Effects of adding low levels of a disulfide reducing agent on the disulfide interactions of ß-lactoglobulin and κ-casein in skim milk.

ABSTRACT

Low concentrations of a disulfide reducing agent were added to unheated and heated (80 °C for 30 min) skim milk, with and without added whey protein. The reduction of the ß-lactoglobulin and κ-casein disulfide bonds was monitored over time using electrophoresis. The distribution of the proteins between the colloidal and serum phases was also investigated. κ-Casein disulfide bonds were reduced in preference to those of ß-lactoglobulin in both unheated and heated skim milk (with or without added whey protein). In addition, in heated skim milk, while the serum κ-casein was reduced more readily than the colloidal κ-casein, the distribution of κ-casein between the two phases was not affected.