Thermal and oxidative stability assessment of synergistic blends of sunflower and sesame oils tailored for nutritionally stable composition of omega fatty acids

The thermal stability of -6 fatty acid-rich oils is a bewildering problem. The synergistic blends of sunflower (SO) (50-80%) and sesame oil (SEO) (20-50%) were optimized for improved thermal stability, better retention of antioxidants, and balanced ratio of -fatty acids (-6 and 9). The oil blends were thermally oxidized by Rancimat (temperature 100, 110, 120, and 130 degrees C; airflow rate 20Lh(-1)) for estimating the induction period (IP) and kinetic rate constant (k) of lipid oxidation. The oils were exhaustively characterized for thermal stability by thermogravimetry and differential scanning calorimetry. The temperature-dependent kinetics of lipid oxidation was described using Arrhenius equation (lnk vs. 1/T) and activated complex theory (lnk/T vs. 1/T). The calculated kinetic parameters, viz. activation energies, activation enthalpies, and entropies varied from 90.80 to 99.17, 87.58 to 95.94, -33.28 to -4.78Jmol(-1)K(-1), respectively (R-2>0.90, p<0.05). The optimized blend (OB) consisted of 50.8 and 49.2% of SO and SEO, respectively, and showed the highest synergism (115%) and IP (100 degrees C) than SO (13.2 vs. 6.1h). This could be attributed to lignans (6304 vs. 5289mgkg(-1))-induced thermal stability and effective retention of tocopherols (270 vs. 197mgkg(-1)). OB possesses balanced composition of -fatty acids (-9, 34.5 vs. 28.7%; -6, 49 vs. 52%) and superior thermal stability (onset temperature, 387 vs. 212 degrees C; oil induction time, 21.6 vs. 15.7min) than SO. It could be recommended over SO for culinary applications while ensuing thermal stability and nutritional benefits.