Kadozan Treatment Affecting Storability Of Harvested Chinese Olive Fruits And Its Action Mechanism

Chinese olive(Canarium album(Lour.)Raeusch)is one of the unique subtropical fruit trees in southern China which has high nutritional and medicinal value.Chinese olive fruit is susceptible to decay at room temperature.The pericarp color of Chinese olive fruit transforms green to yellow during storage.It can be prone to browning and dehydration,which seriously influences the edible flavor and storage quality.In this paper,‘Changying’ Chinese olive(Canarium album(Lour.)Raeusch cv.Changying)fruit,the main cultivated variety in Fujian Province of China,was used as the raw material for experiment.The objectives were firstly to select the optimum concentration of kadozan for Chinese olive fruit by preservation effects on different concentrations of kadozan(chitosan),then to investigate the effects of the optimum concentration kadozan treatment on postharvest physiology,quality and storability.Then the research could be aimed at studying the effects of the optimum concentration kadozan treatment on storability of Chinese olive fruit,from reactive oxygen species metabolism,membrane lipid metabolism,respiratory metabolism,energy metabolism,antifungal substances metabolism,and therefore to explain the mechanism of storability of Chinese olive fruit by kadozan treatment.The results were showed as follows:1.Preservation effects of kadozan treatments of different concentrations for postharvest Chinese olive fruit.Compared with control fruit stroed at(8±1)℃,kadozan treatments of different concentrations(diluted by 250,500,750 and 1000 times,respectively)could delay the respiratory climacteric and the increase in cell membrane permeability of Chinese olive fruit,maintain higher contents of TSS,total sugar,acid and vitamin C,tannin in pulp of Chinese olive fruit,delay the decline in contents of pulp pigment.Kadozan treatment could also decrease pulp disease index and browning index,and keep higher the rate of commercially acceptable fruit and lower water loss percentage.Especially,the effects of the kadozan treatment diluted by 500 times was optimum among them.According to these results,the kadozan diluted by 500 times treatment could be used as the optimum concentration for maintaining physical quality and storability of‘Changying’ Chinese olive fruit.2.Effects of the optimum concentration kadozan(diluted by 500 times)treatment on physiology,quality and storability of harvested Chinese olive fruit.Compared with control fruit,the results indicated that kadozan diluted by 500 times treatment could decrease the respiration intensity and delay the increase in cell membrane permeability of Chinese olive fruit,keep higher nutrient contents including TSS,sugar,acid,vitamin C and tannin in pulp of Chinese olive fruit,delay the decline of chlorophyll content in the pericarp.Kadozan diluted by 500 times treatment could also decrase the disease index,browning index of Chinese olive fruit,and maintain higher commercially acceptable fruit percentage and lower the rate of water loss.According to these results,kadozan diluted by 500 times treatment could enhance storability and storage quality of Chinese olive fruit.3.Effects of the optimum concentration kadozan(diluted by 500 times)treatment on ROS metabolism in pulp of harvested Chinese olive fruit.The results showed that,compared with control fruit,kadozan diluted by 500 times treatment could improve the activities of ROS scavenging enzymes including superoxide dismutase(SOD),catalase(CAT)and ascorbate peroxidase(APX),keep higher glutathione(GSH)and ascorbic acid(AsA),delay increase of superoxide anion radical(O2-·)production rate and malondialdehyde(MDA)content,and keep higher DPPH scavenging activity and reducing power.According to these results,kadozan diluted by 500 times treatment could increase the scavenging activities of ROS,reduce the reactive oxygen species accumulation and membrane lipid peroxidation process,maintain the integrity of cellular membrane structure in pulp of Chinese olive fruit.Therefore kadozan diluted by 500 times treatment could improve storability and maintain storage quality of Chinese olive fruit.4.Effects of the optimum concentration kadozan(diluted by 500 times)treatment on membrane lipid metabolism in pulp of harvested Chinese olive fruit.The results showed that,compared with control fruit,kadozan diluted by 500 times treatment could decline the activities of lipase,phospolipase D(PLD)and lipoxygenase(LOX),delay the increase of phosphatidic acid content,keep higher relative contents of unsaturated fatty acids and index of unsaturated fatty acids(IUFA),maintain lower relative content of saturated fatty acids in pulp of Chinese olive fruit.According to the result,kadozan diluted by 500 times treatment could inhibit membrane lipid-degrading enzymes due to higher relative contents of unsaturated fatty acids.It also could be beneficial to the integrity of cell membrane structure of Chinese olive fruit.Therefore kadozan diluted by 500 times treatment could improve storability and maintain storage quality of Chinese olive fruit.5.Effects of the optimum concentration kadozan(diluted by 500 times)treatment on respiratory metabolism in pulp of harvested Chinese olive fruit.The results showed that,compared with control fruit,kadozan diluted by 500 times treatment could keep lower activities of ascorbic acid oxidase and Cytochrome C oxidase of Chinese olive fruit,hold NAD kinase,maintain higher contents of NADPH and NADP,keep lower NAD and NADH contents.According to these results,kadozan diluted by 500 times treatment could keep lower respiratory terminal oxidase activities of Chinese olive fruit.Therefore kadozan diluted by 500 times treatment could improve storability and maintain storage quality of Chinese olive fruit.6.Effects of the optimum concentration kadozan(diluted by 500 times)treatment on energy metabolism in pulp of harvested Chinese olive fruit.The results showed that,compared with control fruit,kadozan diluted by 500 times treatment could provide and maintain energy for metabolic of Chinese olive fruit.It could keep higher ATP,ADP content and energy charge level,hold the activities of H+-ATPase,Ca2+-ATPase,Mg2+-ATPase.According to these results,kadozan diluted by 500 times treatment could balance osmotic pressure of Ca2+、Mg2+、H+ of Chinese olive fruit through higher energy charge level and the activities of ATPase.It also could maintain the integrity of cell membrane structure of Chinese olive fruit.Therefore kadozan diluted by 500 times treatment could improve storability and maintain storage quality of Chinese olive fruit.7.Effects of the optimum concentration kadozan(diluted by 500 times)treatment on antifungal substances metabolism in pulp of harvested Chinese olive fruit.The results showed that,compared with control fruit,kadozan diluted by 500 times treatment could increase the contents of antifungal substances including lignin,flavonoid and total phenols,increase the activities of disease defense-related enzymes such as phenylalanine ammonialyase(PAL),β-1,3-gulcanase(GLU)and chitinase(CHI),induce the increase of activities of PPO and POD at early storage period.According to these results,kadozan diluted by 500 times treatment could enhance activities of enzymes,improve storability and disease resistance of Chinese olive fruit.