136 UNIVERSITY OF WISCONSIN STUDIES 



interpretation of a large proportion of yeasts and a small 

 proportion of Oidia and vice versa. Only the sum total has 

 a meaning. The yeasts are more persistent, To simplify 

 the language for laymen we call Oidium lactis "mold". 



On the basis of the record made by a number of good plants 

 we have adopted an arbitrary commercial standard of ten or 

 less. This is as good work as the best men are able to do. 

 A count of thirty or more means one or more of the following 

 defects: Failure of pasteurization, i. e., in temperature, in 

 time, or by contamination ; lack of cleanliness or of sterility of 

 utensils and conduits ; or contaminated starter. In every case 

 where we made a personal survey where the count exceeded 30 

 we demonstrated that one of these defects existed to such 

 a degree that the laymen could easily see it when it was 

 pointed out to them. By mail and without making personal 

 trips we have corrected many defects. That we detected dirty 

 cream pipes 500 miles beyond our eyesight and caused them 

 to be cleaned is one of the wonders of our uninitiated. 



When testing pasteurization or when searching for defects, 

 we present a survey of the plant by means of the graphic re- 

 port shown here (see Fig. 3). This maps out the course 

 of the material through the plant and shows where defects 

 occur. In the case exhibited here yeasts and molds in the 

 pasteurized products made their first appearance in the churn, 

 thereby proving it to be the source of contamination. If the 

 cream were the original source of yeasts and molds, then the 

 butter would contain much fewer than the cream because the 

 drainage of the buttermilk and washing of the butter eliminate 

 the larger part of them. But since the churn was the source 

 of the yeasts, their number increased the longer the materials 

 remained in the churn. The working of the butter expelled 

 more yeasts than the churning because the fixtures of the 

 worker are the main refuge of yeasts. These churns were 

 old and difficult to sterilize. Nevertheless this exhibit is ex- 

 cellent work and far above the average. 



Other conditions being favorable, a butter having only a 

 few yeasts and molds is a safer hazard for long distance ship- 

 ments and for storage. Indeed, our records show that the 



