Selectivity of pigments extraction from grapes and their partial retention in the pomace during red-winemaking

The purpose of this investigation was to assess the grape pigment extraction during red-winemaking. The pigment content and profile of skin, wines and pomace of Vitis vinifera grapes with different pigment profiles Syrah, Marselan and Tannat was thoroughly studied. The p-coumaroylated anthocyanin proportions were 37% in pomace, compared to 19% in skins and just 5% in wines, highlighting their poor extraction. Di-methoxylated based anthocyanins, increased their relative contribution in pomace and wines compared to skins, indicating they were less extracted, but more stable once extracted. Remarkably, the caffeoylated anthocyanins presented significantly higher concentrations in pomace than in skins (1.9 fold on average), suggesting that their synthesis could take place during vinification. Malvidin 3-feruloyl-glucoside was found in the Tannat samples being the first evidence of an anthocyanin acylated with ferulic acid in wine. Pigment extraction was selective depending on anthocyanin B-ring substitution pattern and acylation profile.