Making Wine from Grapes
The first step in the process is to crush the purple grapes and remove the stems. Red wine grapes are purple and its juice is light clear. By soaking the juice in contact with the skins, the juice gets darker in color and picks up tannins. The stems would give off a bitter taste to the wine. We put the grapes into an open top container so it can get plenty of air during fermentation. The grapes had a white film on the skins that are now mixed with the juice. This is the wild yeast that accumulated in the vineyard during the months of maturing. If left to ferment the wine, it would be unpredictable with its results. It could make a great wine, but it could also stop fermenting at 10% alcohol and leave you with a sweet wine with dark color and high tannins. It may create too much Hydrogen Sulfide and have an undesirable rotten-egg smell, or create too much Sulfur dioxide and not allow your wine go through malolactic fermentation. Your best choice is to add 40 parts per million (quarter teaspoon for six gallons) of Potassium Metabisulfite to stop that wild yeast and add a yeast that is predictable. Yeast needs vitamins to stay healthy. Yeast nutrient will keep your yeast healthy and allow it to create all the desirable aromas and not the undesirable ones. Add a tablespoon at the beginning and another half way through fermentation. The skins, stems and seeds are left behind and everything is transformed into wine with the help of pectic enzyme, so add a tablespoon of pectic enzyme for every six gallons.