The leaves of a plant are mainly composed of water and when they are separated from the plant they start to wilt and lose their water. Tea leaves are no exception to this rule. When the leaves are plucked, they begin to lose water and wither, a process known in the tea industry as wilting. As tea leaves wilt, their cell walls begin to break down. The chemical components inside come into contact with oxygen and trigger a group of reactions called oxidation. Over the years, tea growers have learned to control the natural tendency of tea leaves to wilt and oxidize to produce a finished tea that has the desired appearance, aroma, and flavor. This is done using the methods we refer to as tea processing.
The most important compounds.
Amazingly, for hundreds of years, tea makers have produced tea using the principles of withering and oxidation, without knowledge of the underlying chemicals. From what we know today, the most important compounds in fresh tea leaves are polyphenols, amino acids, enzymes, pigments, carbohydrates, methylxanthines, minerals, and many volatile flavor and aroma compounds. These components are responsible for producing tea with good appearance, aroma and taste. During tea processing, the various ingredients undergo changes to produce what we call a ready-to-eat or ready-to-eat tea that is processed and ready to be packed or steeped.
The main components in both green and black teas fall under the category of chemical compounds known as polyphenols and a subgroup called flavonoids. Flavanols (commonly called catechins), taflavins, and thearobigins are the main compounds found in black tea, which fall under flavonoids. Green tea mainly contains catechins, and in black tea, most of the catechins are converted to taflavin and tyarobigin during processing. These compounds mainly contribute to the typical brewed color and taste of green and black tea. Other components of black and green tea brew are similar in composition.
Caffeine and theanine are other important components of black and green tea. Flavonoids, caffeine and theanine are biologically active (capable of acting on living organisms) that contribute to the beneficial effects of tea.
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