The effect of powdered thyme sprinkling on quality changes of wild and farmed gilthead sea bream fillets stored in ice Mourad Attouchi, Saloua Sadok * Institut National des Sciences et Technologie de la Mer, Centre La Goulette, La Goulette, Tunisia article info Article history: Received 21 April 2009 Received in revised form 11 July 2009 Accepted 9 September 2009 Keywords: Wild and farmed sea bream Ice storage Thyme addition Liquid-holding capacity Quality parameters abstract The effect of powdered thyme sprinkling on the quality characteristics of fresh and ice-stored wild and farmed gilthead sea bream fillets was assessed. Initially, significant differences in proximate composition and quality attributes were found between wild and farmed fresh sea bream flesh. Throughout ice stor- age, biochemical alteration appeared more pronounced in farmed fish fillets with significantly higher lev- els of TVB-N, TMA-N, and TBA; and a lower liquid-holding capacity (LHC). Thyme powder addition (1% w/ w) exhibited a preservative effect in both fish lots since significant lower levels of TVB-N, TMA-N, free amino acids (NPS), TBA and LHC were observed in thyme-treated fillets during ice storage. However, thyme inhibitory effect was more marked in wild than farmed fish. As revealed by partial least square regression, LHC in both groups was positively influenced by storage time and trimethylamine accumula- tion factors, while it was negatively influenced by thyme treatment and fish origin. Hence, LHC was sug- gested to be related to spoilage bacterial growth. The use of dried thyme extended the shelf life of fish fillets by about 5 days and appeared to be highly valuable to the fish industry as a natural preservative. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Consumer attitudes towards any food product are a major factor influencing its future development. Thus any new wave of prod- ucts on the market has to meet the needs of the consumer, such as foods that offer specific health-oriented benefits or ready-to cook food including fish and seafood products. However, due to its high perishability, the quality and shelf life of fish products are restricted and are defined by several factors including both handling practices and origin. For instance, wild fish acceptability is generally higher than cultured fish (Grigorakis, 2007). Thus existing literature noticeably specifies that significant organoleptic differences always exist when comparing wild and cultured flesh of the same species. Among studied parameters, technological quality attributes were found among the most discriminating parameters between wild and reared fish (Mairesse, Thomas, Gar- deur, & Brun-Bellut, 2005). Thus, the determination of liquid-hold- ing capacity (LHC) in meat and fish is important for economical reasons (weight decrease due to water loss) and for sensory prop- erties (colour, juiciness and tenderness) (Olsson, Olsen, & Ofstad, 2003a). In general, the flesh of farmed fish tends to be softer in tex- ture than wild fish. Therefore it is essential to make an evaluation of high quality fish available to the consumer whether there are differences related to the various post-mortem handling procedure and/or the origin of the fish. Additionally, and because of its greater awareness and safety concern regarding synthetic chemical additives, food preserved with natural additives has become more popular. For instance, the antimicrobial and antioxidant properties of essential oils, and their active constituents derived from various plant organs have been empirically recognised (Burt, 2004; Lee & Shibamoto, 2002). However, any processing technologies used in the production of such compounds have to prove their technical/scientific efficien- cies and the product quality to meet the basic requirement of hy- giene and safety standards. It would therefore be economically more convenient to use powdered spices/herbs as ingredients rather their extracts to preserve food including fish fillets (Smid & Gorris, 1999) as they are generally recognised as safe to con- sume. Beside it is well known that at the core of the traditional Mediterranean cooking, spices and fresh/dried herbs were used for centuries, which current research has confirmed its tremendous health benefits (Burt, 2004; Lee & Shibamoto, 2002). Among the various aromatic plants, thyme (Thymus vulgaris) is a characteristic herb of the Tunisian and Mediterranean environment with various beneficial effects, e.g., antiseptic, carminative, antimicrobial, and antioxidative properties (Baranauskiene, Venskutonis, Viskelis, & Dambrauskiene, 2003). In the seafood sector, such preservative compounds including spices/herbs were equally used to extend the shelf life of fish fillets, but at low levels to avoid strong flavours imparting unpleasant sensorial characteristics (Mejlholm & Dalg- aard, 2002). Despite the numerous comparative investigations on post- mortem quality alteration in both wild and cultured sea bream 0308-8146/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2009.09.038 * Corresponding author. Tel./fax: +216 717358481. E-mail address: salwa.sadok@instm.rnrt.tn (S. Sadok). Food Chemistry 119 (2010) 1527–1534 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem