VISCOSITY OF CAPRINE MILK WITH RESPECT TO FAT CONTENT, SHEAR RATE, AND TEMPERATURE

Abstract

Viscosity of caprine whole milk, 2% fat milk, 1% fat milk, skim milk, and cream were evaluated using a rotationalviscometer. Fat percentage level in the milk was obtained by recombining cream with skim milk. Effects of fat percentage,shear rate, and temperature on the viscosity of milk and cream were investigated. Caprine milk did not exhibit purely Newtonianflow behavior. At high temperatures (>60C), it behaved like a Newtonian fluid. Below this temperature, the milk showedsmall yield stress, signifying non-Newtonian behavior. Viscosity of all the types of caprine milk and cream variedexponentially with shear rate at low temperatures (<60C). At higher temperatures, the relationship was polynomial.Viscosity of cream, however, varied exponentially with shear rate at all temperatures. On the other hand, viscosity decreasedwith the increase in temperature. A polynomial relationship existed in all types of milk except skim milk, which decreasedlinearly with the increase in temperature. Viscosity values were found to increase with the fat content in the milk. Rheologicalmodels for the caprine milk types and cream are presented.