EXPERIMENT STATION BULLETINS. 



531 



disturbances. While the variation in the first instance may be regarded as 

 physiological and normal, in the second instance it may be regarded as bacterial 

 and abnormal. 



It has long been known that rennet in the making of cheese acts more readily 

 upon milk which has ripened for some time than upon wholly fresh milk. So 

 commonly recognized is this that chesse makers employ more rennet in the 

 curding of sweet milk than where a certain amount of acid has developed. Mr. 

 H. C. Oven working in this laboratory, with the action of pepsin and rennet 

 on milk, has contributed some data which confirms the chemical and bacteri- 

 ological experiences given in the foregoing paragraphs. 



PEPSIN THAT IS EMPLOYED FOR CHEESEIMAKING. 



Breed of cow. 



Ayrshire 



Brown Swiss. 

 Holstein 1 



Time of testing. 



9:30 a.m. 



Holstein 2. 



m min. 



4 min. 



39i min. 



No curding 

 in 1 lir. 



10:45 a. m. 



13i min. 



5 min. 



54 min. 



No curding 

 in 1 hr. 



3flOp. m. 



12} min. 



4i min. 



No curding 



in H lirs. 

 No curding 



in 1 hr. 



The time in minutes represents the time required for curding. No curding 

 in a definite time means that it was allowed to stand for the time stated with- 

 out effect and observation was discontinued. The amount of pepsin employed 

 was at the rate of 20 grams to 1000 lbs. of milk. The , temperature maintained 

 was 30° C. 



Another test was made with rennet, such as is employed commonly by cheese 

 makers throughout the State. 



RENNET. 



The time throughout the table is indicated in minutes. The amount of rennet 

 used was at the rate of 4 oz. per 1000 lbs. of milk. The temperature maintained 

 was 30° C. 



*Here again, by the use of enzymes, it is possible to show a marked differ- 

 ence in the response of milk from different cows. It has been our experience 

 throughout that the grade animals give a more uniform milk and that the 

 Holstein shows the lowest acidity, and is slowest to respond to rennet. The 

 Holstein produces the lowest amount of solids, also. It would necessitate far 

 more extensive tests to make the differences manifested by breeds of tenable 

 significance for each breed. We mention this possibility without drawing 

 conclusions so far as breeds are concerned. Our primary purpose is to estab- 

 lish the value of different milks or perhaps the inconstancy of milks in their 

 relation to bacteriological conclusions. Chemically, this irregularity is recog- 

 nized, but in bacteriology it has been disregarded too much. 



*Tlie action of rennet may be dependent upon the acidity of tlie milli. the acidity upon the dib.asic and neutral phos- 

 phates, and perh.aps citrates present, consequently rennet action returns to the mineral constituents of milk, one of which 

 probably figuring more largely than others is lime. 



