COMPOSITION OF NATURAL FATS AND OILS 225 



2.9%. In the case of the milk fats, which are summarized in Table 19, 6 

 values determined by analysis were lower by an average of 1.9% than the 

 random value, while 15 samples gave 2.9% higher results, on an average. 

 The variations on the positive or negative sides are not confined to any 

 particular level of saturated fatty acids. 



The relationship between the saturated fatty acid content and the pro- 

 portion of completely saturated triglycerides is given in Figure 3. This 

 graph shows a marked contrast to Figure 1, in which a similar relationship 

 is plotted for some of the seed fats, 



Longenecker,-*^ has also subscribed to the idea that the distribution of 

 fatty acids in animal fats follows a random pattern. He believes that 

 radically different principles govern the synthesis of many animal fats, as 

 compared with those which are operative in the case of most vegetable 

 fats.*" This view is supported by Norris and Mattil,-^" who have suggested 

 that the enzymes responsible for the esterification may operate quite dif- 

 ferently in the animal and in the plant systems. 



In addition to the two groups of animal fats which seem to follow the 

 random pattern, one series of vegetable fats likewise fits into the same 

 category. These vegetable fats are composed of large proportions of satu- 

 rated fatty acids other than stearic or palmitic acid. Thus, the fat of the 

 Myristica maliharica (nutmeg), in which a high proportion of rayristic acid 

 is found, has a saturated triglyceride content very close to that calculated 

 on the random basis (19% vs. 20.7%). On the other hand, laurel kernel oil, 

 in which approximately 80 % of the saturated acid is lauric acid, has about 

 twice the content of saturated triglycerides which one would expect accord- 

 ing to the chance distribution scheme (40.5% found vs. 20.0% calculated). 

 The ability of the unsaturated acids to produce a large proportion of mixed 

 triglycerides is apparently related to the type of saturated acids with 

 which they are associated. 



The fruit coat fats, likewise, may follow the random pattern more 

 closely than they do that of "even" distribution. As an example, stillingia 

 tallow, which has a saturated fatty acid content of 72.5 mole per cent, has 

 been shown to have 28.4% of completely saturated triglyceride compared 

 with a calculated amount of 38.1%. If the law of "even" distribution were 

 rigidly followed, the trisaturated glyceride could amount to only 5.8 mole 

 per cent. 



In the case of the seed fats, no relationship can be shown between the 

 satiH'ated triglyceride content found and that which should occur if a 

 chance distribution obtained. In the case of Borneo tallow (62.9% satu- 

 rated acids), only 5.1% of GSs was found on analysis, while the theoretical 

 figure for random arrangement l)ase(l upon the value of S'* is 24.9%. 



289 H. E. Longeaecker, Biol. Si/mpo.^iia, 5, 99-115 (1941). 



=80 F. A. Norris and K. F. Mattil, J. Am. Oil Chemists' Soc, 24, 274-275 (1947). 



