The green balls of malolactic and citric acid are turning to tartaric acid now, and depositing sugars as water flow into grape berries decreases. The skins of the grapes are beginning their mysteries, adding the flavours that will define the wine, through CAM photosynthesis (such as you find in pineapples and cactus and cabbages). CAM plants make malolactic acid during the day and convert it to sugars in the night, when they don’t have to lose their water to breathe and take in oxygen. In grapes, CAM synthesis only takes place, slightly, in the skins, but it is enough. The mysteries of fermentation begin here, laying down the compounds that the yeast will transform in their intestinal tracts during fermentation, and which we know as the flavours of wine. Actually, they are the art that yeast make.
These are the deep mysteries. Note how the yeast is beginning to form on the skins of the grapes, in preparation for the transformations of winter. It is all one event, based on this one magical moment: the moment of ripening, when the grapes transform their nature entirely, and before the angels of the yeast reveal it (and the human tongue receives it.) This is an ancient sacrament.