Milk specific gravity

Municipality. Specific Gravity of the Milk. Specific Gravity of the Whey. Total Dry Residue, % Fat, % Sohds not Fat, % ... 

Sulfuric acid is much heavier than milk (specific gravity difference 1.84 vs. 

Quevenne scale chem Arbitrary scale used with hydrometers or lactometers in the determination of the specific gravity of milk degrees Quevenne = 1000 (specific gravity - 1). ka ven, skal ... 

The thermal expansion coefficient governs the influence of temperature on density and therefore it is necessary to specify temperature when discussing density or specific gravity. The density of milk is of consequence since fluid milk is normally retailed by volume rather than by mass. Measurement of the density of milk using a hydrometer (lactometer) has also been used to estimate its total solids content. 

The density of bulk milk (4% fat and 8.95% solids-not-fat) at 20°C is approximately 1030 kg m 3 and its specific gravity is 1.0321. Milk fat has a density of about 902 kg m " 3 at 40°C. The density of a given milk sample is influenced by its storage history since it is somewhat dependent on the liquid to solid fat ratio and the degree of hydration of proteins. To minimize effects of thermal history on its density, milk is usually prewarmed to 40-45°C to liquify the milk fat and then cooled to the assay temperature (often 20°C). 

The density and specific gravity of milk vary somewhat with breed. Milk from Ayrshire cows has a mean specific gravity of 1.0317 while that of Jersey and Holstein milks is 1.0330. Density varies with the composition of the milk and its measurement has been used to estimate the total solids content of milk. The density of a multicomponent mixture (like milk) is related to the density of its components by ... 

Equations have been developed to estimate the total solids content of milk based on % fat and specific gravity (usually estimated using a lactometer). Such equations are empirical and suffer from a number of drawbacks for further discussion see Jenness and Patton (1959). The principal problem is the fact that the coefficient of expansion of milk fat is high and it contracts slowly on cooling and therefore the density of milk fat (Chapter 3) is not constant. Variations in the composition of milk fat and in the proportions of other milk constitiuents have less influence on these equations than the physical state of the fat. 

Parrish, D. B., Wise, G. H., Hughes, E. S. and Atkeson, F. W. 1950. Properties of the colostrum of the dairy cow. V. Yield, specific gravity and concentrations of total solids and its various components of colostrum and early milk. J. Dairy Sci. 33, 457-465. 

It is difficult to summarize the data in the literature, especially when trying to compare milk, its fractions, and its products because the measurements were made at different temperatures, not always clearly specified. Much of the older data is given as specific gravity at 15.5° C/15.5°C, where the value of fresh whole mixed herd milk seldom lies outside the range 1.030-1.035, and 1.032 is often quoted as an av-... 

Table 8.2. Specific Gravity of Milk from Cows of Various Breeds.

The specific gravities of fluid milk products at various temperatures were measured throughout the United States by Herrington for a committee representing 13 Federal Milk Marketing orders (USDA 1965). A unique method was developed whereby the weight of the sample required to fill a Babcock bottle from the 0% to the 4% mark was com-... 

Demott, B. J. 1967. The influence of vacuum pasteurization upon the freezing point and specific gravity of milk. Milk Food Technol. 30, 253-255. 

Stull, J. W., Taylor, R. R. and Ghlander, A. M. 1965. Gradient balance method for specific gravity determination in milk. J. Dairy Sci. 48, 1019-1022. 

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