Development of a simple screening test to detect and determine the microbiological quality of irradiated foods

The direct epifluorescent filter technique/aerobic plate count (DEFT/APC) method is a recognised technique for the screening of irradiated foods. When the APC of an irradiated sample is compared with the DEFT count on the same sample, the APC is found to be considerably lower than that obtained by the DEFT, thus indicating that the sample could have been irradiated. Since the development of the DEFT/APC screening method, the technique has been tested with a limited range of food products. Previous work has indicated that the storage of irradiated foods can, in certain circumstances, allow microorganisms to grow, and thus compromise the ability of the DEFT/APC method to discriminate between irradiated and unirradiated samples. In some cases the method has been shown to give high DEFT count and low APC with food samples that have not been irradiated. Potentially, foods which have undergone a food processing treatment could give a high DEFT count compared to an APC and be erroneously identified as having been irradiated. The work reported here is aimed at analysing a range of irradiated samples (meat, poultry, fish, seafood, herbs and spices), stored under different conditions, to evaluate the applicability of the screening method for use with such products. The effects of other food processes on the DEFT/APC results were also investigated. (UK)