Effect Of Temperature And Different Modified Atmosphere Packaging On Chilling Injury And Quality In Postharvest ’Cuixiang’ Kiwifruit

Kiwifruit has a short shelf life at room temperature after harvesting.Storing at a low temperature is an effective method to inhibit softening and maintain quality of fruit.In current postharvest practices,Kiwifruit is sensitive to low temperature and often displays notable visual symptoms of chilling injury（CI）,accompanied with bitterness of unknown cause,resulting in reduced commodity value and considerable consumer dissatisfaction.It is widely accepted that modified atmosphere packaging（MAP）is useful for maintaining the quality,alleviating the process of senescence and preventing the development of CI of fruit.MAP has been widely used in maintaining fresh of fruit after harvest.At present,there are few studies available on the effects of MAP on changes of physiology and quality and CI in kiwifruit.In this study,we investigated the effects of packaging films with three different thicknesses（MAP20、MAP30、MAP50）combined with two different low temperatures（0℃ and 2℃）on the development of CI and quality in’Cuixiang’kiwifruit.The results are as follows:1.’Cuixiang’ fruit stored at 0℃ showed the decreased respiratory rate and ethylene production,delayed peaks of respiratory and ethylene,reduced weight loss rate and rot rate.Fruit stored at 0℃ were also suppressed firmness,and vitamin C contents decrease and delayed total soluble solids contents increase;but CI occurred and it was also accompanied by slight bitterness in fruit.There was no CI occurred and interestingly,there was no bitterness appeared in fruit stored at 2℃,which maintained higher levels of L*value,total phenolics and flavonoid compounds and lower electrolyte leakage and malondialdehyde concentrations,with higher activities of superoxide dismutase,catalase,peroxidase and ascorbate peroxidise and lower activities of polyphenol oxidase and lipoxygenase.2.CI in‘Cuixiang’fruit was first observed after 49 d of cold storage at 0℃.The main symptoms of CI in‘Cuixiang’fruit were water-soaked appearance,browning and lignification in flesh.At the end of storage,‘Cuixiang’fruit showed 70%CI incidence.3.MAP treatments markedly maintained lower electrolyte leakage and MDA contents,delayed and alleviated CI in‘Cuixiang’fruit.4.MAP treatments reduced weight loss rate and rot rate in‘Cuixiang’fruit,delayed the increase of total soluble solids contents and the decrease of firmness,maintained higher levels of L*value and vitamin C,reduced respiratory rate and ethylene production,delayed the peaks of respiratory and ethylene.MAP treatments kept quality in‘Cuixiang’fruit.Fruit treated by MAP20 and MAP30 had positive effect on fruit quality,but there were CO₂ injury in packing films treated by MAP50,resulting in generated bitterness of fruit stored at 2℃ and exaggerated bitterness of fruit stored at 0℃,produced peculiar smells and off-flavors.5.CI and gas injury were causes of bitterness in‘Cuixiang’fruit when it stored at low temperature.6.CO₂ concentrations in packaging films treated by MAP30 was 4.2%-5.2%,which significantly reduced CI and kept quality,provided suitable storage environments for‘Cuixiang’fruit.In conclusion,‘Cuixiang’fruit stored at 0℃ suffered from severe CI,fruit stored at2℃ avoided CI and kept flavor quality,but could not maintain firmness and extend storage life;MAP treatments delayed and reduced CI,delayed firmness decrease and reduced physiological metabolism levels,but there was CO₂ injury in packaging films treated by MAP50 and exaggerated the bitterness of fruit.There were no CI and CO₂ injury in fruit treated by MAP30,which was an optimum package technique for‘Cuixiang’kiwifruit during cold storage.