PECULIAR CRYSTALLISATION BEHAVIOUR OF PALM OIL DURING DRY FRACTIONATION

Multi-step dry fractionation of palm oil generates fractions with specific physicochemical properties suitable for many food formulations. The present study addresses the pilot scale production of palm olein iodine value 56 starting from palm oil. The aim was to investigate the influence of the tri-saturated triacylglycerol content (StStSt) in palm oil on its crystallisation behaviour. Four StStSt contents were investigated: 7.0%, 7.6%, 8.2% and 9.8%, and the palm oil crystallisation was examined during a period of 240 min. Oil temperatures were recorded, and crystallisation kinetics were monitored by p-NMR; crystal morphology and polymorphic forms were characterised by optical microscopy and powder X-ray diffraction. One of the compositions (StStSt: 7.6%) was crystallising faster. All the crystallised matrices were filtered at 25°C with a membrane press filter; the olein yields, iodine values, cloud points and triacylglycerol compositions were analysed. The olein from the matrix crystallising faster showed a yield, an iodine value and a cloud point higher than expected. A more detailed HPLC analysis of this olein indicated unusual enrichment in OPP and depletion in OPO, which led to the conclusion of an unusual crystallisation behaviour at this specific composition.