Quality analysis of the Dragon and Phoenix Tea Cake made by different raw materials and processing technologies

【Objective】 This study aimed to compare and analyze the differences in taste and metabolites of Dragon and Phoenix Tea Cake of different varieties， tenderness and processing technologies to investigate the diversity of its raw materials， so as to provide a theoretical reference for innovating and optimizing the processing technologies of Dragon and Phoenix Tea Cake.【Method】 Fresh leaves of single bud， one bud and one leaf， and one bud and two leaves of Meizhan and Aijiao Oolong varieties were taken as raw materials to make Dragon and Phoenix Tea Cakes to analyze their metabolites and quality via non-targeted metabolomics and tea sensory evaluation.【Result】 The tea sensory evaluation showed that no significant differences were found in the total scores of sensory evaluation for Dragon and Phoenix Tea Cakes made from different tea varieties （P>0.05， the same below）； the tea cakes made from Meizhan variety had a stronger and mellower taste， while the tea cakes made from Aijiao Oolong variety showed better color and luster of tea powder and foam persistence. Dragon and Phoenix Tea Cakes made from one bud and one leaf， and one bud and two leaves of the two varieties showed significantly higher total scores of sensory evaluation than tea cakes made from single buds （P<0.05， the same below）. After simplifying tea washing and squeezing respectively during tea making， the tea cakes showed better color， luster， and fineness of tea foam， and a stronger， mellower， fresher， and smoother taste profile， with higher total scores of sensory evaluation compared to those made by traditional technologies. Adding water during the grinding step brought more persistent tea foam， but also a stuffy taste of water. Metabolomics results showed that： 1123 metabolites were detected in the tea powder of Dragon and Phoenix Tea Cakes， in which the proportions of phenylpropionic acids and polyketides， as well as lipids and lipid-like compounds were relatively high， accounting for 22.80% and 21.64%， respectively； 498 metabolites were detected in their tea foams， in which the proportions of phenylpropionic acids and polyketides， as well as lipids and lipid-like compounds were relatively high， accounting for more than 10.00%. From tea powder and foam of different tea varieties， 12 and 9 differential metabolites of taste were screened； from tea powder of different tenderness and processing technologies， 12 differential metabolites of taste were screened. In tea powder of Aijiao Oolong， contents of gallocatechin， epigallocatechin， and myricetin 3-O-galactoside significantly decreased， while theobromine content significantly increased； the contents of gallocatechin， epicatechin， epigallocatechin， and glutamic acid were significantly lower in single bud samples of the two varieties compared to samples of one bud and one leaf and one bud and two leaves. Compared with the Dragon and Phoenix Tea Cakes made by traditional processing technologies， skipping tea washing led to a significantly higher theobromine content and significantly higher lower contents of myricetin 3-O-galactoside and glutamic acid； adding proper portions of water when grinding tea， the contents of gallocate-chin， epicatechin， epigallocatechin， kaempferol-3-O-rutinoside， rutin， myricetin 3-O-galactoside， and glutamic acid in the tea cakes significantly increased； no significant change in taste substances was found in tea cakes without the squee-zing process. In the tea foam of Aijiao Oolong， the contents of quercetin 3-O-rutinoside， myricetin 3-O-galactoside， ellagic acid， corilagin， and octadecanamide were elevated； the contents of palmitamide and theobromine in tea cakes in one bud and one leaf and one bud and two leaves were lower than those in single buds； the tea cakes added with proper portions of water when grinding exhibited up-regulation in contents of most differential metabolites， and increased contents of polyphenols including epigallocatechin gallate， （+）-epigallocatechin， myricetin 3-O-galactoside， and of quercetin 3-O-rutinoside.【Conclusion】 Two varieties， Meizhan and Aijiao Oolong， are suitable raw materials for producing Dragon and Phoenix Tea Cakes. The tenderness that fits processing ， not limited to single bud， can be expanded to one bud and one leaf and one bud and two leaves. Tea washing and tea squeezing have no significant effects on tea quality， so skipping these two processes is good for simplifying processing technologies， enhancing production efficiency. Therefore， the pathway of processing technologies of harvesting→steaming→grinding→molding→yellowing is more suitable for modern production demand.