Peculiar crystallization behavior 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 crystallization behavior. Four StStSt contents were investigated: 7.0%, 7.6%, 8.2% and 9.8%, and the palm oil crystallization was examined during a period of 240 minutes. Oil temperatures were recorded, and crystallization kinetics were monitored by p-NMR; crystal morphology and polymorphic forms were characterized by optical microscopy and powder X-Ray diffraction. One of the composition s (StStSt: 7.6%) was crystallizing faster. All the crystallized matrices were filtered at 25°C with a membrane press filter; the olein yields, iodine values, cloud points and triacylglycerol compositions were analyzed. The olein from the matrix crystallizing 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 crystallization behavior at this specific composition.