Effect of Altitude, Shade, and Processing Methods on the Quality and Biochemical Composition of Green Coffee Beans in Ethiopia

Abstract: There are growing demands for high quality coffee in the international market today. This hasgiven coffee producing countries an impetus to increase the quality as well as the quantity of coffee theyproduce. For improving coffee quality and meet market demands, attention has been given to exploringgenetic and environmental factors as well as agronomic and other coffee management practices.However, little information is available in Ethiopia regarding effect of environmental factors such asaltitude and coffee management practices such as shading and processing methods on the quality andbiochemical composition of green coffee beans. This problem has constrained efforts being made in thecountry to further exploit the growing demands for quality coffees in the international market.Therefore, a study was conducted during the 2010/11 main cropping season to determine coffee qualityattributes as a function of altitude, shade, and processing methods. Red ripe coffee cherries werehandpicked from three coffee farms in south-western Ethiopia located at altitudes of 1150, 1545 and1802 meters above sea level, which represented lowland, midland, and highland coffee growing areas,respectively. The coffee cherries were obtained from both shaded and unshaded farms in each of theaforementioned coffee growing areas. The green coffee beans were subjected to both wet and dry coffeeprocessing methods. A total of 36 coded samples (18 washed and 18 unwashed green coffee beans) witha moisture content of about 10.5% were subjected to cup and laboratory tests. Coffee cup test was doneaccording to the procedure of Ethiopian Commodity Exchange (ECX) using 36 green coffee beansamples. Contents of caffeine, trigonelline, and chlorogenic acids were determined usingHPLC/THERMO. Sucrose was determined using GC VARIAN 3800. Univariate analysis of varianceand stepwise multiple regression analyses were conducted using SPSS 16 v2. The results revealed thatcoffee beans originating from the high altitude had significantly higher first grade and Q1 grade pointsthan coffee beans originating from the low and middle altitudes. Unshaded and unwashed coffee gradewas better than the washed and shaded coffee grade. Caffeine content of the beans was affected neitherby altitude, shading, nor by the processing method. Shading affected only the content of beancaffeoylferuloylquinic acids (CFQA), which was found to be significantly higher for the unshaded coffeebean samples than the shaded coffee bean samples. Contents of 4,5-dicaffeoylquinic acid (4,5-DCQA),feruloylquinic acids (FQA), and total chlorogenic acid (TCGA) were significantly higher for coffee beansoriginating from the low and middle altitudes than those originating from the high altitude. Similarly,coffee beans that originated from the low altitude had significantly higher contents of 3,4-dicaffeoylquinic acid (3,4-DCQA), caffeoylferuloylquinic acids (CFQA), and trigonelline than coffeebeans that originated from the high altitude. However, coffee beans that originated from the high andmiddle altitudes had significantly higher contents of chlorogenic acids, i.e., 3-caffeoylquinic (3-CQA) and5-caffeoylquinic acid (5-CQA) than coffee beans that originated from the low altitude. The sucrosecontent of coffee beans that originated from the low latitude was significantly higher than the sucrosecontent of coffee beans that originated from middle and high altitudes. Washed coffee beans containedsignificantly higher amounts of dicaffeoylquinic acid (4,5-DCQA), caffeoylquinic acid (5-CQA),chlorogenic acid (TCGA), and trigonelline than unwashed coffee beans. However, unwashed coffeebeans had significantly higher 3-caffeoylquinic (3-CQA) and caffeoylferuloylquinic acids (CFQA)contents than washed coffee beans. Unwashed coffee beans had higher values for primary defect,secondary defect, odour, total-point and preliminary grade whilst washed coffee beans had better scoresfor acidity, body, and flavour attributes, which distinctly influence the ultimate taste profile of coffeeorigins. It is concluded that coffee bean quality attributes and contents of the associated chlorogenicacids improved in response to increased altitude under both shaded and unshaded conditions regardlessof the type of processing method used. The results imply that growing coffee plants in the highlands andmidlands rather than in the lowlands as well as washing the beans results in the production of coffeebeans with high quality attributes and chlorogenic acid contents that could meet the rising internationalmarket demands for high cup quality