黑苦荞固态发酵富集总酚、总黄酮工艺优化及其抗氧化活性研究

Optimization of total phenolics and total flavonoids enrichment process of black Tartary buckwheat by solid-state fermentation and its antioxidant activity

探究固态发酵促进黑苦荞生物活性成分多酚和黄酮的高效释放,并提高其抗氧化活性。以总酚、总黄酮含量为评价指标,先筛选发酵菌种,然后以发酵时间、装料量、接种量为变量,采用单因素和响应面试验对黑苦荞固态发酵工艺进行优化,分析在最优菌种及最佳发酵条件下固态发酵对黑苦荞营养成分及体外抗氧化活性的影响。结果表明:最优发酵菌种为米曲霉,固态发酵黑苦荞最佳工艺条件为接种量11.0 mL/100 g、装料量28.6 g、发酵时间3.6 d,在此条件下,总酚和总黄酮含量最高,为(27.00±0.43)mg/g和(2.50±0.02)mg/g,分别是空白组、对照组的2.61、2.72倍和2.02、2.16倍,淀粉含量显著降低,蛋白质、脂肪和灰分含量显著升高(P<0.05);发酵黑苦荞多酚清除DPPH和ABTS自由基的IC50((33.08±2.21)μg/mL、(16.41±2.21)μg/mL)显著低于发酵前((50.67±3.13)μg/mL、(28.07±3.42)μg/mL),总抗氧化和总还原能力显著提高(P<0.05)。固态发酵可以显著提高黑苦荞总酚、总黄酮含量和抗氧化活性,为开发黑苦荞功能性食品提供理论依据。

Tartary buckwheat contains abundant polyphenols and flavonoids,which had antioxidant,liver protecting,anti-inflammatory,antitumor,antihypertensive effect and so on.However,the release of func-tional polyphenols in Tartary buckwheat products is difficult.Solid-state fermentation technology was an economically and environmentally friendly production technology,and had become a powerful tool for the release of phenolic substances in grains.During the fermentation process,microorganisms produced hydro-lyzing enzymes such as amylase,pectinase,xylanase and cellulase.Under the action of these hydrolyzing enzymes,the plant cell wall was destroyed,resulting in the release of bound polyphenols,which signifi-cantly increased their content and antioxidant capacity.This study selected black Tartary buckwheat as raw material,and conducted solid-state fermentation with total phenolic and total flavonoid content as evaluation index.Firstly,optimal fermentation strains were screened.Then,the optimization range of fermentation parameters such as inoculation amount,loading amount and fermentation time was determined by single fac-tor experiment,and the optimal fermentation conditions were determined by response surface experiment(three factors and three levels).Finally,the effects of solid-state fermentation on the nutritional composi-tion and in vitro antioxidant activity of black Tartary buckwheat fermented by the optimal strains under opti-mal fermentation conditions were analyzed.The results showed that the optimal fermentation strain was Aspergillus oryzae,and the optimal fermentation conditions were:inoculation amount of 11.0 mL/100 g,loading amount of 28.6 g and fermentation time of 3.6 d.Under these conditions,the content of total phe-nolics and total flavonoids was the highest,(27.00±0.43)mg/g and(2.50±0.02)mg/g,respectively.The content of total phenols and flavonoids was 2.61,2.72 and 2.02,2.16 times higher than that of the blank group and the control group,respectively.The loading amount and fermentation time had significant effects on the content of total phenolics and total flavonoids,and the interaction of loading amount and fer-mentation time had extremely significant effects on the content of total phenolics(P<0.01).The results of nutrient composition showed that the content of starch was significantly decreased,and the content of pro-tein,fat and ash was significantly increased(P<0.05).The in vitro antioxidant results showed that the IC50 of DPPH and ABTS scavenging by fermented black Tartary buckwheat polyphenols((33.08±2.21)μg/mL,(16.41±2.21)μg/mL)were significantly lower than those before fermentation((50.67±3.13)μg/mL,(28.07±3.42)μg/mL).The total antioxidant capacity and total reduction capacity were signifi-cantly increased(P<0.05).In conclusion,solid-state fermentation significantly improved the content of total phenolics and flavonoids and antioxidant activities of black Tartary buckwheat,providing a theoretical basis for the development of Tartary buckwheat functional foods.