USE OF BACILLUS BULGARICUS IN CHEESE STARTERS. 9 
provide some means of keeping the starters at a temperature high 
enough to insure the growth of the B. bidgaricus. A well-insulated 
box was made for this, somewhat on the order of a fireless cooker, 
which maintained temperatures very satisfactorily on nights when 
the outdoor temperature was below freezing. Considerable diffi- 
culty with yeasts was experienced, making frequent changes of cul- 
tures necessary, as noted on another page. The first six cheeses in 
Table -i turned out " nissler," which is an indication of undesirable 
gas formation. In all the experiments except No. 14 the cheese was 
made once a day, using a mixture of morning and evening milks. 
The farmers made no pretense of cooling the milk, and as a very 
large can holding about 200 pounds of milk is used, the large bulk of 
milk cooled very slowly, even on frosty nights. The night milk with 
this treatment had developed so much acid, or such a growth of 
lactic- acid organisms, that in one instance the whey contained 0.19 
per cent of acid at the time the curd was dipped, whereas it should 
have contained normally but 0.12 per cent. In all cases there was a 
marked development of acid. From the results shown in Table 3, 
where the sour-milk starter designated in the table as SM was used in 
a commercial factory, it would appear that a high development of 
acidity in the milk from the growth of ordinary lactic-acid formers 
tends to give a " nissler " cheese. Apparently the milk must be sweet 
when delivered or the B. bulgaricus starters do not suppress all 
undesirable gas formers. 
When it was found to be impossible in the short time at our com- 
mand to induce the farmers to cool their evening milk, they were 
asked to deliver twice a day, as is the custom in the summer months. 
The night milk was then cooled in a kettle by means of a coil through 
which cold water was pumped. But as the temperature of the cooled 
milk was not lower than about 68° F., it could not be said that the 
milk was unusually well cared for. Beginning with experiment No. 
7, for which the night milk was cooled at the factory, we had milk 
sweet enough to work up in a normal manner, and the cheeses were 
all perfectly free from undesirable gas formation. 
The milk delivered generally to the factory was not of the best 
quality. The brick cheese made before these experiments was badly 
gassy, and fermentation tests made with the milk of individual 
patrons at short intervals during the experiments showed that more 
than one-half of the patrons delivered gassy milk, some of the sam- 
ples being very bad. It appeared that the starters were of great 
assistance in overcoming serious trouble with the gassy milk. Ordi- 
narily this factory would not have begun to make Swiss cheese for 
a month later than it was made successfully in these experiments, 
though the higher price of Swiss cheese is a great inducement to 
make this varietv rather than brick cheese. 
