Denaturation of the Serum Proteins in Skimmilk Heated by Direct Steam Injection1,2

Abstract

Summary Denaturation of the serum proteins in skimmilk by direct steam-injection heating was studied over a wide range of times (approx. 8-200 sec) and temperatures (160-300 F). An equation expressing the extent of denaturation as a function of time and temperature was developed. The amount of denaturation varied from about 10% for the least severe treatments to over 80% for the most severe and exhibited a sigmoid relationship to temperature at a given time. There appeared to be lower and upper bounds on the percentage denaturable by steam injection. Steam-injection produced more severe effects at short-time and low-temperature combinations than have been reported for other heat exchange methods, but less severe effects than other methods at high temperatures. Explanations are based on the inherent difference in the methods of heating.