RECEIVING, SAMPLING, AND GRADING. 81 
less than .3% of acid, ete. By means of such a test the acidity 
can quickly be determined. 
The sample cups should be numbered to correspond with 
the number of each patron. The results of the tests should 
be noticed at once, as the action of the atmosphere affects 
the color. 
The acid tests are of value in grading cream, as a sour 
sample of milk or cream is either old or has been improperly 
kept and handled. The number of grades of cream and milk 
and the maximum limit of acid each grade can contain, are 
factors which must be decided according to local conditions, 
by the operator. 
3. Use of the Fermentation Tests.—Curdled, ropy, red and 
blue milk can, as a rule, readily be detected without the appli- 
cation of a special test, but there are cases when a person’s 
senses are not sufficiently acute to detect samples of milk 
containing undesirable fermentations. Several instances have 
recently come within the authors’ notice. A neighboring 
creamery was infested with a peculiar fermentation that 
caused a very rank flavor in the butter. The milk that came 
to the creamery was carefully examined, but without locating 
the source of the trouble. The cause could not be ascertained 
without the use of the fermentation test. 
It is in such instances that a fermentation test is of special 
value. As arule, at least when the trouble first begins, it is 
milk from one particular patron that causes the trouble. This 
milk may appear to be normal, and yet contain germs which 
are very undesirable for the manufacture of the best quality 
of butter. 
Fermentation Te:ts.—There are two tests which may be 
of general use; namely, the ‘“‘ Wisconsin Curd Test” and 
the “Gerber Fermentation Test.” The former is used in 
cheese factories, but the latter is to be recommended in testing 
milk for butter-making. 
Gerber Test.—This test consists of properly made glass 
tubes which fit into a rack. This rack, containing the bottles, 
