Abstract
BACKGROUND: Using a stoichiometric method, this study conducted a comprehensive evaluation of tea quality and categorization based on nutritional indicators such as amino acids and trace elements. Based on multiple indicators, including amino acids, trace elements, etc., the nutritional analysis of five green teas, namely Fanjingshan green tea, Guizhou green tea, Meitan green tea, Tiangui green tea and Xixiu green tea from Guizhou, China, was performed to determine the combustion heat, combustion stability, fat, crude fiber, ash, trace elements and amino acids of five kinds of green tea. RESULTS: The results showed that the order of combustion heat of the five types of green tea was Fanjingshan green tea > Xixiu green tea > Guizhou green tea > Meitan green tea > Tiangui green tea. The combustion heat of the five types of green tea was 3707.968-8670.937 J/g, among which the average combustion heat of Fanjingshan green tea was 8670.937 J/g and the energy was the highest. The results of gray pattern recognition were as follows: Guizhou green tea > Fanjingshan green tea > Tiangui green tea > Meitan green tea > Xixiu green tea. The crude fiber content (%) ranged from 11.13 to 14.63%, with an average content of 12.9975%, followed by Guizhou green tea, Fanjingshan green tea, Meitan green tea, Xixiu green tea, and Tiangui green tea. The fat content (%) was between 0.48% and 1.37%, with an average of 0.8635%, followed by Fanjingshan green tea > Guizhou green tea > Meitan green tea > Xixiu green tea > Tiangui green tea. The ash content (%) was between 4.83% and 5.53%, with an average content of 5.2182%, and decreased in the following order: Fanjingshan green tea > Tiangui green tea > Xixiu green tea > Guizhou green tea > Meitan green tea. Principal component analysis (PCA) revealed that the cumulative contribution ratio of the first three principal components was 88% >85%, and the first three principal components were selected to represent 88% of the 13 trace elements in the five types of green tea.Factor analysis (FA) revealed that the order of the contents of 19 amino acids, namely, CySO(3)H, Asp, Thr, Ser, Glu, Gly, Ala, (Cys)(2), Val, Met, Ile, Leu, Tyr, Phe, His, Lys, NH(4), Arg and Pro, in the 5 green teas was Tiangui green tea > Fanjingshan green tea > Meitan green tea > Guizhou green tea > Xixiu green tea. The ratio of essential amino acid content to total amino acid content was 10.61-18.14%, and the ratio of essential amino acid content to nonessential amino acid content was 11.87-22.15%. Tiangui green tea had the highest amino acid content. The order of comprehensive evaluation of food nutrition using the entropy method (EA) was as follows: Fanjingshan green tea > Tiangui green tea > Guizhou green tea > Meitan green tea > Xixiu green tea. According to the analysis of these indicators, the most common food source was Fanjingshan green tea. Systematic cluster analysis (SCA) of the samples revealed that the five green teas were clustered into three classes. Systematic cluster analysis (SCA) for variables based on different indicators revealed that the 37 variables could be categorized into five groups. This study has important theoretical and practical significance for the determination and comprehensive evaluation of multiple indicators for green tea, which can provide a scientific basis and research significance for nutritional, health, and classification studies of green tea in Guizhou, China.