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采用高效液相色谱法(HPLC)分析绿茶水浸出物及单宁酶水解物中儿茶素成分的变化,通过DPPH、ABTS自由基和·OH清除率试验测定抗氧化活性,以透光率为指标评价澄清度,探讨单宁酶对绿茶儿茶素的转化作用及对其抗氧化活性和澄清度的影响。试验结果表明,在绿茶水浸出物中添加单宁酶,可有效分解其酯型儿茶素(EGCG,GCG,ECG),从而增加非酯型儿茶素(EGC,GC,EC)和没食子酸(GA)的含量。经单宁酶处理后,绿茶水浸出物对DPPH、ABTS自由基和·OH的清除能力均有所增强,其IC50分别降低了23.8%,17.5%和59.2%。此外,经单宁酶酶解处理后的茶水浸出物的储存稳定性和澄清度显著提高。单宁酶可高效水解绿茶水浸出物中酯型儿茶素,从而提高绿茶的抗氧化活性以及茶汤的澄清度和稳定性。
The changes of catechins in green tea extract and tannase hydrolyzate were analyzed by high performance liquid chromatography (HPLC). The antioxidant activity was determined by DPPH, ABTS free radical and · OH scavenging assay. Indicators to evaluate the degree of clarification, to explore tannase on green tea catechins transformation and its antioxidant activity and clarity. The results showed that addition of tannase to green tea extract could effectively decompose its ester-type catechins (EGCG, GCG and ECG) and increase non-esterified catechins (EGC, GC and EC) and gallic acid (GA) content. After tannase treatment, the scavenging capacity of DPPH, ABTS free radicals and · OH were enhanced, and the IC50 of green tea extract was reduced by 23.8%, 17.5% and 59.2%, respectively. In addition, the tea extract after tannase enzymatic hydrolysis storage stability and clarity improved significantly. Tannase can efficiently hydrolyze ester-type catechins in green tea water extracts, thereby improving the antioxidant activity of green tea and the clarity and stability of tea.