Preparation of water-in-oil(W/O)cinnamaldehyde microemulsion loaded with epsilon-polylysine and its antibacterial properties

In order to solve the problems of poor oil solubility of epsilon-polylysine(ε-PL)and the resulting poor antimicrobial performance,a water-in-oil(W/O)microemulsion containingε-PL was constructed by drawing a pseudo ternary phase diagram.The effects of oil phase,surfactant,cosurfactant andε-PL with different components and contents on the area of microemulsion were investigated.The physicochemical properties of microemulsion were discussed by measuring the conductivity,rheology,dynamic light scattering,X-ray small angle diffraction and centrifugal stability of microemulsion,and the inhibitory effect of microemulsion on mold was further studied.The results showed that oil:ethanol was 1:1(w/w),water:glycerol was 3:1(w/w)and 5%-10%(w/w)ε-PL could promote the formation of microemulsion system.The conductivity and rheological confirmed that the transition point of W/O microemulsion was 25%(w/w)in aqueous phase,and the microemulsions with different water contents were Newtonian fluids.The final formulation of microemulsion is the ratio of oil,surfactant and water to 12:8:5.The droplet of microemulsion is elliptical and evenly distributed,which has good centrifugal stability.The combination ofε-PL and cinnamaldehyde with W/O microemulsion system had synergistic inhibitory effect on spore germination and colony diameter of three fungi.This study provides a new method to prevent spoilage of oil-immersed food by constructingε-PL loaded W/O microemulsion,and provides a theoretical reference for the application ofε-PL cinnamaldehyde microemulsion as a natural and efficient antibacterial agent in oil-immersed food.