238 ILLINOIS DAIRYMEN'S ASSOCIATION. 



Cream Separation. — Milk is *'an emulsion of fats in a wat- 

 ery solution of alkaline salts, casein and sugar."* 



Fat being lighter than the water or the solids not fat (sugar 

 casein, etc.) raises to the top when allowed to stand in a vessel, and 

 in so doing carries with it a little of the other solids not fat, and 

 constitutes what we commonly call cream. The heavier portion 

 gravity. 



Cream Ripening. — Speaking generally the ripening of 

 cream is all of the treatment it receives from the time the milk is 

 drawn until it is churned, while specifically and commonly it is the 

 particular treatment given the cream after separation to prepare 

 it for churning. 



The general market wants a butter with a flavor that can on- 

 ly be secured by ripening the cream properly. 



Ripening is a souring of the cream. When cream or milk 

 sours the milk sugar is changed to lactic acid, by lactic acid pro- 

 ducing germ. The bacteriologist finds that there are several 

 forms of lactic acid producing bacteria; also that some forms of 

 bacteria produce acid without thickening or curdling ; others pro- 

 duce the reverse; again some produce gas; while slimy or ropy 

 milk, red, or sometimes called bloody milk are other products of 

 bacterial growth in milk and cream. In general the changes 

 which occur in milk are due to some form of bacterial life. 



Bacteria are minute forms of plant life; they grow rapidly 

 at a temperature of from 60 to 90 degrees ; they require food 

 and moisture like higher forms of plant life; they are prevented 

 from growing by cold ; are killed by moist heat, most of them 

 by a temperature of boiling water ; they may remain inactive for 

 a long time, then grow rapidly when conditions again become 

 favorable ; they grow or multiply usually by division, which may 

 happen every twenty minutes, or may require several hours; in 

 the process of their growth they cause some change in the ma- 



*Wing — Milk and its Products. 



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