Biochemical diversity of tea germplasm and potential for processing of diversified tea products

Abstract

Tea industry in Kenya forms the largest agribusiness contributing up to 4% of the country’s gross domestic product and over 26% of total foreign exchange earnings. However, significant revenue is lost when tea is sold in undiversified form. Therefore, this study aimed at determining the biochemical diversity in Kenyan tea clones and their potential for diverse product development. Samples were obtained from 197 tea clones conserved in Kericho and Kangaita substation and assayed for total polyphenols, catechins, antioxidant activities, caffeine, chlorogenic acid, anthocyanins and theanine using Reverse Phase High Performance Liquid Chromatography (RP-HPLC) and spectrophotometric protocols. The influence of different growing regions, Kangaita and Timbilil, on the levels of catechins and caffeine was also done. The data was subjected to analysis of variance using GENSTAT-C statistical software and the Least Significant Difference (LSD) test used to separate the means. There was a significant clonal difference (P≤ 0.05) in total polyphenols (16.4%- 30.9%) and total catechins (9.46%-25.42%) among the 197 clones assayed. Sixteen (16) clones ready to be released for commercial cultivation, recorded a significant (P≤ 0.05) polyphenol content (mean value of 28.11%), higher than that of standard reference clone, TRFK 6/8 (27.4%), an indication of their suitability in the development of high quality black teas. Fifteen clones were suitable for the manufacture of theaflavin-3, 3’-digallate rich black tea based on their high levels of ECG and EGCG. Clones TRFK 301/5 and TRFK 301/4 had a high EGC/EC and low EGCG/ECG ratios and were suitable for manufacture of less astringent green teas, while clones TRFK 687/1 and 73/7 which had the least caffeine contents at 1.96% and 2.04%, respectively therefore could be utilized in manufacturing low-caffeine beverages. Among the purple colored clones, TRFK 306/1 had the highest anthocyanins content of 1319 mg/l though not significantly different making it suitable for manufacture of anthocyanin-rich beverages or extracts. Remarkable high values of antioxidant activity in 79 clones (90.97 %) compared to the reference clone TRFK 6/8 suggest that these clones can be exploited for their potential health benefits. Clones assayed for chlorogenic acid and theanine showed that clones AHP SC 31/37 and TRFK 6/8 had the highest contents of 0.131% and 1.7%, respectively, and are suitable for chlorogenic and theanine rich teas. On the regional comparison study, clones in Kangaita had significantly higher (P≤ 0.05) total and individual catechins with mean total catechins content of 18.7% compared to 16.2% in Timbilil. Clones in Timbilil however had significantly high caffeine contents (mean value 4.2%) compared to those in Kangaita (3.9%). The observed chemical differences based on clones and regions show that Kenyan teas have a remarkable diversity in biochemical attributes and thus suitable for development of diversified tea products with remarkable geographical indications.