Effect Of Oxalic Acid Treatment On Chilling Injury In Harvested Kiwifruit

The fruits of Kiwi are easy rotten and hard to be stored for a long time.It has been proved that the cold storage condition was thought to be a good method for extending the postharvest life of kiwifruits which can effectively inhibit fruit from softening.However,kiwifruit is susceptible to chilling injury during low temperature storage,which has been a key factor to severely restrict the preservation and quality control of kiwifruit at present.Oxalic acid is a kind of safe,nontoxic and biological metabolism organic acid which can not only delay the postharvest of fruit but also maintain good fruit quality and reduce the harmless from the chilling.In order to explore the effect of oxalic acid treatment on the chilling injury.The Harvested kiwifruit?Actinidia Chinensis ‘Huayou'?were dipped in 5 mmol/L-1 oxalic acid?OA?solution for 10 min at room temperature and then stored at 0±0.5??90% 95% RH?for 90 days,based on the pre-screening experiments of the proper concentration of oxalic acid.Then we explored the changes of phenotypes,quality,active oxygen metabolism and energy charge metabolism which were effected in chilled kiwifruit at 0?.The main results are as follows.1.The kiwifruit chilling injury symptom was gradually worse,the chilling injury index and chilling injury rate was also rising with the extension of storage time.The chilling symptoms of fruits with Oxalic acid treatment were delayed about 10 days than control.After stored for 40 days,the Oxalic acid could significantly inhibit the rising chilling injury index and chilling injury rate of fruits.That showed Oxalic acid could inhibit the cold sensitivity of chilling injury happening and improve the fruit cold tolerance.2.Oxalic acid could delay the fruit firmness and reduce the content of titratable acid,on the same time,maintain higher the soluble solids in the later storage period.In addition,oxalic acid treatment delayed the respiration peak and ethylene release peak,and decreased the peak value to maintain a higher rate of good fruits and lower ratio of weight loss under low temperature storage.The results suggested that Oxalic acid could maintain the quality of kiwifruit at low temperature storage.3.The cell membrane permeability were significantly lower in the Oxalic acid treated fruits compared to the control after stored for 10 days.In addition,the Oxalic acid treatment not only reduced the accumulation of malondialdehyde?MDA?,but also made the fruits maintained a low lipoxygenase?LOX?activity.This suggested that Oxalic acid could maintain the integrity of the cell membrane to improve the cold tolerance.4.Oxalic acid treatment could significantly improve the activities of superoxide dismutase?SOD?,catalase?CAT?,ascorbate peroxidase?APX?and glutathione reductase?GR?,increase the levels of ascorbic acid?AsA?and glutathione?GSH?,moreover,decrease the accumulation of the superoxide anion?????and radical and hydrogen peroxide?H₂O₂?to protect the fruit from reactive oxygen injury,which finally improved the cold tolerance5.Oxalic acid treatment caused a high ATP content in fruit and inhibited the increase of AMP,while had no obvious effect on the ADP content.It was suggested that oxalic acid could maintain a higher ATP and energy charge,which finally release the chilling injury in kiwifruit at low temperature storage.