Reducing Microbial Contamination Including Some Pathogens in Minced Beef by Irradiation

The aim of our experiments was to reduce some pathogenic and spoilage microorganisms in aerobically packed minced beef by ionizing radiation. The microbial contamination of beef is relatively low. Application of the Good Manufacturing and Hygienic Practice improves the quality and safety of foods but the storability of minced meat at 4% is very short. The growth of microorganisms including that of the very few pathogens too, is quite fast, therefore this type of meat product may represent potential health hazard. Ionizing radiation is one of the possible treatments for decontamination of meat, it is a physical method. Radiation can inactivate microorganisms in foods without significant alteration of their sensorial acceptability. We studied the effect of irradiation in aerobically-packed minced beef with natural and high contamination (10⁴ and 10⁸ g⁻¹ initial cell count) and inoculated with a cocktail suspension of E.coli, S.aureus and L.monocytogenes (each strain 10⁶–10⁷ CFU cm⁻³). Polyethylene foil packed samples were irradiated with 1, 2 and 3 kGy and stored at 4°C for 10 days. The survival curves and the D₁₀ values of inoculum-strains and natural microflora, as well as the shelf life values were determined. We concluded from the data that a dose of 2 kGy extends the shelf-life 3-5-times and the inoculated pathogenic strains can be reduced by 7, 5 and 5 log cycles, respectively. During 10 days of chilled storage at 4°C, the reduced viable cell counts did not change except that of L.monocytogenes, which started to grow after 3 days.