Effects of Coffee Roasting Technologies on Bioactive Compounds and Cup Quality of Specialty Coffee Beans Grown in Ethiopia
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Date
2019-11-07
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Addis Ababa University
Abstract
The objective of this research was to study the effects of different type of coffee roasting technologies, namely Drum, Fluidized Bed and Traditional roasters on the cup quality and bioactive compounds of specialty coffee beans grown in Ethiopia. A total of 3 unwashed raw coffee varieties were selected for the study and collected from Yirgacheffe, Harar and Sidama coffee regions in Ethiopia. The sample coffee beans were specialty graded and roasted at light, medium & dark degree of roasts from 150°C - 200°C for 7 to 15 minutes. The roasted coffee beans were evaluated for cup quality at medium degree of roast by three professional cuppers. Next, the amount of caffeine, trigonelline and total chlorogenic acids present in each coffee samples were simultaneously analyzed using a high-performance liquid chromatography (HPLC). The amount of acrylamide formed in Yirgacheffe coffee during roasting was determined using UV-Visible Spectrophotometer. Based on cupping evaluation, traditional roaster resulted at the least total cup score for all the coffee varieties. Among other factors, only varietal difference and degree of roast were found to have significant (P < 0.05) effect on caffeine content of the sample coffee beans. Generally, a significant reduction in trigonelline and total chlorogenic acids content of the coffee beans was observed during roasting process, with darker roasts attaining the least values. A single analysis of variance on experimental results of acrylamide formation in roasted Yirgacheffe coffee showed significant (p < 0.05) differences for type of roaster and degree of roast. The highest acrylamide content, i.e. 2.303ppm was exhibited at light degree of roast using traditional roaster. Finally, drum roaster was found to be the best type of coffee roaster at medium degree of roast since it produced specialty coffee beans with the highest cup quality, optimum bioactive compounds content and minimum acrylamide formation at medium degree of roast.
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Acrylamide, Bioactive Compounds, Cup Quality, Roaster, Specialty Coffee