Study On The Effect Of Pretreatment Combined With Microporous Modified Atmosphere Packaging On Fresh-cut Eggplants And Oranges

Fresh-cut fruits and vegetables are rich in nutrition,convenient and fast,so they are favored by consumers.However,the processing of fresh-cut fruits and vegetables has caused a certain degree of mechanical damage,which greatly aggravates the quality spoilage and shortened shelf life of fresh-cut fruits and vegetables.Therefore,the targeted development of efficient and safe preservation technology is of great significance.In order to use the mathematical model to simulate and determine the packaging parameters of the microporous modified atmosphere packaging of fresh-cut fruits and vegetables,the gas exchange model of microporous packaging and the respiration rate model of fresh-cut fruits and vegetables are studied.On this basis,a gas exchange model for the microporous modified atmosphere packaging of fresh-cut fruits and vegetables was established,and finally verified and applied.The results showed that the noncompetitive inhibition model in Michaelis Menten equation and the established gas exchange model were very suitable for characterizing the respiration rate and the gas concentration changes of fresh-cut eggplants and fresh-cut oranges in the packaging bag.The suitable microcellular modified atmosphere packaging for 150±2 g fresh-cut eggplant and 200±2 g fresh-cut orange was 4-hole diameter 103?m and 5-hole diameter 207?m PET bags,respectively.In order to determine the safe dosage of nano-zinc oxide as coating additive,the antibacterial activity and cytotoxicity of nano-zinc oxide with different particle size were studied,as well as the effect of nano-zinc oxide composite coating with different concentration and particle size on zinc migration of fresh-cut eggplant and fresh-cut orange was studied.The results showed that the smaller the particle size of nano-zinc oxide,the stronger the antibacterial effect and cytotoxicity,and the antibacterial effect on Escherichia coli was better than that of the Saccharomyces cerevisiae.The migration amount of zinc during nano-zinc oxide coating was related to its concentration,but had a smaller relationship with particle size.On the basis of zinc migration,comprehensive consideration of antibacterial activity(the minimum inhibitory concentration of 100 nm zinc oxide on Saccharomyces cerevisiae was 280 mg L^-1),cytotoxicity(100 nm zinc oxide concentration?50 mg L^-1)and the minimum dose principle,400 mg L^-1 100 nm zinc oxide was used for the subsequent coating treatment of fresh-cut eggplants and fresh-cut oranges.Considering that the quality storage of fresh-cut eggplant during cold storage is mainly browning and microbial infection,the combined preservation method of nano-zinc oxide composite coating(100 nm zinc oxide 400 mg L^-1,chitosan 1.5%,glycerol 0.45%)combined with modified atmosphere packaging(103?m,4 holes)on fresh-cut eggplant preservation was studied.The results showed that the combined treatment effectively improved the gas environment in the packaging bag,significantly inhibited the softening,mass loss(1.21%),respiration rate(5.10 m L CO₂kg^-1h^-1)and microbial growth(5.53 l og CFU g^-1)of fresh-cut eggplant during cold storage.At the same time,the combined treatment effectively delayed the decline of total anthocyanin content and total phenol content(retention rate was 70.77%and 88.88%,respectively),effectively inhibited the browning of fresh-cut eggplant,maintained a high visual index(5.67),making fresh-cut eggplant maintain a high quality within 15 days.Considering that the quality storage of fresh-cut orange during cold storage is mainly water loss,peculiar smell and microbial infection,the effect of combined treatment of pressurized argon(2 MPa,30 min)and nano-zinc oxide coating(the same as above)combined with microporous modified atmosphere packaging(207?m,5 holes)on fresh-cut orange preservation was studied.The results showed that the combined treatment could effectively reduce the mass(4.23%)and ascorbic acid loss of fresh-cut orange,reduced the increase of soluble solids,effectively inhibited respiratory rate and the growth of total bacteria and fungi(5.74 log CFU g^-1and 4.83 log CFU g^-1),and maintained high sensory score and water uniformity during cold storage.In addition,the electronic nose test showed that the fresh-cut orange treated with the combination had the least volatile characteristic odor,while the main odor of fresh-cut orange in the later period of cold storage was related to the increase in the content of compounds such as aldehydes,alcohols,esters and terpenes.The combined treatment allowed the fresh-cut oranges to maintain a high quality within 16 days.