Antimicrobial Effect of Cetylpyridinium Chloride on Listeria monocytogenes V7 Growth on the Surface of Raw and Cooked Retail Shrimp

ABSTRACT:  This study examined the concentration of cetylpyridinium chloride (CPC) required to control Listeria monocytogenes on the surfaces of raw and cooked, peeled and shell-on shrimp. Shrimp (5 g) were inoculated by immersion into a 24 h culture of L. monocytogenes (decimally diluted in PBS) for 1 min, followed by air drying for 1 h, to yield between 6.2 log and 7.0 log CFU/g. The raw and cooked shell-on samples had higher L. monocytogenes counts than the peeled shrimp groups after this inoculation process. The shrimp samples were treated by soaking in different concentrations of CPC (0.05, 0.1, 0.2, 0.4, 0.6, 0.8, or 1.0%) solutions for 1 min, with or without a water rinse for 1 min. The samples were bagged, stored at 4 °C for 24 h, and then plated onto Oxford selective media for determination of log CFU/g. All CPC treatments (0.05% to 1.0%) that were followed by a water rinse reduced L. monocytogenes counts on cooked shrimp by about 2.5 log CFU/g. Conversely, treatments not followed by a water rinse reduced L. monocytogenes counts on cooked shrimp by 3 log CFU/g with 0.1, 0.2, or 0.4% CPC, 5 log CFU/g with 0.6% CPC, 6 log CFU/g with 0.8% CPC, and 7.0 log CFU/g with 1.0% CPC. These results indicate that a soaking treatment of CPC has a strong potential to eliminate or reduce L. monocytogenes on the surfaces of shrimp.