Establishment Of Tea Polyphenol Sustained Release System And Its Preservative Properties And Antibacterial Mechanism

The antibacterial tea polyphenol/phytic acid composite microcapsules with competitive sustained release properties were prepared by spray drying method,using the TP and PA as core material,and Ethyl cellulose as wall material.Meanwhile,adding the tea polyphenol microcapsules and lysozyme to PVA solution,TP microcapsule/LZM-PVA composite coatings with continuous release properties were prepared by casting method.Furthermore,the microcapsules and coatings were characterized by SEM,TEM,XRD and FT-IR.The competitive release kinetics of tea polyphenol/phytic acid composite microcapsules and physicochemical properties of TP microcapsule/LZM-PVA composite coatings were researched.Using Sciaenops ocellatus fillets as preservation objects,the preservation performances of microcapsules and composite coatings were measured.And antimicrobial mechanism and action pathway of microcapsules and composite coatings to dominant spoilage bacteria of aquatic products,Shewanella putrefaciens and Pseudomonas fluorescens,were researched.1.The microstructures and core material release kinetics of TP/PA composite microcapsules were researched.And the results show that TP/PA composite microcapsules exhibited competitive release in different media,conforming to the Logistic kinetic mode.Then the preservation properties of TP/PA microencapsulation on S.ocellatus fillets were investigated at 4?storage.The results show that,comparing with the control group,the value of total viable count?TVC?,pH,and TVB-N were significantly inhibited by TP/PA composite microcapsules.Because the core material are sustained release from the microcapsules,at the later stage of storage,the preservative effect of microcapsules embedded with preservative is significantly better than that of non-embedded preservative.And the preservative properties of the composite microcapsules are the optimal.2.Taking the dominant spoilage bacteria of S.putrefaciens and P.fluorescens as the target objects,the antibacterial properties and mechanism of TP/PA composite microcapsules were researched.The results show that Compared with the preservatives unencapsulated,the microcapsulated preservatives have long-lasting antibacterial properties.Moreover,the damage degree to the integrity and permeability of the bacterial cell membrane are increased,and the synthesis and expression of the bacterial protein are changed.The polyphenol and polycyclic structures of TP have good affinity with biological macromolecules,such as proteins,lipids and nucleic acids,which destroy bacterial cell membrane structure.Meanwhile,the cell membrane and cell wall are affected by PA.Furthermore,a synergistic effect of TP and PA is observed,which damaged cell membrane more seriously.Further,it could effectively inhibit the growth of the bacteria,and then good antibacterial properties are presented.3.The TP microcapsule/LZM-PVA composite fresh-keeping coatings with grade-by-grade sustained release properties were prepared by coating method,and its microstructure were characterized,and its physicochemical properties were determined.The results show that the mechanical properties and permeabilities of PVA coatings are improved due to adding TP and LZM.It may be explained that the hydrogen bonding force are formed,because the hydroxyl groups of PVA interacted with the hydroxyl groups of TP and amine group of LZM.Furthermore,the molecular structure become compact,and the intermolecular forces are enhanced.Then the preservation properties of TP microcapsule/LZM-PVA composite coatings to S.ocellatus fillets were measured during 4?storage.The results show that compared with the control,the freshness of S.ocellatus fillets are maintained effectively by the coatings,and the oxidation of protein and fat,and the increase of colony count of fillets are inhibited effectively.After adding TP microcapsule,the physicochemical properties of the coatings film are improved.The preservation properties of the composed coatings are the optimal due to the step by step release of TP from the microcapsules to the coating,abd then to the surface of the fish body.4.The antibacterial properties and mechanism of TP microcapsule/LZM-PVA coatings were studied.The results show that the PVA coating without preservative has no antibacterial properties.TP and LZM could effectively improve the antibacterial properties of the composite coating,inhibit the growth of bacteria,and destroy the cell membrane and cell wall of the bacteria.Furthermore,antibacterial properties were enhanced due to release step by step of TP microcapsules.And the wall material of TP microcapsules is chitosan,which has positively charged-NH³⁺and interacts with negatively charged species on the surface of bacterial cell membranes.It can make cell membrane destroy and permeability enhance.Hence,the antibacterial property of TP microcapsule/LZM-PVA composite coatings is the optimal.