Effects of Exudation Method on Antioxidative Component Content of Persimmon Leaf Tea and Stability of Its Decoction

Abstract

　We examined the effect of the exudation method on the levels of ascorbic acid, astragalin, and total polyphenols of persimmon leaf tea, and on the stability of these components in decoction. We found the optimum exudation method for obtaining high levels of these components differed depending on the component. The study revealed that the optimum exudation method for maintaining a high level of ascorbic acid was either exuding the persimmon leaf tea in 5℃ tap water for 10～60 minutes or in 60～100℃ tap water for over 3 minutes. The optimum storage temperature for maintaining a high ascorbic acid content in the decoction was 5℃. The rates of exudation of astragalin and total polyphenols were increased by a high pressure treatment. Though the thermostability of ascorbic acid in the decoction was low, that of both astragalin and soluble polyphenol was excellent. Even when the decoction was preserved at 90℃ for 24 hours, the astragalin content decreased by only about 10% and the total polyphenol content did not decrease significantly.