86 



LIPIDES (fats and RELATED SUBSTANCES) 



used to advantage in the extraction of delicate perfumes from flowers. 

 Rose petals are spread on glass plates covered with a thin layer of lard 

 and tallow and left in contact with the fat for 24-72 hours. At the 

 end of this time the old flowers are removed and a new lot is added. 

 Finally the fat is extracted with cold alcohol to remove the essence, 

 and the alcoholic solution is concentrated or bottled directly. This proc- 

 ess yields perfumes of the finest quality. 



The substances that often are present in natural fats and, as explained 

 above, impart to them characteristic colors, flavors, and odors are not 

 chemically related to the fats themselves, but are merely associated 

 with them on account of being "fat-soluble," that is, easily soluble in 

 fat. Thus carotene is a fat-soluble pigment. When the cream is churned 

 nearly all of the carotene remains in the butter rather than in the 

 buttermilk, which of course is largely an aqueous medium. Substances 

 that are fat-soluble are usually insoluble in water, and vice versa. 



y 

 CHEMICAL PROPERTIES OF FATS 



Hydrolysis and saponification 



The most important chemical reaction of fats is hydrolysis, with the 

 production of glycerol and fatty acids. This process may be brought 

 about by means of acids, superheated steam, or enzymes. The fat- 

 splitting enzymes are known as lipases. They occur in many tissues of 

 the body and in plant material, especially in oily seeds. A well known 

 fat-splitting enzyme is steapsin, which is secreted by the pancreas and 

 is involved in the digestion of fats. Many bacteria, molds, and other 

 microorganisms produce fat-splitting enzymes. An equation illustrat- 

 ing the hydrolysis of a fat, for example, palmitin, is: 







II steapsin II 



C3H5(OCCuH3l)3 + 3H2O > C3H5(OH)3 + 3HOCC15H31 



Palmitin Glycerol Palmitic acid 



If the hydrolysis is brought about by means of alkali, a soap is formed 

 instead of a fatty acid, and the process is then called saponification: 



O 



II II 



CsHiCOCCuHaOa + 3NaOH > C3H5(OH)3 + SNaOCCuHji 



Palmitin Glycerol Sodium palmitate 



(soap) 



In this equation the formula of sodium palmitate is written in such a 

 manner as to show how it is produced by the action of the NaOH on 

 the palmitin. It might also be written CisHsiCOONa. This substance 



