Changes of Physicochemical Indexes and Flavor Components in the Fermentation Process of Lycium barbarum by Lactic Acid Bacteria

In this experiment,the optimum fermentation conditions of Lycium barbarum by Lactobacillus bulgaricus and Streptococcus thermophilus were studied,and the changes of physicochemical indexes and the flavor components in the fermentation process were analyzed. Based on the sensory score of fermented products,the optimum technological parameters for fermentation of Lycium barbarum by lactic acid bacteria were determined as follows:A combination of Lactobacillus bulgaricus and Streptococcus thermophilus 1:1,a ratio of material to water of 8:1 g/100 mL,an inoculation amount of 4%,and fermentation time 24 h. The sensory score of the fermentation broth under the fermentation conditions was 81 scores. During the fermentation of Lycium barbarum by lactic acid bacteria,the titratable acid increased gradually,the pH value and reducing sugar content decreased continuously,and the number of viable bacteria,soluble solid content and soluble protein content increased first and then decreased. 63 kinds of volatile substances were separated from the fermented Lycium barbarum liquid using solid-phase microextraction and gas chromatography-mass spectrometry,including 12 esters,16 aldehydes,15 ketones,13 alcohols,4 acids,and 3 aromatic heterocycles. Among them,41 new flavor substances had been produced. After 24 h of fermentation,the relative content of flavor substances of aldehydes,ketones decreased,and the relative content of flavor substances of esters,acids and aromatic heterocycles increased.