Thermodynamic analysis of the impact of molecular interactions on the functionality of food biopolymers in solution and in colloidal systems

This review paper analyses the impact of the weak non-specific physical interactions of the food biopolymers (proteins, polysaccharides) both with each other and with the major low-molecular-weight ingredients of the multicomponent food colloids (sugars, mineral salts, small-molecule surfactants) on such key functional properties of the biopolymers as their capacities for the structure formation in a bulk of the aqueous phases and at the interfaces of colloidal systems. The thermodynamic approach, based on the application of a combination of the thermodynamic methods (light scattering, mixing calorimetry, differential scanning calorimetry, tensiometry), is central in this analysis. The contribution from the biopolymer–biopolymer interactions to the structure formation and stability of the aqueous solutions and colloidal systems is divisible into the contributions from the biopolymer self-assembly and from the interactions between different by nature biopolymers. It is shown that both of these types of the biopolymer–biopolymer interactions are crucial to the features of gelation, formation of the adsorbed layers at the surface of the colloidal particles, phase separation, and to the interactions between the colloidal particles in the biopolymer-based colloids. In addition, the impact of the distinct character (complexation or segregation) of the interactions between unlike biopolymers is demonstrated and discussed.