Preparation and characteristics of high internal phase emulsions stabilized by rapeseed protein isolate

Rapeseed protein isolate (RPI) was used as a natural particulate emulsifier for production of high internal phase emulsions (HIPEs) for the first time. RPI was prepared by an alkali solution and acid precipitation process, following mixed with rapeseed oil (oil phase) to form HIPEs using a combination of low-speed stirring and high-speed homogenization. The best condition of homogeneous and stable HIPEs that formed by RPI was at a pH = 9.0 and a protein concentration of 20 g/L. Under this condition, the proteins adsorbed around the oil phase to form a stable network structure. Stable HIPEs could have a maximum oil content of up to 840 g/kg (oil phase/emulsion), and the appearance and microstructure of which containing above 300 mmol/L NaCl did not change significantly ( p = 0.08) after three freeze-thaw cycles. Overall, the HIPEs stabilized by RPI exhibited an excellent oil loading capacity and freeze-thaw stability, which not only utilizes the low value protein resources in the waste rapeseed meal, but also provides a theoretical basis for the application of HIPEs in food industry. • The rapeseed protein isolate (RPI) was used as an emulsifier in food industry. • RPI-based high-internal phase emulsions (HIPEs) were investigated. • The minimum mean size and the maximum G′ were obtained at pH = 9.0 of RPI solution. • Stable RPI-based HIPEs with limit oil phases up to 840 g/kg could be prepared. • 300 mmol/L NaCl had the best improvement on the stability of the RPI-based HIPEs.