Why make a starter?
You can get good results from wine yeast by just sprinkling a newly opened packet directly onto your must. There are times, however, that you really ought to use a starter. Yeast become active and start reproducing much more quickly and reliably in a starter, so in difficult (for the yeast) situations, like trying to restart a stuck fermentation or if you doubt the viability of your yeast (because it’s been sitting on a shelf for years, for example, or you ordered it during a freak heatwave and it may have gotten cooked in a delivery truck somewhere), a starter is worth the effort. You may also want to make a starter if you need your yeast to dominate the must quickly. Maybe you don’t like to use sulfite or you had to leave your must sitting for longer than you expected before you could pitch your yeast.
Some people use starters routinely. This is probably unnecessary, but it doesn’t hurt.
How do you make a starter?
First, you should rehydrate your yeast according to the directions on the package.
In the photo, I’ve sprinkled the yeast into a quarter cup (about 50 ml) of warm water and let it sit for five minutes. Coming out of dormancy is stressful, and a lot of yeast cells die. Warm water, with no additives like nutrient or sugar, is the least stressful way to do it and results in the largest population of live yeast.
While you’re waiting, dissolve a tablespoon of sugar (12 grams) and a pinch of nutrient in
a cup 2.5 fluid ounces (75 ml) of water. Once your yeast is rehydrated, add it to the sugar water. You should see signs of activity in less than an hour.
In about four hours, it should be active and foamy and you can add it to your must.
You can let it continue for a up to a day, but there is probably no advantage in it. Any benefit from additional growth will be offset by having your must sit around with no yeast in it. If you do want to let the starter grow for a while, maybe because you made the starter before you prepared your must, then keep an eye on it every few hours and add sugar water, 1 tablespoon (12 g) sugar to each half cup (120 ml) if activity subsides. If you made the starter to restart a stuck fermentation, it’s better to add must to the starter, in a new fermenter, gradually.
Update 7/13/2010 – Changed the recommended sugar concentration
My original recipe for a starter was about 5% sugar, but I now use 10%. That’s about two tablespoons (24 g) of sugar to each cup (240 ml) of water. The yeast will have something to chew on either way, but 10% sugar is about halfway to the 20% or so common in wine musts. That makes it less of a drastic change. It means the starter might take a little longer, and can be left a little longer, before pitching.