Study On The Release Of Polyphenols From Coarse Grains By Lactobacillus Plantarum And Its Application

In recent years,with the in-depth understanding of the nutrition of coarse grain,coarse grain products have been widely concerned by consumers.Polyphenols are rich in grains,which have the functions of antioxidant,anti-cancer,bacteriostasis and prevention of cardiovascular diseases.Lactic acid bacteria are widely used in the food field as starter,which can ferment grains to promote the release of polyphenols.However,in the environment of food processing and gastrointestinal digestion,lactic acid bacteria face the stress of temperature,acid and alkali,salt and other factors,which affect the activity and performance of the strain.Exploring the influence of various stress factors on the performance of lactic acid bacteria can better guide the application of lactic acid bacteria in coarse grain fermentation.In this study,a strain of lactic acid bacteria R3 isolated from dairy products was selected as the research object,and its species and genus were identified by molecular biological identification.The survival rate was used as the index to evaluate the ability of fructose oligosaccharide,galactose oligosaccharide,yeast cell wall MP60 and soybean husk dietary fiber to improve the resistance of lactic acid bacterium R3 to stress.Four kinds of coarse grains(millet,millet,lentil and oat)were fermented by lactic acid bacteria R3 to study the effects of fermentation on the release of phenolic substances and antioxidant properties of the four grains during simulated digestion in vitro.To optimize the process of enzymoly-assisted fermentation to release the phenol of coarse grain,to prepare coarse grain noodles,and to evaluate the effect of fermented coarse grain powder on the quality of dried noodles;In vitro simulated digestion was used to evaluate the variation of polyphenol content in the different digestion stages of the noodles.The main results are as follows:1.The strain R3 was identified by molecular biological methods,and the homology between the strain R3 and Lactobacillus plantarum was 99%.The strain R3 was confirmed to be Lactobacillus plantarum by comparing with the developed tree.2.The results of single factor stress experiment showed that high concentration of NaCl,bile salt,ethanol,H₂O₂ and low pH had significant inhibitory effect on the growth of Lactobacillus plantarium R3.The stress conditions in the intervention stress experiment were selected as follows:pH3.5,1 m M H₂O₂,8%ethanol,6%NaCl and 0.6%bile salt.The results of intervention stress experiment showed that dietary fiber,fructose oligosaccharide,galactose oligosaccharide and MP60 could improve the survival rate of Lactobacillus plantarum R3 under various stress conditions.The survival rates of 2%soybean husk dietary fiber to Lactobacillus plantata R3 under acid stress,ethanol stress,oxygen stress,bile salt stress and NaCl stress were 64.89%,120.56%,108.21%,95.55%and 105.05%.3.Enzymatic hydrolyzy-assisted fermentation treatment improved the release of total phenol and total flavonoids and ABTS free radical scavenging rate of the four grains in simulated oral cavity,stomach and intestine three stages.Among them,after simulated digestion,the fermented lentil powder could release 567.68mg/100g of total phenol and531.86mg/100g of total flavonoids,which were better than the other three kinds of cereals.4.By comparing the release of total phenols and total flavonoids and ABTS free radical scavenging rate of lentil powder treated by five different fermentation processes in simulated digestion stages in vitro,the optimal fermentation conditions were obtained as follows:0.5%xylanase,1%protease and 1%?-amylase combined enzymatic hydrolysis of lentil powder for 8 h,and Lactobacillus plantularum R3 fermentation for 12 h.Under the optimal conditions,the total phenol release and total flavonoids release of fermented lentil powder were increased by 10.95%and 32.30%,respectively,and the ABTS free radical scavenging rate reached 92.52%.5.Compared with whole wheat noodles,fermented lentil noodles have the nutritional characteristics of high protein and low fat;Lentil noodles show a light yellow color,lentil aroma.When the fermented lentil powder was added at 10%,it had better palatability,higher total sensory score(85.25),lower cooking loss rate and lower breaking rate(9.22%and4.44%).When the adding amount of fermented lentil powder was more than 10%,the cooking loss rate and bar breaking rate of the noodles increased,while the water absorption rate decreased continuously.The hardness,resilience and elasticity of the noodles are reduced.After simulated digestion in vitro,the release content of polyphenols in the noodles was significantly increased,adding 10%fermented lentil powder in the simulated intestinal digestion stage of the noodles reached 141.44mg/100g,which was significantly higher than that of whole wheat noodles.The results of this research will provide data support for guiding the efficient and scientific use of rich phenolic acid resources of cereals in our country,and provide theoretical basis for the unique value of cereals in the food industry.