A nitrogen factor for European pike-perch (Sander lucioperca), northern pike (Esox lucius), and sheatfish (Silurus glanis) fillets

Abstract

Measures for consumer protection against food adulteration and misleading labeling are integrated into EU legislation, including methods for detection of misleading practices. Verification of meat content is available for marine products but not for freshwater fish because of the lack of standard nitrogen factors. The aim of this study was to establish nitrogen factors for European pike-perch Sander lucioperca (Linnaeus, 1758), northern pike Esox lucius Linnaeus, 1758, and sheatfish Silurus glanis Linnaeus, 1758. The study involved analysis of 808 fillet samples obtained in spring (March–April) and autumn (October–November) harvest seasons, 2018–2019, from seven Czech Republic fish rearing facilities. Samples with and without skin were analyzed for nitrogen content, dry matter, protein, ash, and fat according to established ISO methods. The recommended nitrogen factor for European pike-perch with the skin is 3.28 ± 0.09 and without the skin is 3.21 ± 0.09; for northern pike with the skin is 3.18 ± 0.09 and without skin is 3.15 ± 0.09; and for sheatfish with skin is 2.73 ± 0.13 and without skin is 2.75 ± 0.12. The established nitrogen factors will enable analysis of meat content to ensure that consumers are purchasing correctly described and labeled fish products.

Quantitative and Qualitative Assessment of European Catfish (Silurus glanis) Flesh

“…In our study, flash moisture ranged between 77.68 ± 0.45% and 79.45 ± 0.37% in relation to feeding type. Close values for the same trait were reported by other authors [15,16,55].…”

“…There were also observed fluctuations due to the activity of alteration microorganisms as well as oxidative processes that appeared on the sample surface [64,69,72]. Moreover, for the case of lipids, the literature indicates close values to those obtained in the current study [15,16]. Linhartova et al (2018) [73] indicated catfish flesh lipids contents of 4.13% in intensive rearing system samples and 2.97% in the semi-intensive system.…”

“…During the six evaluation sessions for this constituent, no statistical significance occurred between groups. In a study on the chemical composition of flesh gathered from aquaculture featuring catfishes with live weights close to the aquaculture catfishes analysed in the current study (1813.51 g), Honzlova et al (2021) [16] mentioned comparable values for protein content (16.35-18.12%).…”

“…European catfish is one of the species leaving strong impressions in consumers' sensory memory, and consumers have benefitted from an increasing trend among farmers throughout the last years. The flesh is highly appreciated by consumers due to its average content of lipids and high content of proteins but also due to its remarkable sensory traits, especially developed after some special cooking processes [15,16].…”

Nitrogen factors for rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis) fillets

“…Suitable methods for determining the meat content in freshwater fish products are absent. The reason for this state is the absence of species-specific nitrogen content (nitrogen factor) for freshwater fish, except for the Nile mouthbreeder (Oreochromis niloticus) (CA 2004), common carp (Cyprinus carpio) (Honzlova et al 2021a), and European pikeperch (Sander lucioperca), northern pike (Esox lucius), and wels catfish (Silurus glanis) (Honzlova et al 2021b).…”