Botulism Risk Prevention with Protective Cultures in Extended Shelf-Life, Cook-Chill Meals

Selected Commercial hot-fill meals were challenged with nonproteolytic Clostridium botulinum and protective cultures (PCs), Lactococcus lactis (7.0 X 10(7) cfu/g) or pediococcus pentosaceus (6.0 X 10(8) cfu/g) or their mix. The PCswere enumerated on M17, De Man, Rogosa, Sharpe (MRS) and maltose tryotic soy agar, C. botulinum, on salicin tryptic soy agar, and background microflora, on plate count agar. Botulinal toxin was detected by the immunoassay and bacteriocins, by well diffusion assay. In the products supporting active growth of C. botulinum the co-incubation with the PCs singularly and as a mixture reduced C. botulinum populations to undetectable levels and prevented toxigenesis, their PH was reduced to 4.2-5.0. The use of a mixture did not produce a more rapid inhibition than the singular PC. The bactericidal effect on C. botulinum populations was associated with bacteriocin production (100-400 IU/g) if nisin and 35 AU/g of pediocin A) by the PCs. Static C. botulinum populations in products with low PH and vegetable-based products were unaffected by the PCs. This confirmed the bacteriostatic effect of low PH and demonstrated that ungerminated C. botulinum spores were resistant to inhibition.