Texture profile analyses in tench ( Tinca tinca L., 1758) from extensive and intensive culture

The aim of the study was to evaluate the differences in texture profile of tench flesh. Texture profile analyses in tench, two years old, (Tinca tinca L.) was investigated using instrumental texture profile method, focused on hardness, springiness, cohesiveness, gumminess and chewiness performed with Texture Analyser TA.XTPlus. One group of fish was raised extensively in natural earth pond conditions; the other group was intensively cultured in a recirculation system, feeding on a commercial diet for 7 months. Twelve fish (6 females and 6 males) from each group were used for analyses. Flesh of male tench in both groups was harder, more gummy and chewy, compared to female. Springiness was lower in tench male from intensive culture and cohesiveness lower in females from both groups. The result of texture analysis in the extensive culture group was 16.01 N for hardness and 0.72, 0.66, 10.73 and 7.69 for springiness, cohesiveness, gumminess and chewiness, respectively. In the intensive culture group it was 15.16 N for hardness and 0.59, 0.52, 8.06 and 4.96 for springiness, cohesiveness, gumminess and chewiness, respectively. The results proved that the flesh of fish raised extensively is harder, springier, more cohesive and more gummy, and thus more appealing to consumers. This is the first similar study of texture profile of tench. Cohesiveness, hardness, muscle, springiness, flesh quality Textural quality is primarily a sensory attribute that is quantified in foods by several instrumental methods. According to Bourne and Szczesniak (2003) and Cardoso et al. (2009), texture profile analysis (TPA) is a resulting force-generated time curve used to quantify a number of textural properties that correlate well with the results from sensory evaluation. Post mortem textural changes are caused directly or indirectly by physicochemical changes in myofibrillar proteins (Křižek et al. 2011) and changes in extracellular structure such as the loss of fibre compaction and the increase of extracellular space between fibres (Ingolfsdottir 1997; Popelka et al. 2012). Muscle texture is also affected by other variables such as fish rearing, seasonality and methods of capture, handling and processing (Johnston et al. 2000; Periago et al. 2005). The main quality indicators for fresh fish are fat, colour, texture and freshness. Other indices commonly cited are white stripes (connective tissue), bloodstains, marbling and melanin. Double compression used in the instrumental procedure enables performing TPA as a plot of force-time curves (Rahman 2006). Other terms describing texture are firmness, stiffness and the yield point (Vacha et al. 2007). Many attempts have been made to correlate physical measurements with sensory evaluation of texture (Johansen et al. 1991; Chamberlain et al. 1993). Reproducibility of texture measurements is affected by the sampling technique due to heterogeneity of the fillets (Nesvadba et al. 2004). Therefore, it is difficult to find a representative average sample in fish and measurements of textural properties may depend on the location within the fillet. Some authors recommend raw fish to be tested in the form of a fillet or a part of a fillet (Stejskal et al. 2011). The aim of the ACTA VET. BRNO 2013, 82: 421–425; doi:10.2754/avb201382040421 Address for correspondence: Frantisek Vacha University of South Bohemia Faculty of Fisheries and Protection of Waters, Institute of Aquaculture Husova tř. 458/102, 370 05 Ceske Budějovice, Czech Republic Phone: +420 387 774 649 E-mail: fvacha@frov.jcu.cz http://actavet.vfu.cz/ study was to evaluate the differences in texture profile of tench flesh under two different ways of fish rearing and determine the effect of sex. Materials and Method