Physicochemical properties of acorn (Quercus acutissima Carr.) tea depending on steaming and hot-air drying treatments

Abstract

This study was performed to determine the effects of preconditioning process (Con, roasting; SR, steaming and roasting; HDR, hot air drying and roasting; SHDR, steaming hot air drying and roasting) and roasting on the antioxidant and physicochemical properties of acorn (Quercus species) tea. Each sample was extracted in 95°C hot water for 5 min. The color values of lightness and yellowness were the highest in HDR, and redness were the highest in the control. The total sugar content was the highest in SHDR. Total polyphenol and total flavonoid contents of HDR tea were higher than those of teas prepared by the different processes. DPPH and ABTS radical scavenging abilities of HDR were 75.66% and 98.16%, respectively, which were higher than those of other teas. In the sensory evaluation, HDR tea was ranked significantly higher than other teas in terms of flavor, taste and overall acceptability. Finally, acorn tea treated with drying was superior to other treatments in antioxidant and quality properties. The result suggests that HDR can be applied to acorn tea to achieve better quality and functionality.