-42 STATE BOARD OF AGRICULTURE. 



GENERAL DISCUSSION. 



Our findings that a number of bacteria died during churning cannot 

 be taken as universally true because the acidity of our cream is high 

 and the total number of living organisms was near the maximum. It is 

 the general knowledge and belief that when bacteria in cultures have 

 reached the maximum number they die more or less rapidly due to the 

 deleterious effect of Avaste products; this, and not the agitation in the 

 churn, may be the prime cause of the death we observed. An underripe 

 cream in which bacteria are capable of increasing to far greater num- 

 bers, if churned, might not show a reduction in numbers during the 

 churning operations. It is obvious that the difficulties encountered in 

 differentiating the various types in order to obtain a total count of any 

 particular group are so great that the results, at best, are subject to 

 great variations. Although it may be concluded that the numbers of 

 the various types of microorganisms not including acid producers, or- 

 ganisms especially tolerant to acids, show little or no increase in sour 

 cream after pasteurization. The same may be said of most microor- 

 ganisms in butter. 



SUMMARY. 



1. The microorganisms in butter are for the greater part those that 

 were in the cream. 



2. Neither the buttermilk nor the freshly churned butter contain per 

 unit volume as many living bacteria as the ripened cream. The average 

 from our data shows that about 30 percent of the bacteria living in 

 ripened cream fail to grow after the mechanical agitation in the churn. 



3. The process of washing and salting removes about 50 percent of 

 the microorganisms from the unsalted butter. 



4. Positive tests for peroxidase and reductase were obtained in the 

 cream and in the butter, but not in starter, in ripened cream or in but- 

 termilk. The negative results are due to a temporary inactivation by 

 high acidity. 



5. Bacf. lactis acidi is the predominating type throughout the man- 

 ufacture of butter. Other organisms appearing frequently in our sam- 

 ples are Micrococcus lactis varians, Micrococcus lactis aureus, Micrococ- 

 cus lactis alhidus, Streptococcus lactis fulrus, Bact. lactis album, B. coli, 

 torulae (liquefying and non-liquefying) and Oospora lactis. 



