苦荞对发酵豆乳纳豆激酶活力、风味及抗氧化活性影响

相较于纳豆，以纳豆芽孢杆菌发酵获得的发酵豆乳食用更方便，但同样存在纳豆激酶活性低、风味不良等缺点。作者首先研究了苦荞、糙米、薏米、藜麦、燕麦粉对纳豆芽孢杆菌产纳豆激酶能力的影响。结果表明，添加苦荞的效果最好，当添加质量分数为3%时，纳豆芽孢杆菌液体发酵的酶活力由原来的5 803.12 U/mL提高到23 326.23 U/mL；然后研究了苦荞粉对纳豆芽孢杆菌发酵豆乳的纳豆激酶活力、风味及抗氧化活性的影响。结果显示，当添加的苦荞质量为大豆质量的50%时，发酵豆乳的纳豆激酶活力、挥发性盐基氮质量浓度和总抗氧化能力分别为 4 460.28 U/mL、3.45 mg/dL和16.34 mmol/L，分别为纯大豆发酵所得豆乳的161.42%、79.84%和196.39%。添加苦荞能够明显提高发酵豆乳中纳豆激酶活力，并且改善风味和抗氧化活性。该研究可为开发富含纳豆激酶、食用方便的纳豆食品提供借鉴。

Effects of Tartary Buckwheat on Nattokinase Activity, Flavor and Antioxidant Activity of Fermented Soybean Milk

Compared to natto, the fermented soybean milk produced by Bacillus natto fermentation is convenient to consume. However, it suffers from disadvantages such as low nattokinase activity and poor flavor. In this study, we first investigated the effect of adding different grains (tartary buckwheat, brown rice, coix seed, quinoa, oat flour) to enhance the ability of Bacillus natto to produce nattokinase. Results showed that tartary buckwheat was the most effective additive, increasing liquid enzyme activity from 5 803.12 U/mL to 23 326.23 U/mL when added at a 3% mass fraction. Then we evaluated the effects of tartary buckwheat powder on nattokinase activity, flavor and antioxidant activity of fermented soybean milk by Bacillus natto. Results showed that when the amount of tartary buckwheat was added at 50% mass of soybeans, the nattokinase activity, volatile base nitrogen mass concentration and total antioxidant capacity of the fermented soybean milk were 4 460.28 U/mL, 3.45 mg/dL and 16.34 mmol/L, respectively, and accounting for 161.42%, 79.84% and 196.39% of fermented soybean milk from pure soybean fermentation, respectively. Addition of tartary buckwheat significantly enhanced nattokinase activity, improved flavor, and increased antioxidant capacity of fermented soybean milk. This research provides valuable references for the development of nattokinase-enriched and convenient-to-consume natto products.