Study On The Fermentation Technology And Microbial Diversity Of Machilus Angustifolia Eagle Black Te

Hawk tea is a kind of natural green beverage with a long history,and its health care efficacy and pharmacological properties are of great significance to human health.In recent years,the related research of Hawk tea mainly focuses on the products development of Litsea coreana and the pharmacological effects of its extracts,while the research on the utilization of other Hawk tea species resources,process technology,product quality and microbial diversity of Hawk dark tea is very scarce.Therefore,in this study,Machilus.Rehderi,one of the main source plants of Hawk tea,was processed into sunning crude tea,then it was made into Hawk dark tea through the traditional dark tea processing technology,in this process,by improving and optimizing the parameters of the pile-fermentation,the optimum pile-fermentation parameters and process flow of Hawk dark tea were explored.Subsequently,the quality components(include amino acids and volatile substances)and drinking safety of Hawk dark tea were further detected to evaluate the quality and drinking safety.Finally,the microbial community in the pile-fermentation process of Hawk dark tea was high-throughput sequenced to determine the microbial diversity.The following are the main results and conclusions of this study:1.Research on the pile-fermentation technology of Hawk dark tea processed by Machilus.Rehderi:The results of single factor experiment showed that the best pile-fermentation temperature was 35℃,the best moisture content was 65%,and the best time was 24 h.Based on this,the L9(3~3)orthogonal experiment was designed to determine the optimal parameters of pile-fermentation technology of Machilus.Rehderi:pile-fermentation temperature was 35℃,moisture content was 62%,and the time was24 h.2.Quality analysis of Hawk dark tea processed by Machilus.Rehderi:Sensory evaluation showed that under the best pile-fermentation parameters,the Hawk dark tea had bright orange-red liquor color,rich camphor fragrance,strong sweet and mellow taste.The physicochemical test showed that the contents of water extract,total flavonoids,total phenols,soluble sugar and total free amino acids were 25.74%,2.42%,24.58%,1.05%and 1.54%,respectively.A total of 15 kinds of amino acids were detected by automatic amino acid analyzer,and the total content was 5.668 mg/g.A total of 108 kinds of volatile compounds were detected by GC-MS,mainly including terpenes,ketones and esters,among them,1,7,7-trimethyl-tricyclo[2.2.1.0(2,6)]heptane,δ-cadinene andα-pinene were the main components of the aroma of the tea.In addition,the detection of heavy metal lead,pesticide residues and pathogenic bacteria showed that Hawk dark tea met the drinking standards.The results of quality analysis showed that the product of Hawk dark tea processed by Machilus.Rehderi obtained in this study was of good quality and was safe to drink.3.Microbial diversity analysis of Hawk dark tea processed by Machilus.Rehderi during pile-fermentation process:Based on Pac Bio SMRT sequencing platform,the microorganisms of Hawk dark tea samples were sequenced by full-length ITS sequence and full-length 16S amplicon,and then the sequencing data were analyzed by bioinformatics methods.The results showed that 126 genera and 105 species belonging to 12 phyla were detected,including Cyanobacteria,Bacteroidota,Firmicutes and Proteobacteria;The dominant genera were Chloroplast,Bacteroides and Faecalibacterium,and the main species were Cinnamomum camphora and Bacteroides vulgatus;As for fungi,8 phyla,276 genera and 370 species were detected.The main phyla were Ascomycota,Mortierellomycota and Basidiomycota;At the genus level,they were mainly Mortierella,Cladosporium and Fusarium,and at the species level,they were mainly Mortierella rishikesha and Mortierella hyalina;Based on the KEGG and Fun Guild databases,the functional prediction analysis of bacterial and fungal communities was carried out.Carbohydrate metabolism,Amino acid metabolism and Energy metabolism are the main functions of bacteria,while most of the dominant functions of fungi belong to saprophytic groups.The results showed that the microbial diversity in the pile-fermentation process of Hawk dark tea processed by Machilus.Rehderi was very rich.