Effects of Complex Coacervation on the Structure and Texture of Plant-Based Protein-Polysaccharide Composites

Developing plant-based foods that mimic meat and seafood attributes is crucial for addressing environmental, animal welfare, and health concerns. However, accurately replicating the structure, texture, and functionality of animal-based products with plant ingredients is challenging and to tackle this, soft matter physics principles is applied. Our study utilized coacervation and thermal gelation of gellan gum (GG) and potato protein (PP) to create meat-like biopolymer composites. The primary goal was to investigate if we could control the structural organization and rheology of these composites by adjusting pH to modulate electrostatic interactions between PP and GG."The z-potential of the complexes was positive at pH 4, near zero at pH 5, and negative at pH 6, attributed to the reduction in the positive charge on PP when the pH was raised towards their isoelectric point; GG remained strongly negative at all pH values. Large clumps were formed at pH 4 due to strong electrostatic attraction between PP and GG. However, fibril structures were formed after heating at pH 6, which was mainly attributed coacervate formation. Interestingly, a substantial quantity of air bubbles was generated during the blending of the PP and GG mixtures at pH 4, which influenced the structure and rheology of the heat-set composite gels. At pH 6, fewer air bubbles formed due to disability to stabilize air-water interfaces. The electrostatic complexation also influenced the dynamic shear modulus of the composite gels during heating and cooling, with final shear modulus as pH 4 > pH 6 > pH 5. By controlling the ratio of negative and positive molecules via pH, the electrostatic attraction or repulsion can be manipulated to create different microstructures in protein-polysaccharide composites. Our findings highlight potentials of using coacervation to create meat analogs with fibrous structures and gel strengths, which may facilitate the design of plant-based foods texture.