338 CREAM AND CREAM RIPENING 



have a salutory influence upon it. Below about 18.5 C. 

 (65 F.) the beneficial lactic acid bacteria are checked, 

 and the organisms likely to give rise to bitter flavours 

 and offensive odour are assisted : above 21 C. (70 F.) 

 gas-producing forms often flourish, and the cream and 

 butter become " oily." 



Appearance and smell will sometimes guide an experi- 

 enced buttermaker in determining the ripeness of the 

 cream, but it is generally advisable to determine by 

 chemical means the degree of acidity acquired, for it is 

 found that when the cream contains .5 to .6 of acid 

 (calculated as lactic acid), the process has usually ad- 

 vanced as far as it is advisable to allow it to go. Care 

 should be taken to prevent the acid from becoming 

 greater than this, or precipitation of the casein in lumps 

 takes place, and these appear later as white specks in 

 the butter and seriously deteriorate its flavour and 

 keeping quality. Acidity in itself is not necessarily an 

 accurate gauge of correct ripening for acid products, and 

 the development of agreeable flavour and aroma are 

 different and distinct features of the process : never- 

 theless, under normal conditions experiment has shown 

 that the degree of acidity mentioned is generally 

 correlated with suitable ripeness for butter-making 

 purposes. 



At the temperatures indicated above ripening should 

 be complete in one or two days in summer and three or 

 four days in winter. 



Encouragement should be given to the aerobic bacteria 

 by frequent stirring of the cream so as to ensure an 

 adequate supply of air throughout the liquid ; bad 

 flavours are frequently associated with exuberant growth 

 of anaerobic species. 



