240 MANUAL OF MILK PRODUCTS 



of a natural starter is the lactic acid fermentation. There is no 

 way for ascertaining immediately whether a given lot of milk 

 will develop a good lactic acid fermentation. It is thought that 

 clean, sweet milk is more likely to produce the desired fermen- 

 tation. But the lactic acid fermentation itself shows that milk 

 was contaminated with bacteria. This self-same milk is not 

 sweet when the fermentation has progressed far enough to 

 'turn' the milk. 



"The obtaining of a good natural starter depends upon 

 chance as well as judgment. Hence, the best method of selec- 

 tion is to take several small samples of milk, each sample from 

 a different dairy, let them ferment at a temperature that is 

 favorable to the lactic acid fermentation (60°-75°F.), and exam- 

 ine them when they have coagulated. A good lactic fermenta- 

 tion produces a smooth curd free from gas, and there is no 

 wheying off for a long time. Wheying off is usually associated 

 with a bad flavor. The desirable flavor is best learned by expe- 

 rience. It should be acid, pleasant, and clean. A disagreeable 

 odor is an undesirable quality, but often a starter that makes 

 good butter will show a stale or stuffy odor when it is ripened 

 in a closed vessel. Although the logical test of a starter is to 

 ripen cream with it and see what kind of butter it makes, ex- 

 perience soon teaches a butter-maker what starter makes the best 

 butter so that he is soon able to judge a starter simply by sense 

 tests. Having several samples of fermented milk or starters to 

 choose from, the chances of getting a good starter are, of course, 

 much better than where only one sample is taken. The variety 

 affords comparisons and it is easier to judge the quality. When 

 a good starter is found, it can be built up and carried on in 

 the same manner as a commercial starter. 



"The relative merits of skim-milk and whole milk for carry- 

 ing on starters are points of controversy. Theoretically, whole 

 milk is not as good because its fat does not afford any food for 

 the bacteria. It is generally admitted that it is better to select 



