CONSTANTS FOR IDPiNTIFK'ATION OF FATS AND OILS 241 



wei^lit of the fat. The rehilionship of these vahics to those of some simple 

 triglycerides is recorded in Table 25. 



Table 25 



SArONIFIC.VTION XUMBERS OF SoMK 81MPLE TrIGLYCKRIDBS 



In the case of the natural fats and oils which are largely mixed tri- 

 glycerides containing several varieties of acids, the saponification values 

 usually lie between 190 and 200. In a few cases in which an unusually 

 large proportion of short-chain acids is present in the fat, high saponifica- 

 tion values are the rule, i.e., coconut oil, 253, butter fat, 227. In several 

 instances in which longer chained acids make up a large proportion of the 

 fatty acids (as erucic acid in rapeseed oil), saponification values markedly 

 lower than those for the common fats are the iTile, for example, mustard 

 oil, 174, rapeseed oil, 173. 



(5) Free Fatty Acids 



Although refined oils are largely devoid of free fatty acids, considerable 

 amounts of these constituents may be present in the crude oil. The 

 presence of such acids may be an index of the purity of the oil. Such 

 fatty acids may result from decomposition of the oil due to chemical treat- 

 ment or to bacterial action. The rather high levels of free fatty acids 

 ordinarily found in olive oils are a reflection of the lipases present in the 

 pulp of the olive, which may occur as impurities in the oil. Palm oil is 

 reported in some cases to contain as much as 75% in hydrolyzed form. 

 The degree of edibility of a fat is generally considered to be inversely pro- 

 portional to the total amount of free fatty acids. 



The amount of free fatty acids is sometimes expressed as the acid num- 

 ber (or acid value), which is defined as the nuynher of milligrams of potassium 



