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The form and size distribution of tripalmitin (PPP) crystals formed by quenching a solution in a batch crystallizer have been studied using scanning electron microscopy and a laser diffraction technique. Although the accuracy of the laser technique for particle sizing was affected by the nonsphericity of the crystals, the technique proved to be effective and very reproducible. Crystals recovered by filtration and sonication for laser sizing exhibited markedly different particle size distributions (PSD) and shapes compared to those prepared using another standard route, namely, suspension in butanol and centrifugation. Solutions of 2-10 wt% PPP in a paraffin solvent were crystallized at 25-40°C and displayed two ranges of behavior: (i) rapid growth under strongly supersaturated conditions, yielding narrow PSD of plate and needle-like crystals; and (ii) slow growth in the metastable regime, yielding spherulitic aggregates of platelets that broke down under sonication during preparation for laser sizing. Suspension in alcohol followed by centrifugation yielded aggregates that did not break down under sonication, indicating that the sample preparation route affected the result of the analysis.The crystallization behaviors of palm oil and palm olein, the liquid fraction of palm oil, have been studied at length. Palm oil is a complex natural product, composed of more than 12 triglycerides that make up as much as 94% by weight of the oil. In addition, it also contains up to 5% diglycerides (1). Tripalmitin (PPP), present in significant quantities in palm oil, has long been associated with the unwanted formation of crystals and subsequent clouding of palm olein (2,3). In foodprocessing industries, palm oil blends are frequently mixed with other ingredients and partially crystallized to give a plasticized fat. However, during subsequent transport of the crystallized oil blend, deposition of PPP and other fats can occur onto the wall of delivery pipelines, a phenomenon known as "coring." Depositions of this type in process equipment can lead to increased maintenance, cleaning, and fuel costs (4) and also to more severe concerns related to hygiene, which are of prime importance in food processing (5). Analogous situations exist in the oil industry, where the formation of wax can be a major problem in oil well tubing and submarine pipelines (6), and models have been developed to predict and circumvent the buildup of unwanted deposits (7).The quality of plasticized fat is related both to the extent of crystallization and the size of crystals present in the suspension. In the food fat coring scenario, particle size distributions (PSD) are particularly important because the mode of particle transport to the wall and subsequent adhesion are strongly related to particle size and shape. Information on particle size and shape is required to identify and model the mechanisms involved in deposition (e.g., Ref. 8). Previous studies have focused on measurement of PPP crystal size by optical methods (9). Although laser diffraction has b...

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