Effect of High Heat Treatment on the Viscosity of Model Milk Systems

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Abstract
Previous heat treatment had no effect on the viscosity of a 5% lactose solution, a 15% sucrose solution, a synthetic milk salts system and a Na caseinate dispersion. A slight increase was found in the viscosity of skimmilk as a result of previous heat treatment. Somewhat greater effects of heat were observed in whole milk, systems containing 16%, milk solids-nonfat and other more concentrated systems. Viscosity values were related to concentration by means of the Arrhenius equation. The assumption that the viscosity of a mixture should be the sum of the viscosities of its components was true in a number of systems. Deviations were interpreted as indications of interaction between the components which were found in heated systems containing sugar and milk solids-not-fat. Difficulties arise in evaluating the contribution of fat to the total viscosity, but indirect evidence showed an interaction between fat and other milk constituents. Increase in viscosity which cannot be predicted from consideration of the Arrhenius equation are believed to be of practical importance in a number of dairy products.