Wine 101: Double </font>Agent</font> </font>Bentonite</font>
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By Tim Vandergrift, Technical Services Manager, Brew King Limited</font> </font>
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<td>February 02, 2001 --</font>
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Bentonite
is a fining agent. Fining is the action of removing particles that make
a haze in wine by combining them with materials that bind to them and
force them out of suspension, leaving the wine clear and bright. It not
only improves a wine?s appearance; it also makes sure that it is stable.
Stable means that it won?t change if appearance, taste, aroma, or
chemical composition while in storage.
Bentonite is a type of
clay, known as aluminosilicate. Its technical name is Montmorillonite.
It?s found with various minerals attached to it, such as sodium, calcium
and magnesium. It was originally found in Fort Benton, Wyoming (where
the name came from). It?s used in winemaking, beauty treatments, mineral
extraction, water treatment, and kitty litter.
When used in
winemaking, it is stirred into the wine to remove proteins and other
haze causing particles. It works through adsorption. This means that it
attaches itself to a particle, and together they are too heavy to stay
in suspension, falling to the bottom of the carboy, leaving the wine
clear and stable. Bentonite settles out so completely that it does not
leave any residue of taste or colour behind.
Some wine kit
companies (like Brew King) add their bentonite on the first day, and
some add it after fermentation. This is one of the fundamental
differences between kits that you may have noticed. The reasons behind
it go beyond technology, straight into winemaking philosophy.
When
bentonite is added on the first day, it disperses through the wine and
most settles to the bottom within a few hours. At the end of 48 hours,
however, the bentonite is back in circulation. This is because of the
process of gas nucleation that the CO2 in the wine is undergoing.
As
the yeast ferments the sugar, it converts it into carbon dioxide (CO2)
and alcohol. The bubbles of gas don?t actually appear out of nowhere:
they want to come out of suspension on some kind of a point, where a
nucleus of gas can form the beginning of a bubble. Thus we get the term
?nucleation?. This point could be a scratch in the carboy, a bit of
grape material, or a particle of bentonite. The bentonite is surrounded
by a bubble of gas and floats up to the surface of the wine. When the
bubble bursts, the particle of bentonite drops back down to the bottom
of the carboy, all the time working to adsorb the other particles
clouding the wine. In this way, the bentonite is circulated around the
wine continuously for days, doing its job.
When bentonite is
added to a wine kit post-fermentation, it does not have the advantage of
the CO2 lift that it would get during fermentation. Therefore the
winemaker is obligated to stir it through the wine repeatedly, ensuring
the thorough dispersal.
In addition, because the bentonite will
quickly settle out before it can effectively clear the wine,
significantly more is needed when used post-fermentation. Brew King kits
typically use 10 or 15 grams of bentonite, while some companies use up
to 80 grams! Not only does this amount cause the formation of a deep,
loose sediment bed; it also has the effect of stripping the wine.
Finings
are considerably more powerful than most people suspect. With a
sufficient dosage of finings it is possible to strip a red wine to the
point where it becomes ?white?. Too much finings can lead to a stripping
of colour and flavour, making it necessary to formulate much darker and
stronger wine kits to compensate. By adding the bentonite on the first
day, the formulation can be much closer to the desired finished wine,
without extra additions or manipulation.
Although it may seem a
little odd to be adding clay to your wine, when the finished product is
clear and delicious, you?ll be glad that there was a little bentonite to
polish it up.
Potassium Metabisulphite is a stable source of
sulphur dioxide in winemaking. The use of sulphur compounds is not a
recent innovation. The great Dutch shipping empire popularised the use
of sulphur in the 16th century by refusing to ship any wines not
treated. They insisted on sulphites because sulphite treated wines were
the only ones that survived a long sea voyage without turning into
vinegar.
Sulphites work by releasing free sulphur dioxide, which
inhibits yeast, mould and bacteria. It does this in two ways: one, it
kills some of the organisms outright, and two, it blocks the surviving
organisms ability to reproduce. If your winemaking equipment is
physically clean and you've rinsed it with a sulphite solution, nothing
will grow on it.
Sulphites are also added directly to wine after
fermentation, to help prevent oxidation. Oxidation in wine follows the
same pattern that you see in the cut edge of an apple-the wine turns
brown and takes on a flat 'cardboard' taste.
Sulphur binds with the oxygen in the wine and prevents this damage.
Many
people worry that they may be allergic to sulphites. True sulphite
allergies are very rare. It's more likely that they have a histamine
reaction to red wine, or that they have been over exposed to sulphites
in the past. In the 1970's restaurants would douse their salad bars with
2000 PPM (parts per million) sulphite solutions in order to keep the
produce fresh. Mixing with food acids, such as dressings or vinegar,
would cause the salad to release clouds of sulphite gas, provoking
unpleasant reactions.
Some facts that might clear up any misunderstanding about sulphites:
Sulphites
are a recognised food additive. The federal government controls their
use. All commercially available wines in the province of British
Columbia contain sulphites, even those labelled 'Kosher' or 'Organic.
The legally allowable amount is 70 PPM.
Nearly all dried fruits
and meats contain sulphites. Raisins, for instance, have up to 250 PPM.
The amount of sulphite provided in wine kits will result in a level of
between 15 and 30 PPM in a finished wine.
All grape-based wines
produce Sulphites naturally during fermentation, up to a level of about
10-PPM. Even with no addition of outside sulphites, wines will still
contain them.
This is not to say that sulphites are totally
benign. People with asthma or emphysema should avoid inhaling sulphite
powder or the gas that comes off the prepared solution. It can act as a
bronchial constrictor, aggravating any breathing problems. Also, adding
extra sulphites to wine is of no benefit, as it can spoil the flavour,
giving it a 'burnt match' smell. It's important to follow directions for
sulphite additions. The upshot of sulphite use is this: without
sulphites you'd have to be very careful to keep all of your equipment
sanitary and you'd still have to drink your wine quickly, before it
spoiled, probably within one or two months.
Potassium Sorbate:
Used
For: Prevents renewed fermentation in sweet wines. Inhibits
reproduction of mould and yeast. ? g of Sorbate dissolved per litre of
wine will prevent spoilage. 5 ml (one Teaspoon) = approximately 2.8 g.
Bad
Ideas: Must not be added until fermentation has finished. If sorbate is
added to a wine during malolactic fermentation, it will be converted to
a compound with a strong and disagreeable odour.
Hazard classification: Not hazardous. GRAS (Generally Recognised As Safe) by Agriculture Canada.
Chitosan
is a non-proteinaceous fining agent, a polysaccharide of the Sucrose
Polymer family. It is derived from chitin extracted from ocean
shellfish, the same organic material that makes up fingernails and human
hair. It works by a process of molecular adsorption, where the Chitosan
has an electrical charge, which attracts oppositely charged particles
clouding the wine, binding them and pulling them out of suspension.
It
s also used as a food additive and dietary supplement. Although it is
derived from shellfish, there is absolutely no danger of any allergic
reactions to the product, as there are no allergens left after the
Chitosan is processed.</font></font></td></tr></t></table></font>
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