So now you have your juice racked and almost ready to start fermentation. The temperature of the juice should be at least 60 degrees in order to add yeast. Always use a good wine yeast culture that you have purchased from a winemaking store. There are several types to choose from and they can guide you depending on what type of wine you are making. The only recommendation I will give is NOT to use Montrachet yeast, no matter what anyone tells you. The chances of getting hydrogen sulfide (rotten egg smell that can turn into something much more nasty – see Winemaker Questions) are very high with this particular yeast. There are many other yeast choices that are better.
The relationship between yeast, sugar, and alcohol is key to making wine. The yeast feeds on the sugar and converts it into alcohol and carbon dioxide (which explains why fermentation is fizzy). If you do not have enough sugar in your juice, you will not have enough alcohol in your finished wine to make it a good, keeping quality wine with proper body and mouth feel. Your goal is to ripen fruit to at least 21 or 22 brix (see From Plant to Bottle: The Grapes – To Pick or Not to Pick for information on measuring sugar content or brix). If this has not happened and you need to increase the sugar level, the addition rate that I use is 2.27 ounces per gallon for white wine and 2.4 ounces per gallon for red wine, per desired brix increase. An example of this calculation is as follows: If you have 20 brix and want 22 brix in your white wine, the calculation is 22 minus 20 = 2 times 2.27 ounces for each gallon of juice you have. This equals 4.54 ounces of sugar per gallon to bring your 20 brix must up to 22 brix, which should give you about 12% alcohol if the fermentation goes to completion (which is, of course, what we all hope will happen).
I have read many different opinions on how much sugar should be added and have tried them all with my results falling short of what I had hoped to achieve. The alcohol level always seemed to be lower than I expected. The above information comes from Jacques Recht, whom I mentioned earlier in this blog. He writes a great column for Wine East Magazine that is extremely informative. The explanation as to how he comes to the conclusion on these additions is very complicated with a lot of mathematics and chemistry involved that I will not go into. However, part of the explanation is that not all of the sugar is converted into alcohol; some is used as energy for the yeast and some is used by direct oxidation into water and CO2. Therefore, it is difficult to be absolutely accurate. Apparently there is also a difference in sugar usage between red wine fermentation and white wine fermentation. Hence, the difference in addition rules.
Since I started using these addition guidelines I have come much closer to my finished alcohol goal than ever before and have been very pleased with the results. So I am sticking with it.
Next Week: Yeast, start your engines!