Temperature robustness and viscoelasticity of soy protein-stabilized palm oil emulsions containing glycerol monostearate and oat fiber.

Most studies of high oil content soy protein-stabilized emulsions have focused on fluid systems, with limited attention given to the thermo-mechanical behavior of firm emulsions. This study examined the thermal robustness and mechanical properties of palm oil-based emulsions stabilized with soy protein isolate, glycerol monostearate (GMS), and oat fiber. Glycerol monostearate markedly reduced droplet size and distribution breadth, whereas fiber had little effect on initial droplet characteristics. On heating to 80 °C, GMS-containing emulsions broke down completely whereas those without GMS retained their structural integrity, highlighting a trade-off between emulsification efficiency and thermal robustness. All emulsions showed solid-like behavior at 20 °C, with the storage modulus (G') greater than the loss modulus (G″), and with fiber-containing samples showing the greatest firmness. Fiber mitigated heat-induced softening, increasing elasticity by up to ~40 % at 80 °C relative to fiber-free emulsions. Puncture tests at 20 °C demonstrated a firming effect of fiber and a softening effect of GMS. Glycerol monostearate also reduced protein adsorption, but increased interfacial elasticity upon cooling. Glycerol monostearate improved emulsification and interfacial structuring but compromised thermal stability. Oat fiber enhanced mechanical strength and mitigated, but did not prevent, heat-induced breakdown, suggesting its potential to improve the temperature tolerance of structured emulsions, as in plant-based fat alternatives. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.