Multi-scale structure and rheological properties of acid-induced soy protein and β-lactoglobulin gel to develop plant-based milk alternatives.

Soy protein isolate (SPI) and β-lactoglobulin (β-Lg) were selected with varied mixing ratios and heating strategies to explore acid-induced gelation in achieving novel textures. SPI/β-Lg ratio exerted a more pronounced effect on acid-induced gel than heating strategies. With the increase of SPI/β-Lg ratio, the stiffness and elasticity of co-gels generally increased (γc: 2.51-3.93%), accompanied by increased protein aggregates and higher interfacial protein adsorption. SPI could effectively substitute 50% of β-Lg without compromising gel properties. Compared with co-protein gels, co-protein emulsion gels exhibited 9.26-28.06% lower hardness and reduced storage modulus (G'), but showed 1.03-17.24% higher water-holding capacity (WHC), as confirmed by CLSM and SEM observations. Moreover, mix-then-heat gels outperformed heat-then-mix gels, with hardness and WHC increasing by 9.78-37.37% and 1.42-3.61%, respectively. And G' values of mix-then-heat emulsion gels showed about 5.41-43.61% elevation over their heat-then-mix counterparts. The results highlight SPI as an alternative protein to develop gelled food with diverse textures.