Differentiation of scombroid fish species (tunas, bonitos and mackerels) by isoelectric focusing, titration curve analysis and native polyacrylamide gel electrophoresis of sarcoplasmic proteins.

Differentiation of scombroid fishes was possible by electrophoresis of sarcoplasmic proteins using either isoelectric focusing (IEF), titration curve analysis, or native polyacrylamide gel electrophoresis (PAGE). By IEF with Phast-Gels 3-9 species specific patterns, characterized by a few bands in the cathodal part of the gels, were obtained. This type of gel was also used for titration curve analysis. Here, too, the closely related species Thunnus thynnus and T. albacares gave different protein patterns. Native PAGE, native cathodal electrophoresis in Clean Gel 10% with buffer pH 5.5, proved to be a fast and simple method for differentiation of scombroid fishes. As most of the prominent sarcoplasmic proteins of these species have pIs in the neutral or alkaline pH range, they are positively charged at pH 5.5 and move to the cathode.