Chemistry and Biological Activities of Processed Camellia sinensis Teas: A Comprehensive Review

Abstract

Tea is a typical processed beverage from the fresh leaves of Camellia sinensis [Camellia sinensis (L.) O. Kuntze] or Camellia assamica [Camellia sinensis var. assamica (Mast.) Kitamura] through different manufacturing techniques. The secondary metabolites of fresh tea leaves are mainly flavan‐3‐ols, phenolic acids, purine alkaloids, condensed tannins, hydrolysable tannins, saponins, flavonols, and their glycoside forms. During the processing, tea leaves go through several steps, such as withering, rolling, fermentation, postfermentation, and roasting (drying) to produce different types of tea. After processing, theaflavins, thearubigins, and flavan‐3‐ols derivatives emerge as the newly formed compounds with a corresponding decrease in concentrations of catechins. Each type of tea has its own critical process and presents unique chemical composition and flavor. The components among different teas also cause significant changes in their biological activities both in vitro and in vivo. In the present review, the progress of tea chemistry and the effects of individual unit operation on components were comprehensively described. The health benefits of tea were also reviewed based on the human epidemiological and clinical studies. Although there have been multiple studies about the tea chemistry and biological activities, most of existing results are related to tea polyphenols, especially (‐)‐epigallocatechin gallate. Other compounds, including the novel compounds, as well as isomers of amino acids and catechins, have not been explored in depth.

The effects of different types of mulch on soil properties and tea production and quality

“…Tea plant (Camellia sinensis) is a perennial economic crop in China 1,2 and the young leaves harvested from the tea are one of the most popular beverages worldwide as a result of their flavor and taste. 3,4 In China, the area for tea plantation and tea production, respectively, comprised 2.93 million hm −2 and 2.43 tons in 2016, and were 1.69-and 2.56-fold higher than in 2000. In 2017, tea exports reached 1.611 billion RMB in China, the highest tea export value worldwide.…”

Feature-Based Molecular Networking Analysis of the Metabolites Produced by in vitro Solid-State Fermentation Reveals Pathways for the Bioconversion of Epigallocatechin Gallate

“…2,3 In recent years, dark teas have been studied for their health benefits, such as anti-diarrheal, anti-hyperlipidemic and anti-hyperglycemic activities. 4,5 Unique to the dark teas, the manufacturing process includes a microbial fermentation stage, during which tea leaves (at 20 to 60% initial moisture) are piled together for a certain period of time, ranging from a half a day to several months. 3 The piles for fermentation are huge with the height up to 3m, creating an environment where the heat produced by the microbial fermentation increases the temperature up to 80 °C.…”

“…6 In this post-fermentation stage, a series of complex chemical changes occur, which subsequently contribute to the unique quality characteristics and health benefits of dark teas. 4,5 The sample names in the yellow frames are expressed as 'medium_strain ID'. For example, PDA_FEc.1-1 means the extract of the PDA medium incubated with the fungal strain FEc.1-1 (ID of Eurotium cristatum), while PT_FA.8-1 means the extract of the PT medium incubated with the strain FA.8-1 (Aspergillus sp.).…”

Quality Evaluation of Green and Dark Tea Grade Using Electronic Nose and Multivariate Statistical Analysis

“…Tea is one of the most pleasant and welcome beverages around the world (Maruyama et al., ; Shiono, Yamamoto, Yotsumoto, & Yoshida, ; Zhang et al., ). Among them, Xi‐hu Longjing and Pu‐erh teas are the two most popular ones, especially in China, which behave great commercial value in the international market (Lee et al., ; Wang et al., ).…”

“…Hence, to develop a new method to cover the shortage of the experiential sensory assessment, tea researchers have attempted various ways to explain tea quality form chemical and physical aspects. Unfortunately, the composition of tea and its volatile components are extraordinary complexes (Joshi & Gulati, ; Kuhnert, Dairpoosh, Yassin, Golon, & Jaiswal, ; Zhang et al., ). Thus, it is not an easy work to effectively realize the tea quality inspection and classification using a single technique.…”