Purity Criteria in Edible Oils and Fats

A review is presented of edible vegetable oil purity criteria developed at the Leatherhead Food Research Association. Most of the work involved accurate determination, by modern GLC techniques, of the fatty acid compositions of oils extracted in the laboratory from oilseeds of known origin and history. All of the main production areas throughout the world were represented in the collection of over 600 samples of commercial oilseeds. No botanial curiosities or hand picked specimens were included as the work related to commercially available edible oils. The fatty acid compositions of the major vegetable oils are reviewed, and the influence this had on the revision of Codex Alimentarius Fats and Oils Specifications is discussed. The development of purity criteria based on the composition of fatty acids at the triglyceride 2-position, triglyceride compositions by high temperature GLC, sterol compositions and tocopherol concentrations are also reviewed. In the case of maize oil a significant new development is the authentication of the oil by stable carbon isotope ratio measurement. The possibilities of this exciting new technique are reviewed in the light of 40 results on maize oils of various origins, together with over 60 results on a selection of other oils and fats.