Thus, the study suggests no significant effect of gamma treatment (up to 10 kGy) on the structural and mechanical quality of the prawns. The resultant effect of the 20 kG (M. rosenbergii-shear force: 34.2 N, toughness: 0.86 Nm, cohesiveness: 0.27; P. monodon shear force: 37.7 N, toughness: 0.96 Nm, cohesiveness: 0.37) was similar with the control and lower doses. The dose 20 kGy was too high and not feasible for radiation pasteurisation, however, it was assumed that the effects would be enhanced at such higher dose that could help in easier detection and better understanding of the changes induced in the mechanical properties that could be correlated with the structural changes. So, the dose was included only for 0 day of storage and not for other treatments (days of storage) for both the species of prawns. Similar to the present observation, increased firmness of the prawn muscle samples during cold storage had been also reported by Nip and Moy (1988), and might be due to certain chemical changes associated with post mortem decomposition of the samples (Hale & Waters, 1981; Hose & Lightner, 1980).