The Key Technology In The Processing Of Pasteurized Fermented Soybean Milk

In recent years,the research and development of fermented soybean milk products has become a hot spot in the legume industry.The traditional technology developed soybean milk with nutrient loss,which can not meet the health needs of consumers.The three strains were determined by the preliminary screening of lactic acid bacteria,and then the strains were compounded.The key technical parameters of fermented soymilk were determined by orthogonal test.Moreover,The quality and flavor of pasteurized soybean milk product was studied.The purpose of this paper was to develop a new type of fermented soybean milk product with simple process conditions and rich nutrient content,which can fill a big blank in soybean industry and laid a foundation for further research and development of soybean products.The main conclusions of the experiment were as follows:(1)In this experiment,the growth of seven strains of Lactobacillus brevis,L.plantarum(NBRC15891),L.casei,L.paracasei,L.rhamnosus,L.acidophilusand L.plantarum(laboratory-preserved)were conserved.Combined with the comprehensive analysis of sensory evaluation,the suitable strain for fermenting soybean milk was screened out.Through the growth characteristics of seven strains,such as growth curve,acid production,acid resistance,protein and lipolytic capacity,resistance to artificial gastric juice,and tolerance to bile salt,the acid fast and viable strains were selected.The fermentation characteristics were determined by the p H value,titration acidity,viable count,texture,free ammonia nitrogen,whey precipitation and sensory quality during fermentation.The strains with high fermentation ability and the sensory score were selected.The main results were as follows: in the acid resistance experiment,when the p H of the culture medium was reduced to 3.0,the total number of colonies of Lactobacillus plantarum(laboratory preservation)was the highest,reaching 3×10~7CFU / mL,followed by L.rhamnosus.In the fermentation experiment,Lactobacillus plantarum(laboratory preservation)had faster acid production and total colonies.When the fermentation end point(pH 4.6)was reached,the free amino nitrogen content of Lactobacillus plantarum(laboratory)was higher,reaching 18.7%.Sensory evaluation analysis showed that Lactobacillus plantarum(laboratory preservation)value was the highest,reaching 78 points,followed by Lactobacillus casei and Lactobacillus rhamnosus,respectively 75.4 and 72.6.L.plantarum(laboratory-preserved),L.rhamnosus,and L.casei,were used in the following experiments.(2)Through the early screening test,the most suitable three strains of fermented soybean milk were selected.And the sensory evaluation was used as the influencing index to optimize the key process parameters of the fermented soybean milk in the process by orthogonal test.Theresults showed that the highest score was obtained when the ratio of Lactobacillus plantarum(Lactobacillus plantarum),Lactobacillus rhamnosus and Lactobacillus casei was 2: 1: 1.The optimum fermentation conditions were as follows: the fermentation conditions were 85?,15 min,the inoculation amount was 5%,the fermentation time was 6 h,and the fermentation temperature was 37?.(3)After the above experiment,it was concluded that the sterilization condition was the key technology to influence the sensory characteristics of the fermented soybean milk,and the effects of different pasteurization conditions on the quality of fermented soybean milk were studied in depth.Four kinds of pasteurization conditions were used at 65?/30 min,75?/20 min,85?/15 min and 95 ? /10 min.The nutrient composition,anti-nutritional factors,fermentation characteristics and flavor characteristics of fermented soybean milk were determined.With the increase of pasteurization temperature,the content of protein,fat,amino acid and reducing sugar decreased,and the content of protein,fat and reducing sugar decreased by 18.38%,28.57% and 41.57%respectively.The contents of anti-nutritional factors such as tannin,phytic acid,saponin,polyphenol and trypsin inhibitor decreased by 8.57%,38.32%,24.09%,39.97% and 57.43%.In the same fermentation time,with the increase of pasteurization temperature,the lower the pH of fermented soybean milk,the faster the end point of fermentation(p H4.6),the more bacteria,the higher the sensory score after ripening,up to 80 points.The following conclusions were obtained:There were 28 main flavor substances identified from fermented soymilk produced by four kinds of different pasteurization conditions.These volatile components were mainly divided into alcohols,aldehydes,ketones,acids and esters,among them,11 kinds of alcohols,6 kinds of aldehydes,ketones 5,5 kinds of acids,esters 1 species.The content of n-hexyl alcohol decreased from 18.85% to 15.64%,and the relative content of n-caproaldehyde decreased from 18.9% to16.1%,while the content of n-hexanol decreased to 18.65%,while the content of the volatile flavor the relative content of 2,3-butanedione increased from 9.2% to 12.52% with the increase of pasteurization condition,and combined with sensory evaluation,the pasteurization condition of65?/30 min under pasteurization condition The fermented soymilk produced by fermented soymilk was comparatively large,and the fermented soymilk obtained under the condition of 85?/15min95?/10 min pasteurization had rich bean flavor.Volatile flavors such as 1-penten-3-ol,pentanal,octanal and butyl acetate were identified only in fermented soymilk prepared under the pasteurization conditions of 65 ? /30 min,and other pasteurization conditions the fermented soybean milk was not detected,which also constitutes one of the reasons for its thick bean flavor.