Enumeration of Hydrogen Sulfide-Producing Bacteria from Anaerobically Packaged Pork

The influence of medium composition, pH, incubation time and gaseous atmosphere during incubation on enumeration of H₂S-producing bacteria from anaerobically packaged pork was determined. Samples of anaerobically packaged pork were plated and H₂S-producing bacteria isolated. Stock cultures of these isolates were prepared, diluted and pour-plated with Lead Acetate Agar (LAA) containing various concentrations of cysteine (0.001 to 0.005%) at different pH values (5.0 to 8.0). The inoculated plates were incubated at 21°C for various periods (3 to 6 d) under different gaseous atmospheres (N₂, CO₂ or mixtures of both). The conditions resulting in optimized recovery and enumeration of H₂S-producing bacteria from anaerobically packaged pork consisted of pour-plating the isolates with LAA to which 0.003 to 0.005% cysteine was added and pH adjusted to 7.5-8.0 plus incubation in an atmosphere of 5%CO₂-95%N₂ for 5 to 6 d at 21°C.