As far as I can tell, detractors of commercial yeast have two concerns. One is that commercial wine yeasts might be genetically modified. But they are not. ’Taint legal. They are simply “wild” yeasts that have been studied, selected for beneficial properties, grown in large quantities, dried, and bagged up. Second is the concern about flavors that are imparted by packaged yeast. As I have explained, not only is this concern naively overstated, but in my experience, uninoculated wines are more prone to microbial flavor intrusions than commercial yeast fermentations.
