Abstract
A series of studies was conducted to improve the practical management of tankan (Citrus tankan Hayata) ‘Tarumizu 1 go’. Seasonal changes in fruit growth, peel color, and other important parameters of internal fruit quality such as sugar content and acidity of juice together with juice vesicle growth and respiration rate were monitored throughout the production cycle. The findings showed that mean fruit mass increased between July and December. Increased juice vesicle weight is considered to contribute to this increase in fruit mass. The rate of fruit growth decreased from December onward. The number of juice vesicles per section was determined by July and did not show any increase thereafter. The weight of juice vesicles increased dramatically between July and November and then increased gradually. The length of juice vesicles slowly increase between August and February. Juice vesicle respiration decreased rapidly between July and November, and remained constant thereafter. Coloring of the peel started from October, but delayed that of fruit pulp. Brix rose from October. This was attributed to the increase in sucrose, the principle sugar component. There was a slight increase in glucose and fructose content towards fruit maturity, though these sugar contents were lower. The titratable acidity fraction reached its peak in August and decreased drastically through September into December. A level around 1% was maintained thereafter. The change in the titratable acidity fraction coincided with that of citric acid fraction which comprised more than 90% of the total acid fractions. Though malic acid was also found, its concentration was consistently low.
