an ideal cider blend: A
high sugar content. This, in my opinion, is the first quality to
consider in a blend destined for cider making. I like to aim for a
specific gravity (SG) of 1.060 or higher for the late-season cider
blends and 1.055 for the first-season ciders. Naturally, this is not
always possible, because some years the sugar content is not as high,
and furthermore, in some terroirs such high sugar concentrations can’t
be obtained. In any case, it is always advantageous to maximize the
sugar richness, even if it means discarding the apples of some varieties
that are lacking in sugar. A balanced acidity. We should ideally
maintain the total acidity (TA) of the blend between 5 and 7 g/ L of
malic acid, although acidities as low as 4 g/ L and as high as 8 g/ L
may be acceptable for some special types of blends. The higher values
will go with a refreshing cider, one that is sparkling and festive, or
with a cider that will remain sweet. The lower values are adequate for a
cider that contains more tannins, of the traditional English style, for
example. A tannin content corresponding to the desired style. In
general, North American ciders have a rather low tannin content, while
most European ciders have a lot more. These tannins bring body to the
cider, as well as some bitterness and astringency. This element probably
is the most important in determining the style of cider. A low content
of nitrogenous matters. Remember that these are nutrients for the yeast
and low concentration allows a slow fermentation. Hence, we should
reject apples that mature very early in the season and those that are
grown using intensive orcharding practices.
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Blending > Page 368 · Location 4950
For the sugar and acidity, these properties are easy to measure, and we
can predict the values for the blend if we know them for the individual
varieties. For the tannins, we need to taste the juice and, ideally,
also the fruit before pressing;
Highlight(yellow) - Chapter 13:
Blending > Page 369 · Location 4952
And for the nitrogenous substances the only way to estimate them is by
the knowledge of the cultural practices in the orchard.
Highlight(yellow) - Chapter 13:
Blending > Page 369 · Location 4953
I insist on the sugar concentration of the apples. There are many
reasons for this. First, yes, it is the sugar that gives the alcohol,
and we always want enough alcohol to insure the cider will keep well.
But also, the apples that are rich in sugar are those that ripen later
and have more flavor. Most of the time a high sugar content goes hand in
hand with a low nitrogen content, because the cultural practices that
produce highly nitrogenous apples also produce diluted apples in terms
of sugar.
Highlight(yellow) - Chapter 13:
Blending > Page 369 · Location 4958
the quality of the cider is first and foremost dependent on the quality
of the apples used to make it.
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Blending > Page 369 · Location 4959
Now let’s look again at the ideal blend, but in terms of the apples
needed to obtain the maximum quality: Apples of late maturation. These
apples have the best flavor and the most sugar. Note that certain
varieties of midseason apples are also of high quality for cider. Apples
that are fully ripe or even at the limit of being overripe. This is when
we get the maximum flavor, combined with a reduction of the nitrogenous
matters. Well-ripened apples ferment more slowly but may be harder to
press and yield a little less juice. We sometimes use the term
“sweating” for apples that have been kept for maturation. Apples from
old standard and unfertilized trees. This insures a low nitrogenous
content and a slow fermentation. Small and scabby apples. Some scab may
even increase the quality of the juice by concentrating the sugars and
flavors, but it will reduce the yield. All other things being equal,
smaller apples always have more flavor than larger ones.
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Blending > Page 370 · Location 4972
The ideal blend should be our target. This blend would have an SG over
1.060 (and thus a potential alcohol of over 7.7 percent), and its
acidity would be between 5 and 7 g/ L of malic acid. The good blend is
when the apples don’t have quite enough sugar whatever we do. We can
still make an excellent cider, but it will not have as much alcohol. I
do, however, require an SG of 1.050 (potential alcohol 6.4 percent) or
better for the blend to be considered a good one. On the left, we can
see an area for low-acidity blends, which would be typical for a cider
from the southwest of England, for example. For such a blend to make a
good cider, however, the tannin needs to be high and compensate for the
lack of acidity. Slightly lower SGs are also seen in such blends. On the
right, we have an area for sharp blends, which have an acidity slightly
higher than the ideal. This would be acceptable for a festive sparkling
cider with little tannin or for a cider that retains some residual
sweetness. We also see on the graph a brown line that represents the
possible blends from two juice samples: a low-acidity juice, SG 1.050,
TA 2 g/ L, and a sugar-rich juice, SG 1.065, TA 8.5 g/ L. The line
represents the location of the possible blends of these two juices. A
half-and-half blend would be exactly at the midpoint of the line. But I
would prefer a blend of two-thirds sugar-rich juice with one-third of
the low-acidity juice, represented by the brown dot located at a third
of the length of the line.
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Blending > Page 371 · Location 4985
It can easily be seen from this graph how difficult it is to integrate
some low-sugar apples into a blend while maintaining an overall good
blend. Hence, apples in this group would not be used in a quality cider
blend except in special circumstances, where such an apple has a
particular character that we want to integrate in the cider. With such a
graph, it becomes possible to plan a blend and determine the proportions
of each apple type to obtain the ideal blend. Naturally, it is necessary
to know the properties of each variety, and for this a sample of juice
will have to be pressed in order to measure the SG and TA. Fortunately,
we get to be able to anticipate those numbers from previous years’
experiences. This graphical approach for planning a blend will, however,
become overly confusing when there are many varieties to blend. In
general, it is more practical to use a computer with the spreadsheet
that will be presented a bit later.
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Blending > Page 372 · Location 4998
better evaluation of the tannin may be obtained from tasting both the
fruit and the juice.
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Blending > Page 373 · Location 5005
Ciders from North America and from the eastern regions of England are
most often made without any tannin-rich apples, using essentially eaters
and cookers.
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Blending > Page 373 · Location 5010
The only thing that really counts is not to overdo it. Too much hard or
bitter tannin may render the cider unpleasant: we want only a slight
touch of bitterness to give an interesting character.
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Blending > Page 373 · Location 5012
As a last point, if you blend a cider with a high tannin content, it is
better to make it low in acidity. It seems that the tannins and the
acids complement one another: if there is a lot of one, there should be
relatively less of the other.
Highlight(yellow) - Chapter 13:
Blending > Page 374 · Location 5015
As I mentioned earlier, I tend to blend the juices before fermentation.
Generally, I press the varieties individually and record the SG and TA
from each. As each pressing session advanced, I often found myself
wondering if the resulting blend would be well balanced, and if it
wouldn’t be preferable to add some low-acidity or maybe some high-sugar
varieties to complete the blend. For this, we need to make what is
called a weighted average. For example, if I have three juices in
quantities Q1, Q2, and Q3, and these juices are at SG1, SG2, and SG3,
respectively, then the weighted average for SG would be: SGavg
= (Q1 SG1 + Q2 SG2 + Q3 SG3) / (Q1 + Q2 + Q3) And the same calculation
would be done for the TA. This is exactly what the spreadsheet I have
developed does. This is an Excel spreadsheet that will also work with
Open Office and Libre Office. You will find it with the companion
materials of this book under the name BlendWiz.xls in Appendix 2.
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Blending > Page 376 · Location 5080
present here two examples of typical blends that I do for my ciders.
First-Season blend This blend is made with apples that ripen by
September 10 to 15th and are pressed on the last days of September or
beginning of October.
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Blending > Page 376 · Location 5089
Late-Season blend
Highlight(yellow) - Chapter 13:
Blending > Page 376 · Location 5090
This blend is made with my late-ripening varieties, which are harvested
in October. The pressing may be done by mid-November.
Highlight(yellow) - 14.1: The
Sulfite > Page 378 · Location 5108
The chemical compound that we commonly call sulfite is in fact sulfur
dioxide, and its chemical formula is SO2. Sulfite is used
extensively in the making of cider and wine because it has some very
useful properties: Sulfite is an antiseptic that kills microorganisms
when used in a sufficient dose and in an acid medium. Bacteria are the
most sensitive to its action, followed by yeasts of the apiculate type,
and finally yeasts of the genus Saccharomyces, which are more resistant.
Sulfite is also an antioxidant, which binds chemically with oxygen and
with other molecules produced by primary oxidation. Once bound with an
SO2 group, a molecule that could potentially cause some
oxidation becomes deactivated and cannot interact anymore with the other
cider constituents. This effectively protects the cider against
oxidation and also against some disorders that need some oxygen to
develop.
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Sulfite > Page 379 · Location 5115
In practical terms for cider making, we use sulfite for the following
reasons:
Highlight(yellow) - 14.1: The
Sulfite > Page 379 · Location 5121
Sterilization of the must, a day or two before inoculating some cultured
yeast. And since microorganisms don’t all have the same sensitivity
toward sulfite, it is possible to adjust the dosage in such a way as to
eliminate only the bacteria or, if the dose is strong enough, all the
wild yeasts. Protection of the cider once the fermentation is complete.
During active fermentation, the carbon dioxide gas that is produced,
being heavier than air, acts like a blanket to prevent oxygen from
coming into contact with the cider. However, when the fermentation is
complete, air could then come into contact with the cider surface. The
antioxidant property of sulfite will then give some protection. Curative
effect. When the cider is attacked by some bacteria or fungus, we may
sulfite it to kill and eliminate the organisms in question and to
protect the cider against further attack.
Highlight(yellow) - 14.1: The
Sulfite > Page 380 · Location 5129
When we add a certain amount of SO2 to the apple juice or
cider, a good part of it combines more or less rapidly with certain
constituents in the juice and with the products of the fermentation.
This is referred to as the bound SO2. The rest is said to be
free, meaning that it remains active. It is through the action of
combining, or binding itself, with different molecules that the free
SO2 protects the cider.
Highlight(yellow) - 14.1: The
Sulfite > Page 380 · Location 5134
As the fermentation progresses, more and more of the SO2 that
was initially free becomes bound with some products of the fermentation,
such that once the fermentation is complete, there may not be any free
SO2 left, or very little of it. Some cider makers will add a
second dose of SO2 as they rack at the end of fermentation or
at bottling time to insure the protection of the cider during
maturation. When such an additional dose is given, there is a larger
proportion of the SO2 that remains free, but still not all of
it. The chemical equilibrium between free and bound SO2 is
dynamic and quite complex,
Highlight(yellow) - 14.1: The
Sulfite > Page 381 · Location 5145
At this moment and for a short while, almost all the SO2 is
in the free state, but it will combine rapidly with the juice
constituents. It is during this period that the sulfite has its maximum
sterilization effect and can kill bacteria and yeasts present in the
juice. After a day, half or more of the initial SO2 is
already in the bound state, and the free part is greatly reduced. The
juice is thus much less toxic for the yeasts and can be inoculated with
a selected strain of yeast; the fermentation may then proceed.
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Sulfite > Page 382 · Location 5159
This model is extremely simplified and doesn’t take into account many
factors,
Highlight(yellow) - 14.1: The
Sulfite > Page 382 · Location 5161
Different biochemical reactions that occur during fermentation will
interact with SO2 and this may increase or decrease the
quantity of SO2.
Highlight(yellow) - 14.1: The
Sulfite > Page 382 · Location 5163
Some yeasts under certain conditions may produce up to 30 ppm of
SO2.
Highlight(yellow) - 14.1: The
Sulfite > Page 382 · Location 5166
A last word on the dynamic equilibrium between the different forms of
SO2: in the bound state, part of the sulfite is permanently
bound, but another part is bound in a reversible way, meaning that some
of the bound SO2 may become free again when the concentration
of free SO2 decreases. Also, in the free state there are two
forms, and the important one is said to be molecular or soluble, as it
is really this form that is active. The fraction of the free SO2
that is in the molecular form is dynamic and variable, most notably in
relation to the pH, the temperature, and the alcohol concentration of
the cider. The effect of pH is very important: the fraction of the
active molecular form may be ten times higher at pH 3 than at pH 4, and
this means that the lower the pH (i.e., the more acidic the cider), the
more efficient the SO2. This explains why the dosage of
SO2 in the must is done in relation to the pH. The
concentration of the molecular form of SO2
required to obtain an antiseptic action is around 0.5 to 1 ppm,
depending on whether we want a selective effect on only some sensible
organisms or a total effect.
Highlight(yellow) - 14.1: The
Sulfite > Page 383 · Location 5178
We usually specify the dosage of sulfite in parts per million (ppm) of
SO2 (see Appendix 1). Usual doses are generally between 20
and 200 ppm. In many countries the law forbids adding more than 200 ppm
of SO2 to the cider. As mentioned earlier, the recommended
dosages of SO2 are given as a function of the pH, because
when the pH is high, the free SO2 is less efficient, and we
need to add a lot more sulfite to obtain the same effect.
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Sulfite > Page 384 · Location 5185
Highlight(yellow) - 14.1: The
Sulfite > Page 384 · Location 5187
The sulfite dose obtained from this graph is calculated to provide 1 ppm
of molecular SO2 in an average apple juice and should
normally be sufficient to give complete control of wild yeasts. Then,
one or two days after introduction of this sulfite, it will be possible
to inoculate a cultured yeast. When the juice pH is 3 or lower, the
acidity is considered high enough to protect the cider, and thus sulfite
addition is not required. When the juice pH is higher than 3.8, it is
recommended to blend in more acidic apple varieties or add some acid to
increase the acidity and lower the pH to 3.8 or less. This is because
the amount of sulfite that would be required to efficiently protect such
a low-acid cider would be more than the maximum legal dose of 200 ppm.
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Sulfite > Page 385 · Location 5192
In practice, most small-scale cider makers use indicator strips to
measure the value of the pH. These strips don’t have great precision; an
uncertainty on the order of pH 0.2 to 0.3 would be normal. Considering
this, a three-level recommendation would often be more appropriate: pH
between 3.0 and 3.3: addition of 50 ppm of SO2 pH between 3.3
and 3.6: addition of 100 ppm of SO2 pH between 3.6 and 3.8:
addition of 150 ppm of SO2
Highlight(yellow) - 14.1: The
Sulfite > Page 385 · Location 5201
if a malolactic fermentation is desired, the initial sulfite dose has to
be reduced because the SO2 would kill the lactic bacteria
that make this fermentation possible (see section 14.4 on malolactic
fermentation). On the other hand, if the apple lot used to make the
juice contains a lot of rotten fruit, the sulfite dose would then need
to be increased, because such apples contain more compounds that will
combine with the SO2, with the result that the concentration
of free SO2 will be lower than expected.
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Sulfite > Page 385 · Location 5206
For making a perry, it is recommended to increase the dosage by 50 ppm
over the standard guidelines given above, because pear juice contains
more sulfite binders than apple juice, thus a smaller fraction of the
total SO2 will remain in the free state.
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Sulfite > Page 385 · Location 5208
When sulfite is added at the end of the fermentation, the objective is
to insure a sufficient level of free SO2 to protect the cider
during maturation. The dose doesn’t need to be strong enough to kill
microorganisms, as it does for the first addition. The difficulty is in
adding the right amount, which involves making an analysis of the free
SO2 remaining in the cider and then calculating the required
amount to bring the quantity of free SO2 to the desired
level, which will vary depending on the pH and the cider maker. In
general this ideal level will be somewhere between 10 and 50 ppm. This
procedure is usually done only in a larger-scale operation, however.
Small-scale and amateur cider makers most often use a dose defined as a
fraction of the initial SO2
addition, such as a third or a half, for example.
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Sulfite > Page 386 · Location 5216
If you can taste the sulfite when drinking the finished cider, this
means you have added too much, and next time you need to add less.
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Sulfite > Page 386 · Location 5220
Caution: When manipulating sulfite powder or a sulfite solution, always
avoid inhaling the fumes, as they are very irritating.
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Sulfite > Page 386 · Location 5221
For the small-scale cider maker, the main sources of sulfite will be
potassium metabisulfite, sodium metabisulfite, and Campden tablets.
These products are easily found in any wine-making supply shop. The
professional may use other forms better adapted to large volumes of
production. Potassium metabisulfite is a white salt that theoretically
contains 57 precent of its mass in SO2. In practice, we
generally consider this half of its mass, and thus 100 grams will give
50 g of SO2. Sodium metabisulfite, also a white salt,
theoretically contains 64 percent of its mass in SO2, but, as
for the previous compound, we count a little less in practice: about 55
to 60 percent. It also contains about 25 percent sodium. Although the
quantity of sodium is very small, some cider makers object to using it
to sulfite the must, preferring potassium metabisulfite. As a
sterilization solution, both forms are equivalent. Campden tablets are
in fact made of potassium metabisulfite and calibrated to give 50 ppm of
SO2 in 1 imperial gallon (1.2 US gal, or 4.5 L) of juice or
cider. Hence, four tablets are required to dose 50 ppm in a 5-gallon
batch. Personally, I don’t like these tablets very much because they
first need to be reduced to a powder with a mortar, and they are
difficult to dissolve.
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Sulfite > Page 388 · Location 5254
Sulfite has been used in wine and cider making for centuries, and it has
been a very important factor to obtain a good-quality product. However,
its use does have some inconveniences: Sulfite is a toxic and corrosive
product. It is important for the cider maker to avoid inhaling its fumes
and to manipulate it with caution. It may even provoke asthma attack.
Some people are very sensitive to sulfite and may detect it in the
finished cider even if the dose is not excessive. When a cider that
still contains free SO2 is drunk, it is then relatively easy
to detect, having something of the taste of sulfur or burnt matches, and
in my opinion this is a defect. Many people believe that sulfite in
wines and ciders is a cause of headaches and hangovers after an evening
when a bit too much has been drunk. As far as I know, this has never
been scientifically proven, but I think it is plausible, in particular
if the sulfite was overdosed. Sulfite may prevent the malolactic
fermentation desirable for some cider styles. For all these reasons,
many cider makers prefer not to add sulfite to the must and to the
cider. However, when making this decision, it is important to weigh all
the factors and to accept a higher risk of getting a spoiled cider
batch. Among the factors that plead in favor of not adding sulfite,
there are: The fact that many yeasts naturally produce SO2
during fermentation, some strains more than others. For example in the
documentation for Lalvin’s EC-1118 yeast, it is said that this strain
may produce up to 30 ppm of SO2 when the cider is low in
nutrients. Thus, if the juice was fairly acid, as is often the case with
North American apples, this may be sufficient to fully protect the
cider. Modern equipment, in particular glass carboys and stainless steel
vats, are much easier to clean and sterilize than were the wooden
barrels used in the old days. Further, if careful precautions are taken
to prevent air from coming into contact with the cider and if the cider
room is kept perfectly clean, the risk of proliferation of a bad
microorganism is greatly reduced. Many modern selected yeast strains
have a dominating effect and will not let another type of population
develop in the same medium. After inoculation of a strong yeast
population, then, and as long as this population is active, there is
little to fear from contamination by another microorganism. Almost all
commercial wines and ciders contain added sulfites. However, if we are
making our own cider for our own consumption, it is justified to desire
a product that would be the most natural possible and thus that would
not contain any chemical additive. For a commercial cider maker, the
fact of not adding sulfite may become a sales argument and give some
added value to the product for a certain market niche. On the other
hand, the economic loss from a spoiled batch of cider could be very
important.
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Sulfite > Page 390 · Location 5281
The most critical period for an unsulfited cider is when all sugars have
been fermented: at this point there is no more carbon dioxide gas
produced that would protect the cider from air, and the yeast population
decreases and cannot remain dominant. Protection from air contact is
then the key to avoiding contamination.
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Sulfite > Page 391 · Location 5296
Potassium sorbate has some antifungal properties and in particular some
inhibiting effect on yeasts and other microorganisms, such as those
responsible for film yeast. It isn’t used by itself but in combination
with sulfite, thus permitting the cider maker to reduce the sulfite
dose. In particular, sorbate is often used with ciders that contain some
residual sugar, since it helps prevent a restart of the fermentation.
Sorbate will not stop an active fermentation. But if the yeast
population has been greatly reduced by some other means (a cold shock,
for example), it will help prevent the population from rebuilding
itself.
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Sulfite > Page 392 · Location 5301
When sorbate is used, malolactic fermentation has to be avoided, because
the combination of sorbate and lactic acid produces some molecules that
smell somewhat like geranium and would thus spoil the cider. This means
that some free SO2 is required to prevent malolactic
fermentation (between 10 and 50 ppm, depending on the pH).
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Sulfite > Page 392 · Location 5304
Ascorbic acid (vitamin C) is an antioxidant that may help to protect a
cider as it “captures” the oxygen that could come into contact with the
cider. It is most often used at bottling time in association with
sulfite, dosage of which can then be reduced.
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Sulfite > Page 392 · Location 5309
Testing of SO2 may be important for two reasons: The amount
of free SO2 should be measured before adding more SO2
during the maturation of the cider or before bottling, in order to add
the right amount for the desired protection. The amount of total SO2
may be checked in a commercial cider to make sure the value doesn’t
exceed the maximum legal dosage,
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Sulfite > Page 393 · Location 5316
Different methods exist to test the concentration of free and total
SO2
in a cider. The most accurate method, and the one that would be used in
specialized laboratories, is the Ripper titration with iodine. This
method is well documented in most oenology books but requires some
chemicals that are not easily obtainable by a hobbyist as well as
sulfuric acid, which is potentially dangerous. Kits for the Ripper
titration are sold by specialized merchants, but most cider makers use
either titrets or small electronic analyzers, which are much easier to
use.
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Sulfite > Page 393 · Location 5320
Titrets are ampules containing chemicals into which you add a measured
quantity of the cider to be tested. Titrets test only for free
SO2, its concentration being indicated by a color change.
Highlight(yellow) - 14.1: The
Sulfite > Page 393 · Location 5322
The accuracy is approximately ± 10 ppm of SO2 over a range of
10 to 100 ppm. The cost of these titrets is quite reasonable, at
approximately $ 2 per test.
Highlight(yellow) - 14.1: The
Sulfite > Page 393 · Location 5323
Electronic analyzers are available at different prices, the more
expensive the more accurate.
Highlight(yellow) - 14.2: The
Yeast and Yeast Nutrients > Page 395 · Location 5347
For the purposes of this discussion, I classify the different yeast
types in a very crude way:
Highlight(yellow) - 14.2: The
Yeast and Yeast Nutrients > Page 395 · Location 5348
The Saccharomyces group. This family of yeasts is the most important for
the complete transformation of sugar into alcohol. Thus, they are
considered strong fermenters. In cider it is S. cerevisiae that is the
most common. These yeasts generally have a high tolerance to
SO2, meaning that a normal sulfite dose will not kill them.
They are also tolerant to alcohol, some strains being able to ferment up
to 17% ABV (whereas a wild strain would likely not tolerate such a high
alcohol strength). They are also efficient fermenters, producing more
alcohol per given quantity of sugar than other yeasts. These yeasts are
not present in great numbers in the apple itself but colonize the juice
from spores that are in the press cloths, the air—in fact, everywhere in
the cider house. The non-Saccharomyces, or starting, yeasts. These are
often referred to as the apiculate yeasts, and the most important
species of this group is Kloeckera apiculata. We call them “starting
yeasts” because they are abundant on the apple skin and in the flesh, so
they can start their fermentation work very quickly after pressing is
done. However, their alcohol tolerance is low, and they will die when
the alcohol strength reaches 2 to 4 percent. They are also sensitive to
SO2, and a normal sulfite dose will eliminate them. For the
fermentation, they are not as efficient as S. cerevisiae, producing
about 20 percent less alcohol from the same quantity of sugar, so
overall their contribution to the total alcohol of the cider is
relatively small. However, many authors and also many cider makers
consider their contribution to the flavor and bouquet of the cider very
important, because the action of these yeasts adds some complexity and
richness to our favorite drink. The spoilage yeasts. These are the
unwanted yeasts. In this group are the yeasts responsible for the film
yeast sickness (Pichia and Candida species), and the Brettanomyces,
which give some off-flavors. In general these spoilage yeasts need
oxygen to colonize a cider, thus the recommendation to keep air out of
the fermentation vessel is intended to keep these unwanted yeasts under
control.
Highlight(yellow) - 14.2: The
Yeast and Yeast Nutrients > Page 397 · Location 5381
Numerous strains of yeast have been isolated and are available as pure
cultured yeast. The main advantages of using such yeasts are the
reliability and predictability of the final product, as well as the
reduced risk of a stuck fermentation, as cultured yeasts are usually
strong fermenters. Another important point is that their features are
documented, and a fairly complete data sheet should be available for all
the strains sold by major companies. These data sheets will normally
give information on such characteristics as: Species and subspecies.
Most often this is Saccharomyces cerevisiae cerevisiae, though for
champagne yeasts the subspecies would be S. cerevisiae bayanus. The
latter is considered a finishing yeast, and it is more tolerant of high
alcoholic strengths. Production of SO2. Some yeast strains
are known to produce a relatively large quantity of SO2, up
to 30 ppm for the Lalvin EC-1118, for example. Competition (or killing)
factor. This indicates that the particular strain produces a toxin that
impedes other species and strains of yeasts from colonizing the medium
and competing with the main yeast. Yeasts can be positive (contain the
toxin), sensitive (no toxin and are killed by the toxin), or neutral (no
toxin but are not killed by the toxin). Note that this toxin only
affects other yeasts and will not act against bacteria. Temperature
range at which the yeast will thrive. Fermentation speed. Alcohol
tolerance. Production of hydrogen sulfide (H2S), an unwanted
compound that smells like rotten eggs. Some yeasts are known to produce
higher levels of H2S or to do so more commonly. Interaction
with malic acid. Some yeasts (e.g., Lalvin 71B) are known to metabolize
up to 20 percent of the malic acid present in the must, thus softening
the cider. Flocculation. This indicates that the yeast will deposit as
large flocs and yield compact lees on the bottom of the container. This
property is sought mainly for champagne yeasts used for in-bottle
fermentation.
Highlight(yellow) - 14.2: The
Yeast and Yeast Nutrients > Page 398 · Location 5401
The standard method of cultured yeast fermentation is to do a
sterilization of the must by a full sulfite dose (see the preceding
section on sulfites), followed, a day or two later, by the inoculation
of a strong population of the selected yeast strain. This procedure thus
eliminates the spoilage yeasts and the non-Saccharomyces as well as most
wild Saccharomyces yeasts, so that the strain used for inoculation will
clearly dominate the fermentation and leave its characteristic flavor
profile. The main criticism concerning this approach is that the flavor
profile is considered unidimensional and lacking in complexity, and in
particular lacking in the flavor compounds produced by the apiculate
yeasts. Many commercial cideries will, however, use this approach
because of its reliability and consistency, as well as the decreased
risk of spoilage. This approach would also be the most recommended one
for a novice cider maker, as it will insure consistent results from the
fermentation while the cider maker gains experience in the other aspects
of cider making.
Highlight(yellow) - 14.2: The
Yeast and Yeast Nutrients > Page 399 · Location 5417
Most of the cultured yeast strains have been isolated from
wine-producing regions and thus are wine yeasts. There are additionally
a few cider yeasts that have been isolated. (Beer yeasts are also
available but are generally not recommended for cider.) Pure selected
yeasts are available either in dried or liquid form. Dried is more
common and less expensive (at least for the most popular strains), but
it requires the yeast to be rehydrated before inoculation to the must.
Personally, I tend to use the Lalvin dried yeasts, largely because they
are readily available from a store just five minutes from my home. Here
are characteristics of the yeast strains I most often use: Champagne
yeast (Lalvin EC-1118, Red Star “Pasteur Champagne,” Red Star “Prise de
Mousse/ Première Cuvée”). These three yeasts are quite similar and
considered all-purpose yeasts. They are strong fermenters that will
ferment to dryness unless the must is very poor in nutrients. They are
also used to restart a stalled (or stuck) fermentation. Champagne yeast
tolerates cold temperatures, and it gives a very clean, neutral,
slightly sharp flavor to the cider. It is my classic and most often used
strain. Lalvin 71B-1122. This yeast strain is generally recommended for
making primeur wines or vin nouveau, that is, a very young wine. It
gives a fruity character and is also used for making semisweet wines.
One of its useful documented features is that it metabolizes some malic
acid, thus reducing the total acidity by 15 to 25 percent. I use it
mainly when a blend has more acidity than I would like.
Highlight(yellow) - 14.2: The
Yeast and Yeast Nutrients > Page 400 · Location 5430
Other Lalvin yeast strains commonly used and recommended for cider
making are the ICV D-47 and the DV-10.
Highlight(yellow) - 14.2: The
Yeast and Yeast Nutrients > Page 401 · Location 5437
Dried yeast needs to be rehydrated before inoculation to the must.
Highlight(yellow) - 14.2: The
Yeast and Yeast Nutrients > Page 404 · Location 5462
the nitrogenous substances present in the apple juice are a natural
nutrient source for the yeast. However, their concentration may vary
greatly as a function of the apple variety, cultural practices, terroir,
and seasonal conditions. Further, apple juice is generally poorer in
natural nutrients than other fruit juices, like grape juice, for
example. Hence some cider makers will want to supplement the naturally
occurring nutrients with chemical nutrients to insure a strong and
reliable fermentation that will rapidly go to dryness. On the other
hand, many cider makers prefer a slow fermentation and will even be
grateful if the fermentation stops before completion, hence yielding a
cider with residual sugar. For this second category of cider makers,
nutrient addition is definitely out of the question except in special
circumstances or if there is a specific problem. For example, yeast
nutrient may be added to a stuck cider when we want the fermentation to
go a little further, or in some special bottling procedures when a sweet
and sparkling cider is desired.
Highlight(yellow) - 14.2: The
Yeast and Yeast Nutrients > Page 404 · Location 5470
we generally find two substances that may be used as nutrients for the
yeast: Diammonium phosphate (DAP) is a chemical compound containing
ammonium ions that release nitrogen: 21 percent of the weight of DAP is
nitrogen in an assimilable form by the yeast. It is sold in the form of
a water-soluble, white crystalline salt. Thiamine, or vitamin B1,
referred to as a yeast energizer. A very small quantity of thiamine is
essential for the yeast to perform its work of turning sugar into
alcohol, but it is very unlikely that this small quantity will not
already be present in the juice.
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Yeast and Yeast Nutrients > Page 405 · Location 5483
for each 10 ppm of DAP I would add to a stuck cider, the fermentation
would restart slowly, causing an SG drop of approximately 0.004, and
after a few months the fermentation would stop again at this new lower
SG.
Highlight(yellow) - 14.2: The
Yeast and Yeast Nutrients > Page 406 · Location 5495
we may conclude that if we want to restart a stuck fermentation and have
the cider ferment to dryness, then a dosage of 40 to 50 ppm of DAP per
each 0.010 of required SG drop would be fine. But if we want the
fermentation to stick again at a lower SG, then we should use less, and
25 ppm of DAP per each 0.010 of required SG drop would in this case be
recommended from the outcome of the tests
Highlight(yellow) - 14.3: The
Monitoring and Control of the Fermentation > Page 407 · Location 5505
Our objective is to provide the conditions that will maximize the
quality of the cider.
Highlight(yellow) - 14.3: The
Monitoring and Control of the Fermentation > Page 407 · Location 5506
For this, we take actions to insure a slow but regular fermentation,
which will permit the cider to develop its bouquet. A slow fermentation
is beneficial to the cider flavor because many of the flavorful
molecules are volatile, and hence they will have a better chance to stay
in the cider rather than escape to the atmosphere if the fermentation is
slow and quiet and done at low temperature. Additionally, some
interventions done at the right moment may permit us to keep a part of
the original sugar unfermented, hence yielding ciders that naturally
retain some sweetness.
Highlight(yellow) - 14.3: The
Monitoring and Control of the Fermentation > Page 407 · Location 5510
We will reach our objectives by first monitoring the fermentation
carefully. This means that we will regularly measure the specific
gravity (SG) of the cider and determine how fast the fermentation is
proceeding, which we can present graphically. The monitoring will help
us take the right step at the right moment to control the fermentation,
depending upon the type of cider we want to make.
Highlight(yellow) - 14.3: The
Monitoring and Control of the Fermentation > Page 407 · Location 5515
fermentation speed unit (FSU), which is defined as follows: 1 FSU is the
speed of fermentation that corresponds to a drop in SG of 0.001 in 100
days. Hence, a speed of 100 FSU is equivalent to an SG drop of one point
per day.
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speed (FSU) = 100,000 (SG1 − SG2) / N
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The Phases of the Fermentation 1. Period of establishment of the yeast
population During this period the yeast will multiply its population,
but we observe very little activity, as there is no significant
variation in the density or production of the carbon dioxide gas. The
measured speed of fermentation is close to zero. When the cider has been
inoculated with a strong yeast culture and the temperature is relatively
high, this period may be very short, only a few hours. But generally, if
the temperature is lower than 55 ° F (12 ° C), this establishment period
may need a couple of days.
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Monitoring and Control of the Fermentation > Page 408 · Location 5531
While the population is establishing itself, the yeast needs oxygen, and
the fermentation vessel used should be wide enough to provide a good
contact surface between the air and the must. The vessel may still be
closed, as long as there is a good layer of air under the lid. Some
cider makers will stir the cider during this period to aerate it, but I
have never found this to be necessary.
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2. Primary or turbulent fermentation The fermentation will start
gradually as the yeast population gets established. A white to light
brown foam forms on the surface of the must. After a few days this foam
may be an inch or more thick, and the top becomes browner in color as
the fermentation carries some solid deposits to the surface. There is an
important production of carbon dioxide during this phase, which will be
easily noticed if the fermentation vessel is hermetically closed and
equipped with an airlock. The turbulent fermentation may last between
ten days to over a month, depending on the type of apples, how late in
the season they were harvested, the ambient temperature, the nutrient
content of the must, and the strain of yeast used. It is during this
period that the speed of the fermentation is at its maximum, and between
one-third and three-quarters of the initial sugar of the must will be
transformed by the fermentation.
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When the turbulent phase quiets down, the foam vanishes gradually,
leaving some brown deposits on the surface. This indicates the end of
this phase. It is then possible to proceed to the first racking
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3. Secondary fermentation phase There is no set point of transition
between the turbulent phase and secondary phase unless you have opted to
make an early first racking, in which case the moment of this racking
would mark the beginning of the secondary phase. The secondary
fermentation will last until the alcoholic fermentation is finished. It
is in our interest that this fermentation proceed as slowly as possible,
and for this we will try to have a cool temperature in the cider room,
50 ° F (10 ° C) or even less. When everything goes smoothly, the cider
maker doesn’t have much to do during this phase, but it is recommended
to monitor things. If a first racking was done and was effective, the
speed of fermentation should be much lower now than it was during the
turbulent phase. I like it to be around 50 FSU or slightly less. And as
it goes along, we observe a gradual decrease in speed. For all practical
purposes, we may consider the secondary phase complete and the cider
stabilized when the speed of fermentation is about 3 to 4 FSU or lower
over a period of a month, which would correspond to an SG drop of 0.001
during this month. For a cider that was started in late fall, the end of
the secondary phase usually occurs by late the following spring or
around the beginning of the summer.
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4. Malolactic fermentation Malolactic fermentation (MLF) is considered a
phase in this process even though it doesn’t happen for all ciders. It
may happen spontaneously at the end of the secondary phase or be caused
by the inoculation of lactic acid bacteria.
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5. Maturation and clearing of the cider During this last phase of the
fermentation, the cider is very quiet. Carbon dioxide is not produced
anymore, as there is no more alcoholic fermentation. Small quantities
may still be produced by malolactic fermentation, but when we see some
activity in the airlock, the most probable cause is that the cider is
warming up (we are in the beginning of summer by then), and some of the
carbon dioxide that was in solution escapes in gaseous form and may
cause a bit of activity in the airlock. This is because the solubility
of carbon dioxide in water decreases as the temperature rises. In any
case, this is the most critical period for the cider, as it is no longer
protected by the blanket of C02 that is produced by active
fermentation. Hence, it is important to make sure there is as little air
as possible in the vessel.
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Even if the cider is very calm in appearance, there are still chemical
and biochemical reactions happening, and these may enhance the flavor
and aroma of the cider as well as smoothen it. Additionally, this period
of calm will allow the particles in suspension to form a deposit on the
bottom of the vessel, as the cider clears naturally. Once the cider has
cleared, we consider this maturation phase complete and the cider ready
to bottle, but we still may let the cider sit on its lees for a while
before bottling.
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Fermentation Vessels
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quite different from those for subsequent phases. For the primary phase,
a larger vessel is needed, as it is useful to have some extra cider.
Further, a good headspace is required over the must to allow for the
foam that will be produced, otherwise this foam will overflow and spill
onto the floor. Typically, there will also be a relatively large area of
contact between air and the must, and this is quite acceptable at this
stage because the yeast needs oxygen during the population establishment
period. This vessel doesn’t have to be hermetically closed, nor does it
need to be equipped with an airlock, although these two features may
still be desirable.
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Monitoring and Control of the Fermentation > Page 412 · Location 5582
For the secondary and subsequent phases, we want to minimize the contact
with air, since less carbon dioxide is produced as the fermentation
slows. When there is a lot of this gas, it protects the cider, but in
the later phases there is not enough to insure protection anymore.
Hence, the fermentation vessel should have a hermetic lid and an airlock
so no oxygen can enter and reach the cider. It should also provide a
reduced area of contact between the cider and the gas in the headspace
on top of the cider and a minimal volume of headspace. Cider makers
typically use containers completely full of cider or tanks equipped with
lids that are adjustable in height. Alternatively, you can remove the
air from a headspace by injecting carbon dioxide into the top of the
tank to act like a protective blanket over the cider.
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Monitoring and Control of the Fermentation > Page 413 · Location 5589
carboy for the secondary fermentation. Carboys are excellent for this,
as they have a narrow neck, and when they are filled to the top, there
is only an area of about a square inch (5 cm2) of contact between the
cider and the gas in the headspace. Further, the volume of this
headspace is very small.
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Those who use barrels do so mainly because the cider will take some
tannin from the wood, thus the barrel modifies the flavor of the cider.
A second reason is that it is much easier to obtain a spontaneous
malolactic fermentation in a barrel
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However, barrels do have some drawbacks: they are difficult to clean and
disinfect, and the wood pores may host some spoilage microorganisms.
They also need good care to keep them from drying out and leaking. For
these reasons, many cider makers wouldn’t use a barrel under any
circumstances, now that there are modern materials like stainless steel,
glass, or plastic that are more convenient.
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And although some smaller sizes do exist, they are not recommended for
cider making because the ratio of the wood surface to the volume of
cider is too large and makes the cider excessively woody.
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Monitoring of the Fermentation
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In its simplest form, this monitoring will just be notes of the date,
the measured SG, and the speed of fermentation at some more or less
regular time intervals. The temperature measurement is also necessary,
as it allows you to make the correction to the SG reading. And a few
acidity measurements during the evolution of the cider may help identify
whether a malolactic fermentation is actively occurring.
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When should measurements of SG and acidity be taken?
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I suggest the following schedule,
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After pressing of the apples: SG and TA of the fresh juice. This value
of SG is particularly important, as it will permit you to evaluate the
alcoholic strength of the cider.
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At the end of the primary fermentation: SG and calculation of the
average speed during the primary fermentation.
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At the moment of a racking and approximately two weeks later: SG and
calculation of the fermentation speed to assess the effectiveness of the
racking. During the secondary fermentation and the maturation: a
measurement of SG and calculation of the fermentation speed once a
month. During the later phases, when the fermentation has slowed down,
once every two months will be sufficient. By the end of winter, before
the temperature starts to rise in the cider room: TA once or twice so
see if there are variations of the acidity due to the fermentation.
During malolactic fermentation, if it occurs: a few measurements of TA,
to view its evolution. At the moment of the last racking, before
bottling: SG and TA.
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Once the fermentation is started, the cider maker usually doesn’t have
much to do.
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you need to check the airlock regularly and renew the antiseptic
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By the end of the fermentation, you should watch for the possible
outbreak of some spoilage, such as a film yeast
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But mainly you simply have to be patient and let the cider take its time
to make itself.
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professional cider maker might let the cider ferment in a cider house
where the temperature is controlled to about 50 ° F / (10 ° C). A
hobbyist cider maker who lives in an area where there are cold winters
should have a small room which, ideally, should be unheated and have a
window as a temperature-control method.
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Monitoring and Control of the Fermentation > Page 420 · Location 5724
it would be good if the temperature in this room could drop to 40–50 ° F
(5–10 ° C) during the colder part of winter, so that the fermentation
maintains a slow pace.
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Monitoring and Control of the Fermentation > Page 420 · Location 5731
Racking is an operation by which we separate the cider from its lees by
moving the cider from one fermenting vessel to another without
disturbing the lees, which remain in the first vessel.
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An important effect of racking is to reduce the biomass of the cider. By
biomass we mean the organic matters that feed the yeast, as well as dead
and live yeast cells. The dead ones contain some nitrogenous nutrients
that would be released back to the cider by autolysis to feed the new
generation. Hence, a racking decreases the number of active yeast cells
and lowers the essential yeast nutrients in the cider, with the result
that the fermentation slows down. In order to maximize the effect of a
racking, it is preferable to do it when the cider is relatively cold, as
the activity of the yeast is then reduced and there is less agitation in
the cider. With less yeast and fewer nutrients in suspension in the
cider, the separation from the biomass will thus be more effective.
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it is very important not to disturb the lees before or during the
racking, and to rack off only the cider into the new vessel.
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We distinguish three types of racking that may be done on a cider: the
first racking, which is done relatively early; the stabilization
racking, which is optional and may be done during the later phases of
the fermentation to reduce its speed; and the final racking, which is
done once the fermentation is complete.
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The object of the first racking is to move the cider from its primary
fermentation vessel to its secondary vessel, where it will be protected
from air contact during the later phases of fermentation. However, this
racking will also reduce the speed of fermentation, as mentioned above.
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There are two schools of thought as to the best moment for the first
racking. We may call them early and late first racking. An early first
racking is done soon after the foam from the turbulent fermentation has
settled, while the SG is still relatively high. This might be anywhere
from ten days to four weeks after the start of fermentation, and the SG
may be somewhere between 1.020 and 1.040. The point in making the first
racking as soon as possible is to profit from the speed reduction effect
early on: this increases the chances of getting a stuck fermentation,
which would leave the cider with some residual sugar. A late first
racking, on the other hand, is performed when most of the fermentation
is done and the SG is approaching the point of dryness, typically around
SG 1.005. And actually, this first racking may be done at any time
between these two moments. For a dry cider, a late first racking may be
just fine.
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we can see the speed reduction effect caused by an early first racking.
The average speed between days 2 and 19 was 160 FSU. The first racking
was done on day 19, and the average speed between that day and day 50
has fallen to 34 FSU. Thus, this racking was successful in reducing the
rate of fermentation. Whichever moment you choose for your first
racking, you should check the SG and compute the speed of fermentation.
Note that it may be difficult to measure the SG during the turbulent
fermentation because the foam makes the reading difficult. Hence, often
the first SG check is done during this racking.
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Stabilization racking In some circumstances we may do one or more
additional rackings during the secondary fermentation phase. We call
this stabilization racking. Its aim is to reduce the speed of
fermentation to eventually obtain a cider that is stable while still
containing some sugar. By “stable,” we mean that the fermentation can no
longer proceed because the cider doesn’t contain the necessary nutrients
to sustain a yeast population. A stable cider may thus be bottled even
if it contains some unfermented sugar without fear that this sugar will
re-ferment in the bottles. Stabilization racking, then, is an essential
operation to obtain a medium or a sweet cider by natural methods.
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Note that if the objective is to make a dry cider, there is generally no
point in doing a stabilization racking unless there is a particular
reason to slow the fermentation.
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we can see that a stabilization racking was done on day 180 (this was
the end of March). The SG was then 1.0075 and the speed 11 FSU. At this
rhythm the cider would have attained dryness in a little more than two
months (7.5 × 100 days / 11 FSU = 68 days). However, I was aiming for an
off-dry profile with this cider. The stabilization racking was effective
and permitted me to reduce the speed to 2 FSU, and the cider stabilized
itself nicely at a SG of 1.004—just right for an off-dry cider. Note
that for a cider that contains a lot of nitrogenous nutrients, more than
one stabilization racking may be required before the cider becomes
stable.
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Final racking A final racking is done once the maturation and clearing
of the cider is complete and it is ready to bottle or keg. The object is
simply to separate the cider from its lees. The aim is not to slow
fermentation, as it is normally complete and the FSU already at or very
near zero.
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Increasing the speed of fermentation Usually, the cider maker is mostly
interested in slowing the fermentation in order to obtain the best
ciders. However, sometimes we overdo it. One too many stabilization
rackings may make the fermentation overly slow and even make it stick
while the cider is still too sweet. When this happens, the first thing
to do is to increase the temperature of the cider, as this will activate
the yeast. If it is small enough to move, simply bring the carboy into a
warmer location, where the temperature would be between 60 and 70 ° F
(15 and 21 ° C). A small dosage of yeast nutrients, of about 25 to 30
ppm of DAP, could also help at this stage. (Note that 30 ppm is
equivalent to 1⁄8 teaspoon in a 5-gallon carboy; see section 14.2 for a
discussion on yeast nutrient dosage.) These measures are generally
sufficient, and within a couple of weeks the fermentation will gain some
strength and you will start to see more bubbles in the airlock. After
about a month in this warmer location, an SG measurement should show an
increase of the fermentation speed.
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In order to diagnose a true stuck fermentation, you should have two
equal SG readings taken one month or more apart while the temperature is
at least 60 ° F (15 ° C). If at this moment the cider has reached a
sufficient alcoholic strength to conserve itself, that is, at least 4%
ABV, you will then have obtained a naturally sweet cider without effort.
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Let’s take a hypothetical cider whose juice’s original SG was 1.065 and
where the fermentation stuck at an SG of 1.025. The cider would then
have a strength of 4.5% ABV, and it would have about 5 percent residual
sweetness, which would make it a sweet cider.
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On the other hand, if this same hypothetical cider had stuck at an SG of
1.040, its alcoholic strength would not be sufficient to insure its
keeping quality. You would then have to restart the fermentation.
Assuming you have already increased the temperature and added some yeast
nutrients as recommended for speeding up a slow fermentation, the
possible remaining options would be to aerate the cider and to inoculate
a new yeast culture.
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Aeration will be more efficient if combined with addition of yeast
nutrients, and you may add another small dose at this point, depending
on the dosage you added previously. You might aim for a total dosage of
100 ppm, which would be sufficient to insure an SG drop of 0.020 in the
cider.
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The above treatment will not work instantly. Presumably, the yeast
population was very small at the moment of aeration and nutrient
addition, so it will take a while before a new population builds up
again. It may be a good month before you can see that some fermentation
activity has started again.
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Ullage refers to the headspace volume on top of a wine or cider and is a
term used mainly in the context of barrel fermentation. Some evaporation
occurs through the wood, and it is necessary to regularly fill up the
void caused by this evaporation in order to prevent the air from coming
into contact with the cider. Nowadays most cider makers prefer to use
fermentation vessels made of modern materials like plastic, stainless
steel, or glass. With these materials, there is no evaporation; however,
there is always a quantity of cider that is lost during the racking
operations. For example, if you do a stabilization racking from a
5-gallon carboy into another one of the same dimension, you will lose
about a quart (or liter) in the operation; hence, you will need this
same quantity to fill up the receiving carboy. Also, you will notice
that as the fermentation proceeds there is a slight reduction of volume
that occurs. Even if you don’t do a stabilization racking, then, you
might need to fill up a void in the carboy when the cider reaches the
maturation phase.
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The preferred method is always to have some extra fermenting cider at
hand. For this, some planning is required. Before starting the
fermentation, insure there is more juice than will be required to fill
the secondary fermentation vessel. Then when you do the first racking,
the extra cider may be kept in a 1-gallon (or whatever size you have on
hand, considering the quantity of extra cider) jug equipped with an
airlock. This cider will ferment at approximately the same rhythm as the
bulk of the cider and may be used as necessary for ullage fill-up.
Another possibility is to freeze some of this extra partially fermented
cider in small containers.
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Other methods are possible for reducing the ullage, which I list here by
order of preference: If the void to fill is small, put some glass
marbles or other filling objects (previously sanitized) into the carboy.
Add some cider from a previous year’s batch. Add fresh apple juice. Add
water, though this will slightly dilute the cider.
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An alternative is to use C02 for blanketing on top of the
cider.
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Malolactic Fermentation > Page 427 · Location 5826
14.4: The Malolactic Fermentation The malolactic fermentation (MLF) is a
biochemical transformation of the malic acid present in the cider. We
have previously seen that the malic acid is the main acid component in
apple juice. This organic acid has a very pronounced and sharp taste.
When MLF occurs, the malic acid is transformed into lactic acid, which
is much less aggressive and smoother. Some carbon dioxide is also
produced during the transformation. The malolactic fermentation is
caused by lactic acid bacteria (LAB), which are much smaller organisms
than the yeast responsible for the alcoholic fermentation. It usually
occurs when the alcoholic fermentation is getting close to completion,
during spring or summer, as the temperatures get warmer in the cider
house. It may happen spontaneously or be provoked by the cider maker by
inoculation of a strain of LAB.
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Malolactic Fermentation > Page 427 · Location 5834
This fermentation is generally considered favorable for ciders that have
high acidity, as it will reduce it noticeably. Moreover, MLF mellows and
gives some roundness to the cider, improves mouthfeel, and often gives
some buttery notes. The bouquet and aromas are also modified and are
more spicy.
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Malolactic Fermentation > Page 428 · Location 5838
Conditions that are favorable or unfavorable to the development of MLF
Temperature. Depending on the strain of LAB considered, a temperature of
at least 60 ° F (15 ° C), plus or minus a few degrees, is generally
believed necessary for the malolactic fermentation to proceed.
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this was the time MLF would be active, and this produced some bubbling
in the cider as carbon dioxide gas escaped.
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Malolactic Fermentation > Page 428 · Location 5843
Note that as the temperature rises in spring, some of the dissolved
carbon dioxide is released by the cider because the solubility of this
gas decreases at higher temperatures. Seeing gas bubbles in the airlock,
then, is not necessarily a sign that MLF is occurring.
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Acidity. Different strains of LAB have varying tolerance to pH, although
in general they prefer a medium that’s not too acidic (i.e., at a pH
higher than 3.5). Some strains will develop only at high pH, while
others may still work at relatively low pH. But a very low pH of the
order of 3.0 will inhibit any strain of the bacteria and prevent
malolactic fermentation.
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Malolactic Fermentation > Page 428 · Location 5848
Sulfite. LAB have little tolerance to sulfite, and a relatively weak
dosage, on the order of 10 ppm free SO2, will be enough to
inhibit them. Hence, if MLF is not wanted, a dosage of approximately 50
ppm of sulfite may be added by the end of the alcoholic fermentation and
before the temperature gets milder. Conversely, if MLF is desired,
sulfite should be limited to the minimum dosage and added to the must
only once the MLF is completed. Aging in wood barrels. Because of the
porosity of the wood, old wooden barrels will retain spores from the
bacteria population of the previous year’s malolactic fermentation even
if they are cleaned and sanitized. Hence, cider makers who use barrels
for maturation of their ciders will obtain a spontaneous MLF without
difficulty.
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Malolactic Fermentation > Page 429 · Location 5855
The transformation takes quite a bit of time before it is completed.
Three months is a good average. It will take longer when the temperature
is lower or when the medium is more acidic. Often, too, the
transformation will only be partial.
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Malolactic Fermentation > Page 429 · Location 5857
Chemical reaction During the malolactic fermentation, a molecule of
malic acid transforms into a molecule of lactic acid plus one molecule
of carbon dioxide:
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Malolactic Fermentation > Page 429 · Location 5859
C
4H
6O
5 →
C
3H
6O
3 + C0
2
Malic acid: C4H6O5
molar mass: 134 g/ mol
volumic mass: 1.61 g/ mL approximately, at 20 ° C (68 ° F)
volume for 1 mole: 83 mL
Lactic acid: C3H6O3
molar mass: 90 g/ mol
volumic mass: 1.25 g/ mL approximately, at 20 ° C (68 ° F)
volume for 1 mole: 72 mL
Carbon dioxide: C02
molar mass: 44 g/ mol
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Malolactic Fermentation > Page 429 · Location 5870
Malic acid is a diprotic acid, which means that each mole contains two
acid equivalents. Lactic acid is monoprotic, so each mole contains one
acid equivalent. This means that if all the malic acid is transformed,
and considering that malic acid constitutes approximately 90 percent of
the original total acidity, then there would be a 45 percent reduction
of the titratable acidity.
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Malolactic Fermentation > Page 430 · Location 5873
From the reaction formula above, we see that for each mole of malic acid
transformed, one mole of carbon dioxide will escape, thus reducing the
total mass of the cider by 44 grams. Additionally, from the volumic
masses of malic and lactic acids, we see there will be a slight
reduction of the volume of the cider, of 11 mL per mole of malic acid
transformed. Note that this last number is indicative only because when
in solution the change in volume could be different. These two effects
combined will cause a slight decrease of the SG of the cider, of one or
two points. If the MLF occurs inside a hermetically closed container,
such as a bottle, then the carbon dioxide will stay in solution instead
of escaping, and this will cause a slight sparkle in the cider.
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The lactic acid bacteria (LAB) Two main genuses of bacteria that are
involved in the malolactic fermentation of cider have been identified:
Oenococcus. Formerly known as Leuconostoc, a coccus type of bacteria.
The species involved is Oenococcus oeni. Lactobacillus. Rod-shaped
bacteria. This genus contains many species, some of which are considered
spoilage bacteria.
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Malolactic Fermentation > Page 430 · Location 5884
Additionally, a third genus, Pediococcus, is known to be involved in the
natural MLF of wines, but I haven’t seen it mentioned in relation with
cider. The Oenococcus bacteria feature a better tolerance to acidic pH.
They are quite efficient in reducing the acidity but have less effect on
the flavor and mouthfeel of the cider than the Lactobacillus. The
Lactobacillus will be more dominant at higher pH, around 3.5 to 3.8,
with ciders that contain a good proportion of bittersweet apples.
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 431 · Location 5890
The commercial cultured MLF strains that may be bought in the trade are
most often monocultures of the Oenococcus type.
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 431 · Location 5892
there are quite a few other typical flavors that may be given to the
cider by the MLF.
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 431 · Location 5894
the Beer Judge Certification Program (BJCP) has defined the following
descriptors for MLF character in the cider: Farmyard: Manure-like (cow
or pig) or barnyard (horse stall on a warm day). Phenolic: Plastic,
band-aid, and/ or medicinal. Spicy/ Smoky: Spice, cloves, smoky, ham.
Additionally, the following descriptors (also defined by the BJCP) apply
to characters given by some other types of LAB, which are considered as
different from those causing MLF: Acetaldehyde: Green apple candy aroma/
flavor Diacetyl: Butter or butterscotch aroma or flavor Mousy: Taste
evocative of the smell of a rodent’s den/ cage. The mousy character is
considered a fault, and is discussed in chapter 16. A little of
acetaldehyde and/ or of diacetyl may be acceptable in some ciders.
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 432 · Location 5905
We may detect if the MLF has happened by monitoring the titratable
acidity (TA).
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 432 · Location 5906
Let’s denote by TA1 the acidity before the beginning of the
transformation. Then, after a complete transformation of the malic acid,
a measurement of the acidity should give TA = 0.55 TA1 if the
malic acid constituted 90 percent of the original acidity. We may then
roughly estimate the fraction of the transformation in percent by the
following calculation: Transformation % = 222 [1 − (TA /
TA1)]
Note - 14.4: The Malolactic Fermentation > Page 432 · Location 5910
Brandon Note:
This is a super funky way to calculate this and go about thinking about
this. Alternative:
TAtarget = TA1 * 0.55
TAleft to go = TAcurrent - TAtarget
TAtotal to do = TA1 - TAtarget
% to go = TAleft to go / TAtotal to do
Transformation % (ie how much mlf has been competed) = 1 - % to go
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 432 · Location 5910
Note that TA1 may be different from the acidity of the must
before the start of the fermentation, because the alcoholic fermentation
may increase or decrease the acidity somewhat. Hence, the value of
TA1
should be measured when the alcoholic fermentation is complete or almost
so, but before the MLF has started, which may be tricky.
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 432 · Location 5914
by the end of the winter the SG is getting close to 1.000, while the TA
has increased to 7 g/ L. This last value would be taken as
TA1.
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 432 · Location 5915
Then by midsummer, if the TA has decreased to 4.5 g/ L, from the above
calculation we would estimate that the MLF is approximately 80 percent
complete.
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 432 · Location 5917
We can also estimate the variation in mass, volume, and SG of the cider
due to the MLF. If we use the same case as above, with a reduction of TA
from 7 to 4.5 g/ L due to MLF, this indicates that 5 g/ L of malic acid
has been transformed (this is 80 percent of 90 percent of 7 g/ L). Using
the molar masses seen above, we may deduce that these 5 grams produce,
per liter of cider: 5 × 90/ 134, or 3.36 g of lactic acid and 5 × 44/
134, or 1.64 g of carbon dioxide.
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 433 · Location 5921
the carbon dioxide gas escapes to the atmosphere, then there is a net
loss of mass of 1.64 g. There would also be a slight change in volume,
which could be estimated as: volume occupied by 5 grams of malic acid:
83 mL × 5 / 134 = 3.1 mL
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 433 · Location 5923
volume occupied by 3.36 grams of lactic acid: 72 mL × 3.36 / 90 = 2.69
mL
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 433 · Location 5924
The difference between these two values, 0.41 mL per liter, is the
reduction of volume attributable to the MLF. To calculate the variation
of SG, we could proceed as follows: if the SG of the cider before MLF is
1.000, its volumic mass is 998.2 g/ L. After the MLF the original liter
is reduced by 0.41 mL and becomes 0.99959 L. The mass is reduced by 1.64
g to 996.56 g, hence the volumic mass after this transformation is
996.56 g / 0.99959 L = 996.97 g/ L, and this last number divided by the
volumic mass of water (998.2) gives SG = 0.9988. Hence, in this example,
where MLF is completed at 80 percent, the SG would be reduced by 1.2
points of gravity.
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 433 · Location 5933
For hobbyists and small-scale commercial cider makers, the Accuvin malic
acid test kit is a simple tool to test for malolactic fermentation.
These are strips on which there is a spot of reagent that changes color
with the concentration of malic acid, and the color of the reagent is
compared with a color chart to estimate the malic acid concentration.
They are somewhat similar to pH strips, but their cost is higher, about
$ 3 to $ 5 per test strip. The measurement range is from 30 to 500 mg of
malic acid per liter.
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 434 · Location 5937
It should be noted that this range is a bit short for cider. If we take
the cider that was given in the example above, it is only when the
transformation is completed at 92 percent that the concentration of
malic acid falls to 0.5 g/ L (i.e., 500 mg of malic acid/ L). Hence,
this test may be useful to identify the moment the MLF is complete but
not for monitoring its evolution during the early stages.
Highlight(yellow) - 14.4: The
Malolactic Fermentation > Page 434 · Location 5947
For reference, we may mention the analysis with a spectrophotometer to
measure the concentration of malic acid and the use of high-pressure (or
high-performance) liquid chromatography (HPLC), both of which
necessitate the purchase of costly equipment.
Highlight(yellow) - 14.5: The
Alcohol > Page 435 · Location 5952
The alcohol in question here is ethyl alcohol, or ethanol, which
shouldn’t be confused with methyl alcohol, or methanol, also known as
wood alcohol. The first is the product of the fermentation of sugar; its
chemical formula is C2H5OH and boiling point 173 ° F (78.5 ° C).
Highlight(yellow) - 14.5: The
Alcohol > Page 435 · Location 5956
We are interested mainly in determining the quantity of alcohol produced
from a certain quantity of sugar and studying how this alcohol
influences the final gravity of the cider.
Highlight(yellow) - 14.5: The
Alcohol > Page 435 · Location 5959
some ciders, when fermented to dryness, have an SG of 1.000, while
others may have an SG as low as 0.995. What causes this difference? And
more important, if we have a finished cider at an SG of 1.000, how do we
know how much residual sweetness it contains, and how do we know that it
won’t ferment down to 0.995 once bottled?
Highlight(yellow) - 14.5: The
Alcohol > Page 435 · Location 5964
A primary element to consider is how much alcohol is produced from a
certain quantity of sugar (the sugar considered here is a reducing
sugar, that is, glucose or fructose).
Highlight(yellow) - 14.5: The
Alcohol > Page 437 · Location 5980
total volume of a mixture of water and alcohol can’t be obtained by
simple addition of the volumes of each component: if, for example, we
mix 1 liter of water with 1 liter of pure alcohol, we will not obtain 2
liters of a mixture at 50% ABV. The final volume will in fact be
slightly less than 2 liters and the alcohol concentration slightly more
than 50 percent. This is because when alcohol and water are mixed
together, there is a volumic contraction that occurs due to a sort of
fusion between the two liquids as they make a solution. For cider, this
means that the volumic contraction will slightly reduce the volume of
the finished cider and increase its density. It is necessary, then, to
use an alcoholometric table to determine the resulting total volume of a
mixture and its density.
Highlight(yellow) - 14.5: The
Alcohol > Page 437 · Location 5985
The tables I use here, by the International Organization of Legal
Metrology (OIML), are available on the Internet.
Highlight(yellow) - 14.5: The
Alcohol > Page 437 · Location 5987
First, we may extract from these tables the values of the volumic mass
(ρ) of water, alcohol, and alcohol-water mixtures at different
temperatures, for a standard atmospheric pressure.
Highlight(yellow) - 14.5: The
Alcohol > Page 437 · Location 5991
Highlight(yellow) - 14.5: The
Alcohol > Page 438 · Location 6052
If we now use the alcoholometric table to determine the final volume, we
proceed as follows: First we determine the alcoholic strength by mass of
the mixture, because although the total volume isn’t equal to the sum of
the parts, the total mass is equal to the sum of the parts in mass
because of the mass conservation laws:
Mass of alcohol : Malcohol = ρalcohol
Valcohol
Mass of water: Mwater = ρwater
Vwater
Taking the same values as above, we then
obtain the masses of alcohol and water: Malcohol = 55.25 g
and Mwater = 928.33 g, and the total mass of the mixture,
which is the sum of the parts:
Mmixture = Malcohol
+ Mwater = 55.25 + 928.33 = 983.58 g
Highlight(yellow) - 14.5: The
Alcohol > Page 439 · Location 6062
From this we have the alcoholic strength by mass (noted AM)
as the mass of alcohol divided by the mass of the mixture:
AM = Malcohol / Mmixture
= 5.62% in mass
Table IIIa of the OIML alcoholometric tables gives us the
volumic mass at 20 ° C of a mixture as a function of the alcoholic
strength by mass:
ρ (5.6%) = 988.41 g/ L ; ρ (5.7%) = 988.26
g/ L
An interpolation between these values gives the searched
value for 5.62%:
ρmixtures = 988.38 g/ L
Finally,
knowing the total mass and the volumic mass of the mixture, we obtain
the total volume:
Vmixtures = Mmixture
/ ρmixtures = 0.9951 L
And as expected, this last
value is slightly smaller than 1 liter. The contraction is 4.9 mL, or
0.49 percent of our initial estimation obtained by the sum of volumes.
And because of this contraction, the alcoholic strength by volume,
instead of being 7% ABV, as initially expected, is really 7.03% ABV.
Highlight(yellow) - 14.5: The
Alcohol > Page 439 · Location 6073
These differences are slight, but it is essential to take this volumic
contraction into account if we want to obtain a correct SG estimation
for an alcoholic mixture.
Highlight(yellow) - 14.5: The
Alcohol > Page 439 · Location 6075
In the following, I denote the volume variation as ΔV (Δ is the Greek
letter delta, universally used in the scientific world to express a
difference), which will have a negative value to indicate this is a
reduction of volume. So we may write: Vmixtures = Valcohol
+ Vwater + ΔV
Highlight(yellow) - 14.5: The
Alcohol > Page 440 · Location 6078
If we repeat this calculation for different values of the alcohol
concentration, we can build a table of the volumic contraction as seen
in table 14.3.
Highlight(yellow) - 14.5: The
Alcohol > Page 440 · Location 6081
Highlight(yellow) - 14.5: The
Alcohol > Page 440 · Location 6110
To use table 14.3, we first need to determine the volumic ratio. In the
case of our example above, the volumic ratio was equal to 7 percent,
that is, the volume of alcohol divided by the sum of the volumes. Table
14.3 indicates that the volume variation is − 0.49 percent. We thus need
to subtract 4.9 mL from the sum of the volumes to obtain the true volume
of the mixture: 995.1 mL. And once we have this result, it is an easy
task to compute the SG of the mixture:
ρmixtures =
Mmixture / Vmixtures = 983.58 g / 995.1 mL = 988.4
g/ L
SGmixture = ρmixtures / ρwater
= 988.4 / 998.2 = 0.990
Highlight(yellow) - 14.5: The
Alcohol > Page 441 · Location 6118
In the following model, I use regression coefficients instead of the
table. We can calculate the volumic contraction as follows: Defining R
as the volumic ratio in percent: R = 100 Valcohol / (Valcohol
+ Vwater) then the volumic contraction in percent will be
given by: ΔV / (Valcohol + Vwater) = 0.0000315
R3 - 0.002135 R2 - 0.0561 R which is valid for
values of R up to 18 percent. Note that this relation and table are
strictly valid only for pure mixtures of water and alcohol. In the case
of cider, if it is dry, the values obtained will be practically exact.
For a sweet cider, the sugar may slightly affect the result.
Highlight(yellow) - 14.5: The
Alcohol > Page 441 · Location 6127
Model for Calculation of the Product of Fermentation
Highlight(yellow) - 14.5: The
Alcohol > Page 441 · Location 6129
First, we need to separate the components of the must. We will take 1
liter at the reference temperature of 20 ° C of this must and determine
the quantity in grams of the total solids, fermentable sugar, and
unfermented solids.
Highlight(yellow) - 14.5: The
Alcohol > Page 442 · Location 6131
We will analyze separately what happens with the fermentable sugar and
the rest of our initial liter of must.
Highlight(yellow) - 14.5: The
Alcohol > Page 442 · Location 6132
From the mass of fermentable sugar, using the Pasteur relation (but the
slightly modified coefficients of 48 percent alcohol and 47 percent
C02, which correspond better to the reality of a fermenting
cider), we obtain the amount, in grams, of the alcohol, carbon dioxide,
and the other products of fermentation. From this we can compute the
volume of the alcohol, as we know its volumic mass at the reference
temperature.
Highlight(yellow) - 14.5: The
Alcohol > Page 442 · Location 6135
Most of the carbon dioxide will escape to the atmosphere and thus is
lost. There may be a small quantity that will remain in solution in the
cider, but we will ignore it. As for the other products of the
fermentation, which include the succinic acid, glycerin, and others, we
don’t know how these will influence the volume of the mixture. We will
simply assume they have the same volumic mass as pure water. This is
probably not exact, but the error would be slight, as the quantity
involved is small. Then we need to analyze the mass and volume of what
is not alcohol: the water, the unfermented solids, and the other
products of the fermentation, which, as mentioned above, are given the
same volumic mass as water, and thus whose mass is simply added to that
of water. By convention, the unfermented solids are expressed as sugar
equivalent; hence, they mix with water in the same way sugar would. We
can calculate an equivalent Brix for this mixture and determine its
volumic mass and volume using the relations seen in section 8.1 on
sugar. And finally, we will mix everything together and apply the
volumic contraction seen above to find the volume and mass of the
finished cider. Once we know these, it is easy to find the specific
gravity and alcoholic strength by volume. This is the second important
assumption of the model: that the volumic contraction with this mixture
is the same as it would be with pure water combined with the same
quantity of alcohol.
Highlight(yellow) - 14.5: The
Alcohol > Page 443 · Location 6159
Highlight(yellow) - 14.5: The
Alcohol > Page 445 · Location 6267
Finally, we may note that the final gravities obtained above could be
lower if we would take into account the malolactic fermentation. As seen
in a previous article, MLF may reduce the final SG of the cider by one
to two additional points, which, in the case of Cider C, would bring the
final SG close to 0.995. The malolactic fermentation would not, however,
modify the alcoholic strength.
Highlight(yellow) - 14.5: The
Alcohol > Page 446 · Location 6271
This model does enable us to answer some of the questions mentioned in
the beginning of this article. In particular, it helps us understand the
influence of different parameters on the final gravity of the cider. It
doesn’t answer everything, though, as we would need to know the exact
value of the sugar content of the must to be able to predict exactly the
conditions of the finished cider, and for this only a chemical analysis
of the must would provide the precise figure.
Highlight(yellow) - 14.5: The
Alcohol > Page 446 · Location 6274
Estimation of Alcoholic Strength by Gravity Drop The simplest and most
commonly used method to estimate the alcoholic strength (AV)
of a cider is by using the difference between the SG of the initial must
and the SG of the finished cider, which we will denote here by ΔSG. We
then have: AV = K ΔSG, where K is a proportionality factor.
Highlight(yellow) - 14.5: The
Alcohol > Page 446 · Location 6279
Values for this factor vary in the literature, from approximately 125 to
130 for cider and up to 136 for wine and beer. Whether we use 125 or 130
or any intermediate value will not have a very significant effect on the
result, as most cider makers are usually only interested in knowing the
alcoholic strength within about 0.5 percent.
Highlight(yellow) - 14.5: The
Alcohol > Page 447 · Location 6288
for a cider that hasn’t had a malolactic fermentation, the use of a
higher value for the factor K, of 129 or 130, would give an excellent
estimation of the alcoholic strength. And for a cider that has had an
MLF, a value of K that is slightly smaller, around 126, 127, or 128,
would give a more accurate estimation.
Highlight(yellow) - 14.5: The
Alcohol > Page 447 · Location 6291
A Simple Method for Measuring Alcoholic Strength
Highlight(yellow) - 14.5: The
Alcohol > Page 447 · Location 6294
residue method, is well adapted for hobbyist cider makers,
Highlight(yellow) - 14.5: The
Alcohol > Page 448 · Location 6301
The principle of the method is quite simple: We take a measured volume
of cider of known SG, from which the alcohol is boiled off. During this
boiling process, some water will also have evaporated, but since the
alcohol has a lower boiling point than water, by the time a fraction of
the water has gone (about a third), then all the alcohol will have
evaporated. Once the alcohol is removed, distilled water is added to
reconstitute the original volume of the cider sample and the SG is
measured. This solution is called the residue, and its SG will be higher
than that of the original cider since alcohol is lighter than water. The
difference between the two values of SG gives us an indication of the
alcoholic strength of the original cider.
Highlight(yellow) - 14.5: The
Alcohol > Page 451 · Location 6403
The vinometer is a simple and inexpensive glass apparatus that looks
roughly like a small funnel with a long, thin stem. It gives an
estimation of the alcoholic strength using the properties of capillarity
and surface tension of the wine or cider. However, a vinometer will give
an accurate result only if a pure solution of alcohol and water is
tested. The residual sugar and other solids in solution in the cider
will alter the result substantially. The tests I have done with a
vinometer on cider didn’t yield sufficiently satisfying results to
warrant its recommendation.
Highlight(yellow) - 14.5: The
Alcohol > Page 455 · Location 6443
Distillation is the most accurate method of measuring alcoholic strength
and is often used in research laboratories. A good, dedicated
distillation apparatus costs less than $ 1,000, and this isn’t really
expensive for a commercial cidery. However, the manipulation requires
precision and is time consuming, which is the main reason why it is not
routinely used in cider making.
Highlight(yellow) - 14.5: The
Alcohol > Page 457 · Location 6468
A final word about volatile acidity (see also chapter 16 on cider
troubles): if the cider contains a sizable amount of volatile acidity,
this acidity will distill with the alcohol and be present in the
distillate, thus altering slightly its density and the result. For a
hobbyist, this error may be neglected, but for the most accurate results
the acidity of the cider should be neutralized with a base before
proceeding with the distillation. When done in a laboratory environment
with a high-quality distillation apparatus, this method yields a result
with an accuracy of approximately ± 0.1% ABV. When done by a hobbyist
with a do-it-yourself kit, the same accuracy cannot be reached, but
probably ± 0.5% ABV or even better could be achieved.
Highlight(yellow) - 14.5: The
Alcohol > Page 458 · Location 6475
For a hobbyist, the estimation by gravity drop or the use of the model
described earlier is generally sufficient. The simple residue method may
also prove useful as a cross-check. For a commercial cider maker,
something better is required, mainly because of the legal requirement to
give a more or less accurate alcoholic strength on the label.
Highlight(yellow) - 14.5: The
Alcohol > Page 458 · Location 6479
in the United States, although the alcoholic strength as given on the
label doesn’t need to be very accurate, the cider maker needs to know
for sure if the cider is above or below 7% ABV, as the tax rate changes
once this level is crossed.
Highlight(yellow) - 14.5: The
Alcohol > Page 458 · Location 6481
The alternative would be to send cider samples to a dedicated laboratory
that does such analyses for wineries and cideries.
Highlight(yellow) - 15.1:
Sweetness in Cider > Page 459 · Location 6495
Many cider makers would like to produce a cider that retains some
residual sugars, as such mild sweetness counterbalances the natural
acidity of the cider and makes it smoother.
Highlight(yellow) - 15.1:
Sweetness in Cider > Page 459 · Location 6496
Unfortunately, the way things normally go is that the yeasts will keep
at their work until all the sugars are fermented, leaving a bone-dry
cider at the end.
Highlight(yellow) - 15.1:
Sweetness in Cider > Page 460 · Location 6500
there is another approach that consists of creating a nutrient-depleted
medium where the yeasts will not find the minimum requirements that
would permit them to perform their task completely. This process
involves a pre-fermentation clarification of the must called a keeve
(défécation in French), where the pectins present in the juice are
modified under the action of an enzyme to develop into a gel that rises
on top of the must and forms a gelatinous crust called a chapeau brun
(brown cap).
Highlight(yellow) - 15.1:
Sweetness in Cider > Page 460 · Location 6507
The Sweetness Perception The amount of residual sugar present in the
cider at the time of consumption will determine the sweetness
perception.
Highlight(yellow) - 15.1:
Sweetness in Cider > Page 460 · Location 6508
We use three main categories for cider: dry, medium, and sweet, and the
dry and medium may be further divided into two subcategories. Table 15.1
indicates the approximate amount of residual sugar required (in grams
per liter) to give the sweetness perception corresponding to each of
these categories.
The approximate specific gravity (SG) in the last line of the table is
based on a cider that would have an SG of 1.000 at complete dryness,
which is normally the case if it was made from a juice that had the
average amount of sugar for its density (see section 14.5 on alcohol),
that wasn’t chaptalized, and that didn’t undergo malolactic
fermentation. Otherwise, the SG at complete dryness may be as low as
0.995, and a correction should be done accordingly.
Highlight(yellow) - 15.1:
Sweetness in Cider > Page 461 · Location 6543
In France,
Highlight(yellow) - 15.1:
Sweetness in Cider > Page 461 · Location 6544
specifies the following categories:
-
Brut: residual sugar less than 28 g/ L (we can see that this
covers from the very dry category up to medium-sweet),
- Demi-sec: residual sugar between 28 and 42 g/ L,
-
Doux: more than 35 g/ L residual sugar, but with an alcoholic
strength of less than 3% ABV.
Highlight(yellow) - 15.2: Bubbles
in the Cider > Page 479 · Location 6758
The effervescence is the feature of a sparkling, pétillant, or fizzy
cider. This effervescence is provoked by a gas, carbon dioxide, which is
in solution in the cider. The gas induces pressure in the bottle, which
thus needs to be robust enough to withstand that pressure. As the bottle
is opened, the pressure is relieved: this decreases markedly the
solubility of the gas almost instantly. Thus, what was initially in
solution in the liquid changes to a gaseous state and escapes the liquid
as bubbles that rise toward the surface.
Highlight(yellow) - 15.2: Bubbles
in the Cider > Page 480 · Location 6763
Also noteworthy: a small part of the carbon dioxide in solution is
transformed into carbonic acid, which modifies the taste of the cider,
giving it a slightly biting and pleasant flavor. The smell is also
modified, as the bubbles contain some of the aromatic qualities of the
cider, which is thereby enhanced.
Highlight(yellow) - 15.2: Bubbles
in the Cider > Page 481 · Location 6780
Volumes of C02 and carbonation There may be different levels
of effervescence depending on the amount of carbon dioxide dissolved in
the cider. An often-used unit of measurement is the number of volumes of
dissolved C02, which is defined as follows: One volume of
C02 (designated 1 vol) corresponds to the quantity of C02
in gaseous form at 0 ° C and atmospheric pressure that would occupy the
same volume as the liquid in which it is dissolved.
Highlight(yellow) - 15.2: Bubbles
in the Cider > Page 481 · Location 6785
For example, if we want to carbonate 1 liter of cider to 1 volume of
C02, we need 1.977 grams of C02 in solution, as
the density of gaseous C02 is 1.977 grams per liter at 0 ° C
under atmospheric pressure.
Highlight(yellow) - 15.2: Bubbles
in the Cider > Page 481 · Location 6788
Then, expressed in volumes of C02, the classes of carbonation
Highlight(yellow) - 15.2: Bubbles
in the Cider > Page 481 · Location 6790
in North America are:
Sparkling (mousseux or bouché in French), when the cider
contains between 3.5 and 5.5 volumes of C02. Such a cider
will form a good foam as it is poured. In France the term cidre bouché
is more often used for a traditionally made farm cider, which can be
slightly cloudy and may contain lees, whereas a cidre mousseux will
normally be perfectly clear and without deposits.
Pétillant, crackling or semisparkling, when the cider contains
between 1.5 and 2.5 volumes of C02. This cider produces a
little foam that vanishes quickly when poured into a glass, but the
sparkle is easily seen by the bubbles rising to the surface.
Still (tranquille in French), when the cider contains no or up
to 1 volume of dissolved C02. This cider doesn’t produce
any foam when poured into a glass, but it may be saturated with C02
(i.e., 1 vol of C02), and in that case there might be a few
rising bubbles indicating a very slight effervescence (these would
usually be seen a little while after pouring, as the cider warms up).
This is called perlant by the French, and there is no proper English
word to qualify it. Perlant ciders are very agreeable to drink, with a
minimal carbonation that enhances the flavor.
Highlight(yellow) - 15.2: Bubbles
in the Cider > Page 482 · Location 6806
Pressure Calculation We may use Henry’s law of gas solubility to predict
the pressure in a closed container of sparkling cider. This same law
will also permit us to determine how much pressure of C02 we
need to force-carbonate a cider. Henry’s law states that at constant
temperature, the quantity of gas dissolved in a liquid is proportional
to the partial pressure of this gas on top of the liquid. The
mathematical formulation is:
c = kH pp
where:
pp is the partial pressure of the gas (in our
case, of the C02),
c is the concentration of the gas in
solution,
kH is the proportionality constant of Henry’s
law. Note that its value varies with temperature and also differs from
one gas to another.
Highlight(yellow) - 15.2: Bubbles
in the Cider > Page 483 · Location 6817
the most practical way to use this law is by expressing the
concentration in volumes of C0
2 (vol) and the pressure in
atmospheres (1 atm is 14.7 psi or 1.013 bar or 101.3 kPa). The value for
the k
H
constant is normally given at a reference temperature, and there exist
equations to calculate the value at different temperatures. From these I
obtained table 15.2.
Highlight(yellow) - 15.2: Bubbles
in the Cider > Page 483 · Location 6847
This permits us to determine that, for example, in a cider that would
contain 4 volumes of C02 in solution, the partial pressure of
carbon dioxide in the container would be 2.5 atm at 32 ° F (0 ° C) and
of 6 atm at 86 ° F (30 ° C). This helps us understand that as the bottle
is opened, the pressure of the gas in the airspace under the stopper
decreases suddenly, meaning the concentration of C02 in
solution has to decrease proportionally: the gas that was in solution
thus escapes the liquid, provoking the effervescence. Also, we can see
that the warmer the bottle will be at the moment of opening, the less
C02 may remain in solution, so there will be more escaping
and sparkling.
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Now, this partial pressure of C02 is not the same as the
real, or effective, pressure the container (i.e., the bottle) will have
to endure. On one hand, the partial pressure is an absolute pressure,
and we want a relative pressure: we need to deduct the atmospheric
pressure that surrounds the exterior of the bottle, 1 atm.
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in the Cider > Page 484 · Location 6855
On the other hand, at the moment of bottling there was some air in the
bottle, also at a partial pressure of 1 atm. However, about half of this
air will dissolve in the cider (still according to Henry’s law, but this
time applied to oxygen and nitrogen), so that at the end the combined
partial pressure of oxygen and nitrogen is around 0.5 atm for a
standard-size bottle. Hence, in total, we need to subtract approximately
0.5 atm from the partial pressure of C02 to obtain the
pressure effectively endured by the bottle. We may then rearrange the
equation seen above to obtain P, the effective pressure: P = (c /
kH) − 0.5 atm
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in the Cider > Page 484 · Location 6861
This pressure calculation is interesting, but it is only really useful
if we know the resistance of the bottle. For example, a good champenoise
bottle is designed to resist 12 atm, and its weight is about 2 lb. (more
precisely, between 860 and 900 grams). For the other types of bottles
containing carbonated drinks, for example, beer, mineral water, or soda
bottles, glass or plastic (PET), it is recommended that the effective
pressure stay under 6 atm. And in all cases it is wise to maintain a
good safety margin.
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in the Cider > Page 491 · Location 6973
a bottle of his cider will have less carbonation if opened and drunk at
sea level, and, conversely, a cider made at sea level and served at high
altitude will have more sparkle. This effect may be explained by the
lower atmospheric pressure at high altitude.
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Working with a C02 Tank
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in the Cider > Page 498 · Location 7079
Purging and blanketing The most simple use for such a tank is for
purging the air from a container and establishing a C02
blanket on top of the cider to protect it from contact with oxygen. For
example, we may inject carbon dioxide into the receiving carboy just
before proceeding with the racking. This then minimizes the contact of
cider with oxygen. Another application is with a carboy that isn’t
completely full of cider: an injection of carbon dioxide will force the
air out and leave a protective blanket. An important feature of C02
is that it is heavier than air and so tends to sink under the air.
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in the Cider > Page 498 · Location 7085
Forced carbonation To do some forced or artificial carbonation, you will
need, in addition to the tank and regulator, a keg that may be
pressurized: either a Cornelius (or Corny) keg of the type used for soft
drinks or a beer keg.
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in the Cider > Page 498 · Location 7089
The setting of the pressure will be done according to a carbonation
chart, easily found on the Internet, or calculated from Henry’s law,
which we discussed earlier.
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in the Cider > Page 498 · Location 7090
For example, if the temperature is 50 ° F (10 ° C), Henry’s law states
that you need to have a partial pressure of 2.59 atm of C02
in order to obtain 3 vols of carbonation. Now, in this case the air will
have been purged from the keg, hence the relative pressure inside the
keg will be this value minus 1 atm, which is the pressure outside the
keg. You then need to set the pressure on the regulator to 1.59 atm,
which is 23 psi. Actually, you would set the pressure a few psi higher
and leave it on for a couple of days. To check if the carbonation is
high enough, shut off the main valve from the tank, open the relief
valve a second to let the pressure drop, and wait awhile until the
pressure is stabilized. If this pressure is 23 psi, the desired level of
carbonation is there. If not, it is necessary to leave it under pressure
longer. Note that the colder the cider, the easier and faster the
desired carbonation will be attained.
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in the Cider > Page 500 · Location 7104
The pressure from a C02 tank may be used as a driving force
for filtering. Filter pads are then required. Often a series of pads are
used, starting with a coarser pad first to remove the larger particles
and using a finer pad to finish the filtration.
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in the Cider > Page 501 · Location 7114
In order to be able to bottle the carbonated cider that is in a keg,
another piece of equipment is required: a filler head. Without it, the
foaming of the cider as it arrived in the bottle would make a mess.
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in the Cider > Page 501 · Location 7115
The filler head may be either a counterpressure filler or a simpler
atmospheric filler. The main difference is that the counterpressure
filler has a stopper, which permits a pressure buildup in the bottle as
it fills, further reducing the foaming.
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in the Cider > Page 501 · Location 7118
filling is done in two operations: first some C02 is injected
into the bottle to purge the air, and then the bottle is filled with
cider.
Highlight(yellow) - 15.3: Ice
Cider > Page 517 · Location 7423
In commercial cideries cold is normally used for stopping the
fermentation. Larger cideries will often have a refrigeration coil on
their fermentation tanks, which permits a precise control of the
temperature and a rapid chilling when required.
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1. At all times: Sanitize the equipment with a sulfite solution or with
a sanitizer. Keep the cider room clean. Do not forget that air is the
worst enemy of cider. Avoid all contact between the cider and a material
such as iron, nonstainless steel, or copper. In fact, the only materials
that should be permitted to come into contact with the juice or the
cider are glass, stainless steel, food-safe plastic, or certain types of
wood.
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2. After pressing and before fermentation: Add pectinase to the juice or
make a debourbage, as this facilitates the clearing of the cider at the
end of fermentation. Sulfite the juice. See the article on sulfite,
section 14.1, to determine the correct dosage. Do not overdose. Blend
the juices in such a way so the pH is low enough to insure protection of
the cider.
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3. Use a primary fermentation vessel with a good closure.
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Cider Troubles and How to Avoid Them > Page 524 · Location 7508
4. Do not wait too long to make the first racking. Leaving the cider in
the primary fermenter when the active fermentation is completed is very
risky because the air then comes into contact with the cider and may
cause the sort of disorder related above.
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5. Maintain a cool temperature in the cider room, 60 ° F (15 ° C) or
less, because spoilage microorganisms will generally proliferate at
higher temperatures, from 68 ° F (20 ° C) on up.
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6. Keep your carboys well filled to minimize the headspace volume: don’t
leave more than 1 in. (2.5 cm) of space between the cider top level and
the bottom of the airlock rubber closure. Alternatively, use some C02
as a protective blanket.
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Cider Troubles and How to Avoid Them > Page 525 · Location 7515
7. During and after the secondary fermentation, and all the time the
cider is in the carboy, check the airlock regularly and make sure it
never gets dry. This is especially important during the winter, as the
cider temperature may become lower and thus by thermal contraction may
suck the sanitary liquid out of the airlock, leaving it dry and
permitting the entrance of air.
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Cider Troubles and How to Avoid Them > Page 525 · Location 7518
This last point is most important. This is the most critical period for
the cider, because the yeast population decreases as the fermentation
ends, and it can’t insure its dominance anymore. Furthermore, no more
carbon dioxide is being produced at this stage, and thus it can no
longer protect the cider. Often also, during the fermentation the cider
level decreases slightly, and if there was half an inch (1 cm) of
headspace at the beginning of the fermentation, for example, we may find
that this headspace has increased to 2 in. (5 cm) by the end of the
fermentation. It is then necessary to raise the level to minimize the
volume of ullage (headspace); see section 14.3. As discussed there,
different methods are possible (listed here by order of preference):
-
Add a bit of cider from the current batch that you have put aside
for this purpose.
-
Put some sanitized glass marbles or other filling objects into the
carboy.
-
Add a bit of finished cider from a previous year’s batch, fresh
apple juice, or water.
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a cider that has been sulfited will better tolerate the presence of air
because of the antioxidant property of SO2. Hence, even more
vigilance is required if you have chosen not to use sulfite.
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Film Yeast or Flower Sickness Film yeast proliferation is probably the
most common problem in cider making.
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Cider Troubles and How to Avoid Them > Page 526 · Location 7543
This sickness is generally caused by a spoilage yeast called Mycoderma
vini or Candida mycoderma, which is an aerobic microorganism that needs
air to develop and reproduce itself. A few other microorganisms of the
genera Pichia or Hansenula may also cause it. Flower sickness appears as
a thin whitish or grayish film on the surface of the cider. If we touch
this film, it breaks easily, and some parts may sink to the bottom of
the vessel. It generally appears once the fermentation is completed and
the cider is left in its carboy, for example, in waiting for it to
clear, when air may come into contact with the cider. Every time I have
seen this, there was either a dry (empty) airlock, a nonhermetic
stopper, or too large a contact surface between the cider and air.
Without air contact, the sickness can’t develop. If we let the flower
develop without intervention, some of the alcohol is broken down, the
cider becomes lifeless and insipid, and an unpleasant smell may appear.
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Fortunately, this sickness is not too serious, and if taken care of
early in its development, it won’t affect the quality of the cider.
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Acetification Acetification is a serious problem that may completely
ruin a cider batch. It is caused by bacteria of the genus Acetobacter,
which are naturally present in the air and on the skin and flesh of the
apples. These bacteria are resistant to sulfite, so unless the juice is
pasteurized, there will always be a small population of these bacteria
that will survive all the steps of the fermentation. However, and
fortunately for us, they need a lot of air and oxygen as well as
relatively high temperatures to develop into a proliferating colony.
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Acetobacters are aerobic bacteria that transform alcohol into acetic
acid; in other words, they transform the cider into vinegar.
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Cider Troubles and How to Avoid Them > Page 528 · Location 7568
It is important to understand that this is the natural end of the
fermentation process. Our job as cider makers is to promote the early
steps that transform the juice into cider, while preventing this final
step toward vinegar. And the method is extremely easy: simply keep the
air out and maintain a cool temperature—
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The first symptoms of acetification may seem similar to those of flower
sickness, with the appearance of a surface film. However, in this case
the film will not break easily and is rather of gelatinous consistency:
this is the vinegar mother that starts to establish itself.
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If you measure the total acidity by titration at this moment, you should
see an increase of the TA because of the acetic acid that forms. If your
cider is at this stage, it is quite difficult to cure, and it might be
better to accept that you are making vinegar.
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The acetic acid features a property that makes it different from other
acids in the cider: it is volatile. This means that it readily forms a
vapor or fumes, easily noticed by sniffing an open bottle of vinegar.
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If there is a lot of volatile acidity, then, it means that acetification
has started. It is important to understand that there will always be a
small quantity of acetic acid in the cider, and this quantity increases
with time.
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We may evaluate the degree of acetification of a cider by measurement of
the volatile acidity. This is more important in commercial operations as
there is a legal limit, which may vary depending on the state or country
of production. Each producer should check local regulations. The
volatile acidity (VA) is normally expressed as grams per liter (g/ L) of
acetic acid equivalent. Important values are:
-
VA < 0.7 g/ L: excellent and practically undetectable by taste;
however, at this level the acetic acid may pleasantly enhance the
flavor of the cider.
-
VA approximately equal to 1 g/ L: still drinkable but should be
watched closely and may not keep long.
- VA > 1.3 g/ L: problematic, becoming unpleasant.
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There are many ways to measure the volatile acidity. The first is a very
rough estimation that may be done by a hobbyist on a kitchen stove and
doesn’t require any special equipment other than a titratable acidity
kit. The principle is very simple: the TA of the cider is measured. Then
a sample of the cider is boiled such that all the volatile acidity
evaporates, and a new value of TA is measured
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The difference between the two values of TA corresponds to the volatile
acids that have been boiled off. In practice, this boiling process needs
to be done with care. The procedure and material required are very
similar to the simple residue method for the measurement of the
alcoholic strength described in the article on alcohol (section 14.5),
except that the TA is measured instead of the SG. Additionally, to make
sure all the volatile acids are evaporated, once about two-thirds of the
cider has been boiled off, it is recommended to refill the boiling flask
with distilled water up to the original level and to boil it once more
until about two-thirds has again been boiled off. This may even be
repeated a third time.
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Cider Troubles and How to Avoid Them > Page 532 · Location 7623
Microbiological Faults: Brett, Mousiness There are many microorganisms
that may give taints and off-tastes to a cider. Among these troubles,
mousiness is a disorder that introduces an odor and taste to the cider
that recalls an overpopulated mouse cage that hasn’t been cleaned for a
long time. Brett, which is the short, affectionate name for
Brettanomyces, is related to horse, barnyard, or stable odors. These
taints are generally attributed to the Brettanomyces spoilage yeast that
may be present in small quantity in the juice because it lives on the
skin of the fruit. Mousiness may additionally originate from lactic acid
bacteria (LAB), in particular some species of Lactobacillus, which are
also involved in malolactic fermentation (MLF). The distinction between
these two faults is not easy, and a badly infected cider could have some
of both. Even a very light contamination of either is, strictly
speaking, considered a fault. However it is not necessarily a disaster
and you might even think it makes the cider more complex and
interesting.
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Sometimes similar taints originating from MLF are even sought after,
like the “old horse” character, a feature of certain ciders from old
cideries in Europe that ferment their ciders in old wooden barrels that
host the responsible microorganisms.
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There is no solution to cure these troubles. The recommendations given
in the beginning of this article are normally sufficient to prevent
them. Sulfite is efficient to control the growth of the Brett yeast and
LAB, as they are sensitive to SO2. Hence, these disorders are
entirely avoidable.
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Cider That Doesn’t Clear When everything goes well, the cider clears
naturally at the end of fermentation.
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Cider Troubles and How to Avoid Them > Page 533 · Location 7644
generally within a month after the fermentation has stopped the cider
has at least started to clear.
Highlight(yellow) - Chapter 16:
Cider Troubles and How to Avoid Them > Page 533 · Location 7645
But once in a while, it will obstinately refuse to clear and will remain
hazy.
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Cider Troubles and How to Avoid Them > Page 533 · Location 7647
Determining what causes a haze is not easy. Pectin is one of the most
common causes, but there are also protein, microbial, and tannin hazes.
Testing for a pectin haze may be done with the alcohol test described in
the article on pectins in chapter 12: if the test is positive for the
presence of pectin, that is, a gel forms or you can see pectin strands,
then there is a good chance this pectin is the cause of the haze. As for
the other possible causes of non-clarification of the cider, this is not
easily determined without analysis.
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Cider Troubles and How to Avoid Them > Page 534 · Location 7652
The best way to avoid a haze in general is by prevention. A pectic
enzyme (pectinase) treatment before the start of the fermentation will
generally (but not always) prevent the formation of pectin hazes. These
enzymes will break the pectin molecules, which will then deposit
themselves with the lees. Microbial or bacterial hazes can usually be
prevented by good sanitation and the use of sulfite.
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Cider Troubles and How to Avoid Them > Page 537 · Location 7675
An extreme form of pectic haze is a pectic gel. This may happen to
ciders that contain a lot of pectin. When the fermentation is fully or
almost completed, the pectin coagulates into a gel that, at the
beginning of the process, may occupy half or two-thirds of the carboy,
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Alcohol is required for this gel to form, and this is why it happens at
the end of fermentation. There isn’t much to do: with time the gel will
compact itself in the bottom and may finally occupy only 20 to 25
percent of the volume, thus leaving the rest as a perfectly clear cider
that can be racked and bottled.
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Sulfur and Rotten-Egg Taints These odors are extremely unpleasant, and
it may be difficult to identify the exact origin and find a remedy. They
are caused by hydrogen sulfide (chemical formula H2S), which
may be produced by the fermentation under certain conditions.
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Cider Troubles and How to Avoid Them > Page 539 · Location 7700
It seems that in general the taint is related either to the type of
yeast or to the nutrients used. Another possible culprit could be if
sulfur was applied in the orchard as a fungicide: some of this sulfur
may stick to the skin of the apples and find its way into the must,
causing excessive sulfur concentration in the cider and eventually these
taints. Sometimes the odor may appear during a very active fermentation
and disappear thereafter without a trace. But other times the odor
persists, and a recommended remedy is to treat the cider with copper,
which eliminates the hydrogen sulfide.
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Cider Troubles and How to Avoid Them > Page 540 · Location 7705
If you often have hydrogen sulfide odors in your ciders, you should try
to change the type of yeast you use and/ or the regime of yeast
nutrients. Some yeast strains are known to produce H2S more
easily than others. This is normally indicated on the technical data
sheet of the yeast, sheets that we can find in the Internet site of the
manufacturer or distributor.
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It also seems that this problem occurs mainly when the fermentation is
very active with juice from early apples and when the temperature is
relatively high: if under those circumstances the nutrients would come
to be lacking, then the yeasts might produce H2S in greater
quantity. On the other hand, slow fermentations at low temperature of
musts that are poor in nutrients are almost never affected, as the
fermentation is never very active under such conditions.
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Caution: Novice cider makers might not make the distinction between
sulfite and sulfide. There is only one letter difference between the two
words, but they represent entirely different things. Sulfite, or
SO2, is added by the cider maker, and when overdosed has the
character of a burning match. Sulfide is hydrogen sulfide
(H2S), as discussed above, and produces an odor of rotten
eggs.
Appendix 1: Units and Measures
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Location 7771
Ppm stands for parts per million. It is a useful unit for small
concentrations. In cider making, we use it, for example, in the dosage
of sulfite, DAP, or enzymes. Thus, 1 ppm is 1 gram of product mixed in 1
million grams of solution, or approximately 1,000 liters of apple juice
or cider. One ppm is also approximately equivalent to 1 milligram per
liter (1 mg/ L) and 10 ppm to 1 gram per hectoliter. We may compute the
quantity of a substance to add in grams to obtain a certain
concentration in ppm with the following relation: (Mass in grams of
substance) ≈ ppm × (volume in liters) / 1,000
Appendix 2: Companion Materials
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Location 7851
The Blending Wizard This spreadsheet is an aid for blending. It will
allow you to predict the SG and acidity of a blend when you know these
numbers for the individual components of the blend, as discussed in
chapter 13. It is based on a very simple, weighted average routine to
compute the SG and acidity of the blend. Please refer to the text in the
above-mentioned article for instructions on how to use the wizard.
www.chelseagreen.com/ blending