EFFECT OF IRRADIATION ON TOTAL PHENOL AND CATECHINS CONTENTS AND RADICAL SCAVENGING ACTIVITY OF GREEN TEA LEAF AND STEM EXTRACT

Abstract

ABSTRACT Green tea (Camellia sinensis) leaf and stem extracts, major by-products of the green tea industry, were compared in terms of biochemical quality and catechin composition after 20 kGy of irradiation. Irradiation decreased total phenolic contents of green tea leaf extracts (GLE) from 98.6 to 79.91 mg/g. However, phenolic contents of green tea stem extracts (GSE) increased from 67.83 to 71.94 mg/g after irradiation. The 50% inhibition concentration (IC50, µg/mL) of GLE and GSE against superoxide and hydroxyl radical also demonstrated that GSE showed higher activity when irradiation was applied. However, catechin and caffeine contents of both GLE and GSE decreased after irradiation at 20 kGy. Results suggest that green tea stems, major by-products of the green tea industry, can be a compatible functional material to green tea leaves for industrial use when cost-effectiveness is considered. In addition, irradiation of GSE may increase its functional activity. PRACTICAL APPLICATIONS Every year, as much as 50 tons of green tea by-products are produced in one green tea production area in Korea alone, but the value of green tea by-products is much lower (approximately 1/100) than that of green tea leaves. It must be the situation not only in Korea but also in other countries. Therefore, the development of a process utilizing green tea by-products is very valuable for the green tea industry and related fields. This report may give useful information about the use of the green tea by-products as a functional ingredient for food and cosmetic products. In addition, use of irradiation to improve the color of green tea extracts from dark to brighter and more transparent was also suggested for the manufacture of more industry-friendly natural materials with biological functions.