Preparation Of Curcumin Nanoemulsion And Its Application In Preservation Of Letinous Edodes

Curcumin has a wide range of biological and pharmacological activities.As a natural photosensitizer and additive,curcumin has the advantages of safety,no toxicity,wide source,green and no pollution.However,its disadvantages such as poor solubility and instability limit its application in food,medicine and other fields.The use of nanoemulsion to curcumin can effectively solve the problems of poor water solubility,stability and low bioavailability.In this paper,the modification of whey protein isolate（Wpi）was achieved through the glycosylation reaction with rhamnose（Rha）to obtain a whey protein isolate-rhamnose conjugate（Wpi-Rha）,Then,the emulsifying ability of Wpi was improved;Wpi-Rha was used as emulsifier to prepare curcumin nanoemulsion by high-speed shearing-high pressure homogenization technology.The processing stability and storage stability of the nanoemulsion were investigated by indicators such as turbidity,centrifugal stability constant and entrapment rate.Combined with photodynamic sterilization technology,the bactericidal effect of curcumin nanoemulsion on Escherichia coli and Staphylococcus aureus was tested.To explore the effect of light conditions on the sterilization effect.The physical and chemical properties of shiitake mushrooms during storage were investigated,and the effect of curcumin nanoemulsion combined with photodynamic sterilization on the preservation of shiitake mushrooms was studied.The contents and results are described below:（1）Preparation of Wpi-Rha conjugate and optimization of its conditions.The Wpi-Rha conjugate was prepared by the glycosylation method.Taking the degree of glycosylation and emulsifying performance as indicators,the mass ratio of Wpi to Rha,the reaction time and the reaction temperature were optimized.The mass ratio of Rha was 1:2,reacted for 8 h at 80℃.Under these conditions,the best emulsification performance of Wpi-Rha was 37.72 m~2/g.In addition,the structural changes of Wpi-Rha were characterized by Fourier transform infrared spectroscopy,endogenous fluorescence spectroscopy,etc.After Rha modification,theα-helix structure of Wpi increased,theβ-sheet structure decreased,and the protein fluorescence intensity increased,indicating that After the glycosylation reaction,both the secondary and tertiary structures of Wpi changed.（2）Preparation and stability of curcumin nanoemulsion.Using Wpi-Rha conjugate as emulsifier and oregano essential oil as oil phase,curcumin nanoemulsion was constructed by high-speed shear-high pressure homogenization technology.Using particle size,PDI and Zeta potential as indicators,the effect of surfactant to oil phase mass ratio（SOR）on the stability of nanoemulsion was investigated.When the SOR is8:2,the particle size of the curcumin nanoemulsion is 185.97±6.65 nm,the PDI is0.21±0.01,and the Zeta potential is-35.17±0.15 m V.At this time,the particle size distribution is uniform and the electrostatic repulsion between oil droplets is large,the emulsion is stable.Under these conditions,the curcumin nanoemulsion still had good stability after different processing treatments（ionic strength,heating,freeze-thaw cycles）.At the same time,after 60 days of storage,the stability of curcumin nanoemulsion remained at a high level,and its storage stability at 4℃was better than25℃.In addition,the cytotoxicity of curcumin nanoemulsion was investigated by LDH method.Compared with Tween-80 stabilized curcumin nanoemulsion,curcumin nanoemulsion stabilized by Wpi-Rha was less cytotoxic and had better cytotoxicity.stability.（3）Photodynamic sterilization of curcumin nanoemulsion and its application in mushroom preservation.The curcumin nanoemulsion combined with photodynamic sterilization was used to treat Escherichia coli and Staphylococcus aureus.When the concentration of curcumin nanoemulsion was 10μmol/L and blue light treatment for 3min,the bactericidal effect on Escherichia coli was the best,and the bactericidal rate was 99.05±0.13%;when the concentration of curcumin nanoemulsion was 10μmol/L,the bactericidal effect on Staphylococcus aureus was the best when treated with blue light for 9 min,and the bactericidal rate was 99.11±0.18%.Compared with the control,when the curcumin nanoemulsion was sprayed on the surface of shiitake mushrooms and supplemented by blue light irradiation,the hardness,elasticity,total phenolic content and total sugar content of shiitake mushrooms decreased,and the color difference,browning index,polyphenol oxidase The increase of the content decreased,indicating that the curcumin nanoemulsion combined with the photodynamic sterilization technology has a better preservation effect.