カンキツ類における果皮酸度の差異, 全酸, 遊離酸, および結合酸濃度間の関係およびそれら酸濃度の果肉汁酸濃度との関係

Abstract

Total, free, and combined acidity of fruit rind were determined on 85 samples from 70 citrus species, to reveal their genetic variations.Free acidity of rind in most samples was below 17me/100g.Total acidity of rind in all samples lay between 4 and 23me/100g.The percentage of free acidity in total acidity was between 12 and 39% with two exceptions of 45% and 58%, and the average of all samples was 22%.Combined acidity in most samples was between 3 and 11me/100g. However, that of nine samples, namely Funadoko, Yuzu, Dancy tangerine, Jimikan, Rusk citrange, Mediterranean mandarin, and Miyauchi Iyo excceded 11me/100g, up to 23.2me/100g.There were high correlation coefficients among the three acidities within each group of samples. However, when all samples were observed as a whole, free acidity and combined acidity did not correlate significantly.Total, free, and combined acid content of rind per fruit were very high in Pummelo, which has the maximum weight of fruit and rind. Sudachi with the minimum weight of fruit and rind showed the lowest content of total, free, and combined acids. Acid content tended to be higher in species with heavier fruit weight and rind weight.However, the proportion of acid in rind to acid in whole fruit had no correlation to proportion of rind weight to whole fruit weight.The acid content of rind in relation to that of whole fruit was 0.8-47.5% for free acid, 2.3-48.7% for total acid, 18.0-72.5% for combined acid. Therefore, in order to get an accurate physiological understanding of the organic acids of citrus fruits, the total, free, and combined acid content of rind tissues should also be determined when estimating those of the whole fruit.