Impact of interesterification on double-stage fractionation of palm oil

Due to its unrivaled technological potential, palm oil remains a material of choice in many food applications. Its physicochemical properties can be modified by fractionation and/or by interesterification. P<sub>2O and PPP are the main triglycerides that play a key role in the functional behavior of palm oil. Furthermore, it is known that P<sub>2O exists in two isomeric forms: POP and OPP, whose ratio is fairly constant in palm oil. This research concerns the impact of compositional modifications, induced by interesterification, on the double-stage palm oil fractionation process. More precisely, it focuses on both the processing variables of the fractionation process (time, temperature) and on the quality of the soft Palm Mid Fraction produced. A commercial interesterified palm oil was selected and fractionation was carried out with a pilot crystallizer ; crystallization was followed by sampling and the fractions quality was evaluated after separation with vacuum and membrane press filters. The percentage of crystallization was determined by p-NMR and crystal morphology was observed with optical microscopy. The crystallization behaviour was compared to that of refined palm oil. The triglyceride composition of the fractions was verified by RP-HPLC-RI throughout the double-stage process and an analytical method was developed to quantify the POP/OPP ratio in majority of the collected fractions. For this, a second stereospecific HPLC method was used in which the triglycerides are first epoxidized, resulting in an improved separation of the stereo-isomers of mono-unsaturated triglycerides. Fatty acid composition, iodine value by GC and SFC profiles by p-NMR were analyzed. The properties of the produced soft Palm Mid Fraction were compared to the ones of a commercial soft Palm Mid Fraction obtained from refined palm oil. The high quantity of OPP concentrated in the produced interesterified fraction had an important impact on the melting behavior, with increased hardness and much steeper profile.