本文研究了利用纳豆芽孢杆菌发酵纳豆过程中活性物质-总酚和异黄酮含量的变化，通过体外模拟消化实验，测定消化过程中总酚、异黄酮含量及抗氧化活性的变化规律。研究发现，由于发酵细菌及高温的作用，从干燥大豆到后熟24 h大豆，总酚含量提高了60.56%，异黄酮含量降低了63.30%。不同发酵阶段纳豆经过体外模拟消化处理，总酚的释放率为70.64%，异黄酮的残余率为21.79%。抗氧化活性测定采用了DPPH、ABTS和ORAC测定法。不同发酵阶段的纳豆经过体外模拟消化后，其DPPH自由基清除能力下降，ABTS和ORAC值有所提高；模拟胃消化阶段，后熟24 h大豆清除ABST自由基能力和ORAC值分别是干燥大豆的1.80和2.22倍；模拟肠消化阶段，后熟24 h大豆清除ABST自由基能力和ORAC值分别是干燥大豆的1.70和1.41倍。总体上来讲，经过发酵的纳豆抗氧化活性得到加强；在模拟消化过程中，胃消化阶段的纳豆具有更高的抗氧化活性。

Changes in the contents of active substances (including total phenols and isoflavones) during the fermentation of natto with Bacillus subtilis natto were studied. Levels of total phenols and isoflavones during the digestive process were measured in an in vitro digestion experiment, and the pattern of changes in antioxidant activity was studied. The results showed that after bacterial fermentation at high temperature, total phenolic content and isoflavone content in the after-ripening soybeans (24 h) were increased by 65.12% and decreased by 63.28%, respectively, compared with those of dry soybeans. The in vitro digestion experiments were conducted on the natto samples at different fermentation stages, and the release rate of total phenolics was 70.64% while the residual rate of isoflavones was 21.79%. Hydroxyl radical (?OH), 2,2-diphenyl-1-picrylhydrazyl (DPPH?), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) scavenging abilities and oxygen radical absorbance capacity (ORAC) were used to determine antioxidant activity. After in vitro digestion, the scavenging ability of DPPH radicals was decreased in natto at different fermentation stages, and both ABTS scavenging ability and ORAC values were elevated. During the gastric digestion simulation stage, the scavenging ability of ABST radicals and the ORAC value in the after-ripening soybeans (24 h) were 1.80 and 2.22 times those of dry beans. During the intestinal digestion simulation stage, the scavenging ability of ABST radicals and the ORAC value of the after-ripening soybeans were 1.70 and 1.41 times those of dry beans. In summary, the antioxidant activity of the natto was increased after fermentation, and the natto from the gastric digestion stage showed higher antioxidant activity during the in vitro digestion process.

学科创新平台项目（CXPT-2015-002-031）