Effects Of Lactic Acid Bacteria Fermentation On Nutrient Composition,Polyphenol Composition And Activity Of Bean Milk

As the main edible beans in China,soy,peanuts and chickpeas not only have rich nutritional value,but also contain many active ingredients which are beneficial to human health.Among them,legume polyphenols have a variety of biological activities,such as antidiabetes,anti-cancer,anti-inflammation and alleviating cardiovascular diseases.The use of microbial fermentation technology to biotransform the nutrients and active components of bean milk can greatly improve the nutritional added value and physiological efficacy of bean milk.This project aims to screen out high-quality lactic acid bacteria with independent intellectual property rights,apply them to ferment soy milk,peanut milk and chickpea milk,study the effect of lactic acid bacteria fermentation on the nutritional composition and functional characteristics of bean milk,and analyze the effects of lactic acid bacteria fermentation on the morphology,composition,antioxidant activity and digestive characteristics of polyphenols in different bean milk,so as to provide a theoretical basis for the development of fermented bean milk products with high nutritional added value and excellent biological activity.In this paper,five lactic acid bacteria(Lactobacillus plantarum Q2.3,L.fermentum LF3.2,L.pentosus Q1.4,L.plantarum G1.4,L.plantarum G1.4,L.plantarum G1.3)were preliminarily screened from 23 traditional fermented foods and healthy human intestines.They were used as fermenting agents for soy milk,peanut milk and chickpea milk.And their acid production capacity and proliferation capacity in bean milk were measured.L.fermentum LF3.2 and L.plantarum G1.3 with the highest acid production and proliferation capacity were selected for subsequent bean milk fermentation experiments.L.fermentum LF3.2 and L.plantarum G1.3 were used to ferment soy milk,peanut milk and chickpea milk,respectively.After fermentation,the soluble protein and sugar contents of the three bean milk species decreased significantly,while the contents of active ingredients such as peptides,free amino acids and free fatty acids increased significantly.In addition,the types and amounts of alcohols,phenolketones and total flavor substances in the three kinds of fermented bean milk increased significantly,while the aldehydes reduced.The changes of these flavor substances could diminish the beany flavor and enhanced aroma of bean milk.In addition,the fermentation of both lactic acid bacteria increased the antioxidant activity and the inhibition of α-amylase and α-glucosidase of the three bean milk species.The morphology,content,composition and antioxidant activity of phenolic substances of soy milk,peanut milk and chickpea milk before and after fermentation were compared.It was found that the fermentation of both lactic acid bacteria could significantly increase the total phenol/flavonoid content in bean milk.Among them,the content of free phenol/flavonoid,insoluble ester phenol/flavonoid and insoluble glycosides phenol/flavonoid increased,and the content of soluble ester phenol/flavonoid and soluble glycosides phenol/flavonoid decreased.Similarly,fermentation increased the antioxidant activity of free phenol,insoluble ester phenol and insoluble glycoside phenol in the three bean milk species,and reduced the antioxidant activity of soluble ester phenol and soluble glycoside phenol.The increase in antioxidant activity of free phenol in fermented bean milk may be related to the increase in the content of monomeric phenol such as gallic acid,chlorogenic acid,p-coumaric acid and ferulic acid.The increase in insoluble ester gallic acid content after fermentation was the main reason for the enhanced antioxidant activity of insoluble ester phenol in fermented soy milk and fermented chickpea milk,while the increase in p-coumaric acid content was the reason affecting the enhanced antioxidant activity of insoluble ester phenol in fermented peanut milk.In addition,lactic acid bacterial fermentation altered the digestive properties of polyphenol in bean milk.Compared with unfermented bean milk,the soluble and insoluble polyphenols in fermented bean milk were released more easily through simulated gastroenteric fluid digestion,and the antioxidant activity was improved.This indicated that the fermentation of L.fermentum LF3.2 and L.plantarum G1.3 could improve the bioavailability of polyphenol in the three bean milk species.In conclusion,L.fermentum LF3.2 and L.plantarum G1.3 were screened as suitable strains for fermenting soy milk,peanut milk and chickpea milk.Lactic acid bacteria fermentation can improve the nutritional value,antioxidant and hypoglycemic activity of bean milk,change the form,content and composition of polyphenol in bean milk,and improve the bioavailability of phenolic in gastrointestinal fluid.