Researchers from Hanzhou and Huazhong used different light sources (ultraviolet, yellow, blue, purple, orange, red, cyan, green and white) to irradiate tea leaves, which were then used to make black tea, during withering. “The results indicated that the yellow, orange and red light withering significantly improved the aroma and taste, imparting the tea a sweet flavor and a fresh and mellow taste. Tea treated with yellow light was scored highest the sensory scores and showed the highest content in catechins, theaflavins, amino acids and aroma components, followed by the orange and red light treatments. The black tea withered with ultraviolet light showed a strong astringency, probably resulting from low contents of theaflavins, amino acids and soluble sugar. The green light irradiation remarkably damaged the aroma and taste of the tea, leading to a strong greenish flavor and an astringent taste, probably owing to the lowest contents of chemical compositions. No significant cumulative effect was found in the hybrid light withering treatments. Therefore, monochromatic yellow, orange and red lights were suggested for withering the black tea to improve its overall quality”.
In conclusion we’d like to add that Franz Guske in his book “Die Arbeit des Friseurs” says that yellow light irradiation promotes memory and provokes the brain to take especially difficult tasks. The point about provoking the brain to most difficult tasks is a bit frightening with regard to the hairdresser, but it seems that it can be recommended to irradiate tea farmers together with their tea during withering.