Composition of oil

Abstract

Abstract International trade in palm oil has increased considerably over the last ten years, and so too has the trade in processed palm oil products, especially palm fractions. It is important to establish reliable purity criteria for palm oil, not only because of the commercial need to verify oil authenticity, but also to comply with foodstuff labelling legislation in many countries. Palm kernel and coconut oils both contain about 47% lauric acid. This gives the oils close similarities in physical and chemical properties. The oils do differ, however, and it is important to be able to distinguish between them. Purity problems can arise as a result of commingling of oils with one another, or as a result of fractionation perhaps coupled with subsequent blending. A research program jointly funded by the (U.K.) Ministry of Agriculture, Fisheries and Foods, the Federation of Oils, Fats & Seeds Associations Ltd (FOSFA International), and the Leatherhead Food RA, was established to study purity characteristics of the major edible vegetable oils. Forty‐seven samples of crude palm oil were obtained from reliable sources, often plantation managers, together with five samples of palm olein and eight samples of palm stearin. Fifty‐four palm kernel and 23 coconut oils were obtained in the laboratory from seed samples of known geographical origins and authenticities. These oil samples were analyzed for fatty acid, triglyceride, sterol and tocopherol compositions; the melting properties were also determined, and in the case of palm oil the compositions of the acids at the triglyceride 2‐positions were measured. Compositional ranges will be presented for the different geographical production areas in each case and related to existing data, e.g., of PORIM and Codex. An initial statistical analysis of the results has shown that a combination of values from the carbon number analysis differentiates palm kernel and coconut oils, and can be used to decide on the proportion of each in a blend. In the case of palm oil samples suspected to be contaminated with palm fractions, it was found useful to plot melting point against iodine value, and to compute the product of the C48 triglyceride content and the palmitic acid enrichment factor.