618 TESTING FOR BUTTDRFAT 



column is clear, translucent, has a golden yellow or amber color 

 and the top and bottom curves are sharply denned. 



The presence of whitish curd in or immediately below the fat 

 column is the result of excessively cold milk and acid, or the use of 

 too little or too weak acid. The presence of charred matter in the 

 fat column is the result of the use of too much or too strong acid, or 

 too high a temperature of milk or acid, or both, at the time of adding 

 the acid. 



The appearance of foam on the surface of the fat column is 

 caused by the use of hard water. The carbonates, when acted on 

 by the sulphuric acid, break down, liberating carbon dioxide gas 

 which, rising through the fat column, gathers on its surface in the 

 form of air bubbles. Where soft water, distilled water, or rain 

 water is not available, the water may be softened by boiling it or by 

 the addition to it of a few drops of sulphuric acid before use. 



All tests which are milky, or foggy, showing the presence of 

 curd or charred matter in or below the fat column, or of which the 

 reading is indistinct or uncertain, should be rejected. Duplicate tests 

 are essential in all work where special accuracy of results is required, 

 such as in official testing and experimental investigations. 



Cream Test 



Cream samples. The taking of cream samples, at the factory, 

 at the cream station and on the cream route is fully discussed in 

 Chapter VI on "Receiving Milk and Cream." 



Cream samples should be tested as soon as possible and not 

 later than three days after they are taken. Composite samples rep- 

 resenting portions of consecutive deliveries of the same patron 

 are prone to be unreliable. Samples should at all times be kept in 

 non-absorptive containers, sealed air-tight and held in the cold. 



Immediately before testing, mix the sample until it pours readily 

 and a uniform emulsion is secured. If in good condition shake, 

 pour, stir or blow until properly mixed. If very thick, warm to 

 85 degrees F. and then mix. In case of lumps of butter, heat the 

 sample to from 100 degrees F. to 120 degrees F. by setting in water 

 bath, mix thoroughly and weigh out at once. For commercial work 

 on a large scale it is advisable to temper all samples to 100 degrees 

 to 120 degrees F. in a water bath previous to mixing. Great care 

 should be exercised to avoid overheating the sample, causing the 



