The effects of dietary oregano oil supplementation on pig meat characteristics P.E. Simitzis, G.K. Symeon, M.A. Charismiadou, J.A. Bizelis, S.G. Deligeorgis * Faculty of Animal Science, Agricultural University of Athens, 75 Iera Odos, 118 55 Athens, Greece article info Article history: Received 31 March 2009 Received in revised form 6 October 2009 Accepted 2 November 2009 Keywords: Pig meat Oregano supplementation Oxidation Quality characteristics abstract The effects of different concentrations of dietary oregano essential oil supplementation on finishing pig meat characteristics were investigated in the present study. Thirty-two barrows and thirty-two gilts were divided into four equal groups. During the experimental period, which started when the animals were 5 months old and finished after 35 days, the first group was fed the control diet (group C), whereas the other three groups consumed the same diet, with the only difference that the feed was supplemented with oregano essential oil at concentrations of 0.25, 0.5 and 1 ml/kg of fed diet (groups OR1, OR2 and OR3, respectively). At the end of the experiment, pigs were fasted for 12 h, weighed and slaughtered. After overnight chilling, a 50 cm loin section was removed from the half of the carcasses (8 pigs per nutri- tional treatment; 4 barrows and 4 gilts) and transported to laboratory for further examination. No significant differences were observed after dietary oregano essential oil supplementation in final body weight (kg), body weight gain (g) and dressing out (%). Tenderness of longissimus muscle, expressed as shear force value, pH values at 45 min and 24 h postmortem, colour parameters and sensory attributes of eating quality were not significantly influenced by the dietary treatment. Moreover, the lipid oxidation results suggested a lack of antioxidant effect for the oregano essential oil. In conclusion, carcass and meat quality attributes were unchanged, indicating that the dietary administration of different levels of oreg- ano essential oil did not exert any effect on pig meat parameters in the present experiment. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Oxidation by free radicals is one of the primary mechanisms of quality deterioration in foods and especially in meat products (Kan- ner, 1994). Oxidative deterioration is initiated in the highly-unsat- urated fatty acid fraction of membrane phospholipids, leading to the production of hydroperoxides, which are susceptible to further oxidation or decomposition to secondary reaction products such as short-chain aldehydes, ketones and other oxygenated compounds that may adversely affect lipids, pigments, proteins, carbohydrates, vitamins and the overall quality of products by causing loss of col- our and nutritive value and limiting shelf-life (Kanner, 1994). In the past, synthetic antioxidants were used with the intention to prevent lipid oxidation by scavenging chain-carrying peroxyl radicals or diminishing the formation of initiating lipid radicals. The last decade, considerable interest has arisen in the use of nat- ural antioxidants that would serve as alternatives to synthetic sup- plements on purpose to improve meat quality, without leaving residues in the product or the environment (Yanishlieva-Maslar- ova, 2001). As a result, there is a strong tendency towards isolating organic antioxidants from natural sources for the protection of ani- mal health and their products against oxidation (Wenk, 2003). Oregano (Origanum vulgare L.) is an aromatic plant with a wide distribution throughout the Mediterranean region (Kokkini, Karou- sou, Hanlidou, & Lanaras, 2004). The essential oil of oregano mainly consists of carvacrol, thymol, and their precursors, c-terpinene and p-cymene. It possesses intense antimicrobial (Lambert, Skandamis, Coote, & Nychas, 2001), antifungal (Adam, Sivropoulou, Kokkini, Lanaras, & Arsenakis, 1998) and antioxidant (Martinez-Tome et al., 2001) in vitro properties, since it contains molecules that have intrinsic bioactivities on physiology and metabolism. Oregano action is mainly attributed to carvacrol and thymol, substances that make the bacterial cell membrane permeable (Lambert et al., 2001) and react with lipid and hydroxyl radicals converting them into stable products (Yanishlieva-Maslarova, 2001). Oregano has already been used with the intention to improve the quality and quantity of animal meat products. Although dietary oregano oil supplementation appeared to improve growth perfor- mance in pigs (Namkung et al., 2004) and broiler chickens (Giann- enas, Florou-Paneri, Botsoglou, Christaki, & Spais, 2005) in some cases, there are also studies, which have demonstrated no effect of oregano on growth characteristics in pigs (Janz, Morel, Wilkin- son, & Purchas, 2007), sheep (Simitzis et al., 2008a) and poultry (Symeon, Zintilas, Ayoutanti, Bizelis, & Deligeorgis, 2009). Further- more, dietary oregano supplementation has improved the poten- tial for meat storage after slaughter in sheep (Simitzis et al., 2008a), poultry (Botsoglou, Govaris, Botsoglou, Grigoropoulou, & 0309-1740/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2009.11.001 * Corresponding author. Tel.: +30 2105294447; fax: +30 2105294442. E-mail address: sdel@aua.gr (S.G. Deligeorgis). Meat Science 84 (2010) 670–676 Contents lists available at ScienceDirect Meat Science journal homepage: www.elsevier.com/locate/meatsci