Identification of Fish Species after Cooking by SDS−PAGE and Urea IEF:  A Collaborative Study

Abstract

A collaborative study, to validate the use of SDS-PAGE and urea IEF, for the identification of fish species after cooking has been performed by nine laboratories. By following optimized standard operation procedures, 10 commercially important species (Atlantic salmon, sea trout, rainbow trout, turbot, Alaska pollock, pollack, pink salmon, Arctic char, chum salmon, and New Zealand hake) had to be identified by comparison with 22 reference samples. Some differences in the recoveries of proteins from cooked fish flesh were noted between the urea and the SDS extraction procedures used. Generally, the urea extraction procedure appears to be less efficient than the SDS extraction for protein solubilization. Except for some species belonging to the Salmonidae family (Salmo, Oncorhynchus), both of the analytical techniques tested (urea IEF, SDS-PAGE) enabled identification of the species of the samples to be established. With urea IEF, two laboratories could not differentiate Salmo salar from Salmo trutta. The same difficulties were noted for differentiation between Oncorhynchus gorbuscha and Oncorhynchus keta samples. With SDS-PAGE, three laboratories had some difficulties in identifying the S. trutta samples. However, in the contrast with the previous technique, SDS-PAGE allows the characterization of most of the Oncorhynchus species tested. Only Oncorhynchus mykiss was not clearly recognized by one laboratory. Therefore, SDS-PAGE (Excel gel homogeneous 15%) appears to be better for the identification, after cooking, of fish such as the tuna and salmon species which are characterized by neutral and basic protein bands, and urea IEF (CleanGel) is better for the gadoid species, which are characterized by acid protein bands (parvalbumins). Nevertheless, in contentious cases it is preferable to use both analytical methods.

Molecular identification methods of fish species: reassessment and possible applications

“…Besides, because most proteins are heat labile, they become irreversibly denatured when the flesh is cooked (e.g., in food products) and thus can no longer be examined by techniques suitable for their native states. It is, however, possible to solubilise some heat-denatured proteins in denaturing solvents such as 2% sodium dodecylsulphate or 8 M urea to obtain species-specific profiles on electrophoresis (Etienne et al 2000). Antibodies used in immunoassay systems are also normally raised against undenatured proteins and thus useful for fresh samples only; even though some antibodies were developed against thermostable proteins (Ansfield et al 2000).…”

Fish Allergen Detection

“…Analytical methods for the detection of fish in foods are necessary to monitor hygiene practices and to ensure compliance with legislation (Poms et al, 2004). A number of different techniques for the identification of parvalbumin by chromatography, isoelectric focussing, or mass spectrometry have been developed (Ross et al, 1998;Etienne et al, 2000;Carrera et al, 2006).…”

Origin Determination and Differentiation of Gelatin Species of Bovine, Porcine, and Piscine through Analytical Methods

“…PAGE is preferred because it is easy, simple, and fast. It has been used in milk, cheese (Mayer, 2005), raw (Chen et al, 2010b) and cooked fish (Etienne et al, 2000). Azira et al (2014) have studied with sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) for determination of bovine and porcine gelatin species with respect to their molecular weight.…”