226 III. CHEMISTRY OF NEUTRAL FATS 



Gamboge butter, which contains 50.5% of saturated acids, has a saturated 

 triglyceride content of only 2.7%, compared with a value of 12.8% calcu- 

 lated for random distribution. In the case of neem oil, which has a smaller 

 amount of saturated acids (32%), the calculated value of GSs is 3.3% while 

 that actually found amounts to only 0.6%. 



Hilditch and his collaborators have recently reversed their earlier view- 

 point that certain animal fats are assembled by an "indiscriminate" ar- 

 rangement. In the first place, they note that the "stearic-rich" animal de- 

 pot fats which fit into the random pattern quite consistently contain 20- 

 30% of palmitic acid. The amount of totally saturated triglyceride is 

 almost exactly proportional to the stearic acid content rather than to the 

 sum of stearic acid and palmitic acid. As the proportion of total saturated 

 acids decreases to 25% (the usual amount of palmitic acid), the quantity of 

 completely saturated triglycerides approaches a figure of 0% 



However, the results obtained with Indian buffalo fat pose a striking 

 contradiction to this conclusion. This fat contains only 19.5% of saturated 

 Ci8 acid (stearic) and 45.6% of the Cie (palmitic) acid. Instead of con- 

 taining under 20% of completely saturated triglycerides, as is the case with 

 other animal fats having a similar proportion of stearic acid, buffalo fat 

 was found actually to have 37.2% of GS3. This would lead us to be cau- 

 tious in concluding that the completely saturated triglyceride content al- 

 ways follows the proportion of stearic acid. Moreover, it should be pointed 

 out in support of the random theory that the quantities of completely 

 saturated triglycerides become inappreciable when the saturated acid con- 

 tent is less than 25%. The calculated values for GS.s are 2.7% for a 30% 

 level, 1.6% for a 25% quantity, and only 0.8% for a 20% content of satu- 

 rated acids. For this reason, one would expect an almost complete dis- 

 appearance of completely saturated triglycerides below a 25% level of sat- 

 urated acids, irrespective of whether palmitic or stearic acid is the acid in 

 question. 



Hilditch and co-workers^^-"*'^^^'^*^-'^^^'^^^"^^^ have proposed that the 

 stearic-acid-rich animal fats and milk fats, also, represent "even" distribu- 

 tion, but are of a special nature. Certain changes are believed to be super- 

 imposed on the original fat formed from oleic and palmitic acids according 

 to the general principles of "discriminate" or "even" distribution. In the 

 case of the body fats rich in stearic acid, it is suggested that a "biohydro- 

 genation" has occiu'red which changes the oleopalmitins into the com- 

 pletely saturated glycerides. The mammary glands also have the power to 

 convert such original mixed triglycerides into the short-chain saturated 

 and unsaturated glycerides characteristic of milk fat. 



2»i T. P. IIil(lit,(-h and Y. A. H. Zaky, Bioc.hem. J., 35, 940-951 (1941). 



282 T. P. Hilditch and J. J. Sleightholnie, Biochem. J., 24, 1098-1113 (1930). 



"83 T. P. Hilditch and J. J. Sleightholme, Biochem. J., 25, 507-522 (1931). 



