Ellagic acid, vitamin C, and total phenolic contents and radical scavenging capacity affected by freezing and frozen storage in raspberry fruit

The ellagic acid, total phenolic, and vitamin C contents in four raspberry cultivars (Heritage, Autumn Bliss, Rubi, and Zeva) grown in Spain were detected and quantified by HPLC in fresh, just frozen, and stored fruits at -20 °C for a one year period. Ellagic acid [207-244 mg kg-1 of fresh weight (fw)], total phenolic (137-1776 mg kg-1 of fw), and vitamin C (221-312 mg kg-1 of fw) contents in raw material were higher in the late cultivars Zeva and Rubi than in the early cultivars Autumn Bliss and Heritage. The freezing process slightly affected the values of extracted ellagic acid, total phenolic, and vitamin C content. At the end of long-term frozen storage (12 months), no significant change of total phenolic content extracted was observed, but significant decreases of 14-21% in ellagic acid and of 33-55% in vitamin C were quantified. Free radical scavenging capacity measured as antiradical efficiency (AE) depends on the seasonal period of harvest. Late cultivars, Rubi (6.1 x 10-4) and Zeva (10.17 x 10-4), showed higher AE than early cultivars, Heritage (4.02 x 10-4) and Autumn Bliss (4.36 x 10-4). The freezing process produced a decrease of AE values in the four cultivars ranging between 4 and 26%. During the frozen storage, the AE values reached after the freezing process remained unchanged.This work was supported through the Spanish-financed Projects ALI95-0105 and ALI98-0820Peer Reviewe