Changes in Physicochemical Characteristics and Antioxidant Activity of Acorn (Quercus acutissima) under Different Heat Treatment Conditions

Abstract

The present study was undertaken to analyze the changes in the physicochemical characteristics and antioxidant activity in acorn (Quercus acutissima) under various temperature treatments: A (140°C), B (150°C), C (160°C), D (170°C), and E (180°C). Each treatment sample was extracted with hot water for 4 h at 60°C. The pH of all heat-treated acorn extracts was significantly lower than that of the control, unheated acorn extract, and the pH was inversely proportional to the treatment temperature (p < 0.05). The sugar content of the acorn extract was significantly higher after heat treatment than that of the control (p < 0.05); however, it was higher than the control only in the groups below 160°C. Total polyphenol content was the highest in the group treated to the lowest temperature (A: 140°C), at 31.59 ± 0.21 mg GAE/g (p < 0.05). Antioxidant activity was influenced in a dose dependent manner (p < 0.05) being 31.03-95.99% for DPPH radical scavenging activity and 20.49-99.51% for ABTS radical scavenging activity in doses of 0.12-1.00 mg/mL of heat treated acorn extract. In conclusion, heat treatment of acorn fruits increased sugar content and antioxidant content as well as activity of acorn extracts, especially under lower heat treatment conditions.