Clostridium botulinum spores and toxin in mascarpone cheese and other milkproducts

A total of 1,017 mascarpone cheese samples, collected at retail, were analy zed for Clostridium botulinum spores and toxin, aerobic mesophilic spore co unts, as well as pH, a(w) (water activity), and Eh (oxidation-reduction pot ential). In addition 260 samples from other dairy products were also analyz ed for spores and botulinum toxin. Experiments were carried out on naturall y and artificially contaminated mascarpone to investigate the influence of different temperature conditions on toxin production by C. botulinum. Three hundred and thirty-one samples (32.5%) of mascarpone were positive for bot ulinal spores, and 7 (0.8%) of the 878 samples produced at the plant involv ed in an outbreak of foodborne botulism also contained toxin type A. The ch emical-physical parameters (pH, a(w), Eh) of all samples were compatible wi th C. botulinum growth and toxinogenesis. Of the other milk products, 2.7% were positive for C. botulinum spores. Growth and toxin formation occurred in naturally and experimentally contaminated mascarpone samples after 3 and 4 days of incubation at 28 degrees C, respectively.