Effect of altitude on biochemical composition and quality of green arabica coffee beans can be affected by shade and postharvest processing method.

Although various studies have assessed altitude, shade and postharvest processing effects on biochemical content and quality of coffee beans, data on their interactions are scarce. The individual and interactive effects of these factors on the caffeine, chlorogenic acids (CGA) and sucrose contents as well as physical and sensory qualities of green coffee beans from large plantations in southwestern Ethiopia were evaluated. Caffeine and CGA contents decreased with increasing altitude; they respectively declined 0.12 and 1.23gkg-1 100m-1. Sucrose content increased with altitude; however, the altitude effect was significant for wet-processed beans (3.02gkg-1 100m-1), but not for dry-processed beans (0.36g kg-1 100m-1). Similarly, sucrose content increased with altitude with much stronger effect for coffee grown without shade (2.11gkg-1 100m-1) compared to coffee grown under shade (0.93gkg-1 100m-1). Acidity increased with altitude when coffee was grown under shade (0.22 points 100m-1), but no significant altitude effect was observed on coffee grown without shade. Beans grown without shade showed a higher physical quality score for dry (37.2) than for wet processing (29.1). These results generally underline the complex interaction effects between altitude and shade or postharvest processing on biochemical composition and quality of green arabica coffee beans.