258 PRACTICAL DAIRY BACTERIOLOGY 



The Fermentation Test. This consists simply in taking small 

 samples of milk from the different dairies, putting them in 

 separate vials or bottles, placing them in a warm temperature, 

 about 90, for a few hours, and carefully examining the results. 

 If the milk curdles in the normal fashion, with a clean smooth 

 curd, the sample may be regarded as satisfactory. If large 

 numbers of gas bubbles appear in any sample of milk, or if ex- 

 ceptionally unpleasant odors arise, it may be assumed that the 

 milk in question contains something that is liable to produce 

 trouble, and it will be wise, therefore, to refrain from mixing 

 the milk from the individual patron with the general day's col- 

 lection. Under these circumstances, a visit to the creamery 

 may soon show the source of trouble and suggest a remedy. 1 



The Curd Test. The curd test is similar in its purpose, and 

 is designed primarily to prevent gassy cheese." It consists in 

 placing in clean vessels fruit cans will serve perfectly well 

 for the purpose about a quart of the milk of each patron. This 

 is heated to 90, and about ten drops of rennet added to it, after 

 which it is allowed to stand until it curdles. The curd is cut, 

 and the whey poured off occasionally, the whole curd being 

 allowed finally to mat together. For this purpose it should be 

 kept at a temperature of about 98. After it has become well 

 matted, the curd is cut open and examined. In the case of good 

 milk, the curd will be fairly smooth, showing only occasional 

 mechanical holes. If, however, the curd proves to be full of 

 pores, indicating the presence of gas within the curd, it is prac- 

 tically certain that the milk contains some of the gas-producing 

 organisms, which are liable to give rise to trouble. Under these 

 circumstances, the milk of the patron in question should be 

 looked upon with suspicion. 



These tests are used quite commonly in some cheese-making 

 countries, but have not, as yet, a very wide application. There 



i'Dugelli. Cent. f. Bact., II., xvii., p. 37, 1907 



2 Babcock, Russell and Decker. 12th Ann. Rep. Wis. Exper. Sta., p. 148, 

 1895. 



