Effect of Seasons on Theanine Levels in Different Kenyan Commercially Released Tea Cultivars and Its Variation in Different Parts of the Tea Shoot

Abstract

A study was conducted to determine the effect of seasons in 23 different Kenyan commercially released tea cultivars. This was done for three seasons viz: cold and wet, cold and humid, hot and dry. The cold and wet season was shown to be the best for obtaining high levels of theanine while the hot and dry season resulted in decrease in theanine levels in most of the test cultivars thus showing seasonal variation on the levels of theanine. Theanine content was determined using High Performance Liquid Chromatography (HPLC). On average, TRFK 31/8 contained 1.20% dw of theanine and highest in green tea while TRFK 56/89 contained 0.97% dw of theanine and highest in black tea. Green tea contained higher theanine levels than black tea and this has been shown in most of the test cultivars. To achieve the health benefits of theanine, one should drink 4 cups of tea brewed from cultivars with 0.63% dw and more of theanine. Also theanine levels were determined in the different partitions of the tea shoot (4 leaves + bud) and the internode contained the highest theanine levels up to 3.26% dw for both cultivars compared to the leafy partitions.