CHANGES IN THE CONTENT OF SUGARS AND ORGANIC ACIDS DURING RIPENING OF COFFEA ARABICA AND COFFEA CANEPHORA FRUITS

Abstract

Changes in concentration (% of dry weight) and content (mg/organ) of sucrose, glucose, fructose and some organic acids in pericarps and seeds of Coffea arabica cv. Mokka, C. arabica cv. Catimor and C. canephora were monitored during the development and ripening of fruits. The coffee fruits were categorized into five stages 1 to 5 which corresponded to young, developing, fully-developed (green), ripening (pink) and fully-ripened (red) fruits, respectively. In all samples, the major sugars in young fruits (stage 1) were fructose (~5% dry weight) and glucose (~3% dry weight). Significant amounts of sucrose were also found in the later stages of development. The concentration of sucrose in ripened pericarp and seeds (stage 5) in two cultivars of C. arabica (19-25% of dry weight in pericarp and 8‒18% in seeds) was higher than those in C. canephora (8% in pericarp and 5% in seeds). Sucrose was accumulated exclusively in seeds of two cultivars of C. arabica. In contrast, both sucrose and the reducing sugars, fructose and glucose, accumulated in pericarps of all coffee samples and in seeds of C. canephora. The concentration of malic acid, citric acid, lactic acid, oxalic acid and quinic acid changed during development and ripening of fruits. The values of most organic acid fluctuated between 0‒1%, except for a transient, high content of quinic acid (>2%) in young fruits. Characteristic accumulation patterns of organic acids were found in different organs; citric acid concentration was high in seeds, but malic acid or oxalic acid was high in pericarps. Possible metabolic routes of metabolites are discussed.