42 BUTTER-MAKING. 
about 175° F. the properties of the enzyme are destroyed Owing 
to this it is easy to detect whether a certain sample of milk has 
been pasteurized or not. Galactase is present in sosmall a 
quantity that it could not be determined in milk quantitatively. 
It must be detected in a qualitative way. 
The test used and invented by Storch, of Copenhagen, 
Denmark, is to put a small quantity of milk in a test-tube, add to 
it a small quantity of a weak solution (2%) of hydrogen peroxide 
(H202), a small quantity of potassium iodide, and a little starch 
solution. The whole mixture is then shaken. If the mixture does 
not change in color, it has been heated to at least 170° F. If it 
turns blue, it has not been heated to a sufficiently high tempera- 
ture to destroy the properties of the enzyme present in the milk. 
Another test which can be used in distinguishing raw milk from 
scalded or boiled milk is to take 10 cubic centimeters of the milk 
to be tested, add 1% of recently prepared aqueous solution of 
“Ortol,’’ and then one or two drops of hydrogen peroxide. If 
the milk has not been heated, a vivid red color is produced. 
Heated milk shows no effect. 
7. Divides the Fat-globules.— The fat-globules in normal 
milk are grouped in minute clusters. When milk is heated, 
these clusters break up, and each globule exists more or 
less independently. When heated to an excessively high 
temperature, and exposed to this temperature very long, the 
fat-globules tend to run together. This can be proved by 
heating milk in an open vat for about half an hour. A small 
amount of yellow fat will then be seen floating on the top. 
8. Caramelizes the Sugar.—The brownish color which the 
milk assumes when it is heated excessively is due to a change 
which the milk-sugar undergoes. Fleischmann claims that the 
sugar begins to change into a substance known as lacto-caramel 
at a temperature of 160° F. This change, however, is not 
pronounced enough to be apparent in the color, unless the milk 
is heated a long time. The higher the temperature is, and the 
longer it is exposed to the heat, the more pronounced is the 
change. 
