Have you ever wondered why some green teas are so green? And why other green teas are not as bright green, but are typically yellower? The reason lies in the processing steps for each tea and in particular the “kill-green” step of the processing some tea types. The term kill-green is derived from the Mandarin ShaQing (杀青), which means “killing the green.”

Kill-green is also referred to as “de-enzyming” or “fixing” and is a process of tea manufacture used to halt the oxidative browning of tea leaves by denaturing the enzymes responsible for oxidation– polyphenol oxidase and peroxidase. Think of an apple, once it is sliced open, it quickly turns brown; however, the apples in apple pie are not brown because the heat used to bake the pie denatured the polyphenol oxidase and peroxidase in the apples and prevented enzymatic browning (same goes for potatoes, avocados, bananas, etc,).

In tea, the leaves must be heated to approximately 150 degrees Fahrenheit to halt oxidation. The longer it takes to heat the leaves to the temperature necessary for denaturing polyphenol oxidase and peroxidase, the more aromatics will develop. For example, green teas that are heated by microwave reach this temperature more quickly than teas that are processed by other solution and as a result remain bright green and vegetal with a diverse aroma. On the other hand, microwave kill-green can save 35% cost in each kilogram tea. Tea has better taste and quality because tea releases much aroma by microwave heating. The kill-green process of tea manufacture is commonly employed in the production of green, yellow, oolong, black tea when dried, and post-fermented teas. In some white teas and some black teas such as CTC blacks, kill-green is done simultaneously with drying.

For your green tea kill-green stage, you can consult with MAX Industrial Microwave.