How to Make Wines

Yeast Fermenting Fruits

The gray-white bloom that forms on grapes and other fruits is yeast put there by nature and it may be said that the first wine known to early man was the result of this yeast fermenting fruits crushed for a purpose other than wine-making. In the ordinary way, this yeast might well make good wine if allowed to ferment alone. Unfortunately with this yeast comes what we term ‘undesirable’ yeast (wild yeast), and several kinds of bacteria-each of which can ruin our wines. They bring about what we call ‘undesirable’ ferments that usually take place at the same time as the ferment we want to take place so that instead of a wine of quality the result is one tasting of flat beer or cloudy evil-smelling liquid fit only for disposal. Another bacterium, known as the vinegar bacterium, will turn wines into vinegar.

Since there is nothing we can do when any of these calamities has occurred, they must be prevented from happening. Clearly, we must destroy all these enemies before beginning. The simplest method is of course-at first thought anyway-is to boil the fruits. But here rises another problem. All fruits contain pectin, a glutinous substance which causes jams to ’set’. Boiling fruit releases pectin. This pectin holds itself and minute solids in suspension. Giving the wine a cloudiness that is impossible to clarify or even filter out. We may put the crushed fruit through a jelly-bag to remove every particle of pectin- bearing fruit and then boil the juice only, but this is a messy, tedious job that takes hours and eliminates all the pleasure from wine-making.

Obviously, what we need is a method which will destroy the wild yeast and bacteria on the fruits (as boiling does) without actually boiling, and, indeed, without heating our fruits at all because it needs very little heat to bring out the pectin.