Sugars and organic acids changes in pericarp and endocarp tissues of pumelo fruit during postharvest storage

Pumelo, a citrus fruit that originated from China and is widely planted there, is popular for its excellent quality and storage properties. Sugars and acids play critical roles in maintaining fruit quality. However, the detailed changes of sugars and acids that occur in pumelo are largely unknown. We measured the soluble sugars and organic acids concentrations in different tissues of Shatian pumelo (Citrus grandis), Guanxi pumelo (C. grandis) and Hirado Butun pumelo (HBP; C. grandis x Citrus paradisi) stored at ambient temperature (10-16 degrees C) by gas chromatography and high-performance capillary electrophoresis. During storage, organic acids and soluble sugars concentrations in the pulp fluctuated significantly instead of simply decreasing or increasing. The variations in citric, malic, aconitic and fumaric acid concentrations showed no substantial difference as did fluctuations in sucrose, fructose and glucose concentrations. In the pulp, the concentration of sucrose was a little higher than, or close to, that of glucose and fructose. However, the sucrose concentration in the pericarp was much lower than that of glucose and fructose. In the pulp of HBP, the change trend of sucrose concentration was opposite that of organic acid concentration after storage for 20 days post harvest (DPH). Sugar/acid ratios in HBP and Shatian pumelo increased with the storage time, while they decreased in Guanxi pumelo. The total concentration of soluble sugar decreased slightly in the pulp, but sucrose concentration decreased significantly (except in the Shatian pumelo); while in the pericarp, the total soluble sugar concentration showed a dramatic decreasing trend, indicating that carbohydrate transport from the pulp to pericarp or carbohydrate redistribution might occur in postharvest citrus fruit. (C) 2012 Elsevier B.V. All rights reserved.