Effects of high-temperature drying on the polyphenolic composition of skins and seeds from red grape pomace

The management and disposal of large amounts of grape pomace (GP) annually generated by the wine industry represent a serious economic and environmental problem. On the other hand, GP can be profitably exploited for many possible purposes as a source of natural phenolic compounds. GP is highly perishable, and it is produced in large amounts during a short period of time: a rapid stabilization by drying is needed to prolong its availability for any further processing. In the case of large amounts of GP to be dried at an industrial level, the balance between costs and final quality of the dried product must be considered. The effect of high-temperature treatments (160–200 °C) for short duration on the polyphenolic composition of GP, and on its stability over time during storage, were studied separately for skins and seeds. The high-temperature treatments caused the enrichment of the polyphenolic content of the skins and the contemporary decrease in that of the seeds. Overall, the dried GP retained over time the polyphenolic composition and the anti-radical properties determined at the end of the drying process. This result is of particular interest in view of the use of dried GP throughout the year for any further processing.