モモ果実の品質保持に対する低温流通の効果

Abstract

In our country white flesh peach fruits are mostly harvested at shipping maturity, i. e. initial stage of ripening, to protect from over-softening and bruising during distribution which is usually carried out at ambient room temperatures (25°C-30°C). 2-4 days are needed from producers to consummers. Recently there has been increased public interest in peaches harvested at the full ripe stage. The fruit is shipped at a low temperature in order to offer higher quality peaches to consummers.The present experiment was designed to simulate the conditions of transportation facilities for distribution. Peach fruit was held for 4 days after harvest at the room temperature of about 27°C or at 3°C. Their tastes were compared by 100 panel members and further quality changes were estimated by measuring total sugar, titratable acidity, ground color of peel and softening. Three cultivars belonging to fruits having white flesh, ‘Sunago’‘Hakuho’and‘Aichi Hakuto’were used in the experiment.1. When harvested at conventional shipping maturity and held at 3°C, there was no advantageous effect of low temperature on the taste of fruits.2. When harvested at full ripe stage and held at 3°C, sweetness was superior to the fruits harvested at shipping maturity and held at room temperature thereafter. At that time, the fruits at 3°C contained 8.8% total sugar and had 40ml of acid determined by titration with 0. 1N sodium hydroxide in 100ml juice, while the fruits held at room temperature displayed 8.3% and 55ml, respectively.3. The decreasing rates of sugar content during 4-day-holding in fruits held at room temperature and 3°C were 3.4% and 1.1%, respectively, and the decreasing rates of titratable acidity were 12.3% and 7.0%, respectively. The ground color of peel in the fruits at room temperature turned from light green to light yellow and fruit flesh softened to some extent during holding, while these changes in the fruits at 3°C were hardly detectable. It seemed therefore that the changes of ground color of peel and softening were strongly influenced by storage and shipping temperatures, but total sugar content and titratable acidity were hardly influenced at all.4. Total sugar content in peach fruits increased with the stage of ripening at harvest time, and then decreased at overripe or senescent stage. Titratable acidity decreased with the stage of ripening. The fruits softened characteristically, and the ground color of peel changed markedly from light yellow during ripening.In conclusion, the optimum time of harvest is the most important factor for distribution of peach fruit having good quality. This time is the full ripe stage of fruits for the case of short-haul transportation facilities as in our country when fruits are held at a low temperature.