COMBINING HEAT-TREATMENT AND SUBSEQUENT INCUBATION-TEMPERATURE TO PREVENT GROWTH FROM SPORES OF NONPROTEOLYTIC CLOSTRIDIUM-BOTULINUM

Refrigerated processed foods of extended durability rely on a mild hea t treatment combined with refrigerated storage to ensure microbiologic al safety and quality, The principal microbiological safety risk in fo ods of this type is non-proteolytic Clostridium botulinum. In this art icle the combined effect of mild heat treatment and refrigerated stora ge on the time to growth and probability of growth from spores of non- proteolytic Cl. botulinum is described. Spores of non-proteolytic Cl. botulinum (two strains each of type B, E and F) were heated at 90 degr ees C for between 0 and 60 min and subsequently incubated at 5 degrees , 10 degrees or 30 degrees C in PYGS broth in the presence or absence of lysozyme. The number of spores that resulted in turbidity depended on the combination of heat treatment, incubation time and incubation t emperature they received. Heating at 90 degrees C for 1 or more min en sured a 10(6) reduction when spores were subsequently incubated at 5 d egrees C for up to 23 weeks. Heating at 90 degrees C for 60 min ensure d a 10(6) reduction over 23 weeks when subsequent incubation was at 10 degrees C in the presence of added lysozyme. The same treatment did n ot reduce the spore population by 10(6) when subsequent incubation was at 30 degrees C.