Study On Preservation Effects And Mechanism Of PBAT Based Spontaneous Modified Atmosphere Packaging On Allium Mongolicum Regel

Allium mongolicum Regel(A.mongolicum)is a high-quality plant resource but highly perishable with short shelf life which restricts the development of A.mongolicum industry.In order to delay the aging and decay of A.mongolicum during storage,it took A.mongolicum as the object of preservation,took modified atmosphere packaging-gas permeability as the key factor,and used biodegradable poly(butyleneadipate-co-terephthalate)as the main body in the study to research the relationships between the barrier properties of PBAT-based modified atmosphere packaging and the postharvest physiological characteristics of A.mongolicum.Further optimized PBAT-based modified membranes that matched the characteristics of A.mongolicum,and explored its effects on the quality,physiology,biochemistry,and microbial diversity of A.mongolicum.Meanwhile,based on UPLC-MS/MS detection platformhe and extensive targeted metabonomics technology,analysed the metabolic reaction and preservation mechanism of A.mongolicum under PBAT-based modified atmosphere packaging.The main research content and results are as follows:1.Changes in postharvest quality and physiology of A.mongolicum regulated by PBAT/PBS,PBAT/PCL,PBAT/PLLA,PBAT/PP film packings were investigated to find the relationship between the barrier properties of blend films and the postharvest physiological characteristics of A.mongolicum.The results showed that the barrier properties of blend films were differently significantly,moreover,the barrier properties were significantly related to the postharvest physiological characteristics of A.mongolicum.Four packings all could effectively reduce the respiration rate,water loss,decay rate and malondialdehyde content significantly and maintain ascorbic acid and chlorophyll contents as well as the morphology,color and typical flavor of A.mongolicum which had high level commercial acceptability.However,the preservation effect packed with PBAT/PP was significantly better than the other three packings in which it could form an optimal atmosphere conditions with O₂ concentration of 0.34-0.53%and CO₂ concentration of 4.53-6.13%which could maintain the postharvest quality and reduce respiration metabolism and surface microorganisms of A.mongolicum.2.The PP/PBAT blend films was prepared by melt extrusion,then packaging performance and preservation effect of PBAT/PP blend films on A.mongolicum were studied.The results showed that PBAT/PP blend system was incompatible.With the increase of PBAT content,the transmission properties of CO₂ and H₂O were enhanced.When the addition of PBAT was increased to 30%,the CO₂ transmission coefficient,CDP/OP and H₂O transmission coefficient were increased by 49.7%,53.3%and 145.5%.In addition,the barrier property of the blend films was closely related to the film thickness,the barrier properties of blend films of 35?m thickness were significantly lower than that of the 25?m thickness.The blend film in which the addition content of PBAT is 30%and its thickness was 35?m packed A.mongolicum,it could formed atomosphere that matched the physiological characteristics of A.mongolicum,with O₂ ranging from 0.48 to 0.66%and CO₂ ranging from 5.98 to 6.53%.It also could significantly reduce respiration rate and extend the shelf life to 20 days with the sensory score out of 6 of A.mongolicum.3.The preservation effects,postharvest physiology and microbiological population of A.mongolicum were studied treated by two methods,one is PP/PBAT pontaneous modified atmosphere packaging and another is SAEW wash combined PP/PBAT pontaneous modified atmosphere packaging.The results showed that PP/PBAT pontaneous modified atmosphere packaging could regulate postharvest physiology and maintain the quality of A.mongolicum by inhibiting respiration rate,membrane lipid peroxidation and membrane damage and the growth and infection of microorganisms.Compared with PE treatment,respiration rate,decay rate,malondialdehyde and relative electrolyte leakage conductivity of A.mongolicum reduced by 59.6%,83.9%,32.7%and 31.7%,Pseudomonas counts and Psychrophile plate counts reduced by 1.6 log CFU·g^-1and1.87 log CFU·g^-1.SAEW wash treatment could reduce initial microbial populations,but cound not inhibit its increase.Analysed the change of microbiological diversity and it was found that Pseudomonas was the dominating spoilage bacteria during the storage in this study.When the concentration of O₂was lower than 0.1%,the abundance of Pseudomonas and Clostridiales were all increased significantly.4.Based on the UPLC-MS/MS detection platform and extensive targeted metabonomics technology,analysed he metabolic differences between PP/PBAT packaging and PE treatment.Meanwhile analysed the metabolic reaction and preservation mechanism of A.mongolicum under PP/PBAT modified atmosphere packaging which provided an important theoretical basis for the preservation mechanism of A.mongolicum.The study found that the KEEG pathway enriched significantly in metabolism of linoleic acid and?-linolenic acid in this experiment.The most of the categories of DAMs was"lipid",which was 86 down-regulated and 3 up-regulated.(5S,8R,9Z,12Z)-5,8-Dihydroxyoctadeca-9,12-dienoate;(9Z,11E)-13-Oxooctadeca-9,11-dienoic acid;9,10-Dihydroxy-12,13-epoxyoctadecanoic acid;9(S),12(S),13(S)-Trihydroxy-10(E)-octadecenoic acid;9-Oxo-10E,12Z-octadecadienoic acid;13(S)-Hydroxyoctadeca-9Z,11E-dienoic acid;9S-Hydroxy-10E,12Z-octadecadienoic acid;9S-Hydroperoxy-10E,12Z-octadecadienoic acid;?-Linolenic Acid;Crepenynic acid;Linoleic acid;(9Z,11E)-Octadecadienoic acid;these compounds participated in the metabolism of linoleic acid.9-Hydroxy-12-oxo-15(Z)-octadecenoic acid;2-Dodecenedioic acid;12-Oxo-phytodienoic acid;13S-Hydroxy-9Z,11E,15Z-octadecatrienoic acid;9-Hydroxy-10,12,15-octadecatrienoic acid;9-Hydroperoxy-10E,12,15Z-octadecatrienoic acid;these compounds participated in the metabolism of?-Linolenic Acid.PP/PBAT packaging may counld inhibit the lipid peroxidation and degradation of membrane and maintain the integrity of cell membranes and the quality of A.mongolicum by regutating the gas composition inside the packing.Furthermore,PP/PBAT packaging could down-regulate amino acids and their derivatives,phenolic acids and flavonoids,up-regulate saccharides and alcohols significantly.