Chlorogenic acid and its isomers enhance casein thermal stability by regulating conformation and function via...

This study explores interactions between six chlorogenic acid (CGA) isomers and casein, milk's functional protein. Covalent binding via phenolic hydroxyls markedly suppressed protein carbonylation, a hallmark of processing-induced protein oxidation, lowering basal carbonyl content from 1.3 to 0.1-0.8 nmol mg^-1 protein (≈40-90% reduction; p < 0.05). Although native casein contained fewer carbonyls than typically reported for oxidatively stressed or heavily processed casein, CGA conjugation still triggered a conformational shift from α-helix to β-turn. Polyphenol modification reduced particle size from 4900 nm to 250-374 nm, while isochlorogenic acid A elevated zeta potential from -26.03 mV to -18.7 mV. Functionally, DPPH radical scavenging capacity increased 2.1-fold and emulsion stability improved by 37.00%. Results demonstrate that CGA isomers remodel casein through covalent crosslinking and hydrophobic interactions, enhancing thermal stability, antioxidant capacity, and emulsifying properties, while the gastrointestinal fate and safety of these CQA-casein conjugates require further investigation before use in real food products.