3 o8 THE CHEMISTRY OF DAIRYING 



natural fats (p. 46), it consists of a mixture of glycerides. 

 Normally, at least, nine different fatty acids enter into its 

 composition, viz. 



Oleic acid Stearic acid Palmitic acid 



Myristic acid Laurie acid Capric acid 



Caprylic acid Caproic acid Butyric acid 



These acids together form about 95 per cent, of the fat, and 

 glycerine the remaining 5 per cent. 



It is impossible to determine exactly in what proportions 

 the several acids are present, but there is no doubt that the 

 first three oleic, stearic, and palmitic preponderate greatly. 

 So far as it is possible to judge from the iodine numbers, melt- 

 ing-point, and other similar evidence, it is probable that on 

 the average the proportions are approximately as follows : 



Per cent. 



Stearin and palmitin . . . 5 \ 



Olein 4 ) 



Butyrin ....... 5 



All others 5 



100 



The melting-points of the predominant fats are : stearin, 

 157 F. ; palmitin, 144 F. ; butyrin, 77 F. Olein is liquid 

 at ordinary temperatures, but solidifies at about 40 F. The 

 melting-point of butter fat, as a whole, varies from about 84 F. 

 to 1 06 F. This is doubtless due to the variation in the 

 percentage of olein in it. 



The characteristic flavour and odour of butter have been 

 attributed mainly to the butyrin and other fats of low molecular 

 weight. Certain breeds of cows tend to produce butter fat of 

 a softer and richer quality than others, but this can be modi- 

 fied, in marked degree, by the food of the animal (p. 179). 

 Such differences in the quality of butter fat must be ascribed 

 to variation in the proportions of the several glycerides of 

 which it is composed. 



Milk Sugar. The carbohydrate of milk is called " lactose," 



