Thermal inactivation kinetics study of Listeria monocytogenes during sous vide cooking

Abstract

ObjectiveTo explore the effect of sous-vide on the thermal inactivation rules of Listeria monocytogenes in different matrix， the thermal inactivation of Listeria monocytogenes in different substrates at different temperatures was studied.MethodsFive lyophiliZed L. monocytogenes strains were inoculated into saline， MH broth， vacuum packed lean pork and streaky pork. The survival rates were evaluated at 55， 60， and 63 ℃. The decimal reduction time （D-value） and temperature dependence （Z-value） were determined for each strain in each matrix.ResultsThe D value and Z value of Listeria monocytogenes in pork were higher than those in normal saline and MH broth， the difference was statistically significant （P<0.01）， and the D value in pork belly was higher than that in lean meat， the difference was statistically significant （P<0.01）.At 55 ℃， the time required for artificially contaminated Listeria monocytogenes to decrease 6lg in sous-vide packed lean pork and streaky pork matrix was about 3~4 h， while the time was 30-40 and 10-20 min at 60 and 63 ℃， respectively.ConclusionUnder the conditions of sous-vide， food matrix and genetic basis of strains have significant effects on the killing effect of Listeria monocytogenes. When cooking at below 60 ℃， the cooking time should be extended to ensure the microbial safety of cooked food.

Keywords

• sous-vide
• listeria monocytogenes
• pork
• thermal inactivation