|racking the saskatoon/rhubarb wine|
Yeast likes the same kind of juice that people do: sweet, with a bit of a tang. It likes the same kind of temperatures we do, too, warm but not too hot. It lives in the juice, swimming around eating sugar and producing carbon dioxide and alcohol. When the alcohol level in the juice gets too high, or if it runs out of sugar to eat, it dies. That is, basically, all you need to know.
If your juice doesn't contain enough sugars, the yeast will starve before it produces much alcohol. If there's really a lot of sugar, the yeast will die of alcohol poisoning before finishing it and you'll have a sweet wine.
If the juice gets too hot, the yeast dies. If it gets too cool, however, the yeast goes dormant and it will wake up again when things warm up.
If you bottle your wine before the yeast has died, it will continue to work in the bottle. Since the carbon dioxide it produces can't escape, you'll end up with a fizzy wine.
Wine is usually protected from contact with the air so that bacteria and yeasts that are not tasty are excluded from joining the party. You do this by putting the juice into a container with an airlock. The carbon dioxide can bubble out, but air can't get in. When no bubbles are being produced, it means the yeast is finished and it's time to bottle the wine.
|Left to right: rhubarb, rhub/saskatoon, last year's rosehip, dandelion|