Thermal Inactivation of Listeria monocytogenes on Ready-to-Eat Turkey Breast Meat Products during Postcook In-Package Pasteurization with Hot Water

Abstract

The inactivation of Listeria monocytogenes during postcook in-package pasteurization was evaluated for fully cooked turkey breast meat products (4-kg packages). The products were surface-inoculated to contain 10(7) CFU of L. monocytogenes per cm2 of product surface. The inoculated products were vacuum-packaged in different thicknesses (0.08 to 0.33 mm) of packaging films and treated with hot water at 96 degrees C. After heat treatment, the products were immediately cooled in an ice water bath at 0 degrees C. The relationship between heating time and product surface temperature was determined for different thicknesses of packaging films. The effectiveness of heat treatment for inactivating the pathogen was affected by product surface roughness. About 50 min of heating time was needed to achieve a thermal kill of 7 log10 CFU/cm2 on products with surface roughness up to 15 mm in depth. The cooling time needed after a heat treatment increased with an increasing endpoint temperature of the heated product and the heat penetration depth reached in the product. The cooling time needed to cool the product from 71 degrees C to 4 degrees C was about 2.5-fold the heating time.

Effect of a post-packaging pasteurization process on inactivation of a Listeria innocua surrogate in meat products

“…The initial numbers of L. innocua were decreased in a similar pattern on sausage and ham samples during the preparation time. Reductions in the preparation time were observed with an increasing temperature over 60 o C. The numbers of L. innocua on the surfaces of sausage samples were reduced more than 7 log, showing negative in enrichment cultures, when the process temperature reached 70 o C. However, surface-inoculated L. innocua on ham was not completely inactivated during post-packaging pasteurization, perhaps due to imperfections on the ham surface (netting marks, wrinkles, and tears) and temperature migration from cold spots to the surface (21,22). No significant (p>0.05) difference was observed between counts on selective agar (MOX) and on recovery agar (TSA overlaid with MOX), indicating that L. innocua cells were inactivated during post-packaging pasteurization.…”

A Predictive Model for the Inactivation of Listeria innocua in Cooked Poultry Products during Postpackage Pasteurization

“…The entire content in the stomacher bag was stomached for 2 min with a Stomacher 400 (Seward Medical, Ltd.). The wash fluid was serially diluted (1:10), and a 0.1-ml portion of the appropriate dilution was plated in duplicate onto modified Oxford medium (MOX; Merck, Darmstadt, Germany) overlaid with tryptic soy agar (TSA; Difco, BD) (MOX-TSA) to allow resuscitation and enumeration of heatinjured cells (25). Plates were counted after incubation at 37uC for 48 h, returned to the incubator, and recounted the next day until colonies did not increase further.…”

“…However, even with the most rigorous hygienic operation, fully cooked poultry products might still be exposed to recontamination during subsequent handling and packaging procedures (18,23). To reduce or eliminate the contamination associated with L. monocytogenes, attention has been turned toward postpackage pasteurization procedures (22,24,25). However, most of the previous research focused on skinless and boneless poultry products; there have been relatively few investigations to evaluate hot water inactivation of Listeria in bone-in, skin-on RTE products such as chicken drumettes, which might have different thermal properties from the boneless skinless chicken products.…”

The use of irradiation in processed meat products

“…In-package thermal pasteurization process is generally effective in reducing or eliminating contaminated L. monocytogenes cells in low fat turkey bologna (McCormick et al, 2003), but product shrinkage and drip loss during the post-package thermal pasteurization process can cause quality issues in post-package products. The effectiveness of in-package pasteurization in inactivating pathogenic organisms depends on package size (Murphy et al, 2003a), packaging materials used, processing temperature and time, pH characteristics, product surface characteristics (Murphy et al, 2003b) and L. monocytogenes strains present (Lemaire et al, 1989).…”