Codex standards to combat fraud

Over the years, the Codex standards for fats and oils have been gradually modified to enhance their usefulness in tackling authenticity problems. The pace of the changes is inevitably affected by the availability of data of sufficient quality for inclusion in the database. One significant source of data used to establish purity criteria for edible oils and fats of major importance has been research in the United Kingdom funded by the Ministry of Agriculture, Fisheries and Food (MAFF) and the Federation of Oils, Seeds and Fats Associations (FOSFA) at the Leatherhead Food Research Association.

To produce meaningful data, it is essential that sufficient samples be collected from representative geographical origins and that the oils be pure. In the MAFF/FOSFA work, over 600 authentic commercial samples of vegetable oilseeds of known origin and history, generally of ten different geographical origins, were studied for each of 11 vegetable oils. The oil from these seeds was extracted in the laboratory, except in the case of palm oil, which was obtained from palm plantations because the parent fruit is perishable and cannot be transported. The extracted oils were analysed to determine their overall FAC. FAC at the 2-position of the triglyceride, sterol and tocopherol composition, triglyceride carbon number and iodine value, slip melting point and solid fat content as appropriate.

Prior to 1981, FAC data were not included in Codex standards because data of sufficient quality were not available. In 1981, standards were adopted that included FAC ranges as mandatory compositional criteria. The MAFF/FOSFA work provided the basis for later revisions to these ranges.

In general, as more data became available, it was possible to propose fatty acid ranges much narrower and consequently more specific than those adopted in 1981. Table 3 gives examples of FAC of oils that were adopted by the Codex Alimentarius Commission (CAC) in 1981 and ranges for the same oils proposed at Step 4 at the Codex Committee on Fats and Oils (CCFO) meeting held in September 1993.

Further MAFF/FOSFA information has enabled the British secretariat of CCFO to propose the inclusion of data relating to sterol and tocopherol/tocotrienol (tocol) composition in the new draft standards. The combination of data on fatty acids with those on sterol and tocol composition provides a powerful method of identifying oils and oil blends.

TABLE 3 - Codex standards for fatty acid composition of oils - Normes Codex pour la teneur en acides gras des huiles vtales - Normas del Codex para la composicin dos grasos de los aceites

Sources: Codex Alimentarius Commission, 1983,1993.

Olive oils

In processing, many crude vegetable oils undergo a bleaching step which involves heating the oil to approximately 103°C under vacuum with the addition of a bleaching earth (often acid activated). The objective is to remove pigments and produce an oil of light-yellow appearance. The bleaching process can be used on olive oil, usually in refining of oils of lower value. However, this process produces other changes within the oil. For example, it causes the dehydroxylation of sterols to produce steroidal hydrocarbons such as stigmasta-3, 5-diene. If an oil has undergone high-temperature deodorization as well, the formation of dehydroxylated sterols will be even greater. However, it is unlikely that these compounds will be produced to any great extent in virgin olive oils; thus their presence is indicative of mixing with either refined olive oil or other vegetable oils. The latest IOOC trade standard for olive and olive-pomace oils sets limits for these compounds (see Table 4), and CCFO will consider this relatively new development in due course.