ウンシュウミカン果実の成熟に伴う糖, 有機酸の変化

Abstract

The sugar and organic acid components of satsuma mandarin (Citrus unshiu Marc.) fruit were investigated. ‘Okitsu Wase’, an early maturing cultivar, and ‘Silverhill’, a common cultivar, were employed in this study. Sugars were identified using a liquid chromatograph and organic acids were determined by a carboxylic acid analyzer. Fruit samples in both analysis were picked at half-month intervals.1. SugarThe predominant sugars analysed were sucrose, fructose and glucose in the juice and peel of both cultivars.Juice: The most pronounced variation was observed in sucrose which increased from 1.08 to 7.53mg and 1.23 to 6.90mg per 100ml of juice in the early and common cultivars, respectively. During the maturation, fructose also increased from 0.81 to 2.06mg and 0.75 to 1.84mg per 100ml of juice in the early and common cultivars, respectively. Glucose remained relatively constant throughout all stages in both cultivars. The total sugars in the early and common cultivars increased from 2.81 to 10.89mg and 4.41 to 9.97mg per 100ml of juice, respectively.Peel: In the early stages of both cultivars, sucrose and glucose were the predominant sugars. Sucrose, fructose and glucose increased gradually during maturation. Sucrose, especially, increased rapidly as the fruit approached full maturity. The total sugars in the early and common cultivars increased from 1.61 to 10.00mg and 1.53 to 11.95mg per 100g of peel, respectively.2. Organic acidThe organic acids detected in both cultivars were glucronic, lactic, acetic, pyruvic, malic, citric, succinic and iso citric acid.In early stages of maturation of each cultivars, citric and malic acids were the predominant organic acids, followed by iso citric acid. The most pronounced variation was in citric acid, which decreased from 2, 022 to 802mg and 2, 148 to 896mg per 100ml juice in the early and common cultivars, respectively.During the maturation, malic acid also decreased from 122 to 39mg and 85 to 37mg per 100ml of juice and iso citric acid decreased from 18 to 5mg and 13 to 8mg per 100ml of juice, respectively, in the early and common cultivars.Glucronic acid decreased with maturation, lactic, acetic and succinic acid remained relatively constant throughout all stages in both cultivars. α-Ketoglutaric acid was not detected at the mature stage in either cultivar. The total organic acid content in the early and common cultivars decreased from 2, 180 to 870mg and 2, 262 to 910mg per 100ml of juice, respectively.