Effect of Natural and Artificial Drying Method on the Quality of Wet Processed Arabica Coffee (Coffea arabica L.)

Abstract

Coffee is the most important crop in the national economy of Ethiopia and still the leading export commodity. The country’s export earnings from this crop exceed all other agricultural products. Though Jimma is well known as the center of coffee diversity and high production potential area in Ethiopia, owing to the improper post-harvest processing technique, of which on-farm processing is the major one, the quality of its coffee does not have deliverable grade status and seeks further improvement. This calls for intensive efforts to identify post-harvest practices and drying techniques and to come up with technical recommendations that enhance coffee quality. Therefore, this experiment was carried out to determine the effect of Natural and Artificial drying method on the quality of wet processed Arabica coffee varieties (Coffea arabica) Accordingly, a study was conducted under state owned coffee farms of Limmu Coffee Plantation (LCP) from October to December, 2012. The experiment was laid out in 4x5 factorial design arranged in CRD with three replications. The two factors comprised five level of temperature: 600 C, 700 C, 800 C, 900 C and sun drying, assigned to the first factor; four initial moisture content: 16%,21%,26% and 40% the second factor Cupping was done by three cuppers at Ethiopian commodity exchange (ECX) coffee cupping laboratory in March, 2012.The data were checked for normality and analyzed using SAS version 9.2 and means were separated using least significant differences (LSD). As a result, the interaction effects were highly significant (P≤0.05) for drying period and significant variations were observed (P≤0.05) for acidity, flavor, total cup quality, total quality and coffee grades. The findings revealed that, depending on different working experience of the state farms and the range of drum temperature. Drying wet processed coffee with an initial moisture content of 16% using an artificial drier whose drum temperature is fixed at 900 C resulted in total quality values ranging from 91 to 100% (91.66%) attaining a “specialty grade 1 ”classification”. While, Coffee with an initial moisture content 40% and dried in an artificial drier with drum temperature ranging from 60 to 900 C resulted in lower quality, the quality standards of coffee and produced low quality commercial grade classified under 3. Hence, using appropriate drying method, it is possible to produce specialty coffee. From the correlation result coffee grade had highly significant (P≤0.05) and negative correlation with acidity (r=-0.69); flavor (r=-0.60); cup value (r=-0.80) and total value (r=0.89); The results of the present study would uplift the quality of wet processed coffee in the area of coffee production, which in turn could enhance the income of individual coffee growers, private investors, exporters in particular and the country at large. However, further study including Identification of the processing techniques and actual differences in quality on distinctively processed coffee, Designing and developing household level electrical assisted or solar assisted artificial dryer to maintain the quality of coffee and identifying the effect of artificial and sun drying on the fungal development in coffee during short time storage and action research to improve the processing practices should be conducted to come up with concrete recommendations