ABSTRACT
Date-palm fruit is an important horticultural fruit in Iran with a high nutritive value due to its contents of minerals, sugars, vitamins and antioxidant compounds. In this research the effects of drying process on phenolic-compounds content and antioxidant properties of two common date varieties in Kerman Province, Iran, namely, Mazafati and Kaluteh, were investigated. Two common date varieties in Kerman province, Iran, namely, Mazafati and Kaluteh, were chosen. They were dried by 2 methods - sun-drying and oven-drying at 500, 600, 700 and 800 C. The phenolic content was measured by the Folin-Ciocalteau method and the antioxidant activity by reducing-power assay, total antioxidant capacity, and DPPH methods. The drying process causes a decrease in phenolic compounds in comparison with fresh dates. The reductions in both total phenolic-compounds content and total antioxidant activity increased by increasing the drying temperature. The highest and lowest contents of phenolic compounds and antioxidant activity were found in the sun-dried and oven-dried [at 800°C] samples, respectively. The Mazafati variety had a higher content of phenolic compounds [780 mg galic acid/100 g dry weight] and a higher antioxidant activity [35% radical scavenging DPPH] than the Kaluteh variety [720 mg galic acid/100 g dry weight and 28% radical scavenging DPPH, respectively]. Keeping date fruits at a constant temperature for a long period also led to decreases in the phenolic-compounds content. Drying process results in decreases in phenolic compounds and antioxidant activity of dates; the higher the drying temperature, the higher in losses in phenolic compounds and antioxidant activity