Evaluation of microbiological safety of shrimp cooked in a microwave oven

The effect of different microwave power levels (240, 400, 560, and 800 W) on the survival of Listeria monocytogenes in inoculated shrimp was investigated. Thermal inactivation rates (D-values) of L monocytogenes were determined using constant temperature water baths to establish the heat resistance of L. monocytogenes in shrimp. Shrimp were inoculated with approximately 5 x 10 ⁵ CFU/g of a five-strain mixture of L. monocytogenes. One hundred grams of shrimp were cooked in the microwave oven at different power levels using cooking times predicted by a mathematical model as well as 20% longer times than those obtained from the model. No viable L. monocytogenes were detected in uninoculated shrimp after microwave cooking, but at least one replication of inoculated shrimp tested positive for the presence of Listeria. No viable L monocytogenes were detected in shrimp cooked at 120% of predicted times.