Influence of temperature and composition on some physical properties of milk and milk concentrates. II. Viscosity

Abstract

Ten different types of milk, arranged in 3 sets, were observed to be pseudoplastic fluids with linear behaviour at high shear rates in a coaxial cylinder rheometer; at low rates of shear all the samples could be considered sufficiently Newtonian and a Höppler viscometer was used for their study. Dynamic viscosity coefficients of skimmilk, half-and-half milk, whole milk and their concentrates up to about 30% total solids were determined every 5°C between 0 and 80°C. For every milk type a quadratic equation relating t to log η was obtained. At a given temperature the concentration dependence of η for the 3 milk sets was expressed by a single relation of the same mathematical model as in the previous case. A general expression was derived to enable η to be calculated at any temperature (0–80°C), and for any concentration (0–30% total solids) whatever the fat to solids-not-fat ratio (0·01–0·4). A nomogram was also constructed for the immediate computation of η without any practical loss of accuracy.