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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
(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)


Page 51


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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