Dynamics of polymorphic transformations in palm oil, palm stearin and palm kernel oil characterized by coupled powder XRD-DSC

• Published in: Journal of Oleo Science
• Main Author: Zaliha O.; Elina H.; Sivaruby K.; Norizzah A.R.; Marangoni A.G.
• Format: Article
• Language: English
• Published: Japan Oil Chemists Society 2018
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048007113&doi=10.5650%2fjos.ess17168&partnerID=40&md5=a35f09a9813b6bc455c3f5063ed83a1c

The in situ polymorphic forms and thermal transitions of refined, bleached and deodorized palm oil (RBDPO), palm stearin (RBDPS) and palm kernel oil (RBDPKO) were investigated using coupled X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Results indicated that the DSC onset crystallisation temperature of RBDPO was at 22.6°C, with a single reflection at 4.2Å started to appear from 23.4 to 17.1°C, and were followed by two prominent exothermic peaks at 20.1°C and 8.5°C respectively. Further cooling to 40°C leads to the further formation of a β’polymorph. Upon heating, a of β’→β transformation was observed between 32.1 to 40.8°C, before the sample was completely melted at 43.0°C. The crystallization onset temperature of RBDPS was 44.1°C, with the appearance of the αC polymorph at the same temperature as the appearance of the first sharp DSC exothermic peak. This quickly changed from α→β’ in the range 25 to 21.7°C, along with the formation of a small βC peak at −40°C. Upon heating, a small XRD peak for the β polymorph was observed between 32.2 to 36.0°C, becoming a mixture of (β’+ β) between 44.0 to 52.5°C. Only the β polymorph survived further heating to 59.8°C. For RBDPKO, the crystallization onset temperature was 11.6°C, with the formation of a single sharp exothermic peak at 6.5°C corresponding to the β’ polymorphic form until the temperature reached −40°C. No transformation of the polymorphic form was observed during the melting process of RBDPKO, before being completely melted at 33.2°C. This work has demonstrated the detailed dynamics of polymorphic transformations of PKO and PS, two commercially important hardstocks used widely by industry and will contribute to a greater understanding of their crystallization and melting dynamics. © 2018 by Japan Oil Chemists’ Society.