CREAM AND ITS PECULIARITIES. 267 



heated to 57.2 degrees and churned. A cooling to 46.4 

 degrees gave about the same result as cooling to 33.8 de- 

 grees. 



In a longer series of experiments afterward undertaken 

 at Rosvang with cream raised in shallow pans, partly at a 

 temperature below 55.4 degrees and partly above 60.8 

 degrees Fahrenheit, it was found that the '^pan cream," 

 raised in temperature below 55.4 degrees Fahrenheit, 

 made a yield of butter only 2.3 per cent more, when the 

 cream was coolod by ice before it was heated to churn- 

 ing temperature ; while of the samples of cream raised in 

 over 60.8 degrees temperature, there was gained 19.2 per 

 cent of butter by the cooling. Hence in practice it was 

 found advisable during hot weather to cool both the 

 *' centrifuge cream" and the ^^pan cream" with ice. 



The chemical changes which occur in cream are pro- 

 duced by the effect of oxidation, and the results of 

 the internal decomposition caused by the breaking up 

 of the atoms of the milk sugar (lactose) in the milk con- 

 tained in^ihe-^'eam, and the consequent formation of 

 lactic acid. This acid is a viscous substance, and has 

 precisely the same effect upon the cream as a solution 

 of gelatine would have, and when cream containing a 

 large quantity of this acid is churned it foams and be- 

 comes beaten up into a still finer and smoother emul- 

 sion but will never make butter. This effect may be 

 thus explained: 



The milk sugar is changed to lactic (or milk) acid by 

 the action of the caseine of the milk in a manner which 

 is as yet somewhat obscure, but it is merely a changed 

 position, as it were, of the elements forming each of 

 these substances. The following diagram of the change 

 is given, with such explanation as may make it plain 

 to those even who are unacquainted with chemistry. 

 x4n atom or volume of sug ir of milk is composed ulti- 

 mately of twenty-four atoms of carbon and twenty-four 



