70 Report of the Department of Bacteriology of the 



A second salt of paracasein and acid called paracasein dilactate 

 is formed from the monolactate by treating the latter with more 

 acid. This compound is insoluble both in water and in dilute 

 salt solutions and as yet little is known as to either its chemical 

 properties or the part which it plays in cheese-ripening-. 



paracasein monolactate is formed in cheese curd by 

 lactic-acid bacteria. 



In order to determine whether paracasein monolactate could be 

 formed in cheese through the activity of lactic acid organisms the 

 following experiment was carried out. 



Fresh milk was curdled by rennet in the presence of ether to 

 prevent acid formation and after the moisture had been satisfac- 

 torily expelled from the curd the whey was drawn and the curd 

 washed in three changes of warm water to remove the major part 

 of the sugar and the water soluble compounds. The resulting 

 mass contained 0.3 per ct. of sugar and about 4 per ct. of salt- 

 soluble compounds. 



Two series of flasks were prepared, each flask containing 50 cc. 

 of water and 25 grams of curd ground with sand (922 mgs. 

 nitrogen). These flasks were sterilized in steam for 10 min- 

 utes at 120° C. After cooling, Series I received an inocula- 

 tion from a pure culture of an acid-forming bacillus agreeing 

 closely with the description of Bacillus lactis acrogcnes. Series 

 II received an inoculation from the same organism and in 

 addition 0.5 grams of sterile lactose in each flask. A similar 

 sterile flask received neither sugar nor organism but 0.5 cc. 

 of chemically pure lactic acid. Two flasks of each series were 

 taken at each analysis. Bacteriological examinations of the 

 flasks at the time they were taken for analysis indicated that 

 they were free from contamination. The amount of nitrogen 

 insoluble in water but soluble in a 5 per ct. solution of sodium 

 chloride at the end of various intervals expressed in percent- 

 age of the total nitrogen is given in the following table. 



