Thermogelation of nanoemulsions stabilized by a commercial pea protein isolate: high-pressure homogenization defines gel strength.

The impact of animal-based food production on climate change drives the development of plant-based alternatives. We demonstrate the use of colloidal thermogelation on a real nanoemulsion system to create structured gels that could be of interest for thermo-mechanical processing of next-generation plant-based food applications. We use a commercial pea protein isolate (PPI) without further purification to stabilize a 20 vol% peanut oil-in-water nanoemulsion at pH = 7 by high-pressure homogenization (HPH) and demonstrate the temperature induced gelation behavior of the nanoemulsion as a function of the HPH processing parameters. Bright-field and laser scanning confocal fluorescence microscopy reveals a diverse microstructure of the aqueous PPI dispersions, with a large amount of insoluble protein particles, cell-wall debris particles, and lipid inclusions. Sedimentation of particulates is prevented by HPH treatment and leads to a loss of the dispersion's thermogelation properties. The non-gelling PPI dispersion stabilizes nanoemulsions and the insoluble components of the PPI dispersions persist throughout the HPH processing. We perform a systematic rheological investigation of the effect of HPH processing on thermogelation and demonstrate that the number of HPH passes and HPH pressure control the average nanoemulsion droplet size measured by DLS at a 90° scattering angle. We show that the droplet size defines the final gel strength with a strong inverse dependence of the elastic modulus on droplet size. Furthermore, processing can lead to heterogeneously structured gels that yield over a large strain amplitude range.