362 WORKING THE BUTTER 



to chill the cream sufficiently long so as to guard against a 

 slushy and leaky body of the butter. 



The exact channels through which overworking of butter 

 deteriorates its flavor and tends to cause such off-flavors as 

 oily, metallic and fishy flavors, are not as yet well understood. 

 Rogers 1 shows experimentally that overworking increases the 

 amount of air present in butter and that the presence of air, in 

 combination with other influences, enhances oxidation of the 

 non-fatty constituents of butter. He further states that the 

 development of a fishy flavor is hastened and made more cer- 

 tain by overworking, which increases the air and the oxidizing 

 surface and that fishy flavor may be produced with reasonable 

 certainty by overworking the butter made from sour cream. 



Rogers' conclusions on this point have not been fully borne 

 out by the work of Hunziker. While overworking certainly 

 does not improve the quality of butter, it fails to produce the 

 distinct defects indicated by Rogers with any degree of regu- 

 larity. Nor does it necessarily increase the air content of but- 

 ter. The incorporation of air in butter begins as soon as the 

 cream is subjected to agitation in the churn and up to a certain 

 'point it increases, greatly retarding the completion of the 

 churning process. In fact the amount of air incorporated in 

 the interior and on the surface of the still microscopic butter 

 granules is so great, that it is difficult to make satisfactory micro- 

 scopic examinations of these granules. After the granules have 

 reached a sufficient size to "break" the fat-in-skimmilk emulsion 

 and to establish a buttermilk-in-fat emulsion which is butter, 

 much of this air is released and the completion of the churn- 

 ing process is facilitated. And from this point on, any further 

 churning and subsequent working appears to effect an expulsion 

 of a portion of the air locked up in the butter, rather than an 

 incorporation of additional air. 



There is a vast difference between' the overworking of but- 

 ter that results from manipulating it with a spatula in small 

 amounts as described by Rogers, and by working it in the com- 

 bined churn and worker. While it is quite conceivable how, by 

 special effort, air may be beaten into soft butter with a spatula, 

 it is much less obvious that the squeezing which the butter 



1 Rogers, Fishy Flavor in Butter, U. S. Dept Agr., B.A.I. Circular 146, 1909. 



