Effect of freezing and refrigerate storage on the antioxidant activity and bioactive substances contents of Opuntia fruits

CORIA CAYUPÁN, Y. S.; NAZARENO M. A.

Palermo

Congreso; VIII International Congress on Cactus pear and cochineal; 2013

Universitá de Palermo

Changes in the antioxidant activity and in bioactive substances contents in fruits and their alcoholic extracts stored at different storage temperatures for 6 weeks after harvest were analyzed as the main objectives of this study. Different Opuntia ficus-indica and Opuntia megacantha fruits (pink, purple, orange and yellow pulps) were collected in physiological ripeness status from Santiago del Estero province, Argentina. Cactus fruits were immediately analyzed after harvest to determine the initial quality parameters and they were stored in various refrigerated conditions: at 8 ° C ± 1 º C in a refrigerator for 4 weeks, at -18 ° C ± 1 ° C in a freezer for 6 weeks. Stored fruits were analyzed at 1, 2, 4 and 6 weeks after harvest. The antioxidant activities at different storage times were determined by conventional methods as those of DPPH and ABTS radicals bleaching. Total betalain contents (betacyanins and betaxanthins) were measured by UV-Vis spectrophotometry and pigment profile variation as a function of storage time by HPLC-DAD. Vitamin C contents (ascorbic acid and DHA) were monitored by HPLC every 2 weeks along treatment time. Variation in total phenolic compound contents was evaluated in the stored fruits by the Folin-Ciocalteu (corrected for ascorbic acid interference). Betacarotene contents in treated fruits were also monitored by HPLC. Changes were observed in the AAR and betalains contents in different Opuntia fruits during freezing and refrigerated storage. The highest pigment degradation was observed after freezing of fruits, followed by freezing extracts. From the results obtained, a correlation was observed between the degradation of betalains with the antiradical activity decrease of fruits and extracts during freezer storage for 6 weeks. Consequently, there is a complex interaction between these pigments and another components present in the food matrix, able to produce variations in the free radical scavenging activity.