The Noval Polymeric Iron Chelator-incorporated Edible Antimicrobial Coating And Its Application In Aquatic Product Preservation

Aquatic product is a healthy food,which readily taints at room temperature,while its quality will be reduced when stored in the frozen environment.Therefore there is a need to develop an efficient cold preservation technology for aquatic products.Metal chelating agents have already been widely used in many fields of food industry,and relevant researches suggested that some chelators possess strong antibacterial activity in vitro.Polymeric chelators may find application in the field of food preservation due to low toxicity.Edible coating and film can be used in food preservative by packaging on the food surface after the foods have been processed.In addition,they serve as barriers between food and environment,rendering them retard the post-processing microbial spoilage.In this study,the monomeric chelator of hydroxypyridinone(HPO)hexadentate ligand was synthesized from methyl maltol,which was then polymerized with 2-hydroxyethyl acrylate,providing polymeric chelators.In vitro antimicrobial activity and cytotoxicity of both monomeric and polymeric chelators were evaluated.At last,the preservative effect of edible antimicrobial zein coating incorporating polymeric chelator on grass carp fish balls was investigated,aiming to develop a new approach for the preservation of aquatic product.The main results that we have obtained are as follows:1.The benzyl-protected bidentate HPO was synthesized starting from methyl maltol via a series of reactions including benzylation,condensation,oxidation,reduction and ammonification,which was then coupled to a tripodal molecule containing three carboxyl groups via amido bond.The obtained compound was subjected to hydrogenation,providing the monomeric chelator of hexadentate HPO with C-C double bond.All the compounds have been fully characterized by NMR,MS and HRMS.The physic-chemical properties of the hexadentate HPO were determined by spectrophotometric titration.The results indicate that this ligand possesses a very high affinity for Fe3+ with logarithm stability constant of its iron complex(logK)of 33.61 and a pFe value of 30.37.2.Polymerization of monomeric chelator and 2-hydroxyethyl acrylate with different mole ratios(0%,1%,3%,5%,7%and 9%)was carried out in the presence of AIBN,a free radical initiator,generating six batches of copolymers.The iron chelating capacity of each polymeric chelator was determined using spectrophotometer,and the utilization rate of monomeric chelator was also calculated.On the consideration of all these factors(including iron chelating capacity,utilization rate of monomeric chelator and yield),the polymer obtained with the molar ratio of 5%was chosen for further investigation.The yield,iron chelating capacity and utilization rate of monomeric chelator were 67.0%,261.7μmol/lg,55.9%,respectively.3.Escherichia coli,Staphylococus aureus,Bacillus subtilis,Salmonella,and Pseudomonas aeruginosa were chosen as the tested strains.In vitro antimicrobial activity of the monomeric chelator and polymeric chelator against the five tested strains was evaluated by inhibition zone,MIC and MBC assays.It has been demonstrated that both monomeric chelator and polymeric chelator possess marked.inhibitory activity against the five tested strains and there is no significant difference between the two chelators.Cytotoxicity of the two chelators was evaluated using a MTT assay,which indicated that both polymeric and monomeric chelators lack obvious toxicity.These results suggest that both of them,especially polymeric chelator,have potential application in food preservation.4.Edible antimicrobial coating was prepared by incorporating polymeric chelator into zein.The preservative effect of this edible antimicrobial coating on grass carp fish balls was investigated by determining the sensory quality,bacterial counts,TVB-N value,TBA value and pH value.The results indicate that the edible antimicrobial coatings(addition amount of polymeric chelator was 1 mg per mL film-forming solution)possess good preservative effect on grass carp fish balls,extending the shelf life up to 20 days.