预浸泡对桃金娘果汁中抗氧化物质和抗氧化活性的影响

本研究将桃金娘整果分别浸泡在不同温度的水、盐酸、柠檬酸、抗坏血酸和亚硫酸氢钠溶液中10、20、30 min,分析不同处理对桃金娘果汁中总多酚、总花青素、总黄酮和抗氧化活性的影响。结果表明,在40⁶0℃水中浸泡,桃金娘果汁中总多酚、总花青素、总黄酮含量和抗氧化活性显著降低,然而在80℃热水和1%盐酸中预浸泡可保持或增加抗氧化物含量。柠檬酸、抗坏血酸或NaHSO₃溶液能降低抗氧化物质的损失程度。同时研究了桃金娘中多酚氧化酶（PPO）和过氧化酶（POD）在不同pH和温度下的稳定性。温度达到100℃、pH小于2时PPO和POD活性才被完全抑制。因此不同的预浸泡方式影响桃金娘果汁PPO和POD的酶活,而抗氧化物质和抗氧化活性的稳定性与PPO和POD的活性负相关。 

Effect of pre-soaking on the antioxidant compounds and antioxidant activity of Hill Gooseberry( R.Tomentosa) juice

In this study,whole hill gooseberries were soaked in different temperature water,HCl,citric acid/ascorbic acid and NaHSO_3 solution for 10,20,30min,respectively.The effect of different soaking methods on total phenolics,total anthocyanins,total flavonoids and antioxidant activity of hill gooseberry(R. Tomentosa) juice were analyzed. Results showed that soaking in water at 40~60 ℃ caused significant degradation of total phenolics,total anthocyanins,total flavonoids and antioxidant activity.However,soaking in 80 ℃ hot water or 1% HCl solution could preserve or increase the antioxidant compounds.Soaking in citric acid / ascorbic acid or Na HSO3 solution could minimize the loss of antioxidant compounds.In addition,the stability of polyphenol oxidase( PPO) and peroxidase( POD) from hill gooseberries were studied under different p H and temperature. PPO and POD were inhibited completely until the temperature reached 100 ℃ or pH<2. Therefore pre-soaking method affects enzymatic activity of PPO and POD.The stability of antioxidant compounds and antioxidant activity is negatively correlated with PPO and POD enzymatic activity.