PRACTICAL USE OF STARTERS. 



L. D. BUSHNELL AND W. R. WRIGHT. 



Bulletin No. 246. 



Dairy methods have undergone great changes in the past decade, 

 due in a large part to the discoveries in bacteriology. 



Micro-organisms play a very important part in milk management be- 

 cause they are constantly found in all milks ordinarily produced and 

 are responsible in a large part for many milk changes, such as bad 

 flavors, bad odors, gases, and souring, which changes are proportional 

 to the cleanliness observed in the handling of milk and cream. Some 

 of the micro-organisms present are essential to some of the stages in 

 the processes of butter- and cheese-making. It follows that some 

 micro-organisms are to be eliminated in one way or another in order 

 to prevent unfavorable conditions arising, while there are some that 

 should be fostered and cultivated because they are necessary in the ripen- 

 ing of cream for butter and of milk for cheese. Micro-organisms, as many 

 plants, suffer at times and are favored at times by certain associa- 

 tions. Some plants favor other plants by growing with them; again 

 these same plants may antagonize still others. Micro-organisms are 

 useful to the growth of other micro-organisms at times and at other 

 times antagonistic, depending upon the kinds brought together and 

 the conditions under which they are associated. Should, therefore, a 

 suitable micro-organism be found necessary or desirable for the manu- 

 facture of the milk product and also antagonistic to obnoxious micro 

 organisms, much could be gained by fostering or cultivating it. 



A growth of micro-organisms in a suitable food substance as milk, 

 whey, or beef tea, is called a culture. If only one species of micro- 

 organism be present the growth is called a pure culture; but if two 

 or more be present the growth is called a mixed culture. For us to 

 be thoroughly familiar with a starter we must understand a culture, 

 because a starter as used in dairy operations is generally a culture 

 containing one species of micro-organisms. In some few instances 

 where two or more micro-organisms are found that harmonize in their 

 modes of growth, a mixed culture is used, thereby perhaps bringing 

 about better results than when developed separately. The starter is 

 used to overcome obnoxious micro-organisms and adds to the finished 

 product the desired flavor, aroma, keeping quality and perhaps other- 

 essential properties. 



Classes of Starters. — Starters are of two general classes, viz., natural 

 and commercial. 



The Natural Starter. — Under the head of natural starters are placed 

 all those originating at home, usually by selecting and setting aside 

 until loppered a quantity of carefully drawn milk. Buttermilk, whole 

 milk, sour cream, and whey are sometimes used in this capacity. A 

 starter produced in this way may contain several species of micro- 



