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The present study demonstrates the siderophore production of two strains of Pseudomonas fluorescens and two of Ps. chlororaphis. The antimicrobial activities of these strains were studied against Salmonella typhimurium, Staphylococcus aureus, Fusarium culmorum, F. oxysporum and Aspergillus niger. Despite equal siderophore activities with various Pseudomonas spp. as measured by the chrome azurol S assay, the study shows how siderophore activity does not correlate with the antibacterial activity against food pathogens or with the antimould activity against pathogenic moulds. Furthermore, the results illustrate how siderophores are able to act both as growth inhibitors and stimulators.

A microbiological screening method for the detection of irradiation of frozen poultry meat was developed on the basis of the combined use of total cell count by the direct epifluorescent filter technique (DEFT) and viable cell count by the aerobic plate count method (APC). Samples of ground, deboned poultry leg were irradiated or not with dose levels of 3, 5 and 7 kGy using an electron beam accelerator. All samples were frozen before the irradiation treatment. The average values of the differences between DEFT and APC counts in control samples and those irradiated with doses of 3, 5 and 7 kGy were 1.14 log units for control samples, and 3.16, 3.68 and 3.79 log units for the irradiated samples. A difference of at least 2 log units can therefore be considered as a limit value indicating probable irradiation treatment necessitating further investigations.

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