Ipi'^T' 



BUTTER 603 



is probably due to the presence of bacteria which are common in 

 these locahties and which produce results in accordance with their 

 nature. 



There are two methods of cream ripening — the natural and the 

 artificial. The natural ripening of cream means merely allowing 

 it to sour spontaneously. It is obvious that by this method the 

 result is more or less haphazard. If the souring process is car- 

 ried on by bacteria which produce an agreeable aroma the result- 

 ant butter will be of fine quality, but if carried on by the type of 

 bacteria producing an unpleasant aroma, an inferior butter will 

 result. The only control possible when cream is allowed to ripen 

 spontaneously is care in the production of a clean milk and pro- 

 tection during the souring process. 



The souring of cream is the result of the activity of types of 

 Streptococcus lacticus. This organism is so universally present 

 in cream that it rarely fails to ripen it. But the aroma varies 

 with different types of Str. lacticus. While some produce an 

 agreeable aroma, others produce an indifferent or even unpleasant 

 aroma. It is held by some investigators that butter aroma is 

 due solely to the action of this organism, while others believe that 

 associated bacteria materially affect it. In any case, it is gen- 

 erally conceded that the aroma is the result of a slight decomposi- 

 tion of butter-fat caused by microbial action. 



Artificial cream ripening is carried on by the use of starters; 

 that is to say, the cream is inoculated either with a batch of sour 

 cream from the last ripe cream or with pure cultures which are 

 purchasable. The batch of soiu- cream used for inoculation is 

 known as a natural starter, while pure cultures are known as 

 artificial starters. 



It is a common practice to save a small amount of ripened 

 cream and mix this with a new lot. Sour cream, when of good 

 quality, contains Streptococcus lacticus in almost pure culture 

 and in enormous numbers. The number present is variously stated 

 to be from 500,000,000 to 3,000,000,000 per cubic centimeter. The 

 new cream, therefore, is seeded with large numbers of desirable 

 bacteria. If a butter maker finds his cream does not ripen in a 

 satisfactory manner, he obtains a natural starter from a neighbor 

 who is obtaining better results. The starter should not be too 

 old, as the high acid content destroys many bacteria and 

 renders the starter inefficient. By keeping a starter on ice it can 

 be used after several days without there being a material de- 

 terioration. 



Artificial starters are gradually superseding natural starters 

 because they enable the butter maker to control his product with 

 a certain degree of perfection. Artificial starters are made from 



