DETERMINATION OF POLYPHENOL CONTENT, ANTIOXIDANT ACTIVITY, CAFFEINE AND LEVELS OF ZINC AND IRON IN SELECTED COMMERCIALLY AVAILABLE BEVERAGES IN ELDORET TOWN

Abstract

Coffee, tea and soya, are widely consumed beverages in Eldoret town. However there is scanty information available on the level of components of these products in the market. A study was conducted to determine the polyphenol content, antioxidant activity, caffeine levels, and the levels of zinc and iron in selected commercially available coffee, tea, and soya beverages. Three brands of each beverage were sampled from retail outlets within Eldoret town. Sampling was done in triplicate. The samples obtained were analyzed to determine polyphenolic content, antioxidant activity, caffeine, zinc and iron content using Foline Caucultue method, 2,2-diphenyl-2-picrylhydrazyl radical scavenging assay, UV-VIS spectrophotometry and Inductive Coupled Plasma Optical Emmision spectroscopy, respectively. The polyphenol levels was, 7.4 %, 19.6 % and 4.4 % in coffee, tea and soya, respectively. Tea beverage had the highest antioxidant activity (81.4 %) among the three beverages while soya had the lowest (9.0 %). There was a positive linear correlation (r2=0.68) between polyphenol content and antioxidant activity of the beverages. Coffee had the highest level of caffeine (4.58 mg/g) as compared to tea (0.985 mg/g) and soya (not detected). A multiple comparison analysis indicated that there was significant difference in the amount of caffeine between coffee and soya and between coffee and tea with p values of less than 0.05. There was no significant difference (p=0.946) in the level of Fe in coffee, tea and soya. Zinc content varied significantly in coffee, tea and soya (p<0.05), with soya having the highest level (50.57 ppm) whereas tea had the lowest (38.23 ppm). Consumers in Eldoret town can get enough polyphenols, caffeine, Fe and Zn nutrients by consuming the three beverages. The study recommends that all manufacturers should indicate the levels of each components of the beverages for the benefit of consumers.