Physicochemical Compositions, Antioxidant Activity, and Sensory Acceptance of Oak Acorn Extracts with Different Air-Roasting Levels

摘要

This study investigated the changes in the compositions and antioxidant activity of hot-water extracts of oak acorns (Quercus acutissima) air-roasted under the following conditions: AR1 (207°C, 60 s), AR2 (214°C, 90 s), AR3 (221°C, 165 s) and AR4 (230°C, 220 s). The sensory intensity and preference for air-roasted acorn tea were also compared with those of commercial acorn tea. As the air-roasting temperature and time increased, the water content of the acorns decreased, the carbohydrate, proteinand total sugar contents increased and the pH decreased. Among the various air-roasting conditions, AR1 showed the highest levels of total polyphenol and tannins (142.02±2.06 mg gallic acid equivalent/g and 5.04±0.04 mg tannic acid equivalent/g, respectively). The l,l-diphenyl-2-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity of AR1 (100 ug/mL) were highest (88.86% and 99.23%, respectively). Moreover, there was higher sensory preference for ARl-tea, and it had lower astringency, higher sweetness and more savory taste than commercial acorn tea. In conclusion, among the various air-roasting conditions, the low-intensity air-roasting of acorns led to higher antioxidant contents and activities and greater sensory acceptance. It is expected that appropriate air-roasting treatments will enhance the utilization of oak acorns as bio-food material.