Applications of mixed polysaccharide-protein systems in fabricating multi-structures of binary food gels—A review

Due to high water content, low calorie and appealing textural characteristics, gel-related foods have recently obtained great interest in the food industry. Compared with the same class of biopolymer mixtures (e.g., polysaccharide-polysaccharide mixtures and protein-protein mixtures), the biopolymer mixtures from different classes often possess more advantages in fabricating binary food gels. By combination of physical properties of polysaccharides and proteins, it is possible to produce multi- or hierarchical microstructures of gels. However, the fundamental principles of fabricating food gels based on mixtures of polysaccharides and proteins need to be further shed light on. In this review, the phase behaviors of mixed polysaccharide-protein systems were discussed, and their relationships with the microstructures of final gels were summarized. Then, the practical applications of polysaccharide-protein mixtures in producing composite binary gels were exemplified. Intermolecular interactions are the predominant factors affecting the phase behaviors between polysaccharides and proteins, which can be regulated by altering some parameters, such as polymer concentration, pH, ionic strength, temperature, etc. The microstructures of final gels are highly dependent on the existing states of both polymers at the time of gelation, rather than their phase equilibrium states. Moreover, the physical properties and gel structures can be further diversified by changing the gel fabrication conditions. Therefore, it is suggested to rationally select polysaccharide-protein mixtures, as well as gel fabrication conditions to attain binary gels with expected properties.