R. B. Calder 



471 



Sample 



No. 



3 



4 

 5-8 



Treatment 

 Kept dry at ordinary temperature for 10 



weeks. 

 Heated dry for 1 hour at 75° C, then kept 



for 10 weeks at room temperature. 

 Jloistened and incubated at 25° C. 

 Moistened and kept at room temperature. 

 Jloistened, incubated at 22° C. for 24 hours 



to change zymogen to h'pase. Then 



heated to .30° C i to 3 lioura. Then 



replaced in incubator. 

 Same as 5-8, but heated at 40° C. 

 Same as 5-8, but heated at 50° C. 

 Same as ,5-8, but heated at 00° C. 



Result 

 No trace of rancidity. 



No trace of rancidity. 



Rancid in 3 days. 

 Rancid in a few days. 

 Rancid in a few days. 



21-24 Same as 5-8, but heated at 65° C. 



25-28 



Same as 5-8, but heated at 70° C. 



29-32 Same as 5-8, but heated at 75° C. 



33-36 Same as 5-8, but heated at 80° C. 



37-40 



Same as 5-8, but heated at 90° C. 



9-12 Same as 5-8, but heated at 40° C. Rancid in a few days. 



13-16 Same as 5-8, but heated at 50° C. Rancid in a few days. 



17-20 Same as ,5-8, but heated at 00° C. Sample heated only i 



hour, became rancid in 

 a few days. Samples 

 heated for 1 hour or 

 longer remamed sweet. 



Half hour sample rancid, 

 others remained sweet. 



All samples remained 

 sweet for 10 weeks. 



All samples remained 

 sweet for 10 weeks. 



All samples remained 

 sweet for 10 weeks. 



No rancidity, but sample 

 heated for 3 hours 

 had a smell, possibly 

 due to decomposition 

 by long heating. 



A second set of experiments was then carried out as follows. Some 

 ground cake was kept warm and moist until it became rancid. It was 

 then ground up with 5 per cent, common salt solution and incubated 

 at 25° C. for 24 hours. The liquid part was then separated by filtration 

 under pressure. It was a brown opalescent liquid with an acid reaction. 

 It was divided into halves, one of which was boiled for 10 minutes. 



Emulsions of castor oil, palm nut kernel oil, and coconut oil were 

 made by means of water and gum arable. Several tubes of each were 

 treated with boiled and unboiled extract of rancid cake as prepared 

 above. Each tube was exactly neutralised with sodium carbonate 

 solution after addition of neutral litmus. All the tubes were then placed 

 in the incubator at 2'/' C. After a few days all the tubes containing 

 boiled extract were still neutral, whilst those containing unboiled 

 extract had all become acid in 12 hours. This experiment shows that 

 it is possible to dissolve the lipase out of rancid palm nut kernel cake. 

 The lipase thus dissolved will turn other oils rancid if brought into 

 contact with them under suitable conditions. 



