Effects of fining on phenolic compounds and colour of red wine obtained with addition of increased amounts of grape solid phase in pomace

The purpose of this work is to study the effect of grape pomace enrichment in solid phase (stems and seeds) on phenolic compounds and colour stability of obtained red wines, before and after use of different fining agents. Results have shown increase in total phenols and flavan-3-ols content after grape solid phase addition. On the other hand, decrease in anthocyanins content has generally been recorded in all wine samples except in wines obtained with addition of 40 g/l of seeds during maceration. Stems addition caused decrease in colour intensity while addition of seeds has increased this colour parameter. The use of four fining agents (albumin, gelatine, bentonite and PVPP) has been investigated and compared, especially in terms of their influence on potential stabilization effect of grape solid phase on wine colour. Fined wines tended to have considerably lower anthocyanin and flavan-3-ol levels, especially in the case of gelatine and PVPP treatment (decrease up to 60 and 70%, respectively). In the case of chromatic parameters, used fining agents caused colour intensity decrease but it is important to emphasize that their values, after fining, are still as high as expected from red wine. This can be explained by the stabilization effect of increased flavan-3-ols content.