Effects of pectin amounts added and drying temperatures on antioxidant properties of mulberry fruit leather

Abstract

This study was conducted to investigate effects of various pectin amounts added (0, 0.5, 1, 1.5 and 2%) and drying temperatures (40, 50, 60, 70, 80, 90 and 1000C) on antioxidant properties of mulberry fruit leathers. Determination of total phenolic content (TPC), total anthocyanin content (TAC), antioxidant capacities (AC), L-ascorbic acid content (L-AA), total soluble solids (TSS) and titratable acidity (TA) of the leathers were carried out. By increasing of drying temperature, there were significant changes (p < 0.05) in values of TPC (from 1213 to 886 mg GAE/100 g DW) and AC (485 to 205 mM TE/100 g DW). TAC was also degraded (from 1014 to 378 mg cy-3-glc/100 g DW), led to a decrease in their AC (414 to 168 mM TE/100 g DW). Similarly trends occurred for TA (1.8 to 1.3%) and L-AA (11.4 to 1.1 mg/100 g DW) and TSS (57.5 to 53.3oBrix). Adding different pectin amounts also resulted in changes of these properties. Generally, increasing pectin concentration increased TSS and TA whereas TPC, TAC, AC and L-AA decreased significantly. In order to maintain the high antioxidant properties for mulberry fruit leathers, it is suggested from the current work that drying temperature should be set from 40 to 50oC with 0 – 0.5% of pectin added. Keywords: Mulberry fruit leather, Drying temperature, Antioxidant capacities, L-ascorbic acid, Pectin amounts, Total anthocyanin contents, Total phenolic contents, Sensory evaluation.