Analytical strategy coupled to chemometrics to differentiate Camellia sinensis tea types based on phenolic composition, alkaloids, and amino acids

Abstract

Catechins, amino acids, and alkaloids are primary chemical components of tea and play a crucial role in determining tea quality. Their composition and content largely vary among different types of tea. In this study, a convenient chemical classification method was developed for six Camellia sinensis tea types (white, green, oolong, black, dark, and yellow) based on the quantification of their major components. Twenty-one free amino acids, 6 catechins, 2 alkaloids, and gallic acid in 24 teas were quantified using ultra-high-performance liquid chromatography (UHPLC). The total catechin contents in these tea samples ranged from 10.96 to 95.67 mg/g, while total free amino acid content ranged from 2.63 to 25.89 mg/g. Theanine (Thea) was the most abundant amino acid in all tea varieties. Catechin and amino acid levels in tea were markedly reduced upon fermentation of tea. Furthermore, high-temperature processing (roasting) during tea production induced degradation and epimerization of catechins, yielding epimerized catechins, simple catechins, and gallic acid. Principal component analysis revealed that major ester-catechins (EGCG and ECG), major amino acids (Thea), and major alkaloids (caffeine) are potential factors for distinguishing different types of tea. Linear discriminant analysis showed that 100% of teas were correctly classified in which (+)-catechin, ECG, EGC, gallic acid, GABA, cysteine, lysine, and threonine were the most discriminating compounds. This study shows that quantification of the major tea components combined with chemometric analysis, can serve as a simple, convenient, and reliable approach for classifying tea according to fermentation level.

Effects of the Baking Process on the Chemical Composition, Sensory Quality, and Bioactivity of Tieguanyin Oolong Tea

“…In details, about 30% of TFs, 10% of theasinensins, and 30% of procyanidins were lost after twice baking. In a previous study, high-temperature processing (roasting) during tea production decreased monomeric catechins and increased gallic acid ( 26 ). Our results supported that the degradation of catechins were universal during the baking process of tea.…”

Sensory and chemical characteristics of Tieguanyin oolong tea after roasting

“…l -glutamic acid can increase the umami taste ( Zhang, Sun-Waterhouse, Su, & Zhao, 2019 ). During the roasting process, free amino acids and saccharides were vulnerable to non-enzymatic reactions under thermal action, such as Maillard reactions and Strecker degradation, which was beneficial for the formation of tea aroma ( Jiang et al, 2020 , Zhou et al, 2019 ).…”

Dynamic Variation of Amino Acid Contents and Identification of Sterols in Xinyang Mao Jian Green Tea

“…The dynamic changes of amino acids (AAs) in tea plants during growth influence the overall taste of green tea infusions [ 1 ]. AAs not only contribute to the different taste characteristics of green tea infusions, but also provide precursors for the development of tea aroma [ 2 , 3 , 4 ]. Therefore, the contents of AAs play an important role in tea quality.…”