Why should I add yeast?

By adding proper wine yeast to a must (unfermented fruit/grape juice), control over the finished product is easier. Wine made without using added yeast (using wild yeast) may not properly ferment, may develop off or odd flavors/aromas, or not turn out right at all. Wild yeast by itself is very sensitive to sulfur dioxide and does not ferment when the alcohol content goes above 5%. By adding yeast specifically designed for winemaking, the winemaker has better control over the finished product and the process itself. A winemaker who depends on the “wild yeast” to make wine is taking a gamble that there is enough “good” yeast around to make good wine. By adding wine yeast, the winemaker knows the wine will ferment the way it should, and will be good in the end.