| Some natural plant extracts have been found to have a wide range of antimicrobial,anti-cancer and anti-inflammatory effects.For example,curcumin has antioxidant,prevention of Alzheimer's disease,anti-inflammatory,choleric and antibacterial effects.Limonene has antibacterial,antioxidant,anti-inflammatory,anti-tumor and other effects,so they can be used as food additives for food preservation,and can also be widely used in the pharmaceutical industry to prevent the occurrence of diseases.However,most of the natural active ingredients are fat soluble substances and are easily affected by light and temperature during storage,so their application value is limited.Nanodelivery system is an ideal drug delivery system,which can improve the solubility and stability of drugs,as well as achieve targeted delivery and slow release.Compared with polymer carrier materials,protein-based nano-delivery systems have attracted much attention due to their biosafety and biodegradability.This study focuses on the effect of sodium caseinate nano-delivery system on the stability and activity of hydrophobic active components,which will have a broad application prospect in food anticorrosion and prevention of microbial infection.1.Sodium caseinate(NaCas)loaded with curcumin was prepared by self-assembly method.The nanoparticles were characterized by FTIR,XRD,UV,SEM and Zeta potential.Under the suitable host and guest ratio,the encapsulation efficiency of curcumin could reach 98.23%.The results of scanning electron microscopy showed that the nanoparticles were typical spherical with a size of about 200 nm.In addition,the temperature stability and light stability of free curcumin and curcumin nanoparticles were studied.The results showed that the nanoparticle structure significantly improved the light stability and thermal stability of curcumin,and the degradation of free curcumin was faster at the same concentration and in the same environment.2.The limonene essential oil emulsion was prepared by high energy emulsification method.With sodium caseinate as surfactant,various factors affecting the emulsion were systematically studied,including high pressure homogenizing pressure and number of cycles,surfactant concentration,oil phase to water phase ratio.Finally,the minimum particle size of essential oil emulsion was obtained when the average pressure was 80 MPa,the circulation was 13 times,and the surfactant content was 1.0 wt%,which reached 120 nm.Then,the storage stability of the prepared emulsion was studied by particle size,potential,turbidity,centrifugal sedimentation coefficient and other parameters.The results showed that the emulsion still maintained good stability after storage at low temperature for 2 months without Oscar ripening,and the microstructure also showed that the emulsion did not aggregate.3.The minimum inhibitory concentration(MIC)of common microbial strains in food(Staphylococcus aureus,Escherichia coli and Bacillus subtilis)was determined.It was found that high pressure homogenization did not affect the antibacterial effect of the emulsion,and nanoscale emulsion was more conducive to enter the bacteria and play a better antibacterial effect.4.It can be seen from the antibacterial growth curve of the emulsion on microorganisms that the bacteria almost did not grow in the experimental group treated with the essential oil emulsion with MIC and 2MIC concentration.It is proved that limonene essential oil emulsion has good bacteriostatic effect.The changes of bacterial structure were observed by scanning electron microscopy,and it was revealed that D-limonene emulsion and curcumin nanoparticles mainly destroyed bacterial cell membrane,resulting in wrinkle and depression of cell membrane,and the bacteria could not grow normally. |
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