Research on Quality Characteristics and Formation Mechanism of Choerospondias axillaris Leaf Insect Tea

In order to deeply understand the quality characteristics and explore the quality formation mechanism of the Choerospondias axillaris leaf insect tea, the sensory quality, main physicochemical components and metabolites of the Choerospondias axillaris leaf insect tea and its raw materials were analyzed by sensory evaluation, physicochemical component detection and non-targeted metabolomics technology in this study. The results showed that the taste of the tea was mellow and sweet, the medicinal aroma was obvious, the color of the tea soup was deep reddish brown, there was a huge difference in sensory quality between the tea and raw materials. The values of L^*, a^* and b^* of the tea soup and 7 main physicochemical components between the tea and raw materials were significantly different (P<0.01), among which, compared with the raw material, the water extract and polyphenols of insect tea were decreased by 35.61% and 42.39%, the caffeine was reduced below the detection limit, and the total flavonoids, fatty acids, crude proteins and amino acids were increased by 195.92%, 316.21%, 17.14% and 5.07%. In the analysis of metabolome data, 463 metabolites belonging to 59 categories were qualitatively identified from the two samples, multivariate statistical analysis indicated that there were significant differences in metabolites between the two samples. A total of 322 different metabolites of 45 classes were obtained, accounting for 69.55% of all metabolites, among which 166 were up-regulated and 156 were down-regulated. Analysis found that fatty acids (36 kinds), benzene and substituted derivatives (34 kinds), carboxylic acids and derivatives (23 kinds), flavonoids (23 kinds) and organooxygen compounds (21 kinds) were the main types of differential metabolites, significantly (P<0.05) up-regulated differential metabolites 3-hydroxyanthranilic acid, prednisolone, pyrazine, phenylpyruvic acid, primaquine and significantly (P<0.05) down-regulated metabolites such as 3-hydroxybenzoic acid, D-4-hydroxyphenylglycine, syringic acid, noreugenin and hydroxyproline, could be identified as the characteristic differential substances between insect tea and raw materials, which might be of significant importance to the quality formation of insect tea. A total of 204 metabolic pathways were obtained through the enrichment analysis of KEGG metabolic pathways. The 5 metabolic pathways most significant affected by differential metabolites were identified as central carbon metabolism in cancer, flavonoid biosynthesis, flavonoid degradation, phenylalanine metabolism, flavonoid and flavonol biosynthesis. The ABC transporter pathway was found to be enriched with the highest number of differential metabolites (15 kinds), followed by flavonoid biosynthesis and aminobenzoate degradation pathways (14 kinds). The metabolic pathways of amino acids, fatty acids, flavones and flavonoids were suggested to play important roles in the quality formation of insect tea. A theoretical foundation and scientific basis were laid by the research results for the development and utilization of special insect tea, and a reference was also provided for revealing the mechanism of quality formation of Choerospondias axillaris leaf insect tea.