Due to the weather condition,summer tea leaves grow rapidly,The contents of amino acids and vitamins reduced, and the contents of anthocyanins, caffeine and tea polyphenols in summer tea are increased obviously, which makes the taste bitter and astringent.It is favorable for the oxidization of black tea.Because black tea is oxidized tea, polyphenolsa can be completely oxidized , so as to reduce the bitter and astringent taste and cerate a slightly sweet fragrance and strong taste.