Lactoferrin binding to transglutaminase cross-linked casein micelles

Casein micelles in skim milk were either untreated (untreated milk) or were cross-linked using transglutaminase (TGA-milk). Added lactoferrin (LF) bound to the casein micelles and followed Langmuir adsorption isotherms. The adsorption level was the same in both milks and decreased the micellar zeta potential, indicating charge neutralization and the formation of complex coacervate-type interactions. For the untreated milks, the adsorption of LF was initially accompanied by an increase in turbidity of the milk and in the size of the casein micelles; however, after several hours, the turbidity and the casein micelle size of these milks decreased markedly. For the TGA-milks, no change in casein micelle size was observed on adsorption of LF, but the turbidity increased due to the increased mass of the casein micelles, and remained constant on holding. These results indicate that the cross-linking of the casein micelles prior to adding LF prevents disintegration of the casein micelles.