| Xinjiang apricot fruit is rich in phenolic compounds,unique flavor,popular with consumers.However,the harvest of apricot fruit is concentrated,and it is easy to soften and rot postharvest,which seriously restricts the export sales of fresh apricot.At present,logistics express delivery has become the main way of fresh apricot export sales,fresh apricot picking often without a long time of pre-cooling directly into the logistics export,logistics packaging is mainly filled with nitrogen(N2),but long time sealed packaging and hypoxia will cause the fruit anaerobic breathing,alcohol and odor problems.How to solve the negative effects of quick pre-cooling and N2 long-time sealing packaging of fresh apricot has become an urgent technical problem to be solved in Xinjiang fresh apricot logistics industry.Project prophase study found that the vacuum precooling can quickly reduce the thermal field of apricot fruit,short-term nitrogen packing can effectively inhibit the growth of microorganisms,vacuum precooling combined with N2 packaging can effectively extend shipping time and quality of apricot fruit,optimization of vacuum precooling and N2 short-term packaging technology,to improve the quality of the xinjiang apricot of sinotrans has important application significance.Therefore,in this study,Xinjiang Li-Guang-apricot and Xiaobai-apricot were used as the main research materials to analyze the changes of fruit quality parameters,cell wall metabolism,active oxygen metabolism and sugar components related enzyme activities under the conditions of vacuum precooling combined with N2 packaging,and to explore the effects of vacuum precooling combined with N2packaging technology on postharved-storage and transportation quality of fresh apricot.This study provided theoretical and technical support for the application of vacuum precooling combined with N2 packaging technology in the storage and transportation of fresh apricot fruit postharvest.(1)Vacuum precooling and N2 packaging treatment of fresh apricot after harvest were screened out.Under the conditions of vacuum precooling(the final temperature of precooling was 2?,4?and 6?)and N2 treatment(the time was 2 h,4 h and 6 h)and storage and transportation temperature was 20?,the parameters related to the quality of fresh apricot post harvest were measured.The suitable temperature of vacuum precooling was determined by hardness,color difference,breathing intensity and ethylene release.The decomposition rate,hardness and cell membrane permeability were taken as the main indexes to analyze the conditions of vacuum precooling combined with N2 treatment.The optimal treatment process was selected as vacuum precooling at 4?combined with N2 treatment for 2 h.(2)The changes of cell membrane integrity and cell wall metabolism related enzymes(pectin methyl esterase,cellulase,polygalacturonase)in fresh apricot under the same final pressure and different final temperature and N2 treatment were studied.This indicates that vacuum precooling combined with N2treatment could effectively slow down the increase of cell membrane permeability,reduce the enzyme activity of cell wall metabolism,maintain the integrity of cell membrane,and prolong the storage period of fresh apricot fruit.Vacuum pre-cooling combined with N2 treatment can effectively inhibit the decrease of original pectin content and the increase of soluble pectin,inhibit the decomposition of cellulose,the activity of pectin methyl esterase was decreased,cellulase and polygalacturonase in apricot pulp,and delay the softening of fresh apricot fruit.By the end of storage,the contents of original pectin,soluble pectin and cellulose in the vacuum pre-cooled fruit with N2 treatment were 0.50%,6.88%and 0.19%respectively.Cellulase activity was 7.25 U·g-1,pectin methyl esterase activity was 9.38 U·g-1,polygalacturonase activity was 9.38 U·g-1.Therefore,vacuum precooling combined with N2 treatment is a fresh way to delay fruit softening and improve fruit storage.(3)The inhibition effect of vacuum precooling combined with nitrogen(N2)treatment on the reactive oxygen species metabolism of fresh apricot during the storage and transportation was studied.The results showed that vacuum precooling combined with N2 treatment could delay the decrease of fruit hardness as well as inhibit the increase of malondialdehyde and cell membrane permeability in postharvest Xiaobai apricot.N2 treatment(2 h)can significantly restrain the respiratory intensity,delay the peak of ethylene and maintain the hardness of apricot.The activities of catalase,superoxide dismutase,ascorbate peroxidase,peroxidase and polyphenol oxidase were also improved by vacuum precooling combined with nitrogen(N2)treatment.On the 18 d of storage,compared with the control group,the hardness of fresh apricot treated by vacuum precooling combined with N2 was increased by 28.68%,and the activities of CAT,SOD,APX and POD were increased by 54.58%,45.34%,56.82%,and 24.87%,respectively.These results demonstrate that vacuum precooling combined with N2 treatment leads to reduce the accumulation of reactive oxygen species and oxidative damage which maintain the integrity of cell membrane and delay the senescence of postharvest fresh apricot.(4)The changes of glycolic acid components under the conditions of the same final pressure and different final temperature and N2 treatment were compared.The main sugars in fresh apricot fruits are glucose,fructose and sucrose,and sucrose is the main sugar,glucose content was the second.The study found that:vacuum precooling combined with N2 treatment could effectively delay the accumulation of soluble sugar and the color change in apricot.Meanwhile,vacuum precooling combined with N2 treatment can significantly reduce the loss of malic acid and citric acid in fresh apricot fruit,and reduce the decomposition rate of organic acids to a certain extent. |
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