| In the food industry,some fat soluble,easily oxidized active substances are not easy to absorb,the nature of instability and other factors,limiting their application.The nano-emulsion has the characteristics of small particle size and large surface area,uniform distribution,the biological activity,the unstable nature of material embedded in the emulsion can play a protective role,so that the active substances can maintain their biological activity long time.Tea polyphenol(TP)is a natural antioxidant,SPI has good emulsification,water and oil absorbing.Therefore,this study intends to use the TP in combination with SPI as emulsifier,the preparation of nano emulsion,after the combination of the two,the adsorption at the oil droplet surface,can enhance the antioxidant for future oil droplets can be fat.The function of soluble material oxidation insoluble in oil and preparation of nano emulsion,maintaining the biological activity,broaden its scope of application,in the field of food at the same time,the carrier TP-SPI nano emulsion can also be used as fat soluble drugs and cosmetics,drug delivery.The research of this paper has certain significance to the application of fat soluble active substances in food and medicine field.In this paper,the effects of the amount of tea polyphenols(TP),soy protein isolate(SPI),oil and pH value on the TP-SPI composite nano-emulsion emulsifying activity,emulsion stability,oxidation resistance,viscosity,potential,average particle size and particle size distribution were studied.The effect of TP on the structure of nano emulsion was investigated by means of laser scanning confocal microscopy,fluorescence spectrum analysis and infrared spectrum analysis,and the mechanism of was analyzed.The following results were obtained.(1)With the increase of the amount of TP,the emulsification stability and antioxidant activity of the composite nanoemulsion were significantly enhanced,the emulsifying activity of the composite nano-emulsion was first increased and then decreased,the viscosity was significantly increased,the particle size of the emulsion particles was decreased,the coefficient of dispersion(PDI)of emulsion particle is reduced,the absolute value of the potential was increased and decreased.Considering the influence of each index,the range of TP concentration was better between 0.15 g/100 m L and 0.25 g/100 m L.(2)With the increase of the concentration of SPI,the emulsifying activity and emulsifying stability of the composite nanoemulsion were significantly enhanced,the antioxidant activity was significantly enhanced,the particle size of the emulsion was significantly decreased,the dispersion coefficient of the emulsion particles was gradually decreased,the absolute value of the potentialwas increased and decreased,the viscosity of the emulsion was gradually increased.Considering the influence of each index,the range of SPI concentration was better between 1 g/100 m L and 1.5g/100 m L.(3)With the increas of the amount oil,the emulsifying activity of the composite nano-emulsion was first decreased and then increased,antioxidant activity was significant decreased,the emulsion stability was increased,the emulsion particles was first decreased and then increased,the dispersion coefficient of emulsion particles was first decreased and then increased,the viscosity was increased and the absolute value of the potential was increased.Considering the influence of each index,the range of the amount oil was better between 4.0:1 and 3.0:1(SPI solution: oil;v/v).(4)With the increase of p H value,the emulsion stability and emulsifying activity of composite nano-emulsion was increased,the antioxidant activity was significantly decreased,the emulsion particle diameter was decreased,the change of the dispersion coefficient of emulsion particles was not significant,the viscosity was gradually increased,the absolute value of the potential was gradually increased.Considering the influence of each index,the range of the p H value was better between 7 and 9.(5)The interaction between TP and SPI can be done spontaneously(?G<0).High pressurehomogenization can increase the SPI and TP binding sites(high pressure homogeneous n = 1.3755,no high pressure homogeneous n = 1.1076).After interacting with SPI,TP still retain some of the homology of TP(the nature of the original).After addition TP,the absorption peaks of the fluorescence spectra were red shifted 6nm,the infrared spectra of SPI amide I band were blue shifted from 1640 cm-1 to 1624 cm-1,the amide II band were blue shifted from 1530 cm-1 to 1526cm-1.The results show that TP makes the two level structure of SPI changed.The SPI alpha helix content decreased from 32.64% to 27.67%,the beta folding structure content increased from48.82% to 57.58%,the beta angle of content is reduced from 18.54% to 14.75%,two level structure of SPI become more comfortable.. |
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