No abstract

Supplemental cereal feeding (maize, wheat and triticale compared with a control group with natural food only) and its effect on fatty acid (FA) expression in the flesh during long-lasting storage of common carp (Cyprinus carpio) was investigated. The fish were cultured in earthen ponds in the Trebon region (Czech Republic). The content of fatty acid was investigated in the flesh of carp during 8 months oflong-lasting storage without additional feeding. Sixty common carp in their third year of life were used for the analyses. The weight of the fish (marketable fish) ranged from 1,358 g to 2,221 g. Polyunsaturated fatty acid (PUFA, n-3) content and composition in fish flesh were determined by gas chromatography (VARIAN 3300). Supplemental cereals caused lower levels of PUFAs and n-3 PUFAs in fish fat. The content of these fatty acids did not decrease, even during 8 months of fish storage. The average percentage of PUFAs in total fat from edible parts was: for maize 13.7% ± 1.58%, for wheat 11.6% ± 1.17% and for triticale 10.7% ± 1.00%. The percentage of n-3 PUFA for maize was 2.5% ± 0.36%, for wheat 3.38% ± 0.44% and for triticale 3.1% ± 0.39%.

The aim of the work was to measure and confirm changes in the qualitative properties of frozen carp flesh (Cyprinus carpio L.) during 84 days of storage at -20 • C, using instrumental texture profile analysis focused on hardness, cohesiveness, and springiness. Hardness in fresh fish was 2.908 N, in fish stored 28 days 1.238 N, after 56 days 0.505 N, and after 84 days 0.491 N. Cohesiveness (dimensionless unit) in fresh fish was 0.838, after 28 days 0.740, after 56 days 0.720, and after 84 days 0.712. Springiness (dimensionless unit) in fresh fish was 0.682, after 28 days 0.625, after 56 days 0.577, and at 84 days of storage 0.534. The texture profile analysis effect was determined by several regression and linear models. It is possible to calculate a certain time period in which changes develop up to the level of 50% of deterioration-in hardness 17.5 days and in cohesiveness 12.9 days, as this was proven to a defined significance level (P > 0.01). Only changes in springiness showed a linear regression in the level of 0.002 (rounded) for each day. Studies showed that the intensity of the most important changes in instrumental textural properties occurred during the initial 56 days after freezing and after up to 84 days of storage the changes continued at a lesser rate.

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 qualityTextural 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 (Křížek et al. 2011) and changes in extracellular structure such as the loss of fibre compaction and the increase of extracellular space between fibres (Ingolfsdóttir 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 (Vácha 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 propert...

No abstract