Detection of irradiated deep-frozen foodstuffs by comparison of DEFT and APC counts

The suitability of a microbiological method based on the comparison of an aerobic plate count (APC) with a count obtained with the direct epifluorescent filter technique (DEFT) for the detection of irradiation of deep-frozen foodstuffs was evaluated. The study was carried out on parsley, mechanically deboned poultry meat (MDPM) and liquid egg white. The foodstuffs were stored at—18°C and examined after storage for 0, 4 and 12 months.
The results showed that this method is discriminating during the whole storage period. Nevertheless, it has been observed that for non-irradiated liquid egg white the difference between DEFT and APC tends to increase with the time of storage. This phenomenon which did not limit the interest of the test, was not observed for the other products tested.