472 



Hancidifi/ it) P((1ni Nut Kernel Calce 



Finally boiled and unboiled extract were added to six samples of 

 the cake which had been heated to 70° C. and incubated for some time 

 without turning rancid. After a few days in the incubator all the 

 samples (with one exception) to which unboiled extract had been added 

 became rancid, whilst the samples mixed with boiled extract remained 

 perfectly sweet. This experiment shows that extracted lipase can 

 turn cake rancid. 



To determine if rancidity is preventable by lieating the dry powdered 

 cake, samples were treated as follows: 



Sample 

 No. 

 1-3 



4-7 



8-11 



Treatment 



Dry powdered cake heated at 30' C. for 

 1 hour, moistenetl, toluene added and 

 placed in incubator at 28° C. 



Heated at 40° C. for 1 hour, otherwise treat- 

 ment same as 1-3. 



Same, but heated at 50° C. 



12-15 Same, but heated at GO°C. 



16-19 Same, but heated at 75° C. 



20-23 Same, but heated at 80° C. 

 24r-27 Same, but heated at 90° C. 



28-32 Same, but heated at 100° C. 



Result 

 In less than a week all 



three samples became 



quite rancid. 

 Ditto 



In a week, three quite 

 rancid, one only slight- 

 ly so. In 10 days the 

 fourth sample also 

 was quite rancid. 



Three quite sweet after 

 17 days, one had a 

 slight trace of ran- 

 cidity. 



No rancidity in any case 

 after three weeks. 



Ditto 



No rancidity after a fort- 

 night in three sam- 

 ples, but tlie fourth 

 was slightly rancid. 



No rancidity in any case 

 after a fortnight. 



Conclusion. 



Palm nut kernel cake, if kept dry and cool, remains sweet for at 

 least 10 weeks. If kept moist and warm it becomes rancid in a few 

 days. The cake contains a zymogen which under the influence of 

 warmth and moisture forms a lipase. The lipase then turns the oil 

 rancid. The lipase can be destroyed by heating the moistened cake to 

 70° C. for a short time. If the dry cake is heated the zj-mogen is usually 

 destroyed, but dry heating is not so certain to destroy it as heating 

 when moist. 



(Received December lOt/i, 1915.) 



