Food-Grade Covalent Complexes and Their Application as Nutraceutical Delivery Systems: A Review

Food proteins, polysaccharides, and polyphenols are 3 major food constituents with distinctly different functional attributes. Many proteins and polysaccharides are capable of stabilizing emulsions and foams, thickening solutions, and forming gels, although they differ considerably in their abilities to provide these functional attributes. Many plant polyphenols exhibit beneficial physiological functions, such as antitumor, antioxidant, antibacterial, and antiviral properties. Proteins, polysaccharides, and polyphenols can form complexes with each other, which leads to changes in the functional and nutritional properties of the combined systems. Recently, there has been considerable interest in understanding and utilizing covalent interactions between polyphenols and biopolymers (proteins and polysaccharides). The binary or tertiary conjugates formed may be designed to have physicochemical properties and functional attributes that cannot be achieved using the individual components. This article provides a review of the formation, characterization, and utilization of conjugates prepared using proteins, polysaccharides, and polyphenols. It also discusses the relationship between the structural properties and functionality of the conjugates, and it highlights the bioavailability of bioactive compounds loaded in conjugate-based delivery systems. In addition, it highlights the main challenges to be considered when preparing and analyzing conjugates. This article provides an improved understanding of the chemical reactions that occur between major food ingredients and how they can be utilized to develop biopolymer-based delivery systems with enhanced functional attributes.