67D-6 |
|
C. J. Steel1, D. BARRERA-ARELLANO1, and M. D. C. Dobarganes2. (1) Food Technology Department, Campinas State University, Cidade Universitária Zeferino Vaz, Campinas, SP, 13.081-970, Brazil, (2) Instituto de la Grasa, Av. Padre García Tejero 4, Sevilla, 41012, Spain A great part of the fats and oils consumed today have been submitted to high temperatures, thus frying fats are an important component of contemporary diets. During frying, fats and oils decompose forming volatile and non-volatile products that alter their functional, organoleptic and nutritional properties. There are means to retard degradation, such as: the process of hydrogenation, that reduces the number of double bonds in the fat or oil, reducing reactive sites, concomitantly reducing iodine value and the presence or addition of antioxidants. In this research work, the influence of iodine value on the formation of dimers and polymers and the role of originally present tocopherols in the protection of fats and oils against thermal degradation were studied. Samples of cottonseed oil and partially hydrogenated cottonseed fats, with iodine values between 60 and 110, tocopherol-stripped or not by aluminum oxide treatment, were submitted to thermal oxidation, at 180¢XC for 10 hours. Thermoxidized samples were collected at 0, 2, 5, 8 and 10 hours, for the determination of dimers and polymers (degradation compounds) and of tocopherols by HPSEC and HPLC, respectively. Tocopherol degradation curves showed a fast destruction rate for the tocopherols present in cottonseed fats and oil (ƒÑ and ƒ×-tocopherols), with residual levels close to zero after 10 hours under thermal oxidation conditions. Dimer and polymer formation was greater in the oil than in the hydrogenated samples, and, for each sample, greater in the treated or unprotected counterpart. Overall, these results suggest the complexity of degradation at high temperatures. Natural tocopherols contributed to decrease polymerization in all the samples, however, tocopherol degradation was faster as the degree of unsaturation decreased, meaning that substrates of low iodine values may be unprotected from natural antioxidants very rapidly and at low levels of polymerization.
Session 67D, Food Chemistry: Lipid and carbohydrate chemistry
|