Application And Technology Research Of Lactic Acid Bacteria In Fermented Sweet Potato Beverage

Sweet potato is rich in nutritional value,but it is insufficient for development and utilization,so it is of great significance for its in-depth development.In this study,Lactobacillus bulgaricus and Streptococcus thermophilus with excellent fermentation performance were combined with Lactobacillus plantarum with ?-aminobutyric acid synthesis ability as fermentation bacteria.In the fermentation process,a lactic acid bacteria fermented sweet potato beverage having a good taste and containing ?-aminobutyric acid was developed.The main research contents and results are as follows:(1)The single-factor experiment was carried out on the fermentation conditions of lactic acid bacteria fermented sweet potato beverage,and the process was optimized by orthogonal test.The optimal process conditions were as follows:the ratio of sweet potato to water was 1:2(w/w).The amount of white sugar added is 4%(w/v),and the inoculation ratio of the fermentation strain is Lactobacillus bulgaricus:Streptococcus thermophilus:Lactobacillus plantarum 1:1:1,and the total inoculum is 3×107 CFU/mL.The fermentation temperature was 39? and the fermentation time was 8 h.The fermented sweet potato beverage prepared under these conditions has good color,flavor and taste,and is mellow and delicate.Subsequently,the prepared lactic acid bacteria fermented sweet potato beverage was subjected to a preservation experiment.(2)The changes of the types and contents of organic acids and volatile flavors were studied in the fermentation of lactic acid bacteria by high performance liquid chromatography(HPLC)and gas chromatography/mass spectrometry(GC/MS)were investigated.The effect of Lactobacillus on the quality of sweet potato beverage during fermentation was studied.HPLC results showed that after fermentation of lactic acid bacteria,the lactic acid content of sweet potato pulp increased by 40 times,while the content of succinic acid increased significantly,which helped to increase the fermentation sour taste of the product.In addition,the contents of malic acid,citric acid and fumaric acid are all reduced,which is beneficial to slow down the irritating odor and improve the overall sour taste of the product to make it softer.The results of GC/MS showed that the main volatile flavor compounds in sweet potato pulp before and after fermentation were ketones,esters,aldehydes,alcohols and other compounds.Through the fermentation of lactic acid bacteria,the kinds and relative contents of ketones,pyrazines and acids in sweet potato pulp increased,while the kinds and contents of aldehydes with pungent odor decreased.The sweet potato pulp fermented by lactic acid bacteria improved the flavor of the product as a whole,making it softer and more acceptable.(3)Qualitative and quantitative study of ?-aminobutyric acid in lactic acid bacteria fermented sweet potato beverage by HPLC.After analysis,no addition of Lactobacillus plantarum D-9 or unfermented sweet potato pulp did not produce ?-aminobutyric acid,only the addition of Lactobacillus plantarum D-9 for fermentation to produce ?-aminobutyric acid,and the content of ?-aminobutyric acid was 235.32 mg/L.