USE OF BACILLUS BULGAEICUS IN CHEESE STABTEBS. 13 



stones sometimes placed in them for maintaining heat must be at the 

 proper temperature and would have to be used with the greatest care 

 or the starter would be heated too high and sterilized. In any case it 

 would be desirable to warm up the starter twice a day. 



At the present time the cheesemakers take whey for the rennet 

 direct from the kettles, usually before the curd is cooked. The 

 starter could be taken in the same way, though it would probably be 

 better to take out this whey after the curd is dipped. The tempera- 

 ture used for heating the curd has no harmful effect on the 

 B. bulgaricus while it checks temporarily the growth of most other 

 organisms, probably including yeasts. This is permissible for carry- 

 ing starters, though some writers have advised sterilizing the whey, 

 which should not be done unless a mother starter is used for reinocu- 

 lating. A putrefied rennet would be the certain result. Some have 

 advised the use of rennet extract if the cheese shows any signs of 

 abnormal gas formation. This might help if the gassy cheese were 

 due to the loss of the bulgaricus culture, but as a general rule it would 

 do more harm than good, for if the bulgaricus were present the use 

 of a greater quantity of the whey would provide a better remedy. 



Cheesemakers would probably insure themselves against occasional 

 trouble from undesirable fermentation if they would set the whey at 

 the usual temperature 24 hours before adding the dried rennet. This 

 would give the B. bulgaricus present a chance to get a good start 

 ahead of any putrefactive bacteria which might be carried by the 

 rennet. 



TROUBLE FROM YEAST. 



Usually it would be desirable to carry a mother starter, or culture, 

 in a separate vessel, the mother starter being the name given to the 

 small starter carried over from day to day for inoculating the main 

 starter. It is necessary to carry this mother starter so that it will 

 not become contaminated with yeast, which is apparently the only 

 foe of the cheesemaker that Bacillus bulgaricus starters will not help 

 to control. All other contaminations of the starter were held in com- 

 plete subjection by the B. bulgaricus. At the factory where our 

 experiments were made the contamination from yeasts was very 

 serious ; although all vessels used were sterilized and the whey starter 

 was boiled, the yeast on one occasion spoiled the starter. The con- 

 ditions in cheese factories seem to be favorable for the growth of 

 yeasts ; the air probably contains large numbers of yeast cells. 



A MOTHER-STARTER CAN. 



To overcome the difficulty from yeast contamination some means 

 are necessary to insure a pure mother-starter which is protected from 



