Study On Fermented Beverage Of Yam Probiotic

Chinese yam is nutrient-rich,containing nutrients and functional ingredients including polysaccharide,allantoin,diosgenin,protein,amino acid,etc.Probiotics are groups of microorganisms that are beneficial to human health.In this study,using probiotics and yams as materials,we aimed to develop a probiotics-fermented beverage of yam and to open up a new way for the high-value utilization of yams.In the study,we first e stablished a protocol for the enzyme hydrolysis of yam.Then,through the strain screening and the optimization of the fermentation process,we determined the ingredients of the probiotic beverage prepared from the fermented yam and examined the stability of the beverage.We also investigated the changes during development of the probiotic fermented drink and conducted quality analysis.The main results are as follows:(1)The parameters in the procedure of yam enzymatic hydrolysis were determined.By single factor and orthogonal experiments,the optimal parameter of enzymatic hydr-olysis of yam was determined,that is,the ratio of solid to liquid was 1:4,the amount of saccharification enzyme was 200 u/m L,the time of enzymatic hydrolysis was 3h,and the p H of enzymatic hydrolysis was 4.5.Under these conditions,the yield of reducig sugar was 34.9±0.12g/m L.(2)The probiotics suitable for fermentation in yam juice were screened and the parameters of the fermentation process were optimized.After studying the growth curves of five probiotics,including Lactobacillus helveticus,plantarum subsp.Plantarum,Lactobacillus paracasei,Lactococcus lactis,Streptococcus thermophilus,and their fermentation characteristics in yam juice,we selected Streptococcus thermophilus as the target bacteria for the following experiments.Using single factor test and orthogonal test of the fermentation parameters,we determined the optimal procedure of yam probiotics fermentation,that is,the quantity of the probiotic inoculated was6%,the temperature of fermentation was 42 ?,the time of fermentation was 10 h,the sucrose content added was 2.5%.Under this fermentation condition,the number of living bacteria in the beverage was 8.834±0.001 lg(CFU/m L),and the p H value was4.20±0.01.(3)The changes of active ingredients in the fermentation process were investigated.The changes of active substances in the preparation of yam-fermented probiotics beve-rage were examined.After fermentation,the contents of soluble polysaccharides,total polyphenols,flavonoids,allantoin and 1,1-diphenyl-2-picrylhydrazyl free radical scavenging ratewere1.46±0.15ug/m L,33.38±2.50ug/100 m L,15.81±2.35 ug/100 m L,1.79±0.05ug/100 m L and 0.80±0.13 mg/m L respectively.(4)A stable beverage fermented by yam probiotics was developed and its quality was assessed.The preparation of the fermented yam probiotic beverage was investigated,and the appropriate formula was determined by scoring its appearance,color,aroma,and taste.The score was the highest(=88)when the added amount of sucrose,honey,and citric acid were 3%,4%,and 0.2%,respectively.Also,the stability of the prepared yam fermented beverage was examined,and the optimal composition of stabilizer was obtained,that is,the added amount of xanthan gum was 0.08%,the added amount of sodium carboxymethyl cellulose was 0.08%,the added amount of pectin was 0.12%,and the added amount of propylene glycol alginate was 0.12%.We quantified the taste index,hygienic index and the number of live bacteria of the probiotics fermented yam beverage under the optimal conditions of production.The taste of the probiotics fermented beverage in yam was of high quality,and all indexes met the standard of beverage.