A YEAST PRODUCING FOAMY CREAM 299 



Lime possesses disinfectant properties in 1, 2 and 5 per cent 

 solutions with three minutes' exposure. 



Boric acid exhibits no killing powers in strengths of 1, 2 and 

 5 per cent after two hours. 



Cresol in 0.5 per cent solution fails to destroy the yeast in 

 two hours while 1 per cent kills in three minutes and 2 per cent 

 in one minute. 



Carbolic acid in 5 per cent solution is likewise efficient within 

 one minute. 



Resistance toward desiccation 



Data showing the ability of the yeast to withstand desiccation 

 are somewhat limited. However, the results obtained demon- 

 strate it to be very resistant to drying. Soil and alfalfa stems 

 were placed in sterile containers and inoculated with milk cul- 

 tures of the yeast. The absence of yeasts in the soil and alfalfa 

 used was assured before inoculation. The substances were 

 examined at frequent intervals to note the effect of desiccation. 

 The yeasts were observed after eighty-six days in large numbers 

 in both substances. No further analysis of the materials was 

 made. 



CONCLUSIONS 



1. A lactose-fermenting yeast is the essential organism in the 

 abnormal fermentation of cream, known as "foamy cream." 



2. Raw or sterile cream inoculated with a pure culture of the 

 yeast shows typical foaming characteristics. 



3. The optimum temperature for growth is near 37°C. This 

 accounts for the prevalence of foamy cream during hot weather 

 only. 



4. The thermal death point of the yeast is near 55°C. for ten 

 minutes. 



5. The yeast offers slight resistance toward efficient disin- 

 fectants. 



6. The organism is quite resistant towards desiccation. 



