An investigation into low-temperature nitrogen plasma environment effect on the content of polyphenols during withering in made Kenyan tea

Summary Low-temperature nitrogen plasma (LTNP) was used to wither green tea leaf to study its effect on the polyphenol content. Using a dielectric barrier discharge chamber to provide the LTNP environment, green tea leaf was withered at various withering times. Made tea samples indicated that LTNP had an effect on polyphenol content. The highest polyphenol content of 78.56 mg g−1 in made tea was attained in 1 h after which it showed a decreasing trend with increasing retention time. For comparison purposes, green tea leaf was also withered in nonplasma environments. Highest polyphenol content of 133.4 mg g−1 in made tea was attained in a sample withered anaerobically in nitrogen gas at room temperature and atmospheric pressure for 18 h. In another sample, green tea leaf was directly macerated and dried without withering and fermenting and had polyphenol content of 101.91 mg g−1 in made tea. These contents were compared with green tea 4, purple tea and oolong tea that are currently manufactured in Kenya.