A standardized method of identification of raw and heat-processed fish by urea isoelectric focusing: A collaborative study

A urea-isoelectric focusing (urea-IEF) method of identifying fish species i n processed fishery products was investigated as an interlaboratory collabo rative study. The technique was optimized with respect to (i) protein extra ction conditions, composition of the extraction solution (urea and SDS solu tions), determination of protein concentrations of the fish extracts (five tested methods); (ii) nature of gel (with carrier ampholytes acid Immobilin es), conditions of rehydration of commercial dry gels, urea concentration; (iii) staining conditions, Coomassie blue and silver staining. The results of various experiments were compared to select the most appropriate methodo logy, with respect to the discrimination power of differentiating species w ith the minimal influence of heat processing, reproducibility, speed, and e ase of application. The method recommended meets the requirements of food c ontrol and customs laboratories.