Yes I've always wondered at what stage the yeast fermentation changes from an aerobic stage ( yeast growth) to an anaerobic ( CO2 productoin) stage, and if it was possible to regulate alcohol production from a given amount of sugar by sitrring the must and promoting more of an aerobic response.

I cover with a good cloth and plunge the cap daily. This keeps the cap moist and helps prevent acetobacteria from growing. I also use this stage to extract colour and tannins.