Relationship between Change in Mitochondrial Function and Chilling Injury of Cucumber Fruit

Abstract

Effect of storage temperature and humidity on the function of mitochondria prepared from cucumber fruits was investigated in relation to the occurrence of chilling injury, The cucumber fruits were packaged in perforated polyethylene bag (dry condition) and non-perforated but not-sealed polyethylene bag (humid condition) and stored at 1, 6 and 15°C, respectively. Pitting, a symptom of chilling injury, was observed at 1°C after 2 days in perforated bag and after 4 weeks in non-perforated bag, while it did not occur at 6 and 15°C in both packages.
Carbon dioxide evolution from the fruits showed a trend to be higher in non-Perforated package than in perforated one throughout the storage at 1 and 6°C. A marked increase of CO₂ evolution was found when the fruits were transferred from 1°C to 15°C, in the same manner in both packages.
The rate of succinate-oxidation of mitochondria prepared from 1°C stored-fruits decreased with advance of storage period, whereas it increased gradually or kept the same level as that prepared from 6 and 15°C stored-fruits. The rate was higher in the fruits in non-perforated bag at every temperature. Respiratory control ratio (RCR) of mitochondria was about 1.6 at the beginning of storage. During the storage at 1°C it rapidly decreased and became about 1.0 after 4 days, indicating disappearance of respiratory control ability. At 6 and 15°C, it decreased reaching to 1.3, but kept the value after that. These trends were similar between the 2 packages regardless of temperature.
The change in ADP/O ratio was also similar between both packages, and it decreased rapidly at 1°C, in contrast to an increase at 6 and 15°C. The reduction of RCR at 1°C was reversible within a week of storage, and was restored when the fruits were transferred to 15°C.
From the results mentioned above, it may be concluded that early occurrence of pitting injury was found under dry condition such as in perforated package at 1°C, while the lowering of mitochondrial function would be induced immediately by low temperature storage at 1°C, irrespective of packaging style or storage humidity.