蒸煮对红小豆及其汤汁抗氧化特性的影响

Effect of cooking on antioxidant activity of adzuki beans and its soup

为保证蒸煮后红小豆及其汤汁抗氧化成分含量,研究选择不同粒形、大小和色泽的3个代表性红小豆品种（系）龙引09-05、中红7号和宝清红,对其蒸煮过程中汤汁p H、色值以及汤汁和豆粒总抗氧化能力、DPPH清除率及总酚含量变化进行跟踪监测,随着蒸煮时间延长,不同品种红小豆汤汁p H均由接近中性（p H 6.8）快速降低至弱酸性（p H 6.1）并保持稳定,汤汁亮度逐渐降低,彩度先增加后稳定在一定水平。品种间汤汁和豆粒总抗氧化能力、DPPH清除率及总酚含量差异均极显著（P〈0.01）。蒸煮过程中,各指标在变化趋势上具有较高一致性,即随着蒸煮时间延长,红小豆汤汁和豆粒总抗氧化能力均由相对最高值明显下降（P〈0.01）,20 min后基本保持稳定（P〉0.05）;在煮沸30 min内蒸煮时间对汤汁DPPH清除率影响显著（P〈0.05）;在煮沸10~50 min各样品豆粒DPPH清除率呈上升趋势,蒸煮时间对豆粒DPPH清除率影响极显著（P〈0.01）,清除率最终稳定在较高水平;汤汁总酚含量先逐渐增大,后呈小幅上下波动,最终稳定在较高水平,蒸煮时间对汤汁和豆粒总酚含量影响均极显著（P〈0.01）;3个红小豆品种（系）以宝清红抗氧化能力和清除自由基能力最强。对各指标间相关性进行分析。结果表明,汤汁的总酚含量与色值具有较大相关性,其中彩度C＊值与总酚含量相关性可高达0.97,具有通过红小豆汤汁彩度值快速预测其总酚含量的可行性,而蒸煮红小豆豆粒中酚类物质含量与其抗氧化能力或者清除DPPH能力无明显相关性。

Antioxidant properties of cooked adzuki beans and soup in terms of p H, color, total antioxidant activity, DPPH scavenging rate, total phenol content were investigated during cooking to ensure its antioxidant ingredients. Three adzuki bean varieties（strains） with different kernel shape, size and color named Longyin 09-05, Zhonghong No.7 and Baoqinghong were selected as materials. p H of all adzuki bean varieties rapidly decreased from nearly neutral p H（p H 6.8） to slightly acidic（p H 6.1） and then kept stable with the cooking time. Brightness gradually decreased while chroma increased firstly and then stabilized at a certain level. Very significant differences（P0.01）were found among the total antioxidant capacity, DPPH scavenging rate and total phenol content of varieties of adzuki beans and soup. The change trends of these properties had high consistency during cooking process, and the bean and soup＇s total antioxidant capacity decreased gradually（P0.01）from the relatively high level, and then remained stable（P0.05）in 20 min.Soup＇s DPPH scavenging rate tended to the declining trends in 30 min, and the difference was significant（P0.05）. The beans＇ DPPH scavenging rates rose slowly with fluctuations from 10 to 50 min（P0.01）, the final scavenging rates were stable at a high level, total phenol content in soup increased gradually at first 30 min, and then had the slight fluctuations till to a high level. The difference of total phenol content on cooking time was very significant in both beans and soup. Among three varieties（strains）, Baoqinghong bean had the highest antioxidant capacity and free radical scavenging ability. The correlations among various indices were analyzed. The results showed that the total phenol content of soup had a significant correlation with the color value, especially the correlation between value of Chroma C＊ and the total phenol content reached0.97. This result suggested that it was feasible to rapidly estimate the total phenolic content of adzuki soup based on the Chroma values. And the content of polyphenols in cooked adzuki bean had no significant correlation with its antioxidant capacity or its ability to scavenge DPPH.