Comparison between free radical scavenging capacity and oxidative stability of nut oils Sara Arranz a, * , Rosa Cert b,2 , Jara Pérez-Jiménez a,1 , Arturo Cert b,2 , Fulgencio Saura-Calixto a,1 a Department of Metabolism and Nutrition, Instituto del Frío, CSIC, c/ José Antonio Novais 10, 28040 Madrid, Spain b Instituto de la Grasa, CSIC, Avenida Padre Garci ´ a Tejero 9, 41012 Sevilla, Spain article info Article history: Received 3 September 2007 Received in revised form 26 February 2008 Accepted 5 March 2008 Keywords: Nut oils DPPH Å Rancimat Tocopherols Polyphenols . abstract Several works have measured free radical scavenging capacity of nut oils, since they may become a sig- nificant source of dietary fat. However, they have not considered kinetic parameters, what was the first aim of this work. Also, it was studied the possible relation between values of free radical scavenging capacity DPPH Å and oxidative stability (Rancimat method) in different nut (hazelnut, peanut, pistachio, walnut and almond) oils. The ranking of antioxidant capacity of nut oils, by both assays, was: pista- chio > hazelnut > walnut > almond > peanut. A significant correlation was found between DPPH and Rancimat methods assays. Tocopherols appear to be the responsible compounds of this antioxidant capacity being neglictible the contribution of polyphenols. An interference effect of phospholipids, pres- ent in methanolic fraction of nut oils, was observed in the determination of polyphenols in nut oils by Folin and ortho-diphenols assays. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction The dietary source of fat has proven to be a key aspect in the development of cardiovascular disease and certain kinds of cancer (Aguilera et al., 2003; Kushi, Lenart, & Willett, 1995; Wagner, Tom- asch, & Elmafa, 2001). The positive health effects of certain vegeta- ble oils, such as olive oil, are due to their fatty acid composition, rich in monounsaturated fat, that prevent cardiovascular disease by several mechanisms (López-Miranda et al., 2006), and also due to their antioxidants (Ramadan & Moersel, 2006; Tripoli et al., 2005) which prevent the attack of biomolecules by free radicals. Since nuts contain a high amount of oil (more than 40%), they are a significant potential source of dietary fat; the consumption of nuts in a traditional healthy diet, such as Spanish Mediterranean diet, is approximately 7 g nuts per day (MAPA, 2006). Nut oils are characterized by a high content of mono- and polyunsaturated fat (Maguire, O’Sullivan, Galvin, O’Connor, & O’Brien, 2004). Also, some nut oils exhibit important antioxidant capacity due mainly to their content of tocopherols (Espín, Soler-Rivas, & Wichers, 2000). Several articles have shown, by DPPH Å (2,2-diphenyl-1-pic- rylhydrazyl) assay, free radical scavenging capacity of heartnut, walnut, peanut, hazelnut and almond oils using different solvents such as ethyl acetate or a mixture hexane/ethyl acetate/methanol (Espín et al., 2000; Li, Rong, Yang, Kramer, & Hernández, 2007; Ramadan & Moersel, 2006). However, antioxidant capacity of the oil from the common pistachio nut has yet to be determined. More- over, these works have not taken kinetic parameters into account, i.e. the lag time before radicals start to attack susceptible sub- strates, such as lipids, proteins and DNA. This information together with data concerning their free radical scavenging capacity, pro- vides a more complete parameter of antiradical efficiency (AE) (Sánchez-Moreno, Larrauri, & Saura-Calixto, 1998). Free radical scavenging capacity is usually measured with the aim of determining possible biological effects of a sample rich in antioxidants since the latter have been related to the prevention of several diseases (Stanner, Hughes, & Buttriss, 2004). In the case of oils, the Rancimat assay is another method commonly used, for determining their oxidative stability, i.e., their half-life. This stabil- ity depends mainly on the acylglycerol composition and on the amount and type of minor components in the oil (Mateos, Trujillo, 0308-8146/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2008.03.021 Abbreviations: AE, antiradical efficiency; AOAC, American Organization of Analytical Chemistry; DMCS, dimethylchlorosilane; DPPH Å , 2,2-diphenyl-1-pic- rylhydrazyl; EC 50 , concentration to deplete the free radical DPPH Å in a 50%; ELSD, evaporative light scattering detector; GC–MS, gas chromatography–mass spec- trometry; HMDS, hexamethyldisilazane; HPLC, high performance liquid chroma- tography; IT, induction time; IUPAC, International Union of Pure and Applied Chemistry; PC, phosphatidylcholine; t EC50 , time taken by the EC 50 to reach the steady state; TMS, trimethylsilyl. * Corresponding author. Tel.: +34 91 549 23 00; fax: +34 91 549 36 27. E-mail address: saraarranz@gmail.com (S. Arranz). 1 Tel.: +34 91 549 23 00; fax: +34 91 549 36 27. 2 Tel.: +34 95 461 15 50; fax: +34 95 461 67 90. Food Chemistry 110 (2008) 985–990 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem