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The Heat Stability and Feathering of Sweet Cream, as Affected by Different Homogenization Pressures and Different Temperatures of Forewarming

From the Research Laboratories, Bureau of Dairy Industry, United States Department of Agriculture

ABSTRACT

1. The heat stability of cream, measured in terms of time of coagulation at 120°C. as affected by butterfat content, temperature of heating before homogenization, and homogenization pressure has been determined. A definite relationship was found in their influence on heat stability.
   
2. An increase of homogenization pressure lowered the time of coagulation. Maximum stability resulting from preheating occurred when 80°C. was used, and minimum stability during sterilization occurred when 60°C. was used. An increase in butterfat content invariably lowered the heat stability of homogenized cream.
   
3. The same general relationship exists in pasteurized as in preheated cream, with the exception that the point of maximum heat stability shifts from 80°C. in preheated creams to approximately 70° to 74°C. in pasteurized creams.
   
4. Where pasteurization was practiced prevention of feathering was partially successful by the treatment producing maximum heat stability, namely pasteurization for thirty minutes at 70° to 74°C.
   
5. The basic criterion for predicting whether or not a cream will feather is quality. Acidity and H-ion concentration were used for quality determinations. Pure, fresh cream of 20 per cent butterfat content and of 0.15 per cent acidity can generally be pasteurized from 65° to 85°C. and homogenized at any pressure up to 3000 pounds without danger of feathering. With optimum treatment 0.165 per cent acidity is the danger line for feathering.
   
6. An increase of viscosity of preheated homogenized cream is accompanied by a decrease in heat stability. It is suggested that variation of potential upon the fat globules may be an important factor hi determining the heat stability of the product.
   
7. In the preparation of sterile cream for market purposes maximum stability during sterilization was obtained by preheating to approximately 80°C. before homogenization.