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Analytical evaluation of degradation in sunflower oil during thermal oxidation using FTIRand the compositional change analysis by gas chromatography

S.Rubalya Valantina, A.Sathya, P.Neelamegham, V.Sudha

Atmospheric oxygen can react spontaneously with lipids and other organic compounds causing structural degradation, which is ultimately responsible for the loss of quality in food. When oil is exposed to frying, the triglycerides are converted into myriad. However, this oxidation process can be prevented or retarded by the addition of synthetic or natural antioxidants. Recent developments in Fourier transforminfrared (FT-IR) spectroscopy instrumentation extend its application to the field of food research, facilitating particularly the studies on edible oils and fats. Commercial sunflower oil is exposed to repetitive and simulated deep-frying at 2500C for five times. In this work, FT-IR spectroscopy is used as an effective analytical tool to study the saturation and unsaturation composition of heated and unheated oils. In addition, an analytical technique for the measurement of carbonyl compounds in oils, produced after heating, has been employed. A novel methodology in gas chromatography (GC-MS) with an electron impact mass spectrum for the fast analysis of compositional variations of fatty acids and antioxidants in repeatedly heated sunflower oilwithminimal sample treatment and the use of non-toxic reagents is also described. It is found that Tocopherol (Vitamin E) disappears in heated oil. The changes in the composition of edible oil confirmthe degradation. Especially the unsaturated fractions of fatty acids have been converted to saturated fatty acids due to repeated heating. This conversion is opined to have adverse effect on the antioxidant regulating system of humans.