Changes of Bovine Milk Protein by Heating as Revealed by DEAE-Cellulose Column Chromatography

Abstract

Effect of heat upon bovine skimmilk protein, whole casein and whey protein was studied by means of DEAE-cellulose column chromatography. Casein and whey protein solution, dialyzed against pH 7.0, 0.02M phosphate buffer, and skimmilk were heated for 20 minutes at 70, 80, 90, 100 and 120°C.
Heating casein solution at 120°C for 20 minutes caused some changes in the chromatogram compared with that of unheated casein. But no change was observed between heated and unheated when casein solution was heated below 100°C. Whey protein, on the other hand, showed changes even at 70°C heating. Characteristic changes in the chromatogram of heated whey protein compared with unheated were a long tailed peak between as- and β-casein position, and marked increase of alkali-eluted fraction. Heated skimmilk protein also showed the same tendency. Since heating below .100°C did not affect on casein, the changes must depend on denatured whey protein. The increase of adsorbability of heated whey protein to DEAF-cellulose is supposedly due to the change in net charge and size of protein molecules.