530 COMPOSITION AND PROPERTIES otf BUTTER 



avoided by using wrappers that are free from metallic specks and 

 by avoiding- any carelessness in the creamery, that causes the in- 

 corporation in butter of metallic elements. The copper coils should 

 never be permitted to scrape against any metal, and if any material 

 or instrument is used to clean the coil or vat lining, that causes vio- 

 lent friction on the copper surfaces, the greatest care should be exer- 

 cised to flush such surfaces thoroughly so as to remove every ves- 

 tige of metallic material before cream is again permitted to enter 

 the vat. 



Chapter XVIII. 



COMPOSITION AND PROPERTIES OF BUTTER, MILK, 

 CREAM, SKIM MILK AND BUTTERMILK. 



Butter. 



Butter is a mixture of butterfat, small amounts of the non- 

 fatty constituents of milk, cream and water, and it may contain 

 added salt and coloring matter. It is an emulsion of diluted 

 buttermilk-in-fat. 



It is composed chiefly of butterfat, water, curd and salt in 

 the case of salted butter, and butterfat. water and curd in the 

 case of unsalted butter. The remaining non-fatty constituents, 

 are the ash, lactose and acid. 



The percentage composition varies considerably with the 

 character of the cream and the method of manufacture. The 

 average composition of butter, made in different localities, dur- 

 ing the several seasons of the year and under diverse methods 

 of manufacture would approximate the following figures : 



Salted Butter Unsalted Butter 



Butterfat .82.5% 84.0 



Water 13.8 14.5 



Salt 2.5 0.0 



Curd 6 .85 



Ash 1 .20 



Lactose 25 .3 



Acid .15 .15 



Total . x 100.00 100.00 



Thompson, Shaw and Norton 1 , in a study of the normal 

 composition of creamery butter, analyzed 695 samples of dif- 



1 Thompson, Shaw and Norton, The Normal Composition of American 

 Creamery Butter, U. S. Dept. Agr., B. A. I. Bulletin 149, 1912. 



