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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

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 50

If properly cared for but little change will be needed (See
under Composite Samples).
The acetic acid should be as near 70 degrees F. as
possible, although a few degrees variation (not over 5
degrees) either way will not cause any serious error.
It is absolutely essential that these precautions as to
temperature should be strictly observed.
The test bottles should be placed in a rack, one can
easily be made by boring holes in a board and nailing a
block under each end, in an upright position. Twvo cc. of
chloroform are measured with each bottle. If a bottle is
not available, chloroform is poured into the test bottle up
to the 4 per cent mark; it thent contains 2 cc., a pipette
should not be used. Next 20 cc. of the 0.25 per cent acetic
acid are added, with a pipette, to each bottle. Theln 5cc.
of the milk, well mixed and at the proper temperature, are
pipetted into each bottle. Care should be taken that this
is accuratlv measured. It should be allowed to run direct-
lv into the acetic acid, and not along the sides of the test
bottle. As many bottles as the machine will hold shouh(l
be prepared with the chloroform and acetic acid before
adding the milk to any of the bottles.
The test bottles are then    inverted  first closill(r
them   by  placing  the  thumb   over  the  neck   and
shaken fairly vigorously for 15 to 30 seconds. A thorough
shaking is necessary to mix the chloroform with the pre-
cipitated casein and thus dissolve out the fat. Otherwise
too high tests will result. As soon as shaken the oottles
are placed in the tester, being careful to have them rest
firmly on the cork cushion at the bottom of each pocket.
The bottles are then whirled for 7 to 8 minutes at
2000 revolutions per minute.  To serve this speed the
handle of the tester is turned 56 times per minute. The
speed can best be regulated by using a metronome, set to
beat audibly 56 times per minute.
After whirling, the test bottles taken from the machine;

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