Dynamic viscosities of milk and cream from 70 to 135 °C

Abstract

SummaryThe dynamic viscosities of non-homogenized and homogenized (2-stage) whole and half skim-milk and cream, of unhomogenized skim-milk and of water-diluted milks were measured at temperatures between 70 and 135 °C; this range includes those temperatures used in ultra-high-temperature (UHT) treatments. A tube viscometer was used at the outlet of a continuous flow indirect heater. Above 85 °C the mean residence time of a milk or cream at the test temperature was 3–6 s.An equation relating viscosity μ and temperature θ of the form In μ = aθ2+bθ+c was derived for each product.It proved possible to relate μ, θ and fat content (0·03–15·5%) in a single equation which was appropriate for all the homogenized milks and creams as well as the non-homogenized skim-, half skim- and whole milk; the equation is considered valid for these products under conditions of indirect UHT sterilization. Viscosity values calculated with the equation, even those relating to temperatures as low as 50 °C, were comparable with those reported in the literature.

Predictions of some product parameters based on the processing conditions of ultra-high-temperature milk plants

“…If the flow is turbulent (i.e., Reynolds number > 4100) the velocity of the fastest particle is considered to be 1.2 Â mean particle velocity (Kessler, 1981;Lewis & Heppell, 2000) so that the B * (adjusted) is B * /1.2. The dynamic viscosities used to calculate Reynolds numbers were based on reported equations for milks and creams between 70 and 135 C (Bertsch & Cerf, 1983). C * , representing the chemical effect relevant to a reference temperature of 135 C, was calculated from the equation C * ¼ !10 ((TÀ135)/31.4) Â dt/ 30.5.…”

Heat‐Induced Gelation of Individual Whey Proteins A Dynamic Rheological Study

“…Generally, temperature, protein concentration and physical state of the dispersed phase determine the rheological behavior. Viscosity characteristics and conditions for gel formation in milk, milk protein concentrates and whey protein concentrates have been investigated by a variety of methods (Bertsch and Cerf, 1983;Buckingham, 1978;FemBndez-Martin, 1972;Kalab et al, 1970;Hermansson, 1975). Studies on gel characteristics were done using instruments based on empirical data like tube viscometers, H(ippler viscosimeter and penetrometers.…”

Surface tension of whole and skim-milk between 18 and 135 °C

“…A knowledge of the surface tension of milk is of value in designing biphasic milk-steam flows which occur in direct ultra-high-temperature (UHT) milk-steam mixture installations (Wallis, 1969;Collier, 1981;Delhaye et al 1981). The present work was thus undertaken to determine the surface tension of milk between 18 and 135 °C, and forms part of a general investigation of the physical properties of milk above 80 °C which includes studies of density (Bertsch et al 1982), viscosity (Bertsch & Cerf, 1983) and specific heat (Bertsch, 1982).…”