Organic Acids in the Ripening Banana Fruit

The nonvolatile organic acids undoubtedly play a role in fruit ripening as they do in many other metabolic processes. As an approach to defining this role in the banana fruit, information is needed on the nature of these acids and on the changes which occur during ripening. Earlier reports (23) indicate the presence of malic, citric, oxalic, and tartaric acids in the banana fruit, with malic acid being the principal acid. Lulla and Johar (13) found only malic and citric acids in 9 varieties of bananas from India. Wolf (25) found the same 2 acids plus an unknown fraction in Colombian bananas. Steward et al. (20) have recently reported the presence of 30 organic acids in alcoholic extracts of the banana fruit. Malic and citric acids were predominant; the other acids occurred in trace amounts. These workers also detected 22 keto acids by extraction of the phenylhydrazones. There is little quantitative information available on the organic acids in bananas or on the changes which occur during ripening. The malic acid concentration has been reported to vary between 0.8 and 7.5 meq/100 g fresh weight (23) and to increase three to sevenfold during ripening (2, 8). Pyruvic, a-ketoglutaric,-and oxaloacetic acids also increase during the ripening (2). The present study was undertaken to confirm the identity of the nonvolatile organic acids of the banana fruit and to determine the concentration of these acids throughout ripening.