Interaction of milk whey protein with common phenolic acids

Phenolics-rich foods such as fruit juices and coffee are often consumed with milk. In this study, the interactions of alpha-lactalbumin and beta-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 x 10(5) to 7 x 10(6) 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 a-helix and an increase in the amounts of beta-sheet and turn structures. (C) 2013 Elsevier B.V. All rights reserved.