The bottle and the test were developed by Stephen Babcock in 1890 as a simple but accurate way to detect adulterations practiced by some dairy farmers, including diluting the milk with water or skimming some cream.[3]
The test was quickly adopted by dairymen, and also by farmers to help the breeding of milk cows.[3] The tests were usually done monthly by an employee of the local Dairy Herd Improvement Association.[citation needed] Babcock's refusal to patent his process or the device greatly helped its widespread diffusion.[4][5]
The test is based on the observation that a suitable amount of sulfuric acid added to the milk will dissolve proteins and other components, except the fat. Heating and centrifuging cause the fat to separate and float to the top, in a layer free of bubbles. The amount of fat in the milk can then be estimated from the volume of that layer. The procedure was commonly carried out in a special flask with a long neck, called a Babcock bottle.[1]
Specifically, the test consisted of the following steps:[6][7][8]
Place 17.6 mL (18 grams) of milk into a Babcock bottle.
Spin the flask in a hand-cranked centrifuge for 5 minutes.
Add water at 60°C until the fat layer is all in the neck.
Warm the bottle to 55-60°C and spin it for another minute.
Immerse the bottle upright in 55-60°C water until the fat layer is settled.
Read out the fat contents from the graduated scale.
The scale on the neck was calibrated so as to give a direct readout of the percentage of fat in the original sample (assumed to be 17.6 mL), in 0.1 percent increments, without the need for computation.[6]
Test for ice cream
The original Babcock test was not suitable for estimating the fat contents of ice cream, since the sugar and other ingredients would be charred by the sulfuric acid and contaminate the fat layer. After thousands of experiments, a modified test, suitable for the purpose, was developed in 1930 by L. K. Crowe at the University of Nebraska. It used a solution of ammonium hydroxide in N-butyl alcohol, and a mixture of sulfuric acid and ethanol.[10]
See also
Wikimedia Commons has media related to Babcock test.
^ abStephen M, Babcock (1890): "A New Method for the Estimation of Fat in Milk, Especially Adapted to Creameries and Cheese Factories". In Annual Report, Agricultural Experiment Station, University of Wisconsin.
^E. B. Hart (1949): "Stephen Moulton Babcock". Journal of Nutrition, volume 37, issue 1, pages 1–7. doi:10.1093/jn/37.1.1
^ abcErnest O. Herreid (1942): "The Babcock Test; A Review of the Literature". Journal of Dairy Science, volume 25, issue 4, pages 342–343. doi:10.3168/jds.s0022-0302(42)95301-3
^ abOtto Frederick Hunziker (1917): "Specifications and Directions for Testing Milk and Cream for Butterfat". Journal of Dairy Science, volume 1, issue 1, pages 38–44. doi:10.3168/jds.S0022-0302(17)94359-0
^ abRoscoe H. Shaw (1917): Chemical Testing of Milk and Cream. U.S. Government Printing Office.