Studies On Storage Effect Of Oxalic Acid And Potassium Oxalate On Kiwi Fruit And Its Physiological Mechanism

Effects of oxalic acid and potassium oxalate treatment on postharvest quality,physiological respons,antioxidant senescence and cell wall hydrolase in 'walter' and'Bruno' kiwi fruit were investigated in this paper.The two varieties kiwi fruit were dipped in 50mM oxalic,75mM oxalic,50mM potassium oxalate,75mM potassium oxalate solutions and water which as control for 10 min respectively,then placed in the storage under the constant temperature of 25?.Determine the effects of oxalic acid and potassium oxalate treatment on the quality change,antioxidant senescence and softening of the cell walls and other related physiological indices of kiwifruit,and explore the oxalic acid and potassium oxalate on kiwi fruit postharvest storage effects and its physiological mechanism.The main results of the research are as follows:1?The effects of oxalic acid and potassium oxalate treatment on the characteristics of Kiwifruit storage qualityThe rust on surface of kiwi fruit were effectively removed,the fruit appearance quality were improved,the weightlessness rate were inhibited,shrinks phenomenon,virus infection and morbidity were reduced for the treatment of oxalic acid and potassium oxalate.The rise of contents of soluble solids and soluble sugar,the content of titratable acid,the decomposition of Vc,the hydrolysis of starch were inhibited in each treatment.Then the peakof the respiration intensity and the rate of ethylene were reduced,and the peak time were delayed.The appearance of kiwi fruit were improved,and the fruit storage quality were maintain well with oxalic acid and potassium oxalate treatment.2?The effects of oxalic acid and potassium oxalate treatment on the antioxidant system of kiwifruitThe activity of antioxidant enzymes refer to superoxide dismutase(SOD),catalase(CAT)and peroxidase(POD)were increased for the treatment of oxalic acid and potassium oxalate,with which the oxygen free radicals were cleared.To the fruits of the two strains,the activity of SOD were maintained in a high level with oxalic acid and potassium oxalate treatment in the storage period,and the activity of SOD was higher than the control throughout the storage period.The activity trend of CAT was similar to the SOD.Compared with the control,the activity peak of POD of ' Walter'fruit treatment appeared 3 days later.The POD activity peak of control and processing group of'Bruno' both appeared in the 15th day after storage,but the control peak was significantly lower than the treatment group,to ease the oxygen free radical damage to the fruit and delay senescence.The rise of the content of MDA was inhibited with oxalic acid and potassium oxalate,but to the two strains fruits,the oxalic acid treatment was better,and the high concentration of oxalic acid was better than the low one,which showed that this treatment was better able to inhibit the accumulation of MDA in the fruit.The protective effect of oxalic acid on kiwifruit membrane permeability was better than that of potassium oxalate.The antioxidant enzyme activity in kiwi fruit were inproved with oxalic acid and potassium oxalate treatment,and then the cell damage were reduced,fruit senescence were delayed.3.The effects of oxalic acid and potassium oxalate treatment on the metabolic enzymes of kiwifruit cell wallThe activity peak time of polygalacturonase(PG)in 'Walter' kiwi fruit was not effected with the treatment of oxalic acid and potassium oxalate,but the peak value of the activity peak was lower than the control.Compared with 'Walter' fruit,the rising trend of PG activity of 'Bruno ' fruit was faster,but the rise of PG activity was also inhibited for oxalic acid and potassium oxalate treatment.Oxalic acid and potassium oxalate treatment did well to reduce the peak value of alpha-galactosidase(a-Gal)activity peak of the two strain fruits,but the inhibitory effect later was obvious.The peak of beta-galactosidase(?-Gal)activity in kiwi fruit were significantly inhibited for Oxalic acid and potassium oxalate treatment in the later storage,and then decreased in a steady phase in fruit firmness,effectively maintain the flesh firmness.To the two strains of kiwi fruit,the peak of xylanase activity were inhibited for the treatment of oxalic acid and potassium oxalate,andthe xylanase activity in 'Bruno' kiwi fruit was maintained at a low level in later storage.The cell wall hydrolase of kiwi fruit could be inhibited with oxalic acid and potassium oxalate treatment,cell wall Hydrolysis rate be reduced and the fruit softening be delayed.