EVALUATION OF ESSENTIAL OILS AS A GLAZING MATERIAL FOR FROZEN RAINBOW TROUT (ONCORHYNCHUS MYKISS) FILLET ÖZLEM EMI ˙ R ÇOBAN 1 Department of Fish Processing Technology, Faculty of Fisheries, Firat University, Elazıg ˘ 23119, Turkey 1 Corresponding author. TEL: +90-4242370000-4536; FAX: +90-4242386287; EMAIL: oecoban@firat.edu.tr Accepted for Publication February 15, 2012 doi:10.1111/j.1745-4549.2012.00722.x ABSTRACT In this study, sage, thyme and clove oils were evaluated as a glazing material for rainbow trout (Oncorhynchus mykiss) frozen. One percent sage, thyme and clove oil solutions were used for glazing. Water-glazed (WG) and nonglazed (NG) rainbow trout fillets were used as controls. Fish fillets were glazed and were stored in a freezer at -18C for 6 months. Samples were analyzed at 1, 2, 3, 4, 5 and 6 months for moisture content, total volatile basic nitrogen, thiobarbituric acid, per- oxide value, free fatty acids and sensorial quality. It was determined that glazed samples had higher moisture content compared to NG trout fillet after 6 months storage. Essential oils were effective in controlling lipid oxidation in rainbow trout fillet (P < 0.05). PRACTICAL APPLICATIONS Freezing is one of the most employed methods used for preserving fresh fish and other seafood products. However, frozen storage does not completely inhibit chemical reactions (e.g., lipid oxidation) that lead to quality deterioration of fish and fish product. The antioxidant property of some essential oils may make it ideal for use as a glazing solution for suppressing lipid oxidation in rainbow trout fillet during frozen storage. INTRODUCTION Freezing is a general preservation method used to control or decrease biochemical changes in fish that occur during storage. Nevertheless, frozen storage does not completely inhibit chemical reactions (e.g., lipid oxidation) that lead to quality deterioration of fish. Many fish species have been examined during storage on ice (Ryder et al. 1993; Nam- ulema et al. 1999; Karungi et al. 2004; El-hanaf et al. 2011). However, the quality of fish muscle will also deteriorate during frozen storage as the fish muscle is abundant in protein and unsaturated fatty acids. Endogenous proteases, which are able to hydrolyze different proteins in the fish muscle, are also important in the deterioration process (Cepeda et al. 1990). Thus, taking some measures to extend the shelf life of fish during cold storage is of major importance. Antioxidants and glazing are the most used methods to delay the onset of oxidation or to slow down the rate of oxi- dation of food (Garthwaite 1992). The most commonly used synthetic antioxidants in the food industry are butyl hydroxyanisole, butylated hydroxytoluene and propylgalate. However, synthetic antioxidants used in foodstuffs may also be cancer promoters. Great interest has recently been shown in natural products because of the numerous benefits to health, such as the antioxidant effects of thyme, sage, clove and others (Beddows et al. 2000; McCarthy et al. 2001; O’Sullivan et al. 2005; Dance-Barnes et al. 2009). The anti- oxidant effects of these EOs are mainly attributed to their phenolic compounds, i.e., carvacrol, carnosic acid, thymol, eugenol and terpenes (Burt 2004; Emir Çoban and Özpolat 2012). During frozen or cold storage, seafood products may develop surface drying and dehydration, which may lead to Journal of Food Processing and Preservation ISSN 1745-4549 1 Journal of Food Processing and Preservation •• (2012) ••–•• © 2012 Wiley Periodicals, Inc.