USE OF BACILLUS BULGARICUS IN CHEESE STARTERS. 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 3 r easts. 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 
