Studies on the development and function of fermented tea product obtained by the tea-rolling processing of third crop green tea leaves and unripe satsuma mandarin fruits

In this study, the author developed of the new fermented tea by tea-rolling processing of third crop green tea (Camellia sinensis) leaves and unripe satsuma mandarin (Citrus unshiu) fruits which are not effectively utilized, evaluated flavor properties of the tea and production condition to raise an oxidation rate of catechin, and investigated the effects of feeding the tea extract on lipid metabolism in rats. The taste of third crop green tea leaves harvested in the summer season is inferior to first crop green tea leaves; thus they are not effectively utilized and in part discarded. In addition, large amounts of unripe satsuma mandarin fruits are thinned out to improve the quality of the remaining fruits and are discarded as waste. The author developed a fermented tea made from third crop green tea leaves and unripe satsuma mandarin fruits by using a green tea processing machine. Kneading of third crop green tea leaves and unripe satsuma mandarin fruits increased solubility of hesperidin to water, hot water and ethanol. Under the condition where green tea leaves and unripe fruits were mixed at the ratio of 3 to 1 and kneaded with a tea roller for 20 min, the elution rate of hesperidin was the highest. This fermented tea contained narirutin, hesperidin, catechins and black tea polyphenols. The elution rate of hesperidin to water was increased by adding black tea extract fraction composed primarily of epigallocatechin-gallate and black tea polyphenols. To clarify the flavor characteristic of the fermented tea by mixed kneading of the third crop of green leaves and unripe satsuma mandarin fruits, the author measured aroma/taste components in the tea. The hot water extract of the tea was less reddish orange color than that of black tea. Aroma of the fermented tea consisted of d-limonene and ocimene isomer derived from unripe satsuma mandarin fruits mainly, and 2-hexenal and linalool produced mainly by fermentation of the green tea leaves, providing fruity fragrance and sweet scent like black tea. The amount of d-limonene and ocimene isomer were higher in this tea than in black tea. The estimated astringent intensity of the tea by taste sensor system was lower than that of black tea, and the estimated acid taste intensity was higher than that of black tea. In taste sensory test, astringent of this tea was to some degree weak. Thus, it was suggested that this tea made from third crop green tea and unripe satsuma mandarin fruits is a new type of fermented tea. The author tried to the improvement of the manufacturing method of this fermented tea. The third crop green tea leaves were withered by blowing air (75degC) for 20minutes in a primary tea-rolling dryer. Then, withered tea leaves were mixed with unripe satsuma mandarin fruits which were sliced finely by slice machine and kneaded with a tea roller. The amount of the catechins in the green tea leaves were decreased by this process, and found that the hot-water extract of mixed tea leaves had a good taste, an aroma and a bright red color. The author established the production method of new fermented tea by mixed kneading of third crop of green tea leaves and unripe satsuma mandarin fruits using a primary tea rolling dryer, slice machine and tea roller. Thus, the good quality of fermented tea was manufactured because it may have superior flavor to green tea. Hesperidin, catechins and black tea polyphenols have been recognized as important components that induce physiological activities. To elucidate the function of a new fermented tea produced by mixing third crop green tea leaves and unripe satsuma mandarin fruits, the author investigated the effects of feeding the tea extract on lipid metabolism in rats. When rats were fed diets supplemented with the tea extract at a level of 0.50% or 0.75% for 4 weeks, hepatic triglyceride concentration was reduced in a dose-dependent manner, and the reduction was significant in rats fed diet composed of 0.75% tea extract compared to those fed the control diet. This effect tended to be more potent than that of unripe mandarin fruits or green tea alone. The fermented tea diet reduced hepatic fatty acid synthase activity in a dose-dependent manner, although not significant. The hepatic cholesterol concentrations decreased in a dose-dependent manner with the fermented tea diet for 2 weeks or 4 weeks. The fermented tea inhibited pancreatic lipase activity in vitro. These results suggest that the tea produced by mixing third crop green tea leaves and unripe satsuma mandarin fruits induces a hypolipidemic property through suppression of hepatic lipogenesis and inhibition of intestinal fat absorption. New fermented tea made from unripe satsuma mandarin fruits and third crop green tea leaves may serve as the new functional food material.