498 BUTTER 



ing from the oxidation of glycerol and thereby constitute a fac- 

 tor tending toward the production, modification or intensification 

 of -the rancid odor and taste. The small amount of lactose nat- 

 urally present in commercial butter, however, must of necessity 

 limit the power of this butter constituent as an important agent 

 in this respect. < 



In the presence of our now available information concern- 

 ing the reactions responsible for rancidity in butter, as briefly 

 outlined in the foregoing paragraphs, the following summary 

 may serve to bring out the most important facts and proba- 

 bilities. 



1. The initial stage of rancidity in butter lies in the hydro- 

 lysis of the butterfat. This produces free fatty acids which, 

 when present in considerable amounts, produce a strong rancid 

 taste and odor. 



2. The hydrolysis of the butterfat is brought about by 

 bacterial and mold action, or by enzyme action, assisted by cat- 

 alizers such as acids and alkalies, and in the presence of water 

 and exposure to temperatures higher than those of commercial 

 refrigeration of butter. 



3. The rancidity of butter may be greatly intensified by the 

 oxidation of the free fatty acids, or of the free glycerol, or both. 

 The action is greatly hastened by exposure of the butter to air. 

 light and heat. 



4. Lactose, upon oxidation, may also assist in the forma- 

 tion of products yielding rancidity. 



5. The curd in butter assists in the development of ran- 

 cid flavor insofar as it furnishes desirable nutrients for the ran- 

 cidity-producing organisms to thrive on. Butter with a high 

 curd content, other factors being the same, therefore is more 

 prone to become rancid than butter with a low curd content. 



It should be understood that rancidity is the result of pro- 

 gressive changes in butter and that most butter, if kept long 

 enough, will ultimately become rancid with age. However, the 

 development of rancidity and the postponement of this common 

 butter defect may be controlled with a reasonable degree of suc- 

 cess, by so handling the cream in its production and the butter in 

 its manufacture and storage, as to minimize, if not eliminate 



