Composition and oxidation level of some vegetable oils consumed in Cameroon, determined by classical and mid infrared spectroscopic methods. In developing countries like Cameroon, the commercial sector is strongly liberalised. There are little or no quality standards, and limited information on the quality of locally consumed foods. Oils and fats, employed particularly for cooking and frying processes, are typical examples. This study evaluates the quality of some vegetable oils obtained in the local market in Cameroon. The oils of different biological origins and processed using different techniques included crude palm oils, refined palm oils, refined and unbleached palm oils, refined cotton oils, soy bean oils and an imported undefined vegetable oil. The Fatty acid composition as well as the free fatty acid, (alpha-tocopherols and unsaponifiable contents were determined with usual chemicals methods and Fourier Transform Infra Red spectroscopy. The level of oxidation of the oils was evaluated using the hydroperoxides colorimetric test, the p-anisidine value and the thiobarbituric acid test. The compositions of most oils were in agreement with indications on producer labels, with respect to their vegetable origin. The imported vegetable oil, with a fatty acid profile similar to that of palm oil, was however outstanding. The imported oil showed polyunsaturated fatty acid (only 13%) and alpha-tocopherol contents (200 mg/kg) that were significantly less than those claimed on the producer labels (500 mg/kg). Although all the oils showed low levels of hydroperoxides (0.7 - 17.7 mmole/kg), the cotton, soybean and traditional crude palm oils contained secondary oxidation products (33.3 - 179.5 nmol eq. MDA/kg). The latter could be consequences of high-temperature refining or poor conditions of storage and distribution. The crude palm oils had large amounts of free fatty acids (7 to 13% of total lipids) with the highest proportion being in the traditional crude palm oil. These palm oils also had a characteristic rancid odour, which could be attributed to lipolysis, a process that is accelerated during traditional processing, as fruits are fermented to facilitate their extraction. The traditional palm oils were also characterised by low alpha-tocopherols content (55 mg as compared to 200 mg/kg in industrial crude palm oil). The low values could be linked to damage caused during physical refining or to oxidation. Our results provide a first view of the quality of commercial edible oils (imported and traditionally-produced) in Cameroon. They revealed the necessity for better quality control of palm oils produced traditionally and of the imported oils. We will further compare the characteristics of these oils with others of controlled processing and distribution conditions.
