346 BUTTER 



in olive and cod liver oils. Butyrin, which is the 

 characteristic fat of butter, melts at about 77 F. 



The proportion of each of these in butter is subject to 

 much variation, due to differences in the physiological 

 condition of the cows and the food supplied to them. 

 The amount of olein may rise to nearly half the total 

 weight of butter fat. It is greatest in the early period 

 of lactation, and may fall to about half the maximum at 

 a later date. With a decrease in the size of the fat 

 globules in the milk the olein decreases, and the butter 

 becomes harder on account of the higher proportion of 

 palmitin and stearin. Mangels, good grass, and green 

 fodder generally tend to produce butter rich in volatile 

 acids and of low melting point ; hay and cotton-cake 

 give harder butter, with higher melting-point. 



Usually about 92 per cent, of the whole consists of 

 palmitin, stearin, and olein, the rest being .made up of 

 the volatile fats, of which butyrin is the chief. 



The approximate relative proportions are given in the 

 following table : 



Per Cent. 



* Palmitin, stearin, and myristin . 49 to 52 



Olein V . . . . 37 42 



Butyrin . : ' . . . 6 7.5 



Caproin, caprylin, etc. . . . ' 2 3 



2. Bacteria in Butter. The number and kinds of 

 bacteria found in butter depend upon the bacterial contents 

 of the cream from which it is made, the amount of added 

 salt or preservative, and the age of the samples. In 

 butter containing more than the usual amount of water, 

 milk-sugar, protein, and other constituents of the cream, 

 bacteria grow rapidly for a time, and I gram of a freshly- 



