Yeast can transform what already exists in grapes by increasing the stature of one or more compounds within the wine, aid in autolysis to contribute to a richer mouthfeel, cause flocculation to ensure the precipitation of dead cells in sparkling wines—all in addition to its primary chore of transforming sugar into alcohol. Along with variety, terroir, oak, the choice of equipment and the particular fermentation and élevage regimes, the choice of a particular yeast strain, or no...