Establishment And Properties Of Sustained Release System Of Tea Polyphenol Compound Preservative

Tea polyphenols/epsilon poly(lysine hydrochloride)microcapsules were prepared by emulsion spray drying method using polylactic acid(PLA)and ethyl cellulose(EC)as wall materials and TP and ?-PL as core materials,and TP-Lips/LZM-chitosan coatings were prepared by tape casting.Meanwhile,the microstructures of microcapsules and coatings were characterized by XRD,FT-IR,SEM and TEM for researching the interaction among the core/wall materials and coating components.And the preservation properties of microcapsules and chitosan sustained-release coatings to Sciaenops ocellatus were researched.In another way,we choose Shewanella putrefaciens and Pseudomonas fluorescens as the objects to reveal the action pathway and antibacterial mechanism of TP/?-PL microcapsules and TP-Lips/LZM-CS sustained-release coating.1.The micro-morphology of TP/?-PL composite microcapsules and their release in different systems were studied.The results showed that the particle size of composite microcapsules ranges from 8 to 10 ?m.In microcapsules,TP and ?-PL were released competitively in different release media.Their release kinetics accorded with Logistic model,and belonged to the joint action mechanism of core material diffusion and wall material corrosion.TP/?-PL composite microcapsules were applied to the preservation of Sciaenops ocellatus fillets at 4 ?.The results showed that TP/?-PL composite microcapsules could effectively inhibit the growth and reproduction of microorganisms and the oxidation of lipid and the degradation of protein in fish meat,the shelf life can be extended by 3-5 days.2.The bacteriostasis mechanism of TP/?-PL composite microcapsules was studied by choosing Shewanella putrefaciens and Pseudomonas fluorescens as the objects which were the dominant spoilage bacteria in aquatic products.The results showed that when treated by tea polyphenols,the morphology of the bacteria was changed,the cytoplasmic structure was destroyed,the intracellular substances dispersed to both sides of the cell membrane,and there were large cavities in the cells,and the cell membrane appeared holes.After treatment with ?-PL,the cytoplasm contracted sharply,accompanied by the decomposition of the cytoplasm.And after treated by TP/?-PL,the cytoplasmic structure of the bacteria was seriously damaged,the intracellular substances were dispersed,stomata appeared between cell walls and cell membranes,and there was a tendency of plasmic wall separation.Tea polyphenols combined with epsilon-polylysine hydrochloride can significantly reduce the integrity of cell membrane,increase the permeability of cell membrane and inhibit ATPase activity.At the same time,compared with tea polyphenols,epsilon-polylysine hydrochloride can decompose the total proteins between 43.0 kDa and 31.0 kDa.3.TP-Lips/LZM-chitosan composite sustained-release coating was prepared by tape casting method.The effects of TP-Lips and LZM on the morphology and physicochemical properties of chitosan coating were studied.The results showed that hydrogen bonds were formed between the hydroxyl group in TP and the free hydroxyl group in chitosan molecule.In addition,TP and LZM disrupt the orderly arrangement of chitosan molecule and destroy the network structure of chitosan,so the tensile strength of composite coating was increased and the elongation at break was decreased.The effect of TP-Lips/LZM-chitosan composite coating on the preservation of Sciaenops ocellatus showed that TP and LZM by the liposomes and chitosan coating could delay the growth of microorganisms,pH,thiobarbituric acid,volatile salt-based nitrogen and the change of the texture of Sciaenops ocellatus fillets,which significantly prolonged the Shelf life by 4~9 d.4.The bacteriostatic properties of TP-Lips/LZM-chitosan composite sustained-release coating and its effects on the integrity of bacterial cell membrane,membrane permeability,the activities of ATPase and AKPase and protein expression were studied with Shewanella putrefaciens and Pseudomonas fluorescens as the antimicrobial objects.The results showed that TP and LZM can significantly improve the bacteriostasis of chitosan coatings.The sustained-release coatings could effectively destroy bacterial cell membranes,increase the permeability of cell membranes,and change the synthesis and expression of bacterial proteins.When tea polyphenols were added to the coatings,the synthesis of protein between 31.0 kDa and 99.0 kDa decreased,while lysozyme had no significant effect on the synthesis and metabolism of total protein.