Shade and postharvest processing effects on arabica coffee quality and biochemical composition in lowland and midland coffee-growing areas of southwestern Ethiopia

Hitherto, studies on shade and postharvest processing (PHP) effects on coffee quality across elevation ranges (ER) are limited. The effects of shade, PHP and their interaction on quality and caffeine, sucrose and chlorogenic acids (CGAs) contents of arabica coffee beans in lowland (1100-1550 m asl) and midland (1550-1900 m asl) were evaluated. The results showed that physical, total preliminary and total specialty qualities were higher for beans grown in midland than those grown in lowland, but CGAs (57.5 g kg-1 dw) were higher for beans grown in lowland. Dry-processed midland coffee had higher physical and total preliminary qualities with lower 3,5diCQA (6.9 g kg-1 dw) and FQA (4.4 g kg-1 dw) than wet-processed lowland and midland coffees. Conversely, wet -processed lowland coffee had lower physical and total preliminary qualities with higher 3,5diCQA (8.7 g kg-1 dw) and FQA (4.7 g kg-1 dw) than dry-processed lowland and midland coffees. Coffee beans grown with shade in lowland had lower acidity than those grown without shade in lowland and midland. But, coffee beans grown without shade in lowland had lower caffeine (13.8 kg-1 dw) than those grown with shade in lowland and midland. Physical and total preliminary qualities were negatively correlated with caffeine, 4-CQA, 3,5diCQA, FQA and total CGAs. This study is the first to show the relationship between ER and PHP in coffee quality and biochemical composition of green arabica coffee beans.