Screening Of Probiotics And Development Of Tartary Buckwheat Polypeptide Fermentation Paste

Yogurt is preferred by consumers for its unique flavor and health benefits.However,compared with traditional fermented dairy products,probiotics with grains as the substrate has the advantages of high dietary fiber,low fat and low cholesterol,and it is a trend to add it to functional foods.Rich in flavonoids,tartary buckwheat is an excellent source for functional foods.This study first screened probiotics that not only adapt to the human gastrointestinal tract but also was suitable for fermentation of Tartary buckwheat.Lactobacilli isolated from healthy human feces and Milk Tofu were tested and screened by tolerance to simulated gastric juice.Probiotic potential was determined based on resistance to simulated gastrointestinal juice and bile salts,antibacterial activity,and cholesterol degradation ability.Results show that 41 bacterial strains with dissolved calcium were obtained from the Lactobacillus isolation medium.Five strains with high tolerance to low pH and simulated gastric juice were selected from the screened strains and identified by 16S rRNA gene sequencing.Three strains were Lactobacillus,named as Lactobacillus plantarum(Lp MT-3),Lactobacillus plantarum(Lp MT-5)and Lactobacillus Salivarius(Ls AF-7).The tolerance of Lp MT-5 in simulated gastrointestinal juice was the strongest,which is the foundation that this microorganism could play a probiotic role.The bile salt tolerance,antibacterial activity and cholesterol-reducing abilities of Lp MT-3 and Ls AF-7 were both strong.Those three strains could be taken as the candidate strains of Tartary buckwheat fermentation paste.Second,flavorzyme from 5 kinds of proteases were selected according to differences in hydrolysis degrees to complete the hydrolysis of tartary buckwheat proteins into active peptides.The best enzyme hydrolysis condition was created by treating tartary buckwheat enzymatic solution with a-amylase to adjust pH to 6,then adding 500 U/g of flavorzyme,allowing 10 h enzyme at 48?,followed by 30 min sterilization at 121?.This paper finally studied the preparation process of Tartary buckwheat polypeptide fermentation paste.Lactobacillus plantarum Lp MT-3 and Lp MT-5 suitable for growth in buckwheat were screened from the candidate strains.The optimum formula and fermentation conditions were identified by single factor and orthogonal test,which is the mix of Tartary buckwheat polypeptide hydrolysate and milk at 9:1,with additional 0.2%sodium carboxymethyl cellulose and 7%sugar.Two strains of Lactobacillus plantarum were cultured separately and mixed at 1:1 as seed.The inoculation amount was 1%.After inoculation,the seed was fermented for 10 h at 37?,followed by coldstorage at 4?for 14 h.After preparation,microbial indicators and chemical index of the paste were determined.The number of lactobacilli was more than 109 CFU/mL.Harmful bacteria had not been detected in accord with national standards.The total flavonoid of Tartary buckwheat polypeptide fermentation paste was 0.23%,the EC50 1.42 mg/mL,the ability to scavenge DPPH·up to 83.9%.Under the same conditions,the removal rate of ordinary yogurt was only 11.2%.Therefore,Tartary Buckwheat polypeptide fermentation paste is a low fat functional food which not only has the advantage of regulating gastrointestinal tract microbial population balance from probiotics,but also reduces cholesterol and has antioxidant activity.It plays a significant role in utilization of Tartary buckwheat resources and development of new functional foods.