June, 1922 



SCIENTIFIC AGRICULTURE 



333 



TABLE II. 



Distribution of Molds (oidium lactis) and Yeasts in 337 lots of creamery butter, all 



Storch Test negative, season 1920. 

 Molds counts 93 Dominion Contest lots 244 Ontario lots. 



June, July, Sept. and Oct. entries fune, July and August 



les Per cent. No. of samples per cent 



the butter is made. Whether the "Storch 

 Test" is sufficient in itself to give what in- 

 formation is required, or whether it needs 

 to be supplemented by a biological test such 

 as the "Yeast and Mold Count" is a question 

 which presents itself for consideration when 

 one learns the microbial content of much of 

 the "Storch Test" negative butter being made 

 at the present time. 



With regard to the efficiency of pasteur- 

 ization, by which we mean the bacteriological 

 thoroughness with which the work is done, 

 experience with milk pasteurizing plants all 

 over the country has indicated that the effi- 

 ciency of the process is frequently quite low. 

 There was no reason to believe that a similar 

 state of affairs did not exist among creameries 

 pasteurizing their cream, particularly in some 

 cases where the details of the work were none 

 too carefully attended to, and where the 

 cream at times arrived at the plant late in 

 the day and there was more or less of a rush 

 to get through. Then again it has been re- 

 peatedly demonstrated with regard to con- 

 ductor pipes, milk and cream pumps, coolers, 

 milk-bottling apparatus, milk utensils, 

 churns, etc., that what is clean to the eye 

 is not necessarily bacteriologically clean, 

 that is to say sterile, by which we mean 

 completely free from all living microorgan- 

 isms-bacteria, yeasts and molds. Extensive 



contamination from unsterilized apparatus 

 has frequently been noted in milk-pasteur- 

 izing plants, reducing thereby, very material- 

 ly in some cases, the final efficiency of the 

 process from a bacteriological point of view. 

 There was no reason to believe that extensive 

 recontaminations were not also commonly 

 occurring in many creameries where pasteur- 

 ization was practised, thereby nullifying to 

 a greater or less extent, the germicidal effect 

 of the heating process to which the cream 

 had been subjected. To determine the ex- 

 tent of this recontamination and its effect 

 on the butter, if any, has been one of the 

 objects of this investigation, as mentioned 

 above. 



Method of Taking Samples and of Making 

 Cultures 



Samples for yeast and mold counts have 

 been taken at the Grading Station, or at the 

 cold storage warehouse where the scoring has 

 been done, from the boxes of freshly made 

 butter with scalded cheese triers, two four- 

 inch plugs being drawn from the box and 

 the lower three inches of each transferred to 

 a sterile 60 c.c. glass preparation jar by 

 means of the handle of a scalded teaspoon, 

 and top screwed on. In a few cases where 

 bacterial counts also were being made, ster- 

 ilized triers and teaspoons have been used. 



