Wine Fermentation
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Wine Fermentation
In short, it is the complex action whereby the living organism of yeast breaks the sugar down into
carbon dioxide and alcohol. The action of the yeast on the sugar continues until the volume of alcohol
has reached somewhere between 12.5% to 14%.
At this stage, the yeast organism is destroyed by the alcohol it has produced and fermentation ceases.
This is what is known as a natural wine. Most commercial products come under this category until
they have been fortified. This period of fermenting in the tub can be a dangerous time. Because of
this, the fermentation process should be completed as soon as possible (even at the risk of losing a
little of the wine's bouquet).
Next, we must then keep the brew warm. Our goal here is to bring about ideal conditions in which the
living organism and yeast cells can multiply more rapidly. Warmth helps to ensure this. The faster
they multiply, the more rapidly they convert the sugar into alcohol and therefore, the sooner the yeast
destroys itself.
Do not be tempted to keep a brew hot during fermentation. During warm weather, any odd spot will
do for a fermenting brew. Also, a warm spot in the kitchen or in an airing cupboard is as good as any
during the winter.
After 14 day of fermentation in a warm place, the wine can be bottled or put into stone jars. This is
the time to add the isinglass.
Isinglass is not needed to clarify flower or fruit wines made with the recipes given at www.e-
homewinemaking.com. These wines will clarify themselves quite readily within a few weeks of
fermentation. Nor is isinglass an absolute need for clearing root wines. However, I have found that
root wines and wines made from a mixture of roots and fruits, do clear more readily with the help of
isinglass. For this reason, some recipes will instruct you to "proceed with isinglass and bottling".
When put into wine, isinglass forms an insoluble cloud which surrounds the minute solids in the wine
and gradually forces them to the bottom of the bottle.
Besides assisting the clearing process, isinglass helps to solidify the lees, thereby rendering them less
easy to disturb while moving the bottles or when wine is poured from a bottle containing lees.
There are many methods of using isinglass, but the one I use myself without fail results is as follows:
Take one quart of the wine and warm it very slowly in a saucepan. Next, crumble 1/8 of an ounce of
isinglass over the surface of this wine and then stir with a fork until everything is dissolved. Then
pour it into the rest of the wine in a circular motion.
Many people advise dissolving the isinglass in a small amount of water. As we've seen, ordinary tap-
water quite often contains wild yeast; the very act, then, of using water might well ruin all of our
efforts to keep wild yeast out of the wine.
When purchased from a chemist in 1/2 ounce or 1 ounce quantities, the amount required is easy to
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calculate, and this is usually plenty for one gallon of wine.
When the isinglass has been added, put the wine into sterilized bottles or jars and cover as already
directed. The wine must then be returned to a warm place, and kept there until all fermentation has
ceased.
If the wine were put in a cold place the yeast might go dormant and the wine would not be able to
ferment. If it were later moved into a warm room, or the weather happened to turn very warm, the
yeast would become active and start fermenting again. In a warm place, fermentation will not fail.
If you happen to notice that the top half-inch of wine has become crystal-clear, seal the bottles at
once! This is a clear indication that fermentation has stopped. Unfortunately, we rarely get this
invaluable guide.
When all fermentation has stopped and when no more small bubbles are rising to the top, the yeast is
dead. Fermentation cannot begin again unless wild yeast or bacteria get into the wine and start that
souring ferment that I've previously mentioned. Perfect air-tight sealing at the earliest possible stage
of production is critical.
Push the cork down hard and seal with sealing-wax. If screw-top bottles are available, use these if you
prefer. Personally, I never use any other kind when I can find them. Remember that the yeast is dead,
so fermentation cannot begin again and explode the bottles or blow the corks unless wild yeast or
bacteria reach the wine. Screw-top bottles are, then, the obvious choice.
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