Effect of harvesting stress and slaughter conditions on selected flesh quality criteria of gilthead seabream (Sparus aurata) Elisabete Matos a, ⁎, Amparo Gonçalves b , Maria Leonor Nunes b , Maria Teresa Dinis a , Jorge Dias a a CCMAR-CIMAR L.A., Centro de Ciências do Mar do Algarve, Universidade do Algarve, Campus de Gambelas, 8005-139, Faro, Portugal b Instituto Nacional de Recursos Biológicos-INRB, I.P./L-IPIMAR, Unidade de Valorização dos Produtos da Pesca e Aquacultura, Av. de Brasília, 1449-006, Lisboa, Portugal abstract article info Article history: Received 7 January 2010 Received in revised form 14 April 2010 Accepted 15 April 2010 Keywords: Sparus aurata Harvesting stress Slaughter method Anesthesia Muscle texture The aim of this study was to assess the independent effects of harvesting stress and slaughter method on seabream flesh quality. Two groups of 32 gilthead seabream (mean body weight: 536 ± 96 g) were subjected to different pre-slaughter harvesting stress: profound anesthesia (PA, low stress condition) and net crowding (NC, high stress condition). Subsequently, fish from both harvesting stress conditions were slaughtered using either ice–salt water slurry (IW), to simulate commercial practices, or a lethal dose of anesthesia (LA), to isolate the effect of the pre-slaughter treatments. Rigor mortis was measured during the first 72 h after death, and muscle from the dorsal area was collected at regular intervals (0, 2, 6 and 48 h after death) during this period, for subsequent biochemical analysis of pH, TBARS, sulfated glycosaminoglycans and hydroxyproline content. Texture in raw and cooked fillets was measured instrumentally, using an Instron texture analyzer. The onset of rigor mortis was earliest for the NC–IW treatment, reaching highest values 2 h after death, while fish from the PA–IW treatment attained highest rigor scores 21 h after death. Resolution of rigor mortis started 3 and 32 h after death in fish subjected to NC and PA, respectively. Both harvesting stress and slaughter method had a significant effect (P b 0.05) on muscle pH, with highest values found in fish subjected to PA conditions, and in those slaughtered by lethal anesthesia. Muscle TBARS were significantly affected by harvesting stress. Collagen and sulfated glycosaminoglycan content of the samples decreased markedly through storage time, but were not significantly affected by harvesting stress conditions or slaughter method. In fish slaughtered in ice–salt water slurry, fillet hardness ranged between 5.0 ± 2.1 and 5.7 ± 1.8 N in raw fillets, and between 4.9 ± 0.9 and 5.6 ± 0.9 N in cooked fillets, but no significant differences among treatments were found. The use of zero withdrawal anesthetic improved muscle pH and delayed rigor mortis, although harvesting and slaughter stress had no major effect on muscle structure of gilthead seabream. © 2010 Elsevier B.V. All rights reserved. 1. Introduction One of the major concerns of the consumer of aquacultured products is quality, namely its safety, freshness and health value. Also, both consumers and producers are becoming increasingly aware of fish welfare issues (Poli et al., 2005; Van de Vis et al., 2003). It is interesting to note that quality and welfare issues are intrinsically linked, as there is evidence that inadequate fish husbandry results in lower meat quality (Ribas et al., 2007; Robb et al., 2000). Under farming conditions, fish quality is known to be influenced by extrinsic factors such as feeding strategies and diet composition (Izquierdo et al., 2005; Morris et al., 2005; Mourente and Bell, 2006), as well as pre- and post-slaughter handling procedures (Ozogul et al., 2007; Robb et al., 2000; Skjervold et al., 1999), which impact on the composition, structure and metabolic characteristics of the muscle tissue (Grigorakis and Alexis, 2005; Johnston, 1999; Mourente and Bell, 2006). Although the biochemical and physiological processes that occur post-mortem are fairly well known (Poli et al., 2005; Verrez- Bagnis et al., 2002), several studies suggest the need to correlate changes in pre- and post-slaughter procedures and consequent biochemical and physiological changes to organoleptic characteristics of fish, namely texture, flavour and aroma (Ayala et al., 2005; Grigorakis and Alexis, 2005; Periago et al., 2005). Fish handling prior to slaughter (exposure to air, high density during crowding and a long crowding period) and slaughtering method have been identified as critical hazards to fish welfare (EFSA, 2009) in gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax). A wide variety of slaughtering practices exists in aquaculture, each one of them inducing a broad range of stress levels. Also, commercially available slaughter methods, such as asphyxia in air and ice–salt water slurry, involve a prolonged period of consciousness prior to death (Ashley, 2007; EFSA, 2009; Poli et al., 2005; Van de Vis et al., 2003). Several studies on the subject, mostly in salmonids, tend to show that fish exposed to high handling stress at slaughter display softer Aquaculture 305 (2010) 66–72 ⁎ Corresponding author. E-mail address: ematos@ualg.pt (E. Matos). 0044-8486/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2010.04.020 Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aqua-online