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)
50 TENTH ANNUAL CONVENTION 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. MAKING THE TEST. 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;
Based on date of publication, this material is presumed to be in the public domain.| For information on re-use, see http://digital.library.wisc.edu/1711.dl/Copyright