Effect of superheated steam on the inactivation of Listeria innocua surface-inoculated onto chicken skin

This study investigated the effectiveness of superheated steam in the decontamination of poultry skin. The steam jet was at a temperature of 160 degrees C and can be superheated up to 500 degrees C, leading to an impinging jet temperature of 400-450 degrees C. Disks of poultry skin were surface-inoculated with about 10(7) CFU/cm(2) Listeria innocua (CLIP 20595) and treated with either superheated or non-superheated steam for up to 60 s. Surface temperature was carefully measured throughout the treatment, and results were analyzed using a previously developed transfer model. The overall pattern of L. innocua inactivation was displaying an initial pattern of rapid decline followed by much slower decline thereafter. Superheated steam was clearly more bacterial inactivation-efficient than non-superheated steam, leading to an average reduction of more than 5log(10) CFU/cm(2) after 30 s of treatment. Large variations in surviving cell numbers were observed between replicates which cannot be explained by variations in the heat treatment. (c) 2007 Elsevier Ltd. All rights reserved.