مشخصات پژوهش

Date-palm fruit is an important horticultural fruit in Iran with a high nutritive value. In this research the effects of freezing process on phenolic-compounds content, antioxidant properties and microbial quality of two common date varieties, namely, Mazafati and Kaluteh, They were frozen and stored for 1, 2, 4, 6 and 8 months at -18 ˚C. The phenolic content was measured by the Folin–Ciocalteau method, the antioxidant activity by DPPH method. Standard plate count agar and Potato Dextrose Agar (PDA) media were used for total count and molds and yeast determination, respectively. The Mazafati variety had a higher contents of phenolic compounds (677.3 mg galic acid/100 g dry weight) and a higher antioxidant activity (22.45% radical scavenging DPPH) than the Kaluteh variety (573.6 mg gallic acid/100 g dry weight and 18.86% radical scavenging DPPH, respectively). The freezing process causes an increase in phenolic compounds and antioxidant activity in comparison with fresh dates. The highest and lowest contents of phenolic and antioxidant activity were found in the frozen date (8 months) (892.12 mg gallic acid/100 g dry weight and 41.33% radical scavenging DPPH, respectively) and fresh date samples, respectively. Freezing process and keeping date fruits at a temperature of -18 ˚C for a long period (1, 2, 4, 6 and 8 months) also led to decreases in microbial activity