Effects of extraction conditions on color quality and antioxidant properties of persimmon (Diospyros kaki Thunb.) leaf tea

Abstract

This study was carried out to investigate the effect of the extraction conditions for persimmon (Diospyros kaki Thunb.) leaf tea (PLT) on its color quality and antioxidant properties. The amount of persimmon leaf (PL) powder and pH influenced the PLT’s color and antioxidant capacity. As the amount of PL powder in tea increased, lightness decreased while yellowness increased. The PLT with the highest amount of PL (10 mg/mL) exhibited the highest 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity and ferric reducing antioxidant power (FRAP). In addition, the PLT with the highest PL showed the highest total polyphenol and flavonoid contents. Subsequently, PLT was prepared using 10 mg/mL PL powder under varying pH conditions. As pH increased from 4 to 7, lightness decreased while redness and yellowness increased. Antioxidant capacity was determined using 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and FRAP assay showed that lower pH exhibited higher antioxidant capacity. The PLT extracted under the lowest pH of 4 showed higher polyphenol and flavonoid contents than that extracted under higher pH conditions. Overall, PLT extraction using a solvent with pH 4.0 showed better antioxidant activities and higher amounts of polyphenolic compounds. Simultaneously, lesser lightness, redness, and yellowness were detected in PLT extracted under pH 4 conditions. In conclusion, to acquire a better functional health benefit in terms of antioxidant capacity, preparing PLT under pH 4 conditions is suggested.