Oil palm can accumulate up to 90% oil in its mesocarp, the highest level observed in the plant kingdom. In contrast, the closely related date palm accumulates almost exclusively sugars. To gain insight into the mechanisms that lead to such an extreme difference in carbon partitioning, the transcriptome and metabolite content of oil palm and date palm were compared during mesocarp development. Compared with date palm, the high oil content in oil palm was associated with much higher transcript levels for all fatty acid synthesis enzymes, specific plastid transporters, and key enzymes of plastidial carbon metabolism, including phosphofructokinase, pyruvate kinase, and pyruvate dehydrogenase. Transcripts representing an ortholog of the WRI1 transcription factor were 57-fold higher in oil palm relative to date palm and displayed a temporal pattern similar to its target genes. Unexpectedly, despite more than a 100-fold difference in flux to lipids, most enzymes of triacylglycerol assembly were expressed at similar levels in oil palm and date palm. Similarly, transcript levels for all but one cytosolic enzyme of glycolysis were comparable in both species. Together, these data point to synthesis of fatty acids and supply of pyruvate in the plastid, rather than acyl assembly into triacylglycerol, as a major control over the storage of oil in the mesocarp of oil palm. In addition to greatly increasing molecular resources devoted to oil palm and date palm, the combination of temporal and comparative studies illustrates how deep sequencing can provide insights into gene expression patterns of two species that lack genome sequence information.

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Effects of heating on some quality characteristics of date seed oil from two cultivars (Deglet Nour and Allig) has been investigated using an accelerated test in a Rancimat system. Fatty acid, viscosity, absorptivity at 232 and 270 nm, colour and total melting enthalpy of Deglet Nour seed oil were less changed compared to that of Allig seed oil, because the former contained a higher amount of total phenolic compounds (526 µg/g against 215 µg/g) and a lower content of unsaturated fatty acids. Viscosity and absorptivity at 232 nm and at 270 nm increased rapidly after reaching the oxidation induction time. Differential scanning calorimetry melting profiles of date seed oils were also changed after heating in the Rancimat. Melting enthalpies seemed to be constant during the initial stages of Rancimat treatment and then reduced after the induction time was reached. The obtained data shows that date seed oils were resistant to thermal treatment during a long period (~30-40 h). This may indicate that they could bear thermal treatments that could be applied in refining procedures or in culinary treatments such as frying and cooking conditions. We could also expect that they may have a good shelf life.

Studies were conducted on some quality characteristics of date seed oil from two date palm cultivars (Phoenix dactylifera L.): Deglet Nour and Allig. The following values were obtained for Deglet Nour and Allig cultivars respectively: unsaponifiable matter 8.92-7.76%, iodine value 45.49-44.08, total phénols 520.81-220.32 ug/g oil, chlorophylls 0.86-0.58 ug/g oil, viscosity 18.50-20.50 mPa.s, refractive index 1.457-1.462, acidity 1.06-2.10mg KOH/g oil and peroxide index 16.00-25.00meq O2/100g oii. Lipid fractionation of date seed oil yielded 98.30-97.30% neutral lipids, 97.26-96.90% triglycérides, 0.25-0.18% phospholipids and 0.36-0.31% sterols. Gas-liquid chromatography revealed that thé major unsaturated fatty acid was oleic acid (39.17-42.13%) while thé main saturated fatty acid was lauric acid (24.34-22.56%). Date seed oil showed high médium molecular weight triglycérides (C32-C42, about 27%). Extinction coefficients at 232nm and 270nm increased slightly during 40days in oven (60°C) showing that date seed oil could be easily stored. The production of oil from date seeds provides thé use of a renewable resource, and at thé same time adding value to agricultural products.