Effects of Rosemary Extract on Methylglyoxal/Glyoxal‐Mediated Glycation of Dairy Proteins During Thermal Processing

Nonenzymatic glycation of dairy products induced by α-dicarbonyl compounds (α-DCs) occurs during thermal processing, leading to the formation of advanced glycation end products (AGEs) that pose potential health risks to human health. Rosemary extract (RE) is a common food antioxidant additive. In this study, RE was employed to counteract two representative α-DCs, that is, methylglyoxal (MGO, 1 mM) and glyoxal (GO, 1 mM), during simulated thermal processing (75°C for 2 h) of whey protein isolate (WPI, 7 mg/mL). Results showed that RE (0.1, 1, and 2 mg/mL) significantly suppressed MGO/GO-induced formation of fluorescent AGEs and concomitant glycoxidation products in a dose-dependent way. Western blotting analyses confirmed that RE interrupted the binding of MGO/GO to WPI, as evidenced by the reduced immunoreactivity of modified proteins. HPLC analysis revealed near‑complete elimination of MGO and GO at 2 mg/mL RE. Molecular docking simulations further demonstrated that the representative compounds (rosmarinic acid and carnosic acid) exhibited strong binding affinities to the protein and effectively shielded potential glycation sites from MGO/GO. However, phenol-protein interactions may compromise the structural properties of WPI proteins at high RE concentrations, which was manifested by the reductions in surface hydrophobicity and intrinsic fluorescence. Collectively, RE was validated as an effective anti-glycation agent to alleviate α-DC-mediated damage in dairy proteins in this study, which might extend its role from a conventional food antioxidant to a potent glycation inhibitor.