660 BACTERIOLOGICAL ANALYSES 



grease and water when boiled, and it will produce little or no foam. 

 Leach 1 finds that a very slight foam is sometimes observable with 

 occasional samples of renovated butter, but nothing like the abun- 

 dant amount of foam produced by genuine butter. 



Appearance of the Melted Fat. Provisional. 2 "Melt from 

 50 to 100 grams of butter or process butter at 50 C. The curd 

 from butter will settle, leaving a clear supernatant fat. On the other 

 hand, the supernatant fat in the case of process butter does not 

 assume that clear appearance, but remains more or less turbid." 

 Butter which has been overworked will also melt in a cloudy man- 

 ner. 1 



The Waterhouse Test 3 



Heat about 50 cc. of well-mixed sweet milk, or sweet skim milk, 

 in a beaker to boiling and add from 5 to 10 grams of the sample to 

 be tested. Stir, preferably with a small wooden stick, until all the 

 fat is melted. Then place the beaker in a dish of ice-cold water and 

 continue the stirring, until the fat hardens and solidifies. If the fat 

 is oleomargarine, it can be readily gathered and formed by the stir- 

 rer into one lump or clot. If the fat is genuine butter, or renovated 

 butter, it cannot be so collected, but it remains, in a granulated con- 

 dition, distributed throughout the milk in small particles. 



CHAPTER XXIII. 

 BACTERIOLOGICAL ANALYSES 



It is frequently desirable and advantageous for the creamery to 

 make bacteriological analyses of its butter, or of the products which 

 enter into the process of manufacture, such as milk, skim milk, 

 starter, cream before and after pasteurization, and to also examine 

 bacteriologically some of its equipment, particularly the cream cans, 

 vats, pipe lines, churns, etc. 



Some creameries make bacteriological determinations of their 

 butter regularly, either of each churning, or once per week, etc. 

 Others in their attempt to locate the cause of certain flavor defects 

 or inferior keeping quality, resort to bacteriological studies of cer- 

 tain stages of the process of manufacture. 



Many of the butter defects are not caused by bacterial action, 



1 Leach, Food Inspection and Analysis, 1914. 



2 Journal Association Official Agricultural Chemists, Vol. II, No. 3, 1916. 



3 Parsons, Journal Am. Chem. Soc., 23, 1901. 



