22 Milk and Its Products 



and even onions, without danger of contamination of 

 the milk. The presence of wild garlic and wild 

 onions in pastures is a source of bad flavor in the 

 milk in a considerable portion of the country. Where 

 this is the case it is, of course, more difficult to 

 overcome the bad flavor; but by allowing the cows 

 to pasture for a comparatively short time only im- 

 mediately after milking, and keeping them up and 

 giving them some dry food for three or four hours 

 before milking, there will be a great deal less an- 

 noyance from this source. 



The non- volatile fats. The non- volatile fats make 

 up about 85 per cent of the whole amount of fat, 

 and consist of a more or less uncertain and variable 

 mixture of several fats, of which olein and palmitin 

 make up the chief part. They are glycerides of the 

 corresponding fatty acids oleic, palmitic, stearic, rayr- 

 istic, etc., and differ from one another chiefly in 

 their hardness or melting point. Olein is liquid at 

 ordinary temperatures ; palmitin and the others are 

 solid. Olein melts at about 41 F., the hard fats at 

 various temperatures from 130 to 150 F. The 

 mixture of the whole,- as we find them in ordinary 

 butter, melts at from 92 to 96 F. The hardness 

 or softness of different butters, depending largely 

 upon varying proportions of olein. Considerable doubt 

 exists as to the relative proportions of the various 

 fats and fatty acids. Browne* gives the following 

 percentages of volatile and non -volatile fatty acids: 



*Jour. Am. Chem. Soe. 21, 823. 



