Technical Reports on Tea

Green tea (Camellia sinensis) has long been recognized as a significant source of catechin and its derivatives which present only in tea. These are called as tea catechins or flavan 3-ols and these include (+)-catechin (C), (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin gallate (EGCG), and (-)-gallocatechin gallate (GCG) that contribute to both antioxidant capacity and organoleptic properties of teas. These compounds provide protection against cardiovascular disease and cancer as well as contain pharmaceutical activities such as antihypertensive, antioxidative, anticarcinogenic, antiarteriosclerotic, hipocholesterolaemic and hypolipidemic properties.

Figure 1. Structures of six tea catechins present in green tea.

Teas from the genus Camellia are generally divided into three main food categories based on their processing method. Green tea (unfermented), oolong tea (partially fermented), and black tea (fully fermented) are manufactured from the same tea plant, Camellia sinensis. For green tea manufacture, leaves are immediately heated or rapidly dried to inactivate polyphenol oxidase (PPO) and native microflora which catalyzes the aerobic oxidation of tea catechins. This process generally protects tea catechins from oxidization, as long as processing steps are carried out in a timely manner. For black tea, tea leaves are crushed and allowed to wither to induce oxidization and fermentation prior to drying. The characteristic color, reduced bitterness and astringency, and general flavor are derived from this process giving black tea a marked distinction from green tea. During fermentation, monomeric flavan-3-ols may undergo oxidative polymerization converting predominantly into bisflavanols, theaflavins, and thearubigins.

The following technical reports are presented in chronological order with the most recent reports at the top.