Respiratory Physiology of Mature-green Mume (Prunus mume Sieb. et Zucc.) Fruits in Four Cultivars Held under Various Controlled Atmospheres at Ambient Temperature

The respiratory physiology of mature-green mume (Japanese apricot, Prunus mume Sieb. et Zucc.) fruits was investigated using four cultivars (Gojiro, Nankou, Hakuoukoume, Shirakaga) ; fruits were held for 7 days at 25 °C under various controlled atmospheres (CA).1. Changes in respiration rates were similar in four cultivars; those held in 3% O2 or higher attained climacteric maximum of O2 uptake and CO2 production rates almost concurrently up to the 3rd day. O2 uptake and CO2 production rates in the fruits depended on the CA conditions, decreasing as the O2 concentration was lowered, or conversely, as the CO2 concentration was increased. Anaerobic respiration of mume fruits occurred at O2 concentration of up to 2% at 25 °C.2. Ethyl alcohol and acetaldehyde production rates increased from the 4th day of CA storage. Fruits held at O2 concentration of up to 1% developed browning injury and produced ethyl alcohol at a high rate; the percentage of fruits with water-core injury was high in the CA condition of low O2 in the absence of CO2.3. Ethylene production rates were suppressed under high CO2 concentrations or O2 levels less than 5%. In 3% O2 or higher, ethylene production rates reached the peak half or one day after the respiratory climacteric peak. However, in all CA conditions, the volume of ethylene produced was highly correlated with that of O2 uptake during the 7-day storage.4. These results indicate that maintaining mume fruits in about 10% CO2 and 3-4% 02 may help to retain optimum quality at 25 °C, but that such CA conditions delayed the respiratory climacteric rises just slightly and increased ethyl alcohol production after the 3rd day of storage. Therefore, under these conditions, the storage period of mume fruits at ambient temperature may be limited to 3 days.