138 Ranciditu of Palm Kernel (unJ other Feeding Cakes 



and in the manufactured cake and meal. The maximum lipolytic 

 activities of the meal and cake are about one-half and one-third re- 

 spectively that of the untreated kernels; while the activity of the kernels 

 is fairly uniform, that of the meal and cake is irregular, indicating that 

 a partial and uneven destruction of lipolytic activity has taken place 

 during the manufacture of the latter products. Under suitable con- 

 ditions, moisture being essential, the lipase acts on the fat liberating 

 fatty acids with a consequent increase in the acidity of the cake. These 

 experiments however have shown that this property is shared by other 

 feeding cakes such as cotton seed, linseed, ground nut and coconut, and 

 that palm kernel cake and meal develop less acidity than other cakes 

 in the same time and under similar conditions. 



Cotton seed and linseed cakes developed over four times as much 

 acidity as palm kernel cake under equal conditions. The degree of 

 acidity, however, cannot here be taken as a measure of rancidity, nor 

 as an index to the palatability of the cake. On the other hand these 

 experiments have shown that the nature of the liberated fatty acids 

 must be taken into consideration in each case, and the explanation of 

 the suggestion that palm kernel and coconut cakes, unlike other cakes, 

 become rancid on keeping, lies in the fact that palm kernel and coconut 

 oils contain glycerides of the lower fatty acids, which when hydrolysed 

 by lipase yield volatile fatty acids, with unpleasant odours. 



The fatty acids of palm kernel oil include 13 per cent, of the volatile 

 fatty acids — caproic, caprylic and capric (see Lewkowitsch, he. cit. ii, 

 p. 614), all of which have an unpleasant odour. Of these the chief is 

 caprylic acid, which has an intense odour of sweat. Consequently the 

 presence of a very small amount of these volatile acids in the cake, due 

 to a slight decomposition of the oil, apart from any production of 

 rancidity, is sufficient to impart to the cake an unpleasant smell. 

 Further, palm kernel cake, even when freshly prepared, has a character- 

 istic smell, probably due, in part at least, to a trace of these volatile 

 fatty acids. 



Coconut oil resembles palm kernel oil in composition, and also 

 liberates caprylic acid, but the oils of linseed, cotton seed, and ground 

 nut yield no volatile fatty acids on decomposition, or at the most mere 

 traces, and are therefore not subject to this objection. Consequently 

 cakes containing them are not liable to develop this pecidiar odour on 

 keeping, which is liable to be taken as an indication of rancidity. 



No attempt has been made to ascertain whether the fatty acids of 

 palm kernel oil are more easily convertible into rancid bodies than the 



