Effect of freezing and freeze-drying techniques on antioxidant activity of tomato fruits

Considering that only a small amount of fruit and vegetables are consumed in their raw state, the evaluation of influence of food processing on naturally occurring antioxidants is a key factor in finding those technological conditions necessary to preserve or improve their original activity and bioavailability. The aim of the present research was to make a preliminary study on the effects of freezing and freeze-drying on the antioxidant activity of two types of tomato cultivars. in clusters and oblongs. Results showed that a polyphenolic fraction is mainly present on the fruit skin in both types of tomatoes. It seemed that oblongs tomatoes had better percentage of polyphenols than those in clusters after freezing; the differences between the two types seemed to disappear after freeze-drying. About AAT, the results showed that the antioxidant activity was quite low, even if tomatoes in clusters were better than oblongs: technological treatments increased, in comparison with raw material, this quality parameter. On the other hand, DPPH radical scavenging activity was stable.