The scientists using high-quality green tea in cancer research always brew their tea at least 15 minutes for their laboratory mice to achieve the best results. Here is the reason.

In ancient China, the harvested whole tea leaves valued as a medicinal herb were dried for storage. It was well known that to brew tea, one must first grind the dried tea leaves into powder in a V-shaped trough fitted with a metal cutting wheel to facilitate extraction of the active ingredients by hot water infusion. This tradition is still partially preserved in Japan where Matcha (pulverized tea) is served in the “Tea Ceremony”.

As the tea-drinking culture spread from the Chinese elite class to the populace in the Song dynasty (960-1279 A.D.), grinding dry leaves to make each pot of tea drink was found to be too cumbersome to the common people. A new technology was invented to release the “tea juice” mechanically before the leaves were dried to eliminate the subsequent grinding step in tea preparation. This new invention of about the 13th century made tea drinking popular among all people in the Middle Kingdom. It took several centuries for the Chinese to perfect that technology. Still few professionals in the tea industry mastered the art properly.

With our current understanding of the tea leaf anatomy and biochemistry, we realize that this then newly invented technology caused the release of the catechin antioxidants from the mesophyll vesicles before the leaf is dried for easy hot water extraction. For the last 700 years, all high-grade green teas have been processed with this technology - so are Dr. Lee’s TeaForHealth^® green teas. 

The process consists of an initial brief high temperature treatment, by gentle pan-frying or steaming, to inactivate the polyphenol oxidases and to preserve the protective epidermis on the surface of the tea leaf by heat coagulation. Then a crushing, rubbing or rolling pressure is applied to each partially dehydrated tea leaf in order to break the membranes of the vesicles in the spongy mesophyll before final drying for storage. Since the released catechins are still within the tea leaf between the two intact layers of epidermis, they are protected from the effects of moisture and oxidation (see anatomy of a fresh unprocessed tea leaf and anatomy of a properly processed tea leaf). It takes 15-20 minutes of hot water infusion for the dry tea leaf to rehydrate and for the catechins to pass through the intact layers of epidermis.

In most green tea leaves sold on the market, improper processing, especially premature crushing, causes the epidermis to crack and the mesophyll vesicles to rupture at the same time, forcing the juicy antioxidant catechins to leak to the leaf surface where they are dried on the epidermis, and thus exposed directly to moisture and atmospheric oxygen (see anatomy of a poorly processed tea leaf). Under these conditions, the tea catechins degrade quickly into bitter polyphenols during storage, and beneficial antioxidant properties are diminished. Since these bitter, partially oxidized former tea catechins, now loosely referred to as polyphenols or flavonoids, are already on the outside of the tea leaf, they dissolve rapidly into the hot tea liquid in less than 3 minutes. Prolonged steeping intensifies the bitter taste of the tea.

Properly processed and stored green teas will retain the antioxidants within the confines of the epidermis layers until the tea beverage is made. To fully extract the antioxidant benefits from these high quality teas, like Dr. Lee's TeaForHealth^® green teas, a longer steeping process is required.

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