Research On The Application Process Of Fermentation Of Pu’er Tea By Eurotium Cristatum

Pu’er tea is a characteristic tea in Yunnan Province,its taste is warm,mellow,with antioxidant,blood glucose and lipid levels,anti-tumor and many other health care effects,and is favored by tea consumers.Nowadays,there are a variety of fermented products of Pu’er tea on the market,but in the traditional production process,the Wudui fermentation process takes a long time,and most of the single-bacteria fermentation process must be completely sterilized at high temperature to achieve stable production,which affects and limits the birth of high-quality Pu’er tea fermentation products to a certain extent.Eurotium cristatum is a probiotic commonly found in Fu brick tea,its existence can not only improve the rough and bitter taste of Fu brick tea,but also give tea a better appearance state,and promote the improvement of tea quality.In order to realize the research and development and stable production of new fermentation products of Pu’er tea,this study used Pu’er loose tea as raw material,and carried out solid fermentation by inoculation of Eurotium cristatum isolated from Fu brick tea,optimized the optimal process production parameters,and monitored the changes of quality-related physicochemical components during the fermentation process,in order to provide reliable technical support for the production process of stable fermentation of Pu’er tea by Eurotium cristatum.The main contents of this study are as follows:Through morphological and molecular biology analysis,the single colony of Eurotium cristatum isolated from the crumbs of Fu brick tea was determined.On strain in the process of the liquid tea powder bed culture determine the growth period of strains and fermentation related major extracellular enzyme activity change trend.During the liquid culture process,amylase activity first increased and then decreased,protease activity basically coincided with the growth cycle,cellulase activity continues to increase,polyphenol oxidase activity was low,and the overall change showed first increase and then fluctuation,pectinase activity increased before the decay period and gradually decreased after reaching the peak at the end of the stable period.At the same time,the DPPH free radical scavenging rate of bacterial liquid during the culture process showed a trend of slow decrease,then rapid decrease and then slow increase,to a certain extent,it shows that fermented Pu’er tea has good antioxidant properties.In the study of the new fermentation process of fermentation of Pu’er tea by Eurotium cristatum,the influence of temperature,water content,inoculation amount,aeration low oxygen time,post-fermentation time and other single factors was comprehensively considered by taking the water extract and tea polyphenol content,microbial number and sensory evaluation of fermented tea as reference indicators,and the optimal process parameters were optimized by orthogonal test:fermentation temperature 28°C,tea water content 35%,10%inoculation amount,aeration and oxygen on the 6th day,and post-fermentation for 3 days.Under these conditions,three parallel experiments of fermented tea were carried out,and the average content of water extract of the final tea was 46.32%,the content of tea polyphenols was 23.61%,the average number of Eurotium cristatum was(3.1±0.4)×10~5 CFU/g,and the golden flower particles on the surface of the tea were full and uniform,the aroma of fungi tea was uniform and pure,the tea soup was golden and deastringent,and the taste was smooth and long.The average sensory quality evaluation score was 95.7 points,indicating that this process conditions were feasible and the quality of Jinhua Pu’er tea was excellent.Under the optimal process conditions,the changes of key physical and chemical components of Pu’er tea during fermentation showed that the contents of water extract,caffeine,theaflavin,theabrownin,water-soluble total sugars,free amino acids and hydrated pectin increased by 13.38%,11.45%,41.56%,160.09%,18.18%,32.27%and103.27%of tea after fermentation,while the content of tea polyphenols and thearubigins decreased by 25.48%and 45.48%,respectively;The Pu’er tea samples before and after fermentation were detected by GC-MS to show 52 main aroma components,the original tea and fermented tea respectively detected 40 species and 39kinds of main volatile components through the content comparison,it was found that the ester components were the most variable,followed by hydrocarbons.After fermentation,the component content with floral and fruity aroma as the main aroma characteristics was greatly reduced,and the component content with grass and oil wax aroma as the main aroma characteristics increased,so it was believed that the"fungus aroma"produced by the fermentation of Pu’er tea by Eurotium cristatum was grassy and woody aroma and oil wax aroma.