Journal of Scientific Research and Development 4 (1): 1-5, 2017 Available online at www.jsrad.org ISSN 1115-7569 © 2017 JSRAD 1 Synergistic effects of fatty acids on the performance of TBHQ in inhibiting the oxidation of corn oil Radiah Ali 1 , Ku Halim Ku Bulat 2 , Alyza A. Azmi 1 , Sabiqah Tuan Anuar 1, * 1 School of Marine and Environmental Sciences, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu Darul Iman 2 School of Fundamental Sciences, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu Darul Iman Abstract: The synergistic effects of saturated and polyunsaturated fatty acids addition on the performance of synthetic antioxidant (TBHQ) in inhibiting the autoxidation of corn oil triacylglycerols were reported. This study utilized the effectiveness of two free fatty acids: palmitic (C16:0) and linoleic (C18:2) acids on TBHQ performance in triacylglycerols, for experimental and theoretical studies. It was shown that the TBHQ performance is depends on the concentration of fatty acids added. The addition of fatty acid decreased the triacylglycerols oxidation, thus gave less effect to the degradation of corn oil after 15 days storage time at 60 o C. The finding was supported by theoretical calculations using B3LYP hybrid functional by Gaussion09 software package, where it was found that the interaction energy is the major contributor to the performance of the TBHQ. In the presence of TBHQ, synergistic behavior was found between fatty acid and antioxidants, where complex with TBHQ were shown to be stable. Thus the addition of fatty acids either C16:0 or C18:2 may reduce the peroxide formation. Key words: Oxidative stability, Synergistic effect, Theoretical study, TBHQ, Palmitic acid, Linoleic acid 1. Introduction * One of the most important indicators for maintaining the quality of vegetable oils is oxidative stability (Tan et al., 2002). Oxidation of lipids not only produces rancid odors and flavor but also can decrease the nutritional properties and safety in food by the formation of secondary products after cooking and processing (Frankel, 1996). The oxidative stability of fats and oils is related to their triacylglycerols (TAGs) composition and antioxidants present Hrncirik and Fritshe, 2005; Mateos et al, 2005) and iron content (Coscione and Artz, 2005). Oxidative rancidity in vegetable oils occurs when heat, metals or other catalysts cause unsaturated oil molecules to convert to free radicals. These free radicals are easily oxidized to yield hydroperoxides and organic compounds such as aldehydes, ketones or acids (Das et al, 2009; Vlachos et al, 2006; Mannekote and Kailas, 2012), which give rise to the undesirable odors and flavors characteristics of rancid oils and fats (Naz et al, 2004). Hydroperoxides are primary products formed by oxidation mechanism is quite unstable and their decomposition products are responsible for oxidative rancidity (Azeredo et al, 2004). It rates can be decreased by addition of primary antioxidants, which compete with lipids, breaking off free radical chain. * Corresponding Author. Vegetable oil oxidation is affected by many factors including the presence of antioxidants (inhibitors) or pro-oxidants (catalyst); temperature, light, oxygen, metals and enzymes (regarding processing and storage conditions) and also unsaturated fatty acid composition and their distribution in TAG molecules (Paradiso et al, 2010; Wasowicz et al, 2004). Corn oil generally is considered to be fairly unstable to oxidation due to relatively high concentration of polyunsaturated fatty acids (PUFA). It consists of high amounts of 1,2,3-trilinoleoyl-glycerol (LLL) (25.6%) and 1,2- dilinoleoyl-3-oleoyl-glycerol (LLO) (20.5%) TAGs. It also contains considerable amounts of 1,2- dilinoleoyl-3-palmitoyl-glycerol (LLP) (16.4%), 1,2- dioleoyl-3-linoleoyl-rac-glycerol (LOO) (10.9%) and 1-palmitoyl-2-oleoyl-2-linoleoyl-rac-glycerol (POL) (10.4%), respectively (Rezanka and Rezankova, 1999). Thus, corn oil is highly susceptible to free radical oxidation reactions giving rise to the formation of lipid peroxides (Mannekote and Kailas, 2012; Valls et al, 2003) even though it was reported having better stability then soybean oil (Isabell et al, 1999). In the vegetable oil industry, synthetic antioxidants such as TBHQ and other chelating agents are effectively being used to increase oil thermal and storage stability as well as decrease aging effect (Che Man et al, 1999; Gordon and Kouřimská, 1995; Karavalakis et al, 2011; Bera et al, 2006). Recently, study shows that the presence of