摘要
This study was conducted to investigate the effects of temperature and pH on polyphenol and flavonoid contents in grape juice and its antioxidant activity. Two groups(group A and group B) were set. Group A was set with different pH values: 3.0, 3.5, 4.0, 4.5 and 5.0; and group B was set with different temperatures: 65, 72, 79, 86 and 93 ℃. The grape juice was treated according to set methods, and two groups of samples were obtained. The contents of polyphenols and flavonoids in each test solution were determined, and the DPPH·free radical system and trivalent Fe reduction system were established to measure and compare the antioxidant activity of groups A and B. The results showed that within the set ranges, the effects of pH and temperature on the content of flavonoids in grape juice were not significant; the test solution with a pH of 4.5 and the test solution with a temperature at 72 ℃ had the strongest capacities of scavenging free radicals, and exhibited scavenging rates of 6.82% and 9.43%, respectively; the test solution with a pH of 4.5 and the test solution with a temperature at 65 ℃ had the strongest capacities of reducing ferric ions. It could be seen from the above four aspects comprehensively, within the set test ranges, the suitable pH was 4.5, and the suitable temperature was 65 ℃.
This study was conducted to investigate the effects of temperature and pH on polyphenol and flavonoid contents in grape juice and its antioxidant activity. Two groups(group A and group B) were set. Group A was set with different pH values: 3.0, 3.5, 4.0, 4.5 and 5.0; and group B was set with different temperatures: 65, 72, 79, 86 and 93 ℃. The grape juice was treated according to set methods, and two groups of samples were obtained. The contents of polyphenols and flavonoids in each test solution were determined, and the DPPH·free radical system and trivalent Fe reduction system were established to measure and compare the antioxidant activity of groups A and B. The results showed that within the set ranges, the effects of pH and temperature on the content of flavonoids in grape juice were not significant; the test solution with a pH of 4.5 and the test solution with a temperature at 72 ℃ had the strongest capacities of scavenging free radicals, and exhibited scavenging rates of 6.82% and 9.43%, respectively; the test solution with a pH of 4.5 and the test solution with a temperature at 65 ℃ had the strongest capacities of reducing ferric ions. It could be seen from the above four aspects comprehensively, within the set test ranges, the suitable pH was 4.5, and the suitable temperature was 65 ℃.
基金
Supported by Shanxi Normal University Quality Engineering Project(2017YZKC-06)
