Effects of Processing Technologies on the Levels of Chlorogenic Acid, Gallic Acid and Theanine in Selected Kenyan Tea Cultivars by HPLC-PDA

Abstract

Chlorogenic acid (CGA) one of tea biomolecules is a natural antioxidant that neutralizes free radicals in the body. It has also anti-obesity, anti-atherosclerotic and anti-cancer properties. Gallic acid exists in form of free acids and esters in plant material. This ubiquitous chemical is one of the many biologically active phenolic compounds of plant origin. Theanine a non-protein amino acid also called L-theanine is speculated to increase the levels of GABA, serotonin and dopamine. It has been used as a nutritional supplement in reducing stress, causing feelings of relaxation and improved mood. The aim of this study was to determine the variation of the levels of CGA, GA and theanine with processing technologies. Six tea cultivars TRFK 6/8, TRFK 11/4, TRFK 12/2, TRFK 31/8, TRFK 54/40 and TRFK 306/1 were selected for use in the study. Their leaf was processed to obtain CTC and orthodox tea products with green and black tea types being made. Profiling was done using High Performance Liquid Chromatography (Shimadzu Japan) equipped with photo-diode array detector (SPD-M20A). Graphical representation of the mean levels of Chlorogenic acid, Gallic acid and L-theanine contents was done using Microsoft® Excel, version 2010. Standard error of the mean was used to determine levels of significant differences. The result showed that TRFK 306/1 had the highest levels of CGA for both CTC and orthodox processing techniques while TRFK 12/2 had the lowest levels. In general, the levels were higher in black teas than in the green tea types. The levels of GA were in the range of 0.28-0.51% in green teas and 0.28-0.55% for the black tea types. At the cultivars level, black teas had significantly high levels of GA than the green teas. The theanine levels ranged at 0.97-1.87% for green teas and 0.79-1.47% for the black tea types.