New Fermentation Technology Of Fruity Kombucha Beverage And Its Effect On Quality

Kombucha is a folk traditional acidic beverage that has been used in Asia for more than2,000 years.It is rich in nutrients such as amino acids,vitamins and tea polyphenols.It is one of the fastest growing beverages among functional foods today.In recent years,kombucha has developed rapidly in North America,Australia and Europe,and has broad development prospects.It is a fermented product with great economic benefits,but it is still in the domestic stage of family production,with weak market competitiveness and low market share.The main reason is that the initial fermentation liquid of kombucha has sour,astringent taste and pungent smell,which limits the consumer group and lacks domestic market attraction and competitiveness.Therefore,this study innovatively proposed a new fermentation process,that is,the step-by-step refermentation process.Based on the initial fermentation of traditional kombucha,apple juice was added after pasteurization,and Lactiplantibacillus plantarum and Candida utilis were inoculated successively for step-by-step refermentation.The aim was to optimize and innovate the flavor and process of kombucha on the basis of traditional kombucha,and to provide theoretical basis for the industrial development of fruity kombucha beverage in the market.The main research contents were as follows:1.The quality changes of fruity kombucha beverages under different fermentation methods were studied.The effects of different fermentation methods on physicochemical indexes,antioxidant capacity,volatile flavor substances and sensory evaluation of fruity kombucha beverages were compared.The results showed that,compared with the fruity kombucha beverage with no refermentation,the p H of the two kinds of different refermentation(mixed refermentation and step-by-step refermentation)increased significantly after the end of fermentation,and the p H of step-by-step refermentation increased more significantly from 2.78 to 3.30,while the total acidity decreased significantly,and the total acidity of step-by-step refermentation decreased more obviously from 27.56 g/L to 17.56 g/L.Compared with the fruity kombucha beverage with no refermentation,the content of organic acids in the two kinds of refermented fruity kombucha beverages significantly decreased after fermentation,and the content of malic acid and citric acid in the step-by-step refermentation were more significantly decreased.The content of total phenols compounds and total flavonoid compounds,DPPH and ABTS free radical scavenging rate of the two kinds of refermented fruity kombucha beverages were significantly higher than those of the fruity kombucha beverage with no refermentation,and the step-by-step refermentation increased more significantly,which were 184.70 mg/m L,338.33 mg/m L,81.67% and 79.61%,respectively.Fruity kombucha beverage with step-by-step refermentation had the most volatile flavor substances,including hexyl acetate and linalool,etc.,and the relative content of isoamyl acetate and ethyl caproate were higher than those of the mixed refermentation and no refermentation.The sensory score of the fruity kombucha beverage with step-by-step refermentation was higher than that of the mixed refermentation and no refermentation,and the overall taste was fuller and softer.In conclusion,step-by-step refermentation was the fermentation method to make fruity kombucha beverage have the best nutritional and sensory quality.2.The optimum process of fruity kombucha beverage with step-by-step refermentation was studied.Under the premise that step-by-step refermentation process was determined as the best fermentation method,the preparation process of the fruity kombucha beverage with stepby-step refermentation was optimized.With sensory scores as the index,the optimal technological conditions of the fruity kombucha beverage were determined by single factor experiment and response surface experiment,considering the required cost and process feasibility: The ratio of water,sucrose and green tea was 200:20:1(w/w/w),the ratio of kombucha strain liquid and tea syrup was 1:9(v/v),the first fermentation time was 7 d,and the first fermentation temperature was 37℃.The ratio of juice and the initial fermentation liquid of kombucha was 5:5,the inoculation amount of Lactiplantibacillus plantarum was 3.3%,the second fermentation time was 23 h,and the second fermentation temperature was 32℃.The inoculation amount of Candida utilis was 2.1%,the third stage fermentation time was 3 d,and the third stage fermentation temperature was 30℃.Under these conditions,the sensory score of fruity kombucha beverage was 96.18,the highest.3.The quality changes of fruity kombucha beverage during storage period were studied.Under the premise of determining the best process of fruity kombucha beverage with step-bystep refermentation,the short storage period was determined by the changes of microbial indexes,and the changes of physicochemical indexes,nutritional components,volatile flavor substances,antioxidant active components and antioxidant capacity of fruity kombucha beverage during the storage period were determined at 4℃ and 10℃,to investigate the storage stability of fruity kombucha beverage.The results showed that under the storage temperature of 4℃ and 10℃,the microbial indexes of fruity kombucha beverage were all within the national limit standards during the 15 d storage period.During the 15 d storage period,the p H and total acidity values of fruity kombucha beverage at 4℃ and 10℃ were relatively stable,and the color remained bright,and the browning index and turbidity did not change significantly.When the storage time reached 15 d,the loss of sucrose,glucose and fructose of fruity kombucha beverage at 4℃ and 10℃ was within the normal range of soluble sugar loss.The loss of free amino acids of fruity kombucha beverage before and after storage was 7.37 mg/L and 10.54 mg/L,respectively,and the changes of flavor amino acids were within the acceptable range.At the same time,the main volatile flavor substances and types did not change greatly,and ethyl caproate,linalool and other aroma substances were detected.Under the storage conditions of4℃ and 10℃,the retention rate of nutrients(vitamin C,total phenols compounds,total flavonoid compounds)of fruity kombucha beverage was higher.In summary,under the storage conditions of 4℃ and 10℃,the fruity kombucha beverage with step-by-step fermentation had good storage stability during the 15 d storage period.