In the previous paper, it was reported that the chilling injury in a cultivar of mume (Japanese apricot) fruits, unlike many other commodities, develop much sooner at 5°-60°C than at 1°C. This paper reports 4 years′ investigation on the aspects of chilling injury in mume fruits in relation to such factors as cultivars, maturity, and storage temperature, as well as polyethylene packaging as preventive measure. A study was also conducted to test van der Plank and Davies′shypothesis that the occurrence of maximum chilling injury at an intermediate temperature which they observed in plums, peaches, and grapefruits grown in South Africa would be a consequence of the interaction of the opposing two-equilibrium and kinetic-factors.
Nine cultivars of mume fruits were picked at the ordinary mature-green stage unless otherwise indicated, and stored at 0°-20°C.
While the primary symptom of chilling injury was pitting on the peel in most cases, but sometimes peel browning appeared first. Development of chilling injury was generally more rapid at 5°C than at 0°C. At 10°C, the injury was not found in 11 out of 24 cases, but sometimes it occurred to a serious degree. At 15°C, no injury was found.
Among cultivars used, Gyokuei was a very susceptible one showing rapid development and higher extent of the injury, while Bungo and Yasawa exhibited less sensitivity. Late-harvested fruits tended to be less susceptible than early-harvested ones even though the appearance at harvest was still in a mature-green stage. The extent of the injury also varied markedly with harvest years.
Packaging with polyethylene film (0.03mm thickness) bag completely prevented the occurrence of the pitting injury of the fruits stored at low temperatures. The incidence of rotting, however, was comparatively sooner in the bags at 5°C, holding at 0°C was needed for long term storage.
Prior to the storage at 5°C, a part of the fruits had been held at 0°C for several days. This treatment delayed the occurrence of the injury, as compared with the fruits of steady-5°C-storage, by an extent that exceeds the duration of 0°C-holding. This seems to be in opposition to van der Plank and Davies′ assumption, since, in addition to kinetic factor, the disposition towards injury (equilibrium factor) was considered more marked at 5°C.