Effects of modified atmosphere package on preservation of green walnut fruit

In order to provide basis of a new simple effective technology for green walnut fruit storage，the effect of modified atmosphere package on refrigerated storage of the fruit was investigated. Green walnut fruit of variety Liaoning No.4 were stored under 0～1℃ with different packages of plastic film, i.e. improved polyvinyl chloride (mPVC), modified polyethylene ( thn-PE, thk-PE) and complex treatment of 1-MCP fumigation plus mPVC to test the effect of modified atmosphere (MA) packages on gas concentrations in each bag, postharvest physiology as well as storability of the fruit. Results showed that among all packages tested thk-PE bags showed strongest MA-effect, which adjusted inner-bag O2 and CO2 volume fraction during storage to 10.1%～13.0%, 4.3%～6.5%, respectively. Both the respiration intensity and ethereal production rate of green walnut fruit showed two-peak type trend during the storage. MA package delayed appearance of each peak and significantly (p<0.01) decreased peak values. Soluble solids content of fruit from both treatment and control all increased during early storage phase and then decreased，but the decrease from each treatment occurred earlier than that from control. MA package significantly (p<0.01) reduced fruit weight loss and thk-PE bag had the best effect. MA packages also reduced the decay rate of fruit. Rotting index of fruit in thk-PE bag was 30.0% after 66 days storage and 68.6% after 95 days, which were significant (p<0.01) lower than that in other packages. Therefore, thk-PE bag can be selected as the suitable MA approach for the storage of green walnut fruit, which can keep 100% preservation rate of walnut after a storage period of about 95 days.