Southern Wisconsin Cheesemakers' and Dairymen's Association / Proceedings of the tenth annual meeting of the Southern Wisconsin Cheesemakers' and Dairymen's Association held at Monroe, Wisconsin, Thurs. and Fri., January 27 and 28, 1910
Hart, T. B.
Variations in the amount of casein in cows' milk and the operation of the casein test, pp. 44-53 PDF (1.9 MB)
SOUTHERN WIS. CHEESEMAKERS' & DAIRYMEN'S ASS'N 51 replaced in the rack an(l allowed to stand 11) minutes after which the percentage of casein can be read directly from the scale on the test bottle. The tests may be allowed to stand longer then 10 minutes (up to 24 hours) before reading without affecting the result, but should never be read in less than 10 minutes. If the edges of the casein pellet are not sharp and clear out it is probably due to too long or too vigorous shaking. A very high or low temperature may also cause ragged edges. The acid must also be of the correct strength. COMPOSITE SAMPLES. Composite samples of milk, as well as samples of fresh milk, call be tested thus making both fat and casein tests from the same sample. Potassium dichromate is the only preservation which can be used. It is used at the rate of one-tenth gram (I , garine) to each 100cc. of milk. The old (large) dichromate tablets formerly on the market con- taine(l four-tentlhs gram of preservative; the new (small) tablets now soll specifically for the casein test contain one- tenth gram of preservative. About one ounce (30 cc.) of milk should be taken daily. One small tablet (or one quarter large tablet) is placed in the small sample jar at the beginning of the week and another added after three days. This avoids too great a concentration of preservative at first. If less milk is taken for a sample, the amount of preservative should be reduced proportionately. Brown or amber colored sample bottles are to be pre- ferred, and should be kept tightly stoppered. Colored bottles are used since it has been found that they largely prevent the action of sunlight on the mixture of [dichromote and casein which would otherwise cause incorrect results. Plain bottles could be used and kept in a light proof cup- board or box, but even with this care they would be ex- posed to the light more or less, while sampling and testing. The colored bottles are far better and can be obtained from the supply houses at practically the same sort as the
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