Having prepared your juice by checking its acidity, pH, and sugar levels and adjusting them as appropriate, it is now time for your yeast addition. The package you buy will usually have instructions on it, but I have a few tips. Yeast must be re-hydrated in water that is about 110 degrees Fahrenheit. If it is too cold, the water will shock the yeast. If it is too hot, it will kill the yeast. This is very important. Stir the yeast into the water and cover it with a clean cloth. Some types of yeast do not mix in smoothly and you will have some lumps. Don’t agonize over this, but do your best to get it to dissolve. Wait 20 minutes and stir the yeast and water vigorously. Incorporating air is very good for the yeast because they need oxygen.
At this stage you could pour your yeast starter into the juice, however, I never do that. I like to grow my yeast so that I have a very strong starter with many more millions of yeast cells than in the original stock. This helps to ensure a quicker start to your fermentation and a better chance of the fermentation going to completion. At this point, I stir some of my juice into the yeast starter, which will help feed the yeast and make it multiply. In my case, since I am dealing with large volumes at the winery, I generally have yeast in about a gallon of water and so I will put in about ½ gallon of juice at a time. At home, you are more likely to deal with amounts like a cup of water and adding ½ cup of juice at a time. Stir vigorously again and cover. Let it sit for a half hour or more, checking it periodically so it does not foam over.
Some types of yeast foam a lot. I have had the occasional 5 gallon pale of yeast rise so much that when I went to check on it the foam was raising the cloth inches above the top of the pale, holding it aloft (an especially good reason to use a clean cloth). Fortunately, because I check my yeast often, I usually manage to get there in time, before I have to clean up the floor or countertop. If you have a yeast that foams quite a lot, you simply have to stir it down more often. Normally you stir it down only occasionally as you see it rising.
When it starts to die down a little, I add another ½ gallon or so of juice and let it work some more. What is happening here is that the yeast is feeding on the sugar in the juice and multiplying itself as well as creating carbon dioxide(which is what causes it to rise). After a few hours, I have a nice starter and that is when I pour it into the tank of juice. Most books will tell you to mix the starter into your juice thoroughly. But I have found that, since my starting juice is often colder at the bottom than the top, I do better if I just pour it into the warm juice at the top. By the next day, the tank is fermenting strongly. This is a tried and true process for me. When I made wine up north, it was often very cold in the cellar already by September or October, when we harvested most of our grapes. With the juice already cold and not having a lot of sophisticated warming equipment, warming the juice up was not really an option there.
Now that you have your wine fermenting, it is particularly important with white wine to control the temperature, if possible. In a large tank, uncontrolled fermentations will easily go over 100° F as fermentation creates heat. This would be of great detriment to the fruit character of your white wine. The preferable temperature is about 60° F. This makes for a long, cool fermentation that will help retain the character of the juice.
Next Week: Let’s Feed That Baby to Keep It Happy!