Influence of complex coacervation on the structure and texture of plant-based protein-polysaccharide composites

Plant-based foods that mimic the sensory attributes of meat and seafood are being developed to address environmental, animal welfare, and health concerns linked to livestock production and processing. However, it has been challenging to accurately replicate the structure, texture, and functionality of many animal-based products using plant-derived ingredients. Soft matter physics principles are therefore being employed to address this issue. In this study, a combination of coacervation and thermal gelation of gellan gum-potato protein mixtures was used to create biopolymer composites with meat-like textures. One of the main aims of the study was determine whether the structural organization and rheology of biopolymer composites could be controlled by modulating the electrostatic interactions between the potato protein and gellan gum using pH adjustments. The zeta-potential of the complexes was positive at pH 4, near zero at pH 5, and negative at pH 6, which was mainly attributed to the reduction in the positive charge on the potato proteins when the pH was raised towards their isoelectric point. In contrast, the charge on the gellan gum remained strongly negative at all pH values. Large clumps were formed at pH 4 due to strong electrostatic attraction between the proteins and polysaccharides. However, fibril structures were formed after heating at pH 6, which was mainly attributed to the formation of coacervates. Interestingly, a substantial quantity of air bubbles was generated within the biopolymer composites during the blending of the protein and polysaccharide mixtures at pH 4, which influenced the structure and rheology of the heat-set composite gels. In contrast, fewer air bubbles were generated during blending at pH 6, which was attributed to differences in the ability of the complexes to adsorb to air-water interfaces and stabilize air bubbles. The electrostatic complexation of the proteins and polysaccharides also influenced the dynamic shear modulus of the composite gels during heating and cooling, with the final shear modulus depending on sample pH: pH 4 > pH 6 > pH 5. Overall, our findings highlight the potential of using coacervation combined with heating to create meat analogs with different fibrous structures and gel strengths, which may facilitate the design of plant-based foods with desirable textural attributes.