Abstract

The main objective of the study was to determine caffeine content of coffee beans (Coffee arabica) collected from Nensebo district, West Arsi Zone, Oromia Region using ultra violet-visible and high performance liquid chromatography methods. The coffee beans were purchased from coffee supplying farmers’ cooperatives in Nensebo district (namely Tulu Gola, Habera, Refisa, Nensebo Chebi and Melka Dembi) and local coffee markets (in Hawassa and Shashemene). The coffee samples collected from the selected sites were mixed (homogenized). The same was done for coffee samples from coffee markets (in Hawassa and Shashemene cities). The samples were roasted and ground using grinding machine. The resulting powders were boiled in distilled water and extracted with dichloromethane. The dichloromethane extracts were subjected to high performance liquid chromatoraphy and ultra violet-visible analyses. The data obtained from spectra the methods used in the study revealed that the caffeine content of the extract homogenized coffee beans of the selected sites in % (w/w) was found to be 1.03 ± 0.001 by high performance liquid chromatography and 1.17 ± 0.01 by ultra violet-visible analysis. Similarly, the caffeine content of Nensebo coffee samples purchased from coffee markets was found to be 1.14 ± 0.01 by high performance liquid chromatoraphy analysis.  The findings showed that the caffeine contents of the coffee samples used in the study was within reported standards, and also relatively lower than reported caffeine contents of coffee beans growing in other parts of Ethiopia. Further studies are recommended to determine the levels of other chemicals constituents and minerals exist in the coffee beans in order to fully determine the properties (quality) of Nensebo coffee.

Key words: Caffeine content, high performance liquid chromatography (HPLC) analysis, ultra violet-visible (UV/Vis), Coffea arabica, liquid-liquid extraction, roasted coffee beans