Optimization Of Fermentation Technology Of Apple Juice By Probiotics And Changes Of Flavor Substances And Functional Components During Fermentation

Different probiotics need different fermentation conditions,and the flavor and nutrients are also different under different fermentation conditions.The purpose of this paper is to optimize the best probiotics and fermentation conditions for apple juice fermentation,and to produce a lactic acid bacteria fermented juice that meets the market demand.Firstly,the fermentation processes of different lactic acid bacteria were optimized by sensory evaluation,and the total number of bacteria,p H,polyphenol content,flavonoid content,antioxidant capacity in vitro,amino acid content and volatile aroma substances in fermentation juice were detected to optimize lactic acid bacteria,and the changes of volatile and functional substances in apple juice during fermentation were studied.The main results are as follows:1.Using PB test and central combination test design principle,combined with BP neural network and genetic algorithm,sensory evaluation was used to optimize the fermentation conditions of five kinds of lactic acid bacteria.The optimized fermentation conditions were as follows: Lactobacillus rhamnosus fermentation time 17 h,fermentation temperature 37 ?,inoculation quantity 1.4%,initial p H 3.9;Lactobacillus plantarum fermentation time 18 h,fermentation temperature 36 ?,inoculation quantity 1.5%,initial p H 4;Lactobacillus Royicus fermentation time 21 h,fermentation temperature 36 ?,inoculation quantity 1%,initial p H 3.7.For Lactobacillus plantarum,fermentation time 21 h,fermentation temperature36 ?,inoculation quantity 1%,initial p H 3.7.Lactobacillus casei fermentation time 16 h,fermentation temperature 38 ?,inoculation quantity 1.8%,initial p H 3.6;accessory cheese fermentation time 18 h,fermentation temperature 36 ?,inoculation quantity 1.6%,initial p H4.2.2.The weight values of different indexes of five kinds of lactic acid bacteria were assigned by the method of coefficient of variation,the score of each kind of lactic acid bacteria was calculated,and the one with the highest score was regarded as the special probiotics for fermented apple juice.After the significant analysis of the difference,Lactobacillus Royale had the highest score in the comprehensive evaluation,with a score of30.32.3.GC-MS and HPLC were used to analyze the changes of volatile aroma,phenols and organic acids during fermentation.The conclusions are as follows:(1)Fermentation can change the type and content of volatile compounds in apple juice,thus affecting the overall aroma and taste.The aroma and aroma of apple juice are formed by the interaction of2-methyl butyl acetate and 2-ethylhexanol with high content and ethyl butyrate and butyl acetate with low content.(2)Fermentation can increase the content of succinic acid and tartaric acid,and decrease the content of shikimic acid,pyruvate,malic acid and citric acid,thus changing the taste and taste of apple juice.(3)Fermentation can increase the contents of Gallic acid and protocatechuic acid in apple juice,so as to improve the antibacterial,antiviral and cancer prevention function of apple juice.In the process of fermentation,the contents of chlorogenic acid,proanthocyanidin B2,caffeic acid,rutin,P-coumaric acid,ferulic acid,quercetin and phloridin decreased,but the contents of total flavonoids,total phenols and antioxidant capacity increased in the process of fermentation.it is proved that fermentation can transform phenols and improve the function of fermented juice.