CAUSE AND PREVENTION OF JIANCIDITY IN 

 PALM NUT KERNEL CAKE. 



By K. B. CALDER, 



Gonville and Caius College. 



{ScJwol of Agriculture, Cambridge.) 



One of the most common complaints of users of palm nut kernel 

 cake is that it is liable to become rancid on keeping. Rancidity develop- 

 ing in an oil-seed residue like ])alm nut kernel cake is likely to be due to 

 splitting of the fats of the cake by a fat-sphtting ferment or enzyme — 

 a lipase — formed under certain conditions. The resting seeds do not 

 contain lipase, but they are likely to contain a zymogen from which 

 under suitable conditions lipase is formed. The lipase would then 

 split the fats or oils with the formation of rancid-smelling fatty acids. 

 According to Reynolds Green, lipases act most rapidly at 55° C. Their 

 activity is slowed at 60° C. At 72° C. the lipase is destroyed, and, of 

 course, its action ceases. 



The following experiments show that rancidity in palm nut kernel 

 cake is due to the formation of a lipase. A quantity of cake was finely 

 ground, and portions placed in a number of bottles. Some were kept 

 dry, others moistened with water. To the moistened samples a little 

 toluene was added to prevent putrefaction. The bottles were well 

 stoppered to prevent evaporation, heated in a water bath as described 

 below, and afterwards kept at various temperatures in an incubator. 



These experiments show that palm nut kernel cake when kept warm 

 and moist for some time becomes rancid, but that it keeps well at the 

 ordinary temperature if dry. The production of rancidity is prevented 

 by heating for a long time to 60° C, or for a short time to 70° C. These 

 facts are in accord with the conclusion that the rancidity is caused by 

 the action of a lipase set free from a zymogen present in the seed. The 

 important practical point is that ranciditv is prevented by heating for 

 a short time to 70° C. 



