Improved conservation of gilthead seabream (Sparus aurata) in ice storage. The influence of doses of rosemary extract added to feed A. Hernández a , B. García García a , M.J. Jordán b , M.D. Hernández a, ⁎ a IMIDA, Acuicultura, Carretera del puerto s/n, P.O. Box 65, 30740 San Pedro del Pinatar, Murcia, Spain b IMIDA, Recursos Naturales y Desarrollo Rural, C/Mayor s/n, 30150 La Alberca, Murcia, Spain abstract article info Article history: Received 21 October 2013 Received in revised form 9 January 2014 Accepted 13 January 2014 Available online 26 January 2014 Keywords: Sparus aurata Quality Shelf-life Rosemary extract Natural antioxidants This study focused on the effects of the dose of rosemary extract (Rosmarinus officinalis) on the quality of gilthead seabream. A control diet (basal diet) and four experimental diets (R600, R1200, R1800 and R2400) with 600, 1200, 1800 and 2400 mg kg -1 of rosemary extract were administered, respectively. The fish were sacrificed and stored on ice at 4 °C for 0, 7, 14 and 21 days. Physical–chemical, microbiological and sensory tests were con- ducted at each sampling point to determine the degree of deterioration suffered by the gilthead seabream. The differences in water-holding capacity (WHC) and the trends in TBARS, TVBN and TMA observed suggest better preservation with the 600 mg kg -1 dose. In addition, the Quality Index showed greater freshness in fish fed diets containing rosemary extract, regardless of the dose; shelf-life also increased by one day with all tested doses, as compared to the control group. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Natural antioxidants are currently in the spotlight within the scien- tific community, which is eyeing them as good substitutes for synthet- ic antioxidants as part of the current trend towards optimizing food safety. There is also a growing interest of consumers in natural, ecolog- ical products that are free of synthetic additives. A large number of natural preservatives have been tested as food additives in recent years, such as: rosemary, sage, oregano, thyme, ginger, pepper, cloves, basil, mint, fennel, parsley, cinnamon, cumin and coriander, among others (Yanishlieva et al., 2006). Among Labiatae, rosemary has been the most studied and the most commonly marketed as an extract (Cuvelier et al., 1996). The rosemary extract components with an antioxidant effect have been well documented and several processes are known for their ex- traction (Chang et al., 1977). Among the molecules described in rose- mary extract are several phenolic diterpenes, the most important of which are carnosic acid and its derivatives, carnosol, rosmanol, epirosmanol, 7-methylepirosmanol and methyl carnosate, which are most abundant in the fat-soluble fraction. Also described were flavo- noids, such as genkwanin, hispidulin-O-glucoside, cirsimaritin, luteolin and isoscutellarein 7-O-glucoside and other phenolic compounds, such as caffeic acid and rosmarinic acid, the latter constituting the main component in the hydrosoluble fraction (del Baño et al., 2003). In a comparative study of commercial extracts, Cuvelier et al. (1996) dem- onstrated that the most active compounds were carnosol, rosmarinic acid and carnosic acid. Another important quality of rosemary extract is its antimicrobial capacity, as demonstrated by Davidson (1993), who observed that non-polar polyphenolic compounds from rosemary had greater activity on Gram-positive bacteria than on Gram-negative bacteria. These com- pounds can act on the cell membrane, affecting its fatty acid composi- tion, and even interact with membrane proteins and change their structure and functionality (Fung et al., 1977). The antimicrobial effect of the rosemary extract as a whole depends to a large extent on the ex- traction method used, with the supercritical fluid technique being the most effective; the resulting extract has an antimicrobial effect that is lower than that of thyme, but greater than that of sage (Ivanovic et al., 2012). The effects of the exogenous use of rosemary in the preservation of fish have been widely studied by many different authors. These studies have been based on freezing fresh fish (Akhtar et al., 1998; Ozogul et al., 2011; Tironi et al., 2010) and storing it in refrigeration (Akhtar et al., 1998; Çoban and Özpolat, 2013; Giménez et al., 2004; Ozogul et al., 2010; Peiretti et al., 2012) or cooking it in different ways with rosemary and then studying its protective properties (Ozogul et al., 2009). All have demonstrated the protective effect of rosemary extract against lipid oxidation and the improvement of several freshness indices, when applied to fillets. However, few studies have focused on the dietary administration of rosemary extract to fish and its subsequent Aquaculture 426–427 (2014) 31–40 ⁎ Corresponding author. Tel.: +34 968 184518; fax: +34 968 181116. E-mail address: mdolores.hernandez6@carm.es (M.D. Hernández). 0044-8486/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aquaculture.2014.01.018 Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aqua-online