Study On The Mechanism Of Compound Preservation Treatment On Softening Of Postharvest Long Jujube

Lingwu long jujube is the dominant characteristic jujube fruit in Ningxia of China,which is popular with consumers due to its large fruit shape,bright color,strong flavor,crisp and refreshing,pleasant taste,and high nutrition.However,postharvest Lingwu long fresh jujube has high respiratory intensity,rapid loss of nutrition value,easy to lose moisture and surface shrinkage,and susceptible to fungal infection and decay.Meanwhile,owing to the accumulation of ethanol would activities,the degradation of macromolecular substances and the decrease of hardness of jujube fruit.Eventually,the jujube fruit would gradually lose its commercial and edible value,and its shelf life would be shortened.Therefore,it has become an urgent problem for industrial development to explore the physiological changes of postharvest jujube fruit,reveal the mechanism of senescence and softening,and choose safe and effective preservation methods.In this work,Ningxia Lingwu long jujube was used as the research material,the effects of 1-MCP,CaCl2 and 1-MCP+CaCl2 on postharvest physiology and storage quality of long jujube fruit were compared through the determination of physical and chemical indexes during postharvest storage.The changes of cell wall substance content and related enzyme activities of long jujube treated with 1-MCP+CaCl2 were analyzed.From the molecular point of view,the regulation mechanism of the effect of compound preservation treatment on softening of postharvest long jujube was performed,which would provide a theoretical basis for the development and selection of suitable storage and preservation technology of long jujube.The detailed contents are as follows:(1)Effects of different preservation treatments on postharvest physiology and storage quality of Lingwu long jujube.Postharvest long jujube was treated with 1-MCP,CaCl2 and 1-MCP+CaCl2 respectively.The effects of treatment methods on weight loss rate,respiration rate,relative conductivity,the long jujube content of MDA,TA,TSS,Vc,and hardness were investigated.The results showed that the optimum preservation method of long jujube was 1-MCP+CaCl2,followed by 1-MCP and CaCl2.The weight loss rate,respiration rate,relative conductivity and MDA content of 1-MCP+CaCl2 treatment were significantly lower than those of the control group(P<0.05).The content of TA,TSS,Vc,and hardness were significantly higher than those of the control group(P<0.05).The comprehensive evaluation further showed that compared with the other two groups of preservation treatment methods,1-MCP+CaCl2 delayed the aging and quality deterioration of jujube fruit,and made the storage quality and nutritional value of jujube fruit better and higher.(2)Effects of 1-MCP+CaCl2 compound treatment on cell wall components and related enzyme activities of postharvest jujube.It was found that compared with the control group,the compound treatment group delayed the increase of PG,PME,β-Gal and Cx cell wall hydrolase activities.Thus,the increase of WSP content was inhibited,the contents of CSP,SSP,HC and CE were decreased,and the hardness of long jujube fruit was maintained,and the softening of jujube fruit was solved in the storage process,so as to extend the storage period.(3)Effects of the mechanism of 1-MCP+CaCl2 on the softening of postharvest jujube fruit.Based on LC-MS non-targeted metabonomics,the effect of 1-MCP+CaCl2 compound preservation treatment on metabolites of long jujube during storage was qualitatively and quantitatively analyzed,and the mechanism of the effect of treatment methods on softening of postharvest long jujube was analyzed.The results showed that 1902 known metabolites were identified in both positive and negative ion modes.The quantity of metabolites and significant enrichment pathways of jujube fruit are different under different storage time and different treatments.Compared with the control group,four enriched metabolic pathways related to softening were selected in the compound treatment group at the end of storage,which were amino sugar and nucleotide sugar metabolism,fructose and mannose metabolism,ABC transport and galactose metabolism,respectively.D-mannose,as a monosaccharide degraded by mannan,the main component of cell wall hemicellulose,participated in these four metabolic pathways and was down-regulated,which indicates that 1-MCP+CaCl2 compound treatment delayed the aging and softening of jujube fruit by slowing down the degradation of hemicellulose,thus achieving the purpose of keeping jujube fruit fresh.