Stability of polyphenolic extracts from grape seeds after thermal treatments

摘要

Five commercial grape seed extracts (GSEs) were put under pasteurisation (HTST and LTLT), cooking, baking and sterilisation conditions. After each treatment, the tannin content, antioxidant activity, browning and characteristics of eight phenolic compounds were determined. For nearly all quantified parameters, significant differences (p 0.05) were found between at least two treatments. The gallic acid, gallocatechin and browning parameters showed a greater tendency to increase in the treatments, and the antioxidant activity showed a greater tendency to decrease. A positive correlation between the tannin content and browning and a negative correlation between the gallic acid and antioxidant activity were found. The GSEs were clearly grouped based on their composition; nevertheless, a grouping based on the treatments did not exist. It can be concluded that the thermal treatments affected the stability of all GSEs in a different manner depending on the phenolic profile of each extract.