140 Ranciditji of Palm Kernel aiul other Feediny Cakes 



shaken at frequent intervals, and in some cases the proportion of the 

 components was adjusted to form an emulsion. Control experiments 

 were performed to determine the increase in acidity due to the separate 

 components of the mixture. The acidity of the mixture was determined 

 by extracting first with warm water and then with alcohol and titrating 

 the extracts with N/2 NaOH using phenolphthalein as an indicator. 

 Owing to the presence of the natural colouring matter from the palm 

 kernels the end point was not very sensitive and the experimental error 

 amounted to ± 0-2 c.c. of N/2 NaOH. 



The action of an emulsion of soya hean oil and palm kernels with or 

 without the addition of acetic acid or water was first tried. Little or no 

 acidity was produced under these conditions, though they were suitable 

 for demonstrating the lipolytic activity of castor seeds, which were over 

 a hundred times more active than the palm kernels. In these experiments 

 the maximum activity of the palm kernels was developed in the absence 

 of acetic acid and in the presence of water. 



The next series of experiments confirmed this result and showed an 

 excess of water to be necessary to the maximum development of acidity. 

 These conditions however were not so suitable for the action of castor 

 seed lipase, and palm kernels in these experiments had approximately 

 one-sixth the activity of castor seeds. Neither the addition of acid nor 

 of palm kernel fat increased the production of acidity. 



The effect on their activity of previously heating the palm kernels 

 was then investigated. Heating with water at 97° C. for 4 hours con- 

 siderably reduced their activity but did not totally destroy it, and 

 heating without the addition of water at 120° C. for 2 hours had a less 

 destructive action. Total destruction of the power to develop acidity 

 was effected by boihng the kernels with water for 3J hours. Shorter 

 periods were tried later in the case of the cake, and one hour's boiling 

 was found to be sufficient. In these experiments the pioduction of 

 acidity was not due to (1) bacteria, since the operations were conducted 

 under sterile conditions, (2) hydrolysis of the fat, since palm kernel fat 

 in the presence of excess of water was not affected under the conditions 

 of these experiments, (3) hydrolysis of other bodies in the kernels, since 

 boiling palm kernels with excess of water for S-J hours produced no rise 

 in acidity, whereas if the acid producing action which takes place slowly 

 at 35° C. was due to hydrolysis it should be accelerated by boiling. This 

 behaviour points to the production of acidity as being due to the action 

 of an enzyme. To confirm this view and determine whether the enzyme 

 acts on the fat or on the other bodies 2:)resent in the kernels a finely 



