Deterioration of Oils and Fats of Hardened Coconut Oil Series. III

Abstract

Palm kernel oil was purified and hardened, and the samples at each stage of the process including crude oil were stored at -20, 5, 15 and 30°C for 6 months, in the same way as done with the coconut oil, of which A.V., P.O.V. and Co.V. were measured in every month. Correlation of these values with crystal growth was examined by electron microscope.1) Palm kernel oil showed the same tendency as the coconut oil ; increase in A.V. was in the order of those at 15 and 5°C, and the increase was more marked in the hardened oil. No change was recognized in those stored at-20 and 30°C.2) Crystal surface of the hardened palm kernel oil under electron microscope showed the presence of “whiskers” in the oil stored at 5°C and that stored at 15°C showed a very rough crystal surface, both being larger than those of hardened coconut oil. Single crystal was small and few in the oil stored at 20°C and the surface was smooth in the stored at 30°C.3) These experimental results indicated that the changes of A.V. were greater in those with rough crystal surface.