Denaturation of Cottage Cheese Whey Proteins by Heat

Abstract

The proteins in cottage cheese whey were comparatively stable to heat; thirty minutes at 91 C were required to denature 80 percent of the proteins, whereas 81 C for 30 min denatured the same amount of protein in skimmilk. The Harland-Ashworth test provided a reasonably accurate index to the extent of heat denaturation, if the pH of the whey was adjusted to 5. 4-6. 5 immediately prior to analysis. The observed whey protein stability did not result from the presence of lactate ion, but resulted from the low pH of the whey. No significant increase in heat denaturation rate was obtained by concentrating the whey prior to heating. Maximum heat stability was usually observed in whey concentrates containing 20 percent total solids. During heating, the buffering capacity of the cottage cheese whey was reduced.