Effects Of Fermentation On Antioxidant And Metabolism Of Nitrite In Edible Legume By Two Kinds Of Bacteria

Polyphenols are the main active ingredients of legumes and are of great significance for the antioxidant function of legumes.Nitrite is the main food safety harmful component of legumes,and the study of nitrite is of great significance to the safe food consumption of legumes.In this paper,two common bacteria,Bacillus subtilis ATCC 6051 and Lactobacillus casei NRRL B-441,were used to ferment mung bean,red bean,cowpea,broad bean,kidney bean,soybean,pea and lentil,respectively,and the changes of phenolic components and antioxidant and bacteriostatic activities of phenolic substances were compared and analyzed.At the same time,the changes of nitrite and nitrate metabolism of legumes in the fermentation process of two bacterial fermentation processes were studied.The conclusion of this article is as follows:1.The total phenolic contents of mung bean,red bean,broad bean,kidney beans,soybean,pea and lentil fermented by Bacillus subtilis ATCC 6051 increased by 172.90%,24.19%,123.78%,57.89%,225.32%,343.17%and 300.00%,respectively,and the total flavonoid content of fermented red beans,cowpeas,kidney beans and soybeans decreased.The content of 19 phenolic compounds in 8 legumes before and after fermentation was analyzed,and it was found that fermentation could affect the content of phenylalanine,catechin,epicatechin,salicylic acid and sinapic acid.The DPPH radical scavenging activity,ABTS~+radical scavenging activity and iron ion reduction ability of fermented mung bean,soybean,pea and lentil phenol extracts were improved.Total phenolic content was significantly correlated with DPPH radical scavenging activity,ABTS~+radical scavenging activity and iron ion reduction capacity(P<0.01),catechins,salicylic acid and sinapic acid are strongly correlated with DPPH,and epicatechin was significantly correlated with DPPH(P<0.05).Bacillus subtilis ATCC6051 fermentation can enhance the inhibitory effect of mung bean,red bean,cowpea,broad bean,kidney bean,pea and lentil phenol extracts on Escherichia coli and Staphylococcus aureus,but has no inhibitory effect on Candida albicans.The experimental results showed that mung bean,soybean,pea and lentil were ideal legumes with high antioxidant activity prepared by Bacillus subtilis ATCC 6051 fermentation,which was suitable for the development of functional foods fermented by Bacillus subtilis ATCC 6051.2.The total phenolic content of cowpea before fermentation of Lactobacillus casei NRRL B-441was the highest,which was 5.53±0.18 mg GAE/g DW.Red beans had the highest total flavonoid content of 11.55±0.16 mg RE/g DW.After fermentation,the contents of total phenols and total flavonoids in mung beans increased the most,which were 182.35%and27.84%,respectively.The total phenol content of cowpea and the total flavonoid content of kidney bean decreased the most,by 43.40%and 82.13%,respectively.After fermentation,the DPPH radical scavenging activity of pea phenol extract increased the most,and the kidney bean decreased the most.The scavenging activity of mung bean phenol extract ABTS~+increased the most,and the kidney bean decreased the most.The iron ion reduction capacity of pea phenol extract increased the most,and the decrease of kidney bean was the most significant.The correlation analysis results showed that the contents of total phenols and total flavonoids were significantly correlated with antioxidant activity(P<0.01).Lactobacillus casei NRRL B-441 fermentation increased the inhibitory effect of mung bean,red bean and broad bean phenol extracts on Escherichia coli,but had no inhibitory effect on Staphylococcus aureus and Candida albicans.The experimental results showed that the fermentation of Lactobacillus casei NRRL B-441 could significantly improve the antioxidant activity of mung bean,broad bean,soybean,pea and lentil,and improve their nutritional quality.3.Both Lactobacillus casei NRRL B-441and Bacillus subtilis have nitrite reductase activity.The nitrite content of fermented legumes of Lactobacillus casei NRRL B-441 reached the highest value on the second day,and the highest value of nitrite content of Bacillus subtilis ATCC 6051 fermented beans appeared at different times.The nitrite content of beans in both fermentation processes was lower than the maximum residue of 20 mg/kg specified in the national standard.Lactobacillus casei NRRL B-441 and Bacillus subtilis ATCC 6051 are ideal strains for fermentation to prepare different soy products,and nitrite food safety control is good.By discussing the effect of two different microbial fermentation on the biotransformation of phenols and nitrite in eight kinds of edible beans,the theoretical basis was provided for the development of different functional foods rich in polyphenols and fermented beans with low nitrite content.