Effect of Variations in Fat and Temperature on the Surface Tension of Various Milks

Measurements of the surface tension of skimmilk, whole milk, and homogenized milk were made at 60, 81, and 102 ° F. with a du Noiiy tensiometer, to obtain data for use in the calibration of laetometers.The results are presented graphically.A consistent difference was apparent between the surface tensions of the three milks, with an increasing divergence occurring with a rise in temperature.The difference between the surface tension of skimmilk and whole milk was about 50% greater at 102 than at 60 ° F. The surface tension of hmnogenized nfilk was intermediate to that of skimmilk and whole milk.The change in the surface tension with temperature for all milks was most marked between 60 and 80 ° ]~.The surface tension of whole milk was not affected significantly by fat in excess of about 4%.The present work on the surface tension of milk was done in connection with research on the calibration of lactometers to be used at the temperature of 102 ° F.