EFFECTS OF ROASTING TEMPERATURE AND TIME ON CUP QUALITY OF LAAGEE COFFEE (Coffea Arabica L.) CULTIVER GROWN IN WESTERN ETHIOPIA

Abstract

Ethiopia is known for the origin and wide diversity of Arabica coffee and has enormous, unexplored potential to produce top specialty coffees. Coffee plays a prominent role in Ethiopia’s economy. A study was conducted on Effects of Roasting Temperature and Time on Cup Quality of Laagee Coffee (Coffea Arabica L.) Cultivar Grown in Western Ethiopia. The experiment was conducted with two factors; Temperature and Time with three levels each. Three roasting temperatures i.e. 160, 180 and 200oC and three roasting times’ i.e.5, 7 and 9 minutes were considered in the study and the treatments were replicated three times. The information were analyzed by SAS (version 9.1). The result showed that the length, width, thickness, frontal surface area, sphericity, aspect ratio and shape index of the green beans were 9.99, 6.53, 4.36 mm, 51.43 mm2, 0.65, 0.65 and 1.86, respectively. Similarly, the engineering properties such as moisture content, hundred beans weight, bulk density, true density, bean volume, porosity, angle of repose were recorded to be 8.53%, 18.77g, 0.69g/cm3, 123g/cm3, 150.28mm3, 44% and 25.47o, respectively. After roasting the beans showed significant changes in physical and engineering properties. The length, width, thickness, frontal surface area, sphericity, aspect ratio and shape index were 11.81, 8.14, 5.51 mm, 69.66 mm2, 0.71, 0.74 and 1.65. Likewise, the value for moisture content, hundred bean weight, bulk density, true density, bean volume, porosity and angle of repose were 1.30%, 14.13g, 0.23g/cm3, 0.55g/m3, 273.74mm3, 0.66% and 18.77o, respectively. The result also showed that the volume change and the weight loss by the roasted beans were 121.52% and 30.43%, respectively. The colorimetric changes after roasting were from 47.18 to 32.43 for L*, from 1.6 to 14.08 for a*, from 12.59 to 19.12 for b*, from 12.61 to 5.60 for c and from 83.17 to 66.40 Ho. Cup quality was evaluated by a team of certified panelists at Jimma agricultural research center coffee processing and quality analysis laboratory. Effects of roasting temperature and time were significant (P<0.05) on cup quality parameters. The highest values of aromatic intensity, aromatic quality, acidity, astringency, bitterness, body, flavor and overall cup quality were 4.16, 4.0, 7.83, 4.16, 4.33, 8.0, 8.16, and 8.16, respectively. According to the cup test result the values of overall quality showed that, all tested samples varied between commercially acceptable and highly acceptable. Highly acceptable values in most cup quality attributes were 77.06, 80.65, 83.14 and 84.11% to treatments of 200oC and 5 min, 160oC and 7 min, 180oC and 5 min, and 180oC and 7 min, respectively.