The effect of gamma irradiation and frozen storage time on the quality of tiger shrimps (Penaeus Monodon)

The effect of gamma irradiation (0, 1, 2, 4 and kGy) and frozen storage (-100C) of 6 months on the microbiological, chemical and organoleptic qualities of whole (WSI) and peeled (PS2) tiger shrimps (Peneaus monodon) were studied. The qualities of the products were compared with blanched shrimps (PSI) ordinarily prepared at a factory. The irradiation dose up to 6 kGy reduced the total bacterial count (TBC) by at least 3 log cycles with D value = 2.13 kGy. The survival of pathogenic microbes was effectively retarded. Although blanching eliminated the pathogenic microbes, the TBC of PSI before storage is still in a range of 105/g. There was an increase in TBC of 1-2 log cycles during storage in all samples. Peeling effectively reduced the TBC of the shrimps. Gamma irradiation and shorter period of storage time did not influence the pH and protein contents of the products. Indole production was slowed down by irradiation at 1-4 kGy, which is comparable to blanching treatment. Organoleptic qualities (colour, ordour and texture) of the products were not effected by irradiation and storage time except for samples irradiated at 6 kGy in which the pink colour faded. There was no significant difference in the organoleptic qualities of irradiated (2 kGy) samples as compared to blanched products. (author)