168 



EXPERIMENT STATION RECORD. 



combines all of the 3 cliaracters, tlie power of producing flavor, acid, and aroma. 

 Some develop flavor witli the acid, others develop aroma with flavor, and others 

 develop aroma without any special flavor. . . . 



"Lastly, it is interesting to notice that among the species of bacteria which pro- 

 duce good flavor in the butter are found some that were quite widely distributed 

 during" the month of June." 



Bacteriological investigations in the dairy, G. J. Leufven {Rpt. 

 Ultima Agl. Inst, 1894, pp. 35-39). — The influence of pasteurization and 

 cooling upon the hacteria content of milk. — Separator skim milk was 

 pasteurized in a "Separator Heater No. 2" and cooled in a cooler. 

 Samples of milk were taken in sterilized flasks directly before and 

 after pasteurization, and also after the cooling. The flasks were left 

 standing at room temperature until the milk was coagulated. In 6 

 trials the average length of time before the milk coagulated was: 

 Unpasteurized milk, 58 hours j pasteurized milk, 112 hours; pasteur- 

 ized and cooled milk, 81 hours. The temperature of the room ranged 

 between 54 and 68° F., the average temperature being 01° F. The 

 results showed that the pasteurized milk became infected while pass- 

 ing over the open cooler. The bacteriological analyses also corrobo- 

 rated this view. 



Number of hacteria per cubic centimeter of milk. 



Pasteurization temperature. 



80° C. (176° r.) 

 85° C. (185°F.) 

 80OC. (176°F.) 

 75° C. (167° F.) 



Unpasteur- 

 ized milk. 



1,868,000 



992, 000 



3, 200, 000 



1, 156, 000 



Pasteurized 

 milk. 



1, 484, 000 

 150, 000 

 542, 000 

 268, 000 



Pasteurized 



and cooled 



milk. 



1, 738, 000 

 192, 000 

 618, 000 

 284, 000 



The lactic-acid bacteria proper were killed by the pasteurization, 

 and generally also the peptonizing forms found in the milk, the bac- 

 teria remaining being only a few forms, chief among which was a 

 micrococcus present in especially large numbers. This form coagulates 

 the casein to a compact mass after a considerable period of time. The 

 bacteria introduced in the cooled milk were largely lactic-acid forms. 

 The bacteria content of the air of the dairy was found to vary between 

 71 and 1,248 bacteria per liter. 



The bacteria content of the air of dairy and cattle ham. — The air was 

 aspirated through sugar filters and the bacteria content of the same 

 determined. The number of bacteria found per liter of air (September 

 28) was as follows : 



In dairy : No. 



Before beginning of daily work 28 



At close of churning 56 



At close of separation and pasteurization 71 



At close of cleaning and scrubbing 26 



Before receiving milk 22 



