The Alchemy of Yeast
They are so small that we tend to forget them. They have different shapes and can reproduce by the thousand, if conditions are favorable. Finally, without them, however wonderfully appetizing the grapes are at the outset, there will be no wine – unfortunately.
I’m talking about yeast, of course. These are the little soldiers who march to the front line and transform the sugar from the grape juice into alcohol and carbonic gas. (The exact equation is, however, rather more complicated I suspect, and enzymes are involved in a big way.) Whatever the case, yeast makes an enormous contribution and plays a most important role in the making of our home wines. The sachets provided in our home wine kits contain yeasts that are particularly well suited to each type of wine. Yeast, which is responsible for the alcoholic fermentation, may be either native or selected. In the first case, it exists in its natural state in the vineyards and appears naturally on the bloom, the waxy coating that covers the grape. Selected yeasts are also quite natural – they have been selected in the vineyards and reproduced in the laboratory – a little like the way in which the nurseryman cultivates and reproduces vine stocks. Some types of yeast possess special qualities: they can, for example, emphasize certain features of the resulting wine – its fruitiness, its more or less silky character and so on. Lallemand, one of the most important producers of yeast for commercial and domestic wine making is located on rue Préfontaine in the east end of Montreal. In principle, yeast stops its work of transforming sugar into alcohol when the latter has reached about 16 per cent by volume. Some of them have higher alco-genic powers and can go even beyond that should it be necessary. Chemistry is all well and good, and even alchemy, because it is all about complex sequences of reactions and transformations. But the important thing, as much for the winemaker as the wine lover who relishes his wines, is to be confident and let our friend, the yeast, do its job. All we have to do is to provide the best possible work environment. For this we only have to follow to the letter the winemaking instructions on each home wine making kit.