DAIRY PRODUCTS CHEESE. 39 



like hot grease, without foaming. Oleo behaves like process butter, but chemical 

 tests and the Waterhouse test described above will indicate whether the sample is 

 oleo or butter, either genuine or process. 



(b) APPEARANCE OF MELTED BUTTER. a 



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

 butter will settle, leaving above it a clear, supernatant fat. On the other hand 

 the supernatant fat in the case of process butter does not assume that clear appear- 

 ance, but remains more or less turbid. 



(c) MICROSCOPIC EXAMINATION. 11 



Place a bit of the butter or process butter on a glass slide, cover it and press into a 

 thin film with cover glass. Examine immediately with a polarizing microscope 

 magnifying from 100 to 140 diameters. When a selenite plate is placed between the 

 slide and the lower nicol a normal butter will give a uniformly blue colored field, 

 showing the absence of fat crystals. On the other hand, process butter gives a blue 

 field, mottled with yellow. 



8. DETECTION OP ANNATO AND SAFFRON IN BUTTER CORNWALL'S METHOD. c 



Five grams fat are dissolved in 50 cc of ether in a wide tube and the solution 

 is vigorously shaken with 12 to 15 cc of a very dilute solution of potassium 

 hydroxid, which must still be alkaline after it separates from the ether solution. 

 It is allowed to stand a few hours, when the aqueous layer is drawn off, evapo- 

 rated to dryness, and tested with sulphuric acid, which in the presence of annato 

 gives first a blue or violet blue, changing quickly to green, and finally to brown. 



Saffron which would be extracted at the same time acts differently when treated 

 with sulphuric acid, not giving the green coloration. 



The aqueous solutions, if not clear enough to use, must not be filtered, as the filter 

 paper will take up large amounts of the color, but can be shaken up again with 

 fresh portions of ether. 



Martin' 1 uses carbon disulphid as a solvent instead of ether, which is just as satis- 

 factory. 



Genuine butters treated in this way give only a very slight trace of coloring matter. 



9. DETECTION OF ANILINE COLORS. e 

 Follow methods described under Coloring Matter (p. Ill and following). 



(C) CHEESE. 

 1. GENERAL DISCUSSION. 



There are two kinds of adulterations practiced with cheese. First, the use of fat 

 other than milk fat, producing a product called filled cheese. Second, the removal 

 of varying amounts of fat, producing skim cheese. The liquefied fats of swine 

 or cattle intimately mixed with skim milk produce filled cheese; therefore the 

 chemical methods for the examination of the fat of filled cheese are the same as are 

 used for the detection of adulterated butter. Skim cheese is made from milk from 

 which part or the whole of the fat has been removed; therefore the determination 

 of fat and nitrogenous compound! will give a good indication as to whether the 

 sample under examination is skim cheese. 



Jour. Amer. Chem. Soe., 1900, 22, 327. 

 Uour. AUNT. Cln-m. Sor.. I'.MMI. !>_. :7. 

 "Chcin. News, vol. 1X.X7. .".">, 49; U. S. Dept. of Agr., Div. of Chem., Bui. 13, pt. 1, p. 28. 



'Analyst, INS:,. | <>. |,;;; 

 \l>|.rn.lix, p. l.VJ. 



