Stability Of Anthocyanin, Clarification And Antioxidant Activity Of Yangmei Juice

Yangmei(Myrica rubra Sieb.et Zucc) is a specific fruit species in China. Because yangmei is rich in anthocyanin, decoloration and precipitation of yangmei juice occurs rapidly during process and storage, which limits its shelf life. Therefore, increasing the stability of anthocyanin, clarifying and preventing precipitation become key problems in the production of yangmei juice. Effects of ascorbic acid, sugar and quercetin on stability of yangmei juice and the dissolved anthocyanin from yangmei, effects of the concentration of tannin and gelatin and ultra-filtration on the clarity and the other physico-chemical index of yangmei juice, the regularity of precipitation of yangmei juice and the main constituent of precipitants from three kinds of yangmei juice and the antioxidant activity of yangmei juice produced with four varieties of yangmei were studied in this dissertation. The results were as follows:Ascorbic acid decreased the stability of color of the anthocyanin solution and yangmei juice. The higher the concentration of ascorbic acid was, the more rapid the degradation of anthocyanin would be. When the anthocyanin solution contained 50mg and 100mg ascorbic acid /L, the concentration of anthocyanin were 70.7% and 43.1% and the corresponding value of Hunter A were 76.2% and 48.8% that for the control after heating for 5h at 70℃, respectively. When yangmei juice contained 50mg and 100mg ascorbic acid /L, the concentration of anthocyanin were 78.8% and 53.0% and the corresponding value of Hunter a were 63.1% and 42.4% that for the control after heating for 5h at 70℃, and the concentration of anthocyanin were 61.6% and 37.3% and the corresponding value of Hunter a were 73.8% and 49.2% that for the control after storage for 6 months at 20℃, respectively.Glucose, fructose and sucrose have different effect on the stability of anthocyanin from yangmei. When the concentration of glucose, fructose and sucrose were 10%, the concentration of anthocyanin in the dissolved anthocyanin from yangmei were 94.7%,51.0% and 64.1% and the corresponding value of Hunter a were 96.3%, 56.9% and 60.4% that for the control after heating for 10h at 80℃, respectively. Although the concentration of glucose, fructose and sucrose had no significant effect on the stability of anthocyanin from yangmei, but the degradation of anthocyanin from yangmei decreaced with increase of the concentration of sugar.Quercetin could increase the stability of the color of yangmei juice significantly. When yangmei juice contained 25mg quercetin /L, its concentration of anthocyanin was 22.32mg/L and the corresponding value of Hunter a was 32.32, but the concentration of anthocyanin in the control yangmei juice was 14.12mg/L and the corresponding value of Hunter a was 20.12 after storage for 6 months at 20℃.