Interaction of milk whey protein with common phenolic acids

• Phenolic acids interacted with the structural subunits of whey protein.
• The quenching mechanism was static quenching when phenolics bound to whey protein.
• The conformation of whey protein was altered due to interact with phenolic acids.

Phenolics-rich foods such as fruit juices and coffee are often consumed with milk. In this study, the interactions of α-lactalbumin and β-lactoglobulin with the phenolic acids (chlorogenic acid, caffeic acid, ferulic acid, and coumalic acid) were examined. Fluorescence, CD, and FTIR spectroscopies were used to analyze the binding modes, binding constants, and the effects of complexation on the conformation of whey protein. The results showed that binding constants of each whey protein–phenolic acid interaction ranged from 4 × 105 to 7 × 106 M−n and the number of binding sites n ranged from 1.28 ± 0.13 to 1.54 ± 0.34. Because of these interactions, the conformation of whey protein was altered, with a significant reduction in the amount of α-helix and an increase in the amounts of β-sheet and turn structures.