干燥方式对无核紫葡萄品质及抗氧化活性的影响

采用自然晒干、热风干燥、荫干和真空冷冻干燥4种常见方法对新鲜无核紫葡萄进行干燥,测定葡萄干的总糖、还原糖、果糖、葡萄糖、总酸、V_C、总酚、总黄酮、总黄烷醇、花青素以及感官指标、抗氧化能力。结果表明:不同干燥方式的无核紫葡萄干品质及抗氧化性差异明显。其中真空冷冻干燥和热风干燥速率最快,分别为3.5,3.0d;荫干速率最慢,为35d。真空冷冻干燥的无核紫葡萄干的总酸、V_C、总酚、总黄酮、总黄烷醇、花青素含量被最大程度保留,分别为34.6%、6.34mg/100g、8.28mg/100g、71.5mg/100g、182.3mg/100g、3.61mg/100g。真空冷冻干燥抗氧化能力强。相关性分析表明酚类物质含量与抗氧化能力有一定的关系。综合分析,真空冷冻干燥适合用于无核紫葡萄的干燥,能较好地保留其营养成分及抗氧化物质含量,抗氧化性强,可作为无核紫葡萄适宜的干燥方法。

Effects of different drying methods on the quality and antioxidant activity of seedless purple grape

The effects of different drying methods on the quality and antioxidant properties of seedless purple grapes were investigated in this study. Four different drying techniques including natural drying, hot-air drying, drying in the shade and vacuum freeze drying was used to dry fresh seedless purple grapes. Moreover, the total sugar, reducing sugar, fructose glucose, total acid, vitamin C, total phenol, total phenolics, total flavonoid, total flavanols, anthocyanins and sensory indicators, antioxidant capacity were detected, in order to compare the effects of different drying methods. The results showed that different drying methods obviously influenced the quality and antioxidant properties of the seedless purple grapes. The time of vacuum freeze drying and hot-air drying were found to be the shortest, 3.5 days and 3 days respectively. Drying in the shade needed the longest time, lasting for 35 days. The total sugar content, total acid content, total phenolic, total flavonoids, total flavanols and anthocyanins of vacuum freeze drying were significantly higher than those of other drying methods, and the antioxidant capacity was also strongest. The correlation analysis showed that the content of phenols was related to the antioxidant capacity. In combination, vacuum freeze-drying was suitable for the drying of non-nuclear purple grapes, and could retain its nutritional and antioxidant content, and the strong antioxidant activity better. Therefore, it could be used as a suitable drying method of purple grapes.