EFFECT OF LONG-TIME STORAGE ON THE CONTENT OF POLYPHENOLS AND ASCORBIC ACID IN OSMO-CONVECTIVELY DRIED AND OSMO-FREEZE-DRIED FRUITS

Abstract

ABSTRACT The objective of the study was to investigate the stability of polyphenols and ascorbic acid in osmo-dried fruits: apples, sour cherries and blackcurrants, stored for 12 months. After 1 year of storage, the content of total polyphenols and anthocyanins in convectively dried blackcurrants was decreased by 45% and 90%, respectively. Flavonols remained highly stable. Convectively dried sour cherries contained particularly labile substances, including cyanidin derivatives, which content decreased by 98% after 6 months. Polyphenols in freeze-dried materials were more stable. After 1 year of storage, their content remained at 60–80% of the initial level. A high stability was in particular observed for delphinidin-3-rutinoside in blackcurrants, and cyanidin derivatives, chlorogenic acid, neochlorogenic acid and quercetin glucoside in sour cherries. The stability of ascorbic acid was also much higher in freeze-dried blackcurrants than in convectively dried fruit. After 1 year of storage, almost 70% of ascorbic acid was preserved in freeze-dried material. PRACTICAL APPLICATIONS Analyzed material was obtained in industrial conditions. Final products were used to produce bars; it can also be used in manufacturing of muesli and similar products. The results of performed analyses show a change in the content of polyphenols and ascorbic acid during product storage and could be useful to define the time in which a product is characterized by the highest content of health-promoting substances.