Preparation Of Microcapsules Of Houttuynia Cordata Oil,Study On Bacteriostatic Mechanism And Application In Pork Preservation

Houttuynia cordata oil has many physiological activities such as antioxidation and antibacterial activity,and may be a potential natural preservative.However,it is not conducive to storage and use due to its volatile,poor stability and strong smell.In order to improve these defects,chitosan and carboxymethyl tamarind gum were used as wall materials to prepare a microcapsule embedding system of Houttuynia cordata oil by a complex coacervation method in this study.The comprehensive performance and antibacterial mechanism of the embedding system were studied,and it was applied to the preservation of pork to explore preservation effect.The main research conclusions are as follows:Through single factor and response surface experiment,the optimum technological conditions for preparing microcapsules were obtained:p H 4.9,glutaraldehyde concentration 0.55%（v/v）,chitosan concentration 0.94%（m/v）,Houttuynia cordata oil concentration 0.27%（m/v）,and the best encapsulation efficiency was 64.68%.The microcapsules obtained under this condition were characterized by structure and functional activity.The results showed that the microcapsules exhibited irregular particle morphology with a uniform size and an average grain diameter of14.44μm.FTIR showed that chitosan and carboxymethyl tamarind gum formed microcapsules through electrostatic interaction.DSC and TGA showed that the stability of Houttuynia cordata oil after embedding was significantly enhanced.The release experiment showed that the microcapsule had sustained release behavior,and the release curve was well fitted with the first-order kinetics（R²>0.97）;At the same time,the sustained-release verified that the antioxidation of microcapsules would be stronger than oil with time.The results of antibacterial activity showed that Houttuynia cordata oil and its microcapsules had the strongest inhibitory effect on Staphylococcus aureus,and microcapsules was stronger than oil.The preliminary exploration of the inhibitory mechanism of Houttuynia cordata oil and its microcapsules on Staphylococcus aureus showed that:1×MIC oil or microcapsules treatment extended the time for Staphylococcus aureus to enter the logarithmic phase to 14 h,while 2×MIC completely inhibited the growth of bacteria.The relative conductivity and leakage of intracellular substances(protein,soluble reducing sugar,nucleic acid OD_260nm)of the cells treated with oil or microcapsules increased with time,and the leakage of microcapsules was higher than that of free oil.Scanning electron microscopy showed that the bacteria treated with Houttuynia cordata oil and its microcapsules were seriously damaged.In addition,the agarose gel electrophoresis table showed that oil and microcapsules didn’t affect the DNA synthesis of bacteria.The fresh-keeping experiment of Houttuynia cordata oil microcapsule on chilled pork showed that microcapsules significantly inhibited the growth of microorganisms during storage,and the total number of bacterial colonies didn’t reach the standard of rotten meat at the 12th day.Secondly,the microcapsules effectively delayed the increase of p H,inhibited the growth of TBARS and TVB-N,reduced the drip loss,and maintained the color and texture of meat.These results showed that the microcapsules of Houttuynia cordata oil could significantly improve the preservation process of pork,and could prolong the shelf life of pork to 12 days.To sum up,the stability and functional activity of Houttuynia cordata oil are improved after embedding,and its effective action time is extended.After being used in the preservation experiment,the shelf life of pork is extended,and the application range of Houttuynia cordata oil is widened.