Protein changes after irradiation and ice storage of horse mackerel (Trachurus trachurus)

The effect of gamma-radiation (1, 5 and 10 kGy) and post-irradiation ice storage on horse mackerel (Trachurus trachurus) muscle proteins was studied using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and urea CleanGel isoelectric focusing (IEF). The irradiation doses of 1 up to 10 kGy used seem to have no significant effect on the proteins of this species. SDS-PAGE showed few changes of the number of bands present. Most noticeable about the electrophoretic patterns were: (i) the gradual decrease in the intensity of some protein bands, particularly that of the MHC and (ii) the absence of any increase in bands associated with low molecular weight fragments with the increase in the irradiation dose. Irradiated samples presented a new high molecular weight (HMW) band (220 kDa) with an intensity independent of the irradiation level, that might be used as a marker. The number of bands in urea CleanGel IEF did not change in both unirradiated and irradiated samples. In the basic section, where major myofibrillar proteins are present, bands' intensity increased with irradiation dosage. At the end of ice storage period, more intense protein bands were detected in the lots irradiated at higher dosages. Results underline the possibility of irradiation treatment up to 10 kGy, if needed for extension of horse mackerel shelf life and safety.