2 DAIRY ANALYSIS 



phospho-proteins ; it contains carbon, hydrogen, oxygen, 

 nitrogen, sulphur, and phosphorus ; in milk it exists as 

 a sab of lini'3 and soda combined with calcium phos- 

 phate ; a^ids precipitate the free casein if dilute, while 

 strong acid* re-dissolve it. Rennet splits casein up 

 in o curd, which 13 a combination of para-casein with 

 the limo and vhe cak-ium phosphate of the casein, the 



FIG. 2. Cream (magnified 400 diameters). 



soda being split off, and whey protein which is free 

 from phosphorus. 



Albumin is a protein which is distinguished by 

 coagulating on heating to 70 C. ; in milk it probably 

 exisos as a salt, and this does not coagulate until the 

 m Ik is acidified. Unaltered albumin is not precipi- 

 tated by acids. 



When micro-organisms act on milk various products 

 are formed ; the most important change is the forma- 

 t ion of lactic acid from the sugar, which causes milk to 

 become sour, and curdles it by precipitating the casein. 



The fat globules are lighter than the aqueous serum, 

 and they tend to rise. Cream (Fig. 2) is the upper 

 portion of milk after standing, and differs from milk 

 practically only in that it contains more fat and pro- 



