Survival of Listeria monocytogenes in experimental chorizos

Chorizos-Mexican-style raw-meat sausages-are a concern in California because their production in small ethnic food markets is unregulated. Their formulation may cause them to appear cooked to the consumer, who may eat the raw sausage without prior proper cooking. Bacterial pathogens in such products may cause illness or even death. Survivability of Listeria monocytogenes in chorizos was evaluated under different storage conditions selected on the basis of an initial survey of uninspected chorizos in California. Sausages were formulated to five different initial water activity (a(w)) levels (0.85, 0.90, 0.93, 0.95, 0.97), stored under four conditions (refrigeration, "Ref," 6 to 8 degreesC under convective air circulation; room temperature, "RT," 24 to 26 degreesC under convective air circulation; hood, "Hd," 24 to 26 degreesC under forced air circulation; and incubation, "Inc," 30 to 31 degreesC under convective air circulation), and sampled after 1, 2, 4, and 7 days. The initial pH was 4.8 and remained near 5.0 from day 1 of the sampling period. An inoculated-pack study using a five-strain cocktail of L. monocytogenes was performed twice for each initial a(w). Results indicated that the three lowest initial a, levels (0.85, 0.90, 0.93) and the Hd and Inc storage conditions were more effective (P less than or equal to 0.05) at reducing L. monocytogenes levels in chorizos than the two highest initial a(w), levels (0.95 and 0.97) and the Ref storage condition, irrespective of storage time. These results can provide a scientific basis for guidelines given to uninspected chorizo producers in California and reduce the risk of foodborne illness.