Effects of different vegetable oils and ultrasonicated quinoa protein nanoparticles on the rheological properties of Pickering emulsion and freeze-thaw stability of emulsion gels

Abstract

Quinoa protein isolate (QPI) dispersions were ultrasonicated to generate nanoparticles, which were applied to emulsify olive, rapeseed and corn oil to form stable Pickering high internal phase emulsions (HIPEs). The effects of different oil phases and ultrasonic intensity on the particle size, zeta potential, rheological properties and microscopic distribution of Pickering HIPEs were analyzed. The contact angle of QPI nanoparticles with 450 W ultrasonic treatment was 68.83 ± 3.32°, which was remarkably higher than natural particles of 53.69 ± 0.84°. Pickering HIPEs exhibited a three-dimensional network structure and high viscoelasticity. The storage modulus of HIPEs with olive oil was higher than HIPEs with rapeseed and corn oil. The HIPEs with high oleic acid content in oil phase showed high viscoelasticity, because the rheological properties of HIPEs were positively correlated with oleic acid content. Furthermore, QPI HIPE gels were prepared and the freeze-thaw stability of HIPE gels was analyzed. The HIPE gels emulsified by natural QPI showed weak freeze-thaw stability, while the HIPE gels stabilized by sonicated QPI exhibited high freeze-thaw stability. Microstructure of HIPEs by confocal laser scanning microscopy also confirmed the finding. Moreover, different vegetable oils had no significant effects on the freeze-thaw stability of the HIPE gels.