138 MARKET DAIRYING 
may be used asa starter. But in the case of unpasteurized 
cream, even though the flavor is good, there are always 
present some undesirable germs which will multiply in 
each successive batch of cream or buttermilk used as a 
starter, so that after a week’s use the flavor may actually 
be bad. Where cream is slightly off flavored and a por- 
tion of this, or the buttermilk from it, is used as a starter, 
it will readily be seen that the taint will not only be 
transmitted but will multiply in the cream from day to 
day. The use of either cream or buttermilk as a starter 
is therefore not to be recommended. 
COMMERCIAL STARTERS. 
Commercial starters may consist of a single species 
of lactic acid organisms, but usually they are imade up 
of a mixture of several species. These starters)are pre- 
pared in laboratories where the utmost precautions are 
taken to keep them free from undesirable germs. 
Preparation. Most of the commercial cultures are 
sent out in one ounce bottles which are hermetically 
sealed. The method of making starters from them is the 
same for all whether they are obtained in the liquid or 
in the dry form. 
In making the first batch of commercial starter, the 
entire contents of the bottle is put into a quart of skim- 
milk, sterilized by keeping it at a temperature of 200° F. 
for two hours, and then cooling to 80° which temperature 
should be maintained until the starter has thickened. A 
new starter is now prepared by introducing the quart of 
starter into fifty pounds of skim-milk, pasteurized by 
keeping it at a temperature of 170° to 185° for thirty 
minutes and then cooling to 65° F. All subsequent starters 
are prepared in the same way except that the amount of 
