Anthocyanins extraction during winemaking

The fermentation usually is complete within 30 or 40 days. During this period additional anthocyanins are extracted from pomace and the color stabilizes due to polymerization between the anthocyanins and tannins. Winemakers call this process pomace "maturation". Moreover, due to the increasing alcohol concentration, many other metabolites are extracted from the pomace. In addition, yeast metabolites contribute to the aromatic complexity of the wine. 

However, the dissolvent effect of SO2 is manifest in rose winemaking, since the phenolic compound concentration is low in this case. In fact, SO2 can be detrimental to white winemaking. This dissolvent effect may also affect red grapes if they are insufficiently ripe, and pigment extractability is poor. In that case, snlfiting facilitates anthocyanin extraction in the early stages, especially during cool-temperature maceration (Section 12.5.2). 

---