Chinese green teas are wok-fired, whilst in Japan they are steamed in a process called ‘fixing’. This is simply the application of heat to kill the naturally occuring enzymes in the leaf that would otherwise enable oxidation.
The liquor of green tea is clean, subtle, fresh and vibrant, and there is no better way to refresh and rejuvenate yourself during the day than to enjoy a cup of naturally sweet, antioxidant-rich green tea.
Umami sweetness is apparent at different intensities depending on the tea, and is directly related to how the tea was cultivated and processed. Some higher grades undergo weeks of under-shade (open-air) cultivation, which inhibits astringent (bitter) tannin formation and promotes theanine, the amino acid which we experience as umami.
It is a testament to the extraordinary care applied in the making of Japanese green tea, to see huge screens of rice straw or synthetic netting erected to cover entire tea fields, then dismantled after two or three weeks to once again allow direct sunlight on to the young, vitamin-rich tea plants.
Steaming is the archetypal Japanese tea-manufacture process. It serves to fix the vivid, dark, emerald colour of the leaf and preserve the natural enzymes packed with flavour. Standard steaming last for less than a minute, while deep steaming imparts a deeper colour and stronger flavour.
The lighter, sweeter and smoother the green tea, the higher the grade.
The finishing method contributes to the tea’s unique appearance, aroma, and taste.
Each region possesses its own traditional styles of tea making, though even within a region there are variations between villages and producers.
Polyphenol oxydase and the polyphenols themselves are stored in the plant’s cells, but when the cells are damaged, say by slicing an apple or dropping and bruising it, the cells are ruptured and the enzyme comes into contact with air. With the help of oxygen in the air, the polyphenol oxidase initiates a series of chemical reactions, transforming the polyphenols and eventually producing melanins (brown pigments).
The general name for this process is “enzymatic browning,” and the fabulous thing (for tea at least) is that it doesn’t just change the appearance of produce: it also alters flavor, scent, and nutritional value.