Influence of processing and storage on the antioxidant activity of apple derivatives

The antioxidant activity of seven apple varieties was determined on fresh fruits and processed products (dried fruits and purees) and during storage. The antioxidant activity of apples correlated with the total phenol concentration but not with ascorbic acid concentration. Apple derivatives showed a lower antioxidant activity than the counterparts of the fresh fruits and the occurrence of browning phenomena during processing resulted in lower antioxidant activity. Dried fruits showed higher antioxidant activity per gram of dried matter than fruit purees probably because of the lower total thermal effect of processing. The antioxidant activity of all products increased within the first month of storage, and then declined. The extent of early increase was related to the polyphenol content of the fruit. Packaging conditions further influenced the antioxidant activity increase during storage possibly by affecting the oxygen availability.