Effect of Headspace CO₂ Concentration on Toxin Production by Clostridium botulinum in MAP, Irradiated Fresh Pork

The effects of five initial levels of CO₂ (15, 30, 45, 60, and 75%) and three irradiation doses (0, 0.5, and 1.0 kGy) on toxin production by Clostridium botulinum in inoculated fresh pork were studied using factorial design experiments. Headspace CO₂ levels increased in all samples during storage at 15°C. In most treatments, spoilage preceded toxigenesis. Toxin production occurred faster in samples initially packaged with 15 to 30% of CO₂ while higher levels of CO₂ (45-75%) delayed toxin production. Low-dose irradiation delayed toxin production at all levels of CO₂ in the package headspace. Contrary to expectations, including a CO₂ absorbent in the package enhanced toxin production by C. botulinum . This was attributed to production of H₂ by the CO₂ absorbent, possibly resulting in a decrease in the oxido-reduction potential of the meat.