title: A combined microwave pretreatment/solvent extraction process for the production of oil from palm fruit: optimisation, oil quality and effect of prolonged exposure.
abstract: BACKGROUND
  Conventional palm oil milling involves multiple stages after fruit collection; in particular, oil clarification introduces water into the pressed oil, which results in a large quantity of wastewater.
  
  
  RESULTS
  A combined process of microwave pretreatment and solvent extraction to mill crude palm oil, without introducing water or steam, is described. An excellent yield (up to 30%) of oil was obtained with pretreatment in a 42 L, 1000 W and 2450 MHz microwave oven followed by hexane extraction. The optimum conditions (10 min microwave pretreatment and 12 h solvent extraction) yielded an oil with a low free fatty acid content (<1.0%) and an acceptable anisidine value (<3.0 meq kg-1). The oil had a fatty acid composition not resembling those of conventional crude palm oil and crude palm kernel oil. In the pretreatment, the leached oil had 6.3% lauric acid whereas the solvent extracted oil had only 1.5% lauric acid. Among the factors affecting the oil quality, microwave pretreatment affected the oil quality significantly; however, an optimised duration that would ensure high efficiency in solvent extraction also resulted in ruptured fruitlets, although not to the extent of causing excessive oxidation. In fact, microwave pretreatment should exceed 12 min; after only 15 min, the oil had 1-methylcyclopentanol (12.96%), 1-tetradecanol (9.44%), 1-nonadecene (7.22%), nonanal (7.13%) and 1-tridecene (5.09%), which probably arose from the degradation of fibres.
  
  
  CONCLUSIONS
  Microwave pretreatment represents an alternative milling process for crude palm oil compared with conventional processes in the omission of wet treatment with steam. © 2016 Society of Chemical Industry.
authors.affiliation: Unit of Research on Lipids (URL), Department of Chemistry, Faculty of Science, University of Malaya, 50603, Kuala Lumpur, Malaysia.
authors.forename: Jason Cx
authors.initials: JC
authors.lastname: Tan
authors.affiliation: Unit of Research on Lipids (URL), Department of Chemistry, Faculty of Science, University of Malaya, 50603, Kuala Lumpur, Malaysia.
authors.forename: Cheng-Hock
authors.initials: CH
authors.lastname: Chuah
authors.affiliation: Unit of Research on Lipids (URL), Department of Chemistry, Faculty of Science, University of Malaya, 50603, Kuala Lumpur, Malaysia.
authors.forename: Sit-Foon
authors.initials: SF
authors.lastname: Cheng
mesh_terms: D028023:Arecaceae / Q000737:chemistry*; D005591:Chemical Fractionation / Q000379:methods*; D005227:Fatty Acids / Q000737:chemistry / Q000302:isolation & purification; D005638:Fruit / Q000737:chemistry*; D008872:Microwaves; D010084:Oxidation-Reduction; D000073878:Palm Oil; D010938:Plant Oils / Q000737:chemistry* / Q000302:isolation & purification*
chemical_list: D005227:Fatty Acids; D010938:Plant Oils; D000073878:Palm Oil
keywords: degradation; fresh palm fruit; microwave pretreatment; oxidation; solvent extraction