Freeze-thaw Stability Of High Internal Phase Emulsions Stabilized By Soy Protein Isolate Particles

Freezing is a common storage method for food,but high internal phase emulsions type food(such as mayonnaise)tend to be unstable after freeze-thaw(such as demulsification),and this will not only shorten the shelf life of food,but also seriously reduce the quality of food.Soybean protein isolate(SPI)heat-aggregated particles had been proved to be a class of superior Pickering stabilizers,and the corresponding low oil phase emulsions had good freeze-thaw stability.In this paper,SPI and soybean oil were used as raw materials,aiming to develop a class of high internal phase emulsions(HIPEs)stabilized by SPI particles,which possessed good freeze-thaw stability.The main contents were as follows:Firstly,under the condition of protein concentration(c=0.25%(w/v)),oil phase ratio(?=0.4),ionic strength(I=300 mM),the effect of SPI particle properties on freeze-thaw stability of corresponding emulsions were studied,by characterizing the size,zeta potential and surface hydrophobicity of SPI particles,and the viscoelastic properties,DSC characteristics,optical microstructure,droplet size,creaming index,flocculation index,coalescence index,interfacial protein adsorption rate,and interfacial protein coverage rate of emulsions.With the surface hydrophobicity of SPI particles increased gradually,the freeze-thaw stability of emulsions improved gradually.This was mainly attributed to the following two aspects: On the one hand,the enhancement of emulsion gel network structure and the improvement of interfacial protein adsorption rate;On the other hand,high energy emulsification(microfluidization)could improve the emulsification efficiency of SPI particles.Secondly,under the condition of c=1.0%(w/v)and ?=0.8,the freeze-thaw stability of HIPEs stabilized by SPI particles under different emulsification methods was studied,by characterizing the size,zeta potential and surface hydrophobicity of SPI particles,and the viscoelastic properties,optical microstructure,droplet size,flocculation index,interfacial protein adsorption rate of emulsions.With the increase of ionic strength(0~300 mM),the freeze-thaw stability of HIPEs prepared by both one-step and two-step emulsification methods improved gradually,but the freeze-thaw stability of HIPEs prepared by two-step emulsification method were better.For the HIPEs prepared by two-step emulsification method,the freeze-thaw stability improved gradually as the ?(0.2~0.6)of initial emulsions increased.The freeze-thaw stability of HIPEs mainly depended on the interfacial protein adsorption rate.The improvement of interfacial protein adsorption rate was beneficial to the improvement of freeze-thaw stability of HIPEs.Lastly,under the condition of c=1.0%(w/v),?=0.8 and I=50 mM,the freeze-thaw stability of HIPEs stabilized by SPI particles under different heating methods was studied,by characterizing the size,zeta potential and surface hydrophobicity of SPI particles,and the viscoelastic properties,optical microstructure,droplet size,flocculation index,interfacial protein adsorption rate of emulsions.For the three heating methods including SPI were not heated before emulsification,and HIPEs were not heated after emulsification;SPI were not heated before emulsification,and HIPEs were heated after emulsification;SPI were heated before emulsification,and HIPEs were not heated after emulsification,the freeze-thaw stability of HIPEs prepared by the second heating method was the best,while the first one was the second,and the third one was the worst.The freeze-thaw stability of HIPEs mainly depended on the interfacial protein adsorption rate and the properties of interfacial protein membrane.The improvement of interfacial protein adsorption rate and the enhancement of interfacial protein membrane were beneficial to the improvement of the freeze-thaw stability of HIPEs.