| Passion fruit has rich nutritional value and outstanding medicinal value.Due to its intense postharvest physiological metabolic activity and serious water loss,its quality deteriorates rapidly.It is difficult to solve the problems of weight loss and microbial growth of passion fruit during room temperature storage at the same time by a single fresh-keeping technology commonly used at present.Therefore,it is of great significance to seek suitable composite treatment methods for the preservation of passion fruit.Microporous packaging（MP）can establish a stable gas environment and a suitable humidity environment in the package because of its specific gas and water penetration and diffusion properties,so as to regulate the consumption of passion fruit nutrients and inhibit water loss.Chitosan has natural antibacterial and film-forming properties,and the chitosan active coating（CH）prepared by combining with other natural active substances has great potential in the antibacterial and fresh-keeping of passion fruit.Based on this,this subject created a dual modified atmosphere microenvironment based on microporous packaging and chitosan active coating（MP-CH）,and applied it to the room temperature storage and preservation of passion fruit to evaluate its effects;the specific results are as follows:1.The changes of physiological and biochemical quality of passion fruit in control（CK）,chitosan active coating（CH）,nonporous packaging（NP）,microporous packaging（MP）and microporous packaging combined with chitosan active coating（MP-CH）during room temperature storage were studied.Both nonporous and microporous packaging treatments could effectively maintain the environmental humidity to inhibit the serious water loss of passion fruit,and the microporous packaging could effectively inhibit the anaerobic respiration and high carbon dioxide damage of passion fruit by adjusting the gas concentration.However,the packaging treatment also led to the rapid reproduction of microorganisms,the addition of chitosan active coating could effectively inhibit the growth of microorganisms,combination of the two made passion fruit establish a balance between water loss and microbial growth.Results showed that compared with the control group,CH,NP,MP and MP-CH treatments had certain effects on inhibiting the shrinkage,the increase of weight loss rate,the increase of p H and the decrease of hardness of passion fruit.CH treatment could regulate the respiration rate of passion fruit,and the dual modified atmosphere microenvironment based on MP and CH further inhibited the increase of the respiration rate of passion fruit.In addition,MP-CH treatment had the best effect in delaying the decline of TSS,Vc and TPC contents in passion fruit.At the end of storage,the contents of TSS,Vc and TPC in the MP-CH group were 1.23,2.25 and 1.92 times higher than those in the control group,respectively.The shelf life of passion fruit was effectively extended from 3 days at room temperature to 12 days.2.The effects of different treatments on reactive oxygen species and cell wall metabolism of passion fruit were studied by measuring the content of reactive oxygen species,activity of antioxidant enzymes,content of lipid peroxidation products in cell membrane,content of cell wall constituents and activity of cell wall degrading enzymes.Results showed that the active oxygen metabolism of passion fruit in the control group was out of balance,the content of active oxygen and peroxidation products continued to increase,and suffered severe oxidative damage;the continuous degradation of cell wall constituents resulted in the destruction of the normal structure of the passion fruit cell wall.MP-CH treatment delayed the increase of O2-·production rate,H2O2 and MDA content by increasing the activities of SOD,CAT and POD,thereby enhancing the antioxidant capacity of passion fruit.In addition,MP-CH treatment also inhibited the degradation of protopectin,cellulose,hemicellulose and the increase of soluble pectin by reducing the activities of PME,PG and CEL in passion fruit,thereby maintaining the stability of the cell wall structure of passion fruit.3.Differential proteins of the fresh passion fruit（F）stored on the 0th day of storage,the control group（CK）and MP-CH group after storage for 12 days were identified,and 5201 credible proteins were obtained.Among them,730 differential proteins were screened out,among which there were 359 differential proteins in MP-CH/CK group（179 upregulated proteins and 180 downregulated proteins）.Taking the differential proteins of the MP-CH/CK group as the research object,GO analysis results showed that differential proteins were mainly involved in metabolism,biological regulation and stress response processes.Among them,the upregulated proteins were involved in the processes of cell,small molecule metabolism,L-ascorbic acid biosynthetic,anthocyanin-containing compound biosynthetic,aspartate family amino acid biosynthetic and regulation of protein stability.It was also related to oxidoreductase activity,structural molecular activity and ligase activity.The downregulated proteins were involved in oxaloacetate metabolism,carbohydrate metabolism,organic substance metabolic,cellular lipid metabolism,pectin catabolism and galacturonan metabolic,and also related to hydrolase activity and pectinesterase activity.KEGG analysis showed that key proteins were involved in metabolic pathways such as phenylpropanoid biosynthesis,protein processing in endoplasmic reticulum,starch and sucrose metabolism,cyanoamino acid metabolism,and the interconversion of pentose and glucuronic acid.Meanwhile,MP-CH treatment enhanced the antioxidant capacity of passion fruit by increasing the expression of DHAR,NADH dehydrogenase,POD,L-galactose dehydrogenase and GST proteins.The increased expression of molecular chaperone Htp G improved the stress protection ability of passion fruit,thereby enhancing stress resistance.In addition,MP-CH treatment reduced the expression ofβ-Glu,PME,PG,and glucan endo-1,3-β-glucosidase proteins,helping to delay the degradation of pectin,cellulose and hemicellulose,thereby maintaining the stability of the cell wall structure of passion fruit. |
