YEASTS AND OIDIA IN PASTEURIZED BUTTER 133 



of raw spontaneously soured cream always contained from 

 10,000 to 100,000 yeasts (per c. c.) and not quite so many 

 Oidia. In the winter the numbers are smaller with the Oidia 

 often preponderating. Properly pasteurized cream, right 

 from the pasteurizer, never contains yeasts or Oidia. Here, 

 then, is the test for pasteurized cream and pasteurized butter ! 

 But cream off the cooler, in the cream vat, in the churn, and 

 the resulting butter, showed many yeasts and Oidia. The 

 first and last cream issuing out of flash pasteurizers was not 

 pasteurized and had to be diverted by a by-pass till a pasteur- 

 izing temperature had been reached and maintained for sev- 

 eral minutes. The last cream had to be heated in a can or 

 held over till the next pasteurization. The outlet of re- 

 tarding and pasteurizing vats formed a long pocket in which 

 cream escaped pasteurization. This pipe was shortened. Raw 

 cream dripped into the pasteurized cream from pipes and 

 conductors that had conveyed the raw cream. These were 

 removed. Raw cream splashed upon the sides and cover of 

 a vat escapes pasteurization and is usually washed into the 

 churn with the hose. This is partly overcome by rinsing with 

 hot water or hot cream during pasteurization. 



No amount of scrubbing of utensils or pipes w r ill produce 

 good bacteriological results. This must be completed by 

 sterilizing by means of hot water or live steam. Permanent 

 steam connections on cream pipes give the best results. The 

 packing glands of vats, pumps, and churns and the wood of 

 churns, as they are today, are difficult to sterilize and furnish 

 some of the yeasts and Oidia. Sometimes the starter becomes 

 contaminated and introduces yeasts and Oidia. It is easy to 

 see how laymen handling both raw cream and pasteurized 

 products may contaminate the latter with their hands, ther- 

 mometer, dipper, and measuring stick. 



In December, 1912, in one plant we began yeast and Oidia 

 counts in a cubic centimeter of butter. The totals ranged 

 from two to fifty. In August, 1913, the counts declined to 

 ten or less. We continued improving methods and equip- 

 ment and educating the men, and by July, 1916, we reduced 

 the counts to zero to five. This efficiency is now main- 



