Comparison of antioxidant loss during storage of freshly-prepared and ready-to-drink green tea

Abstract

Green tea is an important source of antioxidants that can provide protection from cancer and other diseases. Unlike black and oolong, green tea processing does not involve a fermentation stage. Consequently, the antioxidant content of green tea is maintained. The antioxidants in green tea are polyphenols such as catechin, epicatechin, and related compounds. The most important antioxidant in green tea is epigallocatechin gallate (EGCG). Antioxidants are readily degraded by light, heat, and oxygen. Green tea popularity has resulted in a wide variety of commercial products such as bottled, flavored, deffafinated, and dehydrated teas. Bottled tea is called "ready-to-drink (RTD)," and the number of varieties of this convenient beverage is rapidly increasing. This study was carried out using high performance liquid chromatography (HPLC) to determine caffeine, EGCG, and ascorbic acid in both freshly-prepared herbal and ready-to-drink tea. Samples of either freshly-prepared or RTD products were opened and stored in a refrigerator. Caffeine proved to exhibit no loss during storage. However, ascorbic acid and EGCG were slowly degraded during storage.