Co-incubation of clostridium botulinum with protective cultures

Potential neurotoxin production by psychrotrophic Clostridium botulinum is the significant food safety risk in refrigerated foods of extended durability. Protective cultures (PC), nisin-producing Lactococcus lactis (6.3 × 10⁵ cfu/ml) and pediocin A-producing Pediococcus pentosaceus (107 cfu/ml), were co-incubated with C. botulinum type B (6.2 × 10² cfu/ml) in tryptose, peptone, glucose and yeast extract broth for 31 days at 5 °C, 14 days at 10 °C and for 10 days at 15 °C. Bacterial populations, pH, botulinal toxin and bacteriocin production were measured. At 5 °C, the populations of all species did not change during incubation. At 10 and 15 °C, the PCs increased by 1–3log. At 15 °C, C. botulinum increased by 1.5–3log and was not inhibited by the PCs. At 10 °C, this pathogen was not detected after 10 days of co-incubation. The reduction in C. botulinum population coincided with the nisin level produced by L. lactis exceeding 100 IU/ml, but it was not rapid enough to prevent botulinal toxin formation.