Co-incubation of Clostridium botulinum with protective cultures

Abstract

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 × 10 5 cfu/ml) and pediocin A-producing Pediococcus pentosaceus (10 7 cfu/ml), were co-incubated with C. botulinum type B (6.2 × 10 2 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.