| Rice starch is rich in resources,cheap and easy to obtain,and has the potential to prepare Pickering emulsion with small particle size.However,the Pickering emulsion prepared by natural starch has poor hydrophobicity and poor stability.At present,organic anhydride such as octenylsuccinic anhydride(OSA)is used to modify starch hydrophobicity.Fatty acid is a natural component of oil.Compared with natural starch,fatty acid starch ester has better hydrophobicity and is safe and harmless,so it has the potential to prepare food-grade Pickering emulsion.In this paper,fatty acid starch ester was prepared from rice starch with stearic acid and lauric acid as esterification agents by microwave synthesis method.The effects of the amount of fatty acid,water content,hydrochloric acid,microwave time and microwave power on the degree of substitution and reaction efficiency were studied by single factor experiment.The stability and properties of Pickering emulsion prepared from fatty acid starch ester were studied.The results showed that when the amount of stearic acid was 7%,the amount of water was 35%,the amount of hydrochloric acid was 0.1%,the microwave time was 20 min,and the microwave power was 500 W,the substitution degree and reaction efficiency of starch stearate ester were better.When the lauric acid content was 7%,moisture content was 35%,hydrochloric acid content was 0.1%,microwave time was 20 min,microwave power was700 W,the substitution degree and reaction efficiency of starch laurate ester were better.Esterification starch respectively for the hydrogen nuclear magnetic spectra,Fourier infrared spectrum,scanning electron microscope,laser granularity instrument,X-ray diffraction(XRD)and rapid viscosity meter(RVA),differential scanning calorimetry(DSC),thermogravimetric analysis and contact Angle analysis,the results show that fatty acids and rice starch esterification success,fatty acid ester starch granule surface is rough,But didn’t significantly change shape,particle size of starch increased with the increase of the substitution degree increasing,the crystalline structure of starch as A model,cold paste stability,thermal stability of starch ester has changed,with the increase of the substitution degree,the starch particles contact Angle increased gradually,and close to 90 °,showed that fatty acid ester starch granules can be adsorbed on the oil-water phase interface stability.The characteristics of Pickering emulsions constructed with starch stearate ester and starch laurate ester as emulsifiers were studied.The emulsification index,particle size and microstructure of the emulsion were analyzed.The results show that the two starch esters can form stable oil-in-water Pickering emulsion,and the droplets are relatively dense and the size is relatively uniform.The higher the degree of substitution of fatty acid starch ester,the smaller the particle size and the higher the emulsion index.The antioxidant and digestible properties of curcumin embedded in Pickering emulsion were studied.The results showed that the curcumin-containing emulsion prepared by starch stearate ester had better scavenging effects on DPPH and ABTS free radicals than that prepared by starch laurate ester containing curcumin.By simulating human gastrointestinal environment,Pickering emulsion can release curcumin slowly in gastric and intestinal fluid.The release amount of Pickering emulsion prepared by two kinds of fatty acid starch esters is not different,but the release rate of starch stearate is higher than that of starch laurate. |
