Fining of Red Wines with Pomace Cell Wall Material: Effect on Wine Phenolic Composition

Fining is a winemaking technique used to remove unwanted wine components that affect clarification, astringency, color, bitterness, and aroma. One of the objectives of fining is often to reduce the wine tannin content due to its effect on wine astringency. Proteinaceous agents are commonly used with this objective, but problems related with their possible allergenic properties or the excessive enrichment of wine with proteins, which may cause stability and turbidity problems, have led to the search for new fining agents. In this way, the cell wall material from processed grape pomace could be a good alternative since it has a high affinity for tannins. In this work, the effect of cell wall material from processed pomace from Monastrell and Cabernet Sauvignon grapes on the reduction of the phenolic content of red wines is studied and the results are compared with those obtained with commercial fining products. Also, the varietal effect due to the different composition of the cell wall material from these two varieties has been evaluated. The concentration and composition of wine anthocyanins and tannins, before and after the fining process, were analyzed by HPLC and their molecular mass distribution by SEC. The results showed that, at laboratory scale, pomace cell walls have a fining effect that exceeds that of most the protein-based fining agents, even when used at their highest recommended doses. The cell wall material significantly reduced the wine phenolic content, the reduction ranging from 48 to 68% for anthocyanins and from 44 to 64% for tannins, although varietal differences exist regarding the cell wall-binding capacity. Monastrell cell walls exhibited the highest capacity and could be used at much lower doses than those used in this study, reducing the formation of lees and the wine adsorbed on them. The results indicate that this material could be an appropriate alternative for protein-based fining agents in red wine and their use would avoid allergen-related effects.