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

Abstract

Summary The surface tension (γ) of whole milk (4% fat) and skim-milk was determined in the temperature range 18–135 °C by the drop number method. Measurements were carried out in a temperature-controlled chamber under pressure. Above 90 °C, the mean residence time of the milk at the test temperature was 15 s. Surface tension values were calculated by the Harkins and Brown method, corrections being made to account for the kinetic energy of the drops. The results for whole and skim-milk were not significantly different and the combined data (66 values) could be represented by the equation: γ =1·8 10 -4 θ 2 –0·163θ+55·6, (where γ is in mN. m -1 and θ is the temperature in °C) with a residual s.d. of 2·1 mN. m -1 (mean relative error 9·6 % at the 5 % level of significance).