ハウス栽培マンゴー「Ｉｒｗｉｎ」果実の発育および追熟中における呼吸量，糖質および有機酸含量の変化

Abstract

Seasonal metabolic and chemical changes in the developing mango (Mangifera indica L. 'Irwin') fruit cultured in a plastic house at the Yuasa Experimental Farm (34° north latitude, 135° east longitude), Kinki University, at Yuasa-cho in Wakayama Prefecture were investigated. The fruits which had developed from June 14 (young-fruit stage) to August 21 (mature green stage) and the ones which were picked at mature green stage on August 2, 8 and 21 and stored at 25 °C were used. The changes in respiration rate, soluble sugars and starch, and organic acid content were determined.The fruit enlarged rapidly before the endocarp started to harden on July 4, but it slowed after the hardening process stopped on July 19.The respiration rate of fruit during development declined rapidly until July 19, but remained steady thereafter. The postharvest respiration reached maximum value on the 1st or 2nd day after the onset of the climacteric rise. The beginning of coloring and flesh softening coincided with the time when the respiration rate reached the climacteric peak. The emission of aroma began at a few days later after coloring.At harvest on August 21, fructose and sucrose contents were 3.4 g • 100 g-1 FW and 1.9 g • 100 g-1 FW, respectively, whereas, glucose content was 0.2 g • 100 g-1 FW. Fructose was the predominant sugar during development. Starch content increased rapidly from 2.1 g • 100 g-1 FW to 11.7 g 100 g-1 FW between July 19 (completion of endocarp-hardening) and August 21. After ripening, starch became almost undetectable, whereas sucrose increased significantly; fructose increased slightly. As a result, the major sugar was sucrose with the majority of the reducing sugar being fructose. Thus, if the mature green stage fruit has high starch content, it tends to have a high sugar content at the full ripe stage one.Of the organic acids, citric and malic acids were detectable, the former being more abundant than the latter. Citric acid content increased to a maximum of 1.4 g • 100 g-1 FW at the beginning of the endocarp-hardening period then decreased steadily to 0.6 g • 100 g-1 FW on August 21. It decreased further in full ripe fruit.Based on our data, we believe that the time when the skin begins to turn red and/or yellow on the tree, is the optimum harvest stage for the 'Irwin' mango fruit cultured in a plastic house.