Effect of MA Conditions on Occurrence of Kohansho and Quality of 'Kiyomi' Tangor

The effect of MA conditions under high humidity packaging on the occurrence of postharvest Kohansho and the quality attributes of stored 'Kiyomi' tangor (Citrus unshiu Marc. × C. sinensis Osb.) fruit was investigated. Modified atmosphere containing CO2 concentrations less than or equal to 12% and O2 concentrations more than or equal to 10% had no effect on the occurrence of Kohansho under high humidity conditions. However, the occurrence of Kohansho was accelerated when the CO2 level accumulated to 14%. Under the condition that CO2 levels are not too high and O2 levels are not too low, maintenance of a high relative humidity surrounding the fruit is considered to be the main factor for packaging design to prevent Kohansho. Furthermore, excessive CO2 levels (more than 8 %) induced fermentative metabolism, resulting in high ethanol levels. MA conditions had no significant effect on the quality attributes, including firmness, TSS, TA, TSS/TA ratio, and AA contents under the high humidity condition. These qualities were preserved during the storage period, probably resulting from the maintenance of a high relative humidity inside the package. As recommended storage conditions and packaging design guidelines, 'Kiyomi' fruit should be stored particularly under a high relative humidity and should not be exposed to high CO2 levels (>8 %) and /or low O2 levels (<5 %) to prevent Kohansho and preserve high quality.