Nanostructures of protein-polysaccharide complexes or conjugates for encapsulation of bioactive compounds

Bioactive compounds (BCs) have attracted recently substantial interests because of their remarkable healthy and functional properties. However, the vast application in processed foods of these BCs was restricted by their intrinsically deficient solubility, stability, and bioaccessibility. Accompanying the increasing awareness of outstanding functionalities of natural proteins and polysaccharides for developing safer, healthier, and more biocompatible food formulations, application of these abundant and low-cost biopolymers in fabrication of BCs-loaded nanostructures becomes an innovative trend for the processing of designed foods. The approaches commonly used for fabricating BCs-loaded protein-polysaccharide complexes or conjugates-based nanostructures (PPCCNs) and the corresponding characterization methods are described in this review. The application in food system and safety concern of these BCs-loaded PPCCNs are also discussed. The non-covalent complexation and covalent interactions promote the formation of protein-polysaccharide complexes and conjugates, respectively. Bottom-up approaches (such as liquid antisolvent precipitation, pH-driving encapsulation, heating or ionic gelation, and self-assembly) and top-down approaches (such as emulsion-based homogenization) are broadly applied to fabricate these BCs-loaded PPCCNs. Each approach exhibits its outstanding advantages to fabricate the nano-encapsulated BCs with modified stability, controlled release, and functional properties. Characterization of BCs-loaded PPCCNs is mainly completed via investigating the aspects of formation mechanisms, micromorphological properties, and encapsulation profiles. Targeted application and safety issue should be considered during the processing of fortified foods with these BCs-loaded PPCCNs. Overall, the effective encapsulation, protection, and delivery of BCs in PPCCNs are conducive to developing designed foods with accurately controlled fine texture and bioaccessibility of functional components.