Yeast is a single-cell microorganism that’s responsible for the production of enzymes, which ferment the wine. During the fermentation process, yeast releases ethyl alcohol and carbon dioxide. Along with this, it also releases some volatile compounds like sulphur, aldehydes, and esters that contribute to the flavours and aroma that you get to experience while sipping wine. The entire wine profile is actually determined by the kind of yeast used in fermentation. Even the colour of a wine is attributed to yeasts.