Investigation of the Impact of Gallic Acid, Methyl Gallate and their Combination on the Oxidative Stability of Frying Oli

Introduction Thermal process is the most prominent option for treating foods. During the heat treatment, food nutrients response simultaneously but adversely under pH, temperature, moisture, and other provided conditions. It might result in an irreversible transformation of composition and structure that influences oxidative stability and sensory properties. The use of antioxidants is one of the most common methods to prevent edible oils oxidation. Safety concerns of synthetic antioxidants including tert-butylhydroquinone (TBHQ) as food additives have led to increasing demands for natural ones. Phenolic compounds such as Gallic Acid (GA) and Methyl Gallate (MG) represent to possess markedly high activity to scavenge free radicals which are among the most powerful natural sources of oxidative inhibitors in foods. Apart from their antioxidant activity, GA and MG also exhibit multiple biological characteristics such as anti-atherogenic, anti-spasmodic, and anti-microbial activities. This study aimed to investigate the oxidative stability of the in-use sunflower (S) and palm (P) oils as affected by the GA, MG, (GA+MG), and TBHQ to clarify their antioxidant behavior. Materials and Methods Antioxidants Gallic acid, Methyl gallate and TBHQ (Purity>98%) were purchased from Sigma Aldrich, USA. All solvents and chemicals were provided from Merck, Germany and Sigma Aldrich, USA with analytical grade. Antioxidant-free sunflower and palm oil were prepared from Three Goals factory, Neyshabur, and potatoes (Agria variety) from Fariman region, Khorasan Razavi. Results and Discussion Chemical changes, oxidative stability and quality indices of the in-use sunflower oil (S) and palm (P) (65:35 w.t. %) were evaluated during 8-hour heat treatment at 180 °C through GA, MG, GA/MG (25:75, 50:50 and 25:75) and TBHQ. All experiments were carried out in quadruplicate, and data were subjected to analysis of variance (One-way-ANOVA). Mean data were compared based on Duncan's multiple range test at 5% level (p