One of the most common complaints of users of palm nut kernel cake is that it is liable to become rancid on keeping. Rancidity developing in an oil-seed residue like palm nut kernel cake is likely to be due to splitting of the fats of the cake by a fat-splitting 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.