The Wine Pages: Homebrew winemaking
Yeast is the tiny micro-orgnaism that does all the hard work. It is interesting to note that in a fluid ounce of vigourously fermenting must, there exists about 6 billion yeasts. Keeping all these yeasts happy is one of the main occupations of a winemaker. Essentially, if you are nice to them, they'll be nice to you.
A typical happy yeast is not unlike a human being, provided you have a vivid imagination. Yeast can survive in a range of temperatures, but like us they don't like wild fluctuations or extremes. They like to have plenty to eat, ie sugar, and they develop much more enthusiasm for life if you treat them to some nutritous food, ie yeast nutrient.
Other fetishes of yeast include the need for a slightly acid environment, the need for some oxygen and the violent dislike of sterilising agents.
Yeast also has a tendency to get drunk. Once the fermentation reaches about 18%, yeast, like humans, falls into an unconscious heap. In human circles, this heap is called various things such as lightweight, or pissed newt. In the case of yeast it is called lees. Uncousious heaps can also arise in both humans and yeasts because of lack of sugar and nutrients.
We tend to rack wine off the lees and wash them down the sink. This solution is harder to implement in humans.
Drunk yeast can be bought back to life by adding chemicals and shaking. Again see humans.
So now we know how to look after our yeast, what yeast should we use? Many people employ standard wine yeast. This is easily distinguished because it says 'wine yeast' on the label. If you are feeling a little more pretentious however, you can try one of the specialist yeasts. In the real world you can buy wine called burgundy, port and sauternes. Such wines are fermented using the yeast present on the grapes. Essentially, a scientist bod goes around each region scraping yeast off the grapes, then dries it and sells it in little foil packs. The process is a lot more involved than this, but you get the idea.
The homewine maker can then use perhaps a hock yeast to make elderflower wine, or maybe a port yeast with blackberries. The merits of doing this are thought a little dubious by some, but at least it gives you the right to scribble 'Elderflower Hock' on your bottles, should you feel the urge.
When you get home from the shop with your little packet of yeast, it is fairly simple to use. It is perfectly reasonable just to chuck a teaspoon of dried yeast into the must. However to give the yeast a decent start in life, it is considered sporting to mix the dry yeast in a teacup of slightly warm water. Put in a teaspoon of sugar, plus a pinch of acid and nutrient. This will give the yeast something to do. After a few hours the yeast will have woken up and started to froth a bit. This is the moment to stir it into the must.
Now you have some living yeast, you don't really have an excuse to buy any more, unless that is you want to try a different variety. Every time you start a new bucket of must, just slosh half a cup of fermenting wine into the must to provide some yeast. This doesn't work if you are criminal enough not to have some wine fermenting all the time.
Whatever the source, yeast will generally take a couple of days to get its life together and start doing some useful work.
Above all else, always maintain huge wodges of respect and reverance for yeast. It really is something a bit special.