This removes any grape skin particles that might have traveled with the juice from the press. The result is a clean grape must ready for fermentation. The metamorphosis of grape juice to wine. Pure cultured yeasts are selected for their influences on each individual grape variety. Some yeasts do not metabolize colour and are best suited for red wines, some yeasts can tolerate the cold and are great for cold cellars or white wines.
Yeast create the wine by metabolizing the grape sugars.
They digest and breakdown the sugars which then form into carbon dioxide and alcohol. Racking The next step in the winemaking process is after the fermentation has stopped. Racking is the process in which the yeast that has now settled to the bottom of the barrel will be removed. The wine is pumped out of the barrel or tank leaving the yeast behind in the bottom of the container. This process may take place several times before the wine becomes clear.