LIPIDES (fats and RELATED SUBSTANCES) 81 



clear if a study is made of their quantitative distribution. The com- 

 position of the mixture of fatty acids obtained by hydrolysis of some 

 common fats and oils is given in Table 4-5. 



Butterfat and coconut oil are unique in that they yield such a large 

 number of fatty acids, many of which are lower members of the saturated 

 fatty acid series. Note the small number of fatty acids obtained from 

 lard and the large percentage of unsaturated acids given by the oils. 



Nonsaponifiable matter 



In addition to glycerol and fatty acids, natural fats contain another 

 type of material called nonsaponifiablc matter or "nonsap." This is 

 customarily separated after saponification by extracting the alkaline 

 soap solution with ether. The "nonsap" left after evaporation of the 

 ether consists of fat-soluble pigments, sterols, vitamins, antioxidants, 

 and other miscellaneous substances. Although the nonsaponifiablc com- 

 ponents constitute only a small part (1-2 per cent) of most natural fats, 

 they are often of great importance in relation to the flavor, color, keeping 

 qualities, and nutritional value of the fat. 



GLYCERIDES OF COMMON FATS 



Although the percentages of different fatty acids given by hydrolysis 

 of natural fats are fairly accurately known, much less information exists 

 as to the particular glycerides from which these fatty acids are obtained. 

 By crystallizing the fats from acetone and other solvents, a partial separa- 

 tion of the individual glycerides in a number of fats has been made. The 

 separation is a long and laborious procedure, and in no sense complete. 

 All the data accumulated show that the number of glycerides is very 

 great and that they are more complex than w-as previously supposed. 



Since glycerol, C3H5(OH)3, contains three hydroxyl groups, it can be 

 esterified with one, two, or three molecules of acid to give monoglycerides, 

 diglycerides, and triglycerides, respectively. It is this last type which 

 is found in fats. The three acid radicals in a triglyceride may be all 

 alike, in which case the substance is called a simple glyceride; if more 

 than one kind of radical is present, the compound is called a mixed glycer- 

 ide. The glycerides are named according to the fatty acids involved in 

 their formation. 



Thus the ester formed from glycerol and three molecules of palmitic 

 acid is called tripalmitin, or simply palmitin. Its structural formula is 

 written below. Other typical simple glycerides are triolein, tristearin, 

 and tributyrin: 



