The synthesis, biological activities and applications of protein-polysaccharide conjugates in food system: a review

Proteins are important ingredients in the food industry for their excellent nutritional, functional and biological properties, while the application is limited by their sensitivity to environmental stresses such as high temperature, pH changes and ionic strength. The Maillard reaction and transglutaminase-catalyzed glycosylation are the two main effective glycosylation ways to improve the stability and biological properties of proteins by mainly attaching monosaccharides or disaccharides to proteins, while protein-polysaccharide conjugates with superior functional properties are rarely discussed. Therefore, the present study reviews current state of the synthesis, biological activities and applications in the food system of protein-polysaccharide conjugates formed via the Maillard reaction and transglutaminase-catalyzed glycosylation. The biological activities including antioxidant, antimicrobial and immunomodulatory activities of proteins are improved after glycosylation, and the formed protein-polysaccharide conjugates can be applied to stabilize emulsions or deliver bioactive compounds in foods. The bioactivities produced under precisely controlled glycosylation conditions would make protein-polysaccharide conjugates a promising application in foods with healthy properties.