The Density of Milk at Low Temperatures

Abstract

Summary The densities of a variety of herd milks from representative sources in the Washington, D. C., area were determined at low temperatures, to establish volume-weight relationships more accurately than was possible from existing data. Density measurements were made in duplicate over a range of 1 to 10°C. on 101 samples of milk. Specially designed pycnometers, having a capacity of about 46 ml., were used in refrigerated water baths controlled to within ± 0.02° C. The percentage of milk fat in most of the samples was determined by the Babcock method, and in the remainder by the Mojonnier method. The percentage of total solids in 85 samples was determined gravimetrically. The percentages of fat, total solids, and nonfat solids covered the following ranges, respectively: 3.1 to 6.4; 11.6 to 16.1; and 8.2 to 10.2. The range of densities at 0.95, 4.95, and 9.85°C. were, respectively: 1.0312 to 1.0386; 1.0322 to 1.0373; and 1.0298 to 1.0368. Formulas for calculating the density of milk were derived from the data by the method of least squares. The results emphasize that density is more closely correlated with the percentage of nonfat solids than with the percentage of fat in milk.