Study On Process Optimization And Kinetics Of Liquid Fermentation Of Instant Black Tea Powder

In this study,the technology of liquid fermentation was used to treat the summer and autumn teas to improve the aroma and flavor of the tea,and an instant tea product with high nutrient content and good drinking quality was produced to achieve the purpose of improving the comprehensive utilization rate of summer and autumn tea.In this study,two different strains of Aspergillus niger were inoculated with Selenium-enriched Summer and Autumn Tea in Ziyang County,Ankang City,Shaanxi Province.Fermentation of tea was carried out by means of liquid fermentation.Instant black tea powder was prepared by spray drying and monitored dynamically.Methods The functional components were analyzed.The test results are as follows:(1)Liquid fermentation of summer and autumn tea was carried out by using Aspergillus niger in tea,and the liquid fermented tea broth process was optimized using a 4 factor 3 level BBD response surface analysis method.The optimum conditions for liquid fermentation of tea were:15.09 g of tea./100 mL,fermentation time 41.07 h,fermentation temperature 36.16℃,inoculum size 9.14%,the value of theaflavin content reached the maximum(0.943%).(2)By studying the kinetics of the fermentation process,three kinetic models of microbial growth kinetics,product generation kinetics,and matrix consumption kinetics were identified,which were more clearly described in combination with the experimental values and model calculation estimates.Changes of bacterial growth,production and matrix consumption of tea in the liquid fermentation process of summer and autumn tea and their related links.(3)Through the dynamic detection of the contents of the liquid fermentation process,the changes of functional components such as tea polyphenols,flavonoids,caffeine,theanine,and catechins during the 0-48 h fermentation period were analyzed.Trends,and comparisons of changes in aroma components during fermentation,were detected by GC-MS.(4)In the experiment of this thesis,the process conditions for preparation of instant tea powder by spray drying method were also optimized to improve the yield and drinking quality of tea powder.The optimum spray drying process conditions were as follows:soluble solids concentration 20%,air inlet temperature 160℃,air outlet temperature 75℃,and feed flow rate 15 mL/min.