NADES-mediated glycation of casein with mannose and mannose-oligosaccharides: conformation, antioxidant activity, and antimicrobial activity of gastrointestinal digests.

This study aimed to improve the physicochemical and functional properties of casein (CN) via glycation based on natural deep eutectic solvents (NADES). Four glycated CN conjugates (CN-Man1, CN-Man2, CN-Mos1, and CN-Mos2) were prepared with mannose (Man) or mannose-oligosaccharides (Mos) in water and NADES systems under optimized conditions. Structural and physicochemical changes were analyzed. The results indicated that Mos-mediated glycation in NADES was associated with marked conformational changes, and CN-Mos2 exhibited the lowest surface hydrophobicity and the highest thermal stability. Additionally, functional properties including solubility, antioxidant activities, digestibility, and antibacterial activity were evaluated. Glycation was associated with the enhanced functional properties of CN, and these effects varied depending on the sugar type and reaction system. CN-Man2 displayed the highest intracellular and extracellular antioxidant activities, and its digests also possessed the strongest in vitro antibacterial activity. These findings suggest that glycation may induce structural changes in CN, which in turn could modulate its functional properties, providing a preliminary basis for its potential application in functional foods.