Development Of Compound Fermented Beverage Of Siraitia Grosvenorii And Licorice

Siraitia grosvenorii and licorice are traditional Chinese medicine food homologous plants,which have high nutritional value.At present,the research of Siraitia grosvenorii and licorice is mostly about medicinal and blended beverages,and there are only few studies on the use of biological fermentation technology to improve the nutrition and function of products.In this study,the optimal ratio of mixed juice of Siraitia grosvenorii and licorice was determined through lactic acid bacteria fermentation.And we had studied the effects of different lactic acid bacteria on the content of flavonoids,saponins,total phenols and the inhibitory activities of a-glucosidase in the mixed juice of Siraitia grosvenorii and licorice during fermentation.The raw materials were treated by different treatment methods(Hot water extraction,ultrasonic-assisted extraction,and Pulsed electric field-assisted extraction),in addition studied the changes in the active ingredients and functional characteristics of the liquid during the fermentation process of different treatment methods to determine the best processing method for the raw materials.The preparation conditions of the compound beverage were optimized,and the flavor substances and biological functions of the compound fermented beverage were analyzed.The main research contents are as follows:(1)Research for lactic acid bacteria fermentation mixed juice.By comparing the growth and acid production of lactic acid bacteria in different ratios of Siraitia grosvenorii and licorice(w/w),it was found that the growth and acid production of lactic acid bacteria in the mixture of 7:3 was better than that of the other two mixtures,and the total acid content of lactic acid bacteria in the 7:3 mixed juice was between 4.80 g/kg and 5.81 g/kg.The best proportion of the mixed juice(w/w)was finally determined to be 7:3(2)Research for the effect of different lactic acid bacteria fennentation on the active ingredients and functions of Siraitia grosvenorii and licorice mixed juice.The results showed that there was no significant difference in pH value between different lactic acid bacteria(p>0.05)and pH value decreased to about 3.8,the total acid content was significantly different(p<0.05),the total acid content of Lactobacillus plantarum S7 was higher than that of other strains,the total acid content is 6.327 g/kg,and the content of saponin and total phenol in the fermentation broth of Lactobacillus plantarum S7 was 0.620 mg/mL and 1.878 ?g/mL,respectively.The antioxidant capacity and a-glucosidase inhibition rate of Lactobacillus plantarum S7 were 0.720 mmol/L and 29.9%,respectively.(3)Research for the effect of different raw material treatments on the active ingredients and functions of fermented Siraitia grosvenorii and licorice juice.The results showed that there was no significant difference in pH value(p>0.05)between hot water,ultrasonic assisted and pulsed electric field assisted,and the pH value decreased to about 3.6 after 32 h fermentation.There was no significant difference in total acid content(p>0.05),the content of total acid in ultrasonic treatment group was higher than that in other two ways,the total acid content is 6.187 g/kg.There was significant difference in the number of viable bacteria between groups(p<0.05),the number of viable bacteria in the ultrasonic assisted treatment group was higher than that in the other two ways,the number of viable bacteria is 1.26×109 CFU/mL.Compared with the other two methods,the content of saponins in ultrasonic assisted treatment group was 1.080 mg/mL.There was no significant difference in the content of total phenols and flavonoids(p>0.05).The antioxidant capacity,reducing capacity and a-glucosidase inhibition rate of ultrasonic assisted treatment group were higher than those of the other two methods,respectively 0.929 mmol/L,0.420 mmol/L and 65.82%(4)By comparing the fermentation and functional characteristics of the mixed juice,it was determined that the fermentation strain was S7:GC58:grx10=1:1:1.Through single factor and box Behnken test,the formula of the beverage was optimized as follows:adding 0.83 times of water,adding 5.63%compound sweetener and 1.05%whey powder.The optimal fermentation conditions were determined by single factor experiment:fermentation temperature 37?,fermentation time 28 h(5)The physicochemical indexes,microbial indexes and volatile flavor compounds of fermented beverage were determined.It was found that the contents of total acid and saponin in fermented beverage were increased to 5.52 g/kg and 1.32 mg/mL respectively.The content of soluble solid,reducing sugar and total phenol decreased,which were 8.26%,2.36 mg/ml and 0.90?g/ml respectively.Escherichia coli,mould,saccharomyce and Salmonella were not detected,meeting the national food safety standard.The total reduction capacity and a-glucosidase inhibition rate of fermented beverage were 0.388 mmol/L and 61.35%,respectively,which were significantly higher than that of the unfermented beverage(p<0.05).The diameter of bacteriostatic circle to pathogenic bacteria was more than 20 mm.It was found that 20 kinds and 38kinds of flavor substances were detected in unfermented and fermented beverages.The relative contents were 66.63%and 96.64%respectively.In fermented beverage,esters decreased,alcohols,ketones,acids,aldehydes,hydrocarbons and other flavor substances increased.