Rheology and Surface Tension of Selected Processed Dairy Fluids: Influence of Temperature

¹ Department of Analytical and Pharmaceutical Chemistry, Royal Danish School of Pharmacy, Universitetsparken 2, DK-2100 Copenhagen, Denmark

The effects of temperature on the rheological behavior and surface tension of commercial samples of skim milk, 3.5% milk, 38% cream, two different cultured buttermilk products, and buttermilk powder solution were studied using a controlled stress rheometer and the Wilhelmy plate method, respectively. The rheology of the dairy fluids was greatly influenced by temperature but to varying degrees depending on the product tested. The rheological data for skim milk, 3.5% milk, buttermilk powder solution, and 38% cream could be fitted to the Bingham model at all temperatures, and the cultured buttermilk products could be fitted to the power law model. For the uncultured products, viscosity and yield stress decreased as temperature increased. The dairy products exhibited great variation in surface tension, which also was strongly dependent on temperature. For 38% cream, the measurements of surface tension indicated a high degree of instability as temperatures varied, which suggests that the milk fat globule membrane was destabilized at the interface between air and water. This study demonstrates the effect of temperature on bulk and interfacial properties of dairy fluids as fat content and milk fat globule fragments vary.

Key Words: surface tension • viscosity • cream • buttermilk

Submitted on September 4, 1996
Accepted on March 6, 1997

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