Oil-in-water (O/W) emulsions are indispensable in products such as salad dressings, mayonnaise and sauces, where stability at acidic conditions is critical. Although egg yolk offers excellent emulsifying and foaming performance at acidic conditions, its use is limited by allergenicity, flavour carry-over and sustainability concerns. The present study explored xanthan gum (XG) complexes with whey protein isolate (WPI) or soy protein isolate (SPI) as natural, egg-free colloidal stabilisers functioning as emulsifiers for emulsions and emulsion gels, and investigated whether this system could stabilize foams.

At pH 4.0, electrostatic interaction between WPI and XG generated nano-assemblies (~100 nm) with a ζ-potential of –37.3 mV, compared with +6.94 mV for WPI alone. These WPI–XG complexes produced finely dispersed O/W emulsions that showed no visible creaming after 28 days at 25 °C. Cryo-SEM images revealed that the complexes adsorbed at the oil–water interface through a WPI core, while interconnected fibrillar XG structures bridged adjacent complexes to build a steric barrier layer; this characteristic architecture is considered the principal mechanism suppressing droplet coalescence in the emulsion.

SPI–XG complexes, prepared at identical acidic conditions, delivered plant-based O/W emulsions of comparable stability. Plant-based patties formulated with this emulsion gel gelled with κ-carrageenan, konjac mannan and methylcellulose also showed reduced weight loss after cooking and after frozen reheating than counterparts prepared with liquid canola oil, suggesting that oil droplets were effectively trapped within the gel matrix and that oil leakage was efficiently controlled. These results collectively demonstrate the effectiveness of the emulsion gel as a clean-label, allergen-free fat substitute.

Furthermore, experimental results indicated that these protein–polysaccharide complexes not only improve foaming capacity but also enhance foam stability, suggesting their potential use beyond emulsion-type foods. The detailed mechanism of this effect will be examined in future studies, in which we will also investigate optimal combinations of component materials for different food matrices.

Our findings highlight the versatility of XG-mediated protein complexes as multifunctional building blocks for next-generation food hydrocolloids. By providing acid-resistant emulsification, superior foaming and robust gelation in a single system, these complexes support the development of low-protein, egg-free and plant-forward products with improved texture, sensory appeal and environmental sustainability.