Studies On The Preparation Of A Novel Biological Preservative For Aquatic Products

Chlorogenic acid(CGA),a type of plant polyphenol,was conjugated onto gelatin(Gel)to prepare a novel coating material for the preservation of aquatic food in the current study.The structure and biological activities of CGA-Gel conjugation were determined.Terminal restriction fragment length polymorphism(T-RFLP)and High-throughout sequencing were used for identification of the specific spoilage organism(SSO)in swors prawn(Parapenaeopsis hardwickii)during superchilling storage.And the antibacterial activity of CGA-Gel on the SSO separated from swors prawn was evaluated.On the other hand,CGA-Gel was combined with superchilling and the coating preservation effect on swors prawn was detected.Some physicochemical indicators and total bacteria count were determined to evaluate the preservation effect of CGA-Gel,combined with sensory evaluation.The main results were as follows:1.The optimal reaction molar ratio of CGA to gelatin(4:1)was determined according to the CGA content in the CGA-Gel conjugate.And the optimal content of CGA in CGA-Gel was 8.48%.CGA was confirmed to be successfully conjugated onto gelatin according to the assay by 1H nuclear magnetic resonance and Fourier transform-infrared spectroscopy.The antioxidant activity of CGA-Gel was proven to be.higher than that of the free CGA in 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate)radical scavenging,hydrogen peroxide scavenging,ferric ion reducing power and lipid oxidation assays.The minimum inhibitory concentrations(MIC)of CGA against Escherichia coli,Pseudomonas aeruginosa,Listeria monocytogenes and Staphylococcus aureus were I,1.2 and 2 mg/mL,respectively.The antibacterial activity of CGA-Gel was unaffected by conjugation.2.The freezing point of swors prawn was detected to be-3.5?.Therefore,the superchilling temperature was set to be-5.0± 0.5?.3.The result of T-RFLP was in accordance with that of high-throughout sequencing,indicating that the diversity of the spoilage bacteria in sword prawn was decreasing during the storage.Shewanella,Psychrobacter,Pseudomonas species became the dominant bacteria at the final stage of storage.Shewanella and Pseudomonas species were identified as the SSOs of swors prawn.4.The pH value,TVB-N value,TBA value,Ca2+-ATPase activity and total bacteria count were determined during storage,with sensory evaluation.The results indicated that the pH,TVB-N and TBA values were all increasing,and CGA-Gel group exhibited lower rising speed than that of the Control group,implying excellent capability of delaying protein decomposition and lipid oxidation,which were superior to CGA.The Ca2+-ATPase activity of sword prawn was decreasing during storage.CGA-Gel inhibited the decline of Ca2+-ATPase activity,revealing that the protein degeneration of sword prawn could be prevented by CGA-Gel.The total bacteria count was increasing during storage,and the proliferation of spoilage bacteria was delayed obviously by CGA-Gel.The results of sensory evaluation was in accordance with above conclusions,and the quality of sword prawn was as follows:CGA-Gel group>CGA group>Gel group>Control group.