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Supercritical CO2 extraction of waxes from date palm (Phoenix dactylifera) leaves: optimisation, characterisation, and applications.

Al Bulushi, Karima (2018) Supercritical CO2 extraction of waxes from date palm (Phoenix dactylifera) leaves: optimisation, characterisation, and applications. PhD thesis, University of York.

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The low cost, abundant, underexploited and underutilised renewable agricultural waste residue, date palm leaves (Phoenix dactylifera), were extracted using supercritical carbon dioxide (scCO2) to obtain valuable waxes. The extraction process was optimised using second order factorial design to obtain high yield of waxes. Date palm leaves exhibited relatively high yield of wax of 3.49%, as compared to other agricultural residues extracted with scCO2. Diverse range of lipophilic compounds were characterised and quantified including n-alkanes, free fatty acids, free fatty alcohols, long chain aldehydes, sterols and wax esters. Waxes extracted at different extraction pressure and temperature exhibited significant difference in melting profile (ranging from 35 °C for extractions at 40°C and 80 Bar to melting points of 78 °C for extractions at 100 °C and 400 Bar). Thus, suggesting the opportunity to tailor extraction to meet a target application. ScCO2 extraction has several advantages over organic solvent extraction which were demonstrated in this work. Date palm leaves wax was tested as structuring agent for sunflower oil along with other commercial natural waxes. Date palm wax based oleogel exhibited low critical gelling concentrations compared to other waxes. Chemical composition and crystal morphology for the waxes and their gels were further explored to gain better understanding of their gelling behaviour. Date palm wax exhibited good gelling ability and high thermal stability compared to other commercial waxes. The rheological profile for date palm wax based oleogel was comparable with other natural waxes making it a promising structuring agent in food industry. The scale up of scCO2 extraction was studied at semi-pilot scale and resulted in comparable yields, chemical composition and melting profile of wax to the lab scale. Attempts to further reduce the complexity of the wax by fractional extraction, yielding three different wax fractions with varying in texture, composition and physical properties. Economic aspects of the extraction process were explored to further assess the viability of the process. Cost of Manufacture of date palm wax was initially €14.01 kg−1 wax, which could be further reduced to €8.80 kg-1 wax by biomass pelletising. If the extracted biomass was utilised to generate electricity the costs are further reduced to 3.88 kg−1 wax.

Item Type: Thesis (PhD)
Related URLs:
Academic Units: The University of York > Chemistry (York)
Depositing User: Mrs Karima Bulushi
Date Deposited: 03 Sep 2018 10:18
Last Modified: 03 Sep 2018 10:18
URI: http://etheses.whiterose.ac.uk/id/eprint/21257

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