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

Abstract

<h4>Background</h4>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.<h4>Results</h4>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.<h4>Conclusion</h4>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.