Preparation Of Instant Dark Tea By Submerged Fermentation With Eurotium Cristatum And Its Function Research

In recent years,dark tea products have been adopted by an increasing number of consumers all around the world because of its special care efficacy.Use sun maocha as materials,dark tea was proceed by microbes through solid fermentation.Because of the existence of extensive production,long fermentation cycle and difficult to control the process,traditional solid fermentation has restricted the healthy development of dark tea.Eurotium cristatum is one of the advantages fungi in Fu brick tea and get more attention by its function.Our country’s tea tree planting arearanked number one in the world,the resources of summer and fall tea is very rich,but the summer and fall tea has not been effective development and utilization due to its high tea polyphenols contents,low amino acid contents,astringency,low aroma and quality.For the further development and utilization of Summer and fall tea,Summer and fall tea were used as materials,Eurotium cristatumwas used as fermentation fungi to produced a instant dark tea product which rice in mycelial by submerged fermentation,and on this basis we invesgated the functions of Eurotium cristatum and fermentation product.The results were as follows:1.Use mycelial dry weight in tea extract,value of red and turbidity as measure indexs.The effects of inoculum size,liquid-solid ratio and fermentation time on mycelia dry weight,redness,and turbidity of tea infusion were investigated through single factor experimental.Results showed that the effects of inoculum size(6-12%),liquid-solid ratio(10-20 mL/g)and fermentation time(132-204 h)on mycelia dry weight,redness,and turbidity of tea infusion were satisfied.Response surface methodology was successfully implemented with desirability function approach for optimization of fermentation parameters of instant dark tea product.The results indicated that quadratic regression model built between mycelia dry weight,redness,and turbidity of fermented tea infusion and fermentation parameters were significant(R2>0.98).The optimum condition was as follows: inoculum size of 9.35%,liquid-solid ratio of 14.50 mL/g and fermentation time of 169.00 h.At this optimum point,mycelia dry weight,redness,turbidity of tea infusion and D was 5.79 g/L,41.35,76.96 NTU and 0.91,respectively.The contents of tea polyphenols and carbohydrates decreased 29.70% and 38.45%,respectively.Tea pigments and flavonoids levels increased 28.71% and 15.55%,respectively.Fermentation decreased the content of free amino acids and caffeine content increased significantly.The brightness of the tea infusion,red and yellowwere rised during the fermentation,and the turbidity decreased.Compared with Yiyang and Jinwei,sample had a higher score in items of turbidity and special fungal aroma.2.The study of the effects of simulated gastrointestinal tract environment on the viability of the E.cristatum strain shown that the strain was able to survive in the simulated gastric juice at pH 2(78.57% survival rate)and pH 3(82.85%)over an incubation period of 4 h.The E.cristatum also tolerated the simulated intestinal transit at pH 8.0 for 4 h,with survival rates of 92.86%.E.cristatum also has strong capacities against bile and tolerated the bile at 2% for 4 h with survival rates of 84.29%.The results indicated that E.cristatum has strong capacities against gastrointestinal tract environment and have a basic characteristic of probiotics.3.The instant dark tea was dissolved at different concentrations(0,1,2,3,4 and 5 mg/mL)and then mixed with digestive enzymes in gastrointestinal tract environment to study the correlation between instant dark tea and activities of digestive enzymes.Results showed that instant dark tea promoted the activities of pepsase,amylase and protease(R2?0.62),but had no obvious effect on that of lipase.The activities of pepsase,amylase and protease increased with the additional amounts of instant dark tea.4.Through animal experiments,we investigated the anti-obesity effects of instant dark tea(IDT)and freeze-dried,non-fermented instant tea prepared from the same extracts of tea.Results shown that,compared with un-fermented tea,consumption of the high fat diet supplemented with dark tea remarkably reduced body weight,as well as reduced the serum levels of TG,T-CHO,GLU and LDL-C,and decreased the activities of AST and ALT,all of which were effects induced by the high-fat diet.