关键词: 荔枝, 果皮褐变, 花色素苷, pH 值, 温度

Abstract: Anthocyanin in pericarp of litchi fruits (Litchi chinensis Sonn. cv. Huizhi ) was
isolated to study its color and stability at different pH and temperatures. The color of the anthocyanin was changed after dilution in different pH buffers , its color was red at pH1. 47 , orange at pH 3. 30 , colorless at pH 4. 69 and brown at pH 7. 01. At pH 4. 69 , it could return red when acid was added ,
but at pH 7. 01 it could not . The absorption value of anthocyanin at 510 nm decreased as the pH rose and at pH 7. 01 the absorption peak shifted from 510 nm to 498 nm , which was consistent with the color of the anthocyanin in different pH solutions. With the pH decrease , the anthocyanin was more
stable but still showed the usual loss during storage. The color of nthocyanin extract changed into red-brown at pH 1. 47 and 3. 03 , brown at pH 4. 69 , dark brown at pH 7. 01 after storage at room temperature for 20 days. These results showed that the anthocyanin decolored , turned brown and became
unstable as pH increased. The results also showed that the anthocyanin became stable under low temperature.

Key words: Litchi, Pericarp browning, Anthocyanin, pH, Temperature