Evaluation of Oxidative Kinetics of Sunflower Oil Containing Green Tea Extract as a Natural Antioxidant under Rancimat Conditions

Subject Areas :

Nadia Ahmadi ¹ , Mehrdad Ghavami ² , Ladan Rashidi ³ , Maryam Gharachorloo ⁴ , Leila Nateghi ⁵

1 - Department of Food Science and Technology, Science and Research Branch, Islamic Azad University, Tehran, Iran
2 - Department of Food Science and Technology, Science and Research Branch, Islamic Azad University, Tehran, Iran
3 - Research Center of Food Technology and Agricultural Products, Standard Research Institute (SRI), P.O. Box 31745-139, Karaj, Iran
4 - Department of Food Science and Technology, Science and Research Branch, Islamic Azad University, Tehran, Iran
5 - Department of Food Science and Technology, Faculty of Agriculture, Varamin-Pishva Branch, Islamic Azad University, Varamin, Iran

Received: 2023-08-09 Accepted : 2023-11-16 Published : 2024-01-20

Keywords: Kinetic parameters, / Oxidative stability, / Rancimat, / Sunflower oil, / Green tea extract,

Abstract :

This study aimed to compare the antioxidant properties of sunflower oil containing green tea extract (GTE) with the synthetic antioxidant TBHQ by assessing their oxidative stability using the Rancimat method. After 90 days, sunflower oil samples with GTE exhibited enhanced resistance to oxidation, as evidenced by specific fatty acid values indicating saturation and effective prevention of oxidation. Although peroxide values did not differ significantly, suggesting maintained freshness, the PUFA/SFA ratio demonstrated stability in oil containing GTE. The reaction rate increased with temperature; however, oils containing GTE exhibited lower rates due to reduced oxidation, highlighting GTE’s ability to enhance sunflower oil’s oxidative resistance. The Rancimat method, conducted under isothermal conditions at 120°C and 130°C, enabled the calculation of kinetic parameters, including activation energies (Ea), activation enthalpies (∆H++), and activation entropies (∆S++). The Ea, ∆H++, and ∆S++ values for sunflower oil with GTE and TBHQ were compared, with GTE exhibiting the highest oxidative resistance. The linear variation of the kinetic rate constant (k) with temperature, along with temperature coefficients (TCoff) ranging from 6.17 to 8.34 (×10–2 K–1), provided valuable insights into the oxidative stabilities of the samples. The study underscores the synergistic effect of GTE as a natural antioxidant, demonstrating superior stability compared to TBHQ. The derived kinetic parameters offer qualitative consistency and facilitate the evaluation of oxidative stabilities of sunflower oil with GTE at elevated temperatures.