An organic acid solution of 2% acetic, 1 % lactic, 0.1% propionic, and 0.1% benzoic acids was combined with steam surface pasteurization to treat frankfurters during vacuum packaging to eliminate potential postcook contamination with Listeria monocytogenes. The thermal lethality of L. monocytogenes from steam was evaluated at an inoculation concentration of 1 to 6 log CFU/cm(2). About 3-log reductions of L. monocytogenes were achieved when frankfurters were treated by steam for 1.5 s. Combining organic acid treatment with steam pasteurization further inhibited the growth of surviving L monocytogenes cells for 19 and 14 weeks when the packaged frankfurters were stored at 4 and 7 degrees C, respectively. The results from this study provide meat processors with useful information for controlling L. monocytogenes on ready-to-eat meats.

Surface pasteurization by applying steam or hot water before or after packaging of processed foods may be used to eliminate pathogens such as Listeria monocytogenes from ready-to-eat meat and poultry products. Surface pasteurization treatment with a mixture of pressurized steam and hot water was integrated into a continuous vacuum-packaging system to reduce L. monocytogenes from fully cooked franks. The franks (2.54 cm diameter by 15.24 cm length) were surface inoculated to contain up to 6 log CFU/cm2 L. monocytogenes. The inoculated franks were treated at 121 degrees C for 1.5 s in an arrangement of six franks per packaging chamber followed by immediate vacuum sealing of the top films of food packages in the same unit. A 3-log CFU/cm2 reduction of L. monocytogenes on fully cooked franks was obtained using the integrated pasteurization-packaging system. The pasteurization depth was 1.27 mm below the surfaces of the franks. This process provides a commercially applicable means of ensuring food safety by effectively eradicating L. monocytogenes from ready-to-eat meat and poultry products at the very last possible step of food packaging before reaching retail consumers.

During processing of ready-to-eat (RTE) deli meats, any secondary processing procedures such as peeling and cutting introduce the distinct possibility of cross-contamination between equipment, personnel, and food. To eliminate or reduce pathogens such as Listeria monocytogenes and ensure food safety, RTE deli meats can be pasteurized prior to or after packaging. In this study, ambient steam in-package pasteurization was compared with pressurized steam prepackaging pasteurization to reduce L. monocytogenes from fully cooked RTE bologna. The bologna (14cm diameter×1.5cm thickness) samples were surface-inoculated to contain about 8log10 of L. monocytogenes. To achieve 2 log reductions for L. monocytogenes, the bologna samples needed to be treated for about 10s in pressurized steam at 131°C or for about 2.5min in ambient steam at 100°C. The pasteurization time using pressurized steam treatment was about 75–90% shorter than using ambient steam treatment. Pressurized steam treatment may be integrated into a vacuum packaging unit to effectively eradicate L. monocytogenes from RTE meats just prior to sealing the retail packages to further reduce the treatment time, avoid post-treatment recontaminations by pathogens, and improve food safety without detrimentally affecting meat quality.

ABSTRACT: This study was to evaluate the effectiveness of steam or steam in combination with an antimicrobial agent to control Listeria monocytogenes on ready-to-eat (RTE) franks. The franks were surface-inoculated to contain 6 or 3 log10(colony-forming units [CFU])/cm2 of L. monocytogenes and treated with steam or steam in combination with an antimicrobial agent, immediately followed by vacuum-sealing the top films of frank packages (6 franks per package in a single layer). Three log (CFU) /cm2 of reductions were achieved at the both inoculation levels for L. monocytogenes on franks. At an inoculation level of 3 logs, no outgrowth of L. monocytogenes was obtained on the treated franks after storing at 4.4°C or 16°C for a combined 47 d. This study provided an alternative approach for controlling L. monocytogenes in packaged franks.

At 55 to 70 degrees C, thermal inactivation D-values for Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes were 19.05 to 0.038, 43.10 to 0.096, and 33.11 to 0.12 min, respectively, in ground turkey and 21.55 to 0.055, 37.04 to 0.066, and 36.90 to 0.063 min, respectively, in ground beef. The z-values were 5.73, 5.54, and 6.13 degrees C, respectively, in ground turkey and 5.43, 5.74, and 6.01 degrees C, respectively, in ground beef. In both ground turkey and beef, significant (P < 0.05) differences were found in the D-values between E. coli O157:H7 and Salmonella or between E. coli O157:H7 and L. monocytogenes. At 65 to 70 degrees C, D-values for E. coli O157:H7, Salmonella, and L. monocytogenes were also significantly (P < 0.05) different between turkey and beef. The obtained D- and z-values were used in predicting process lethality of the pathogens in ground turkey and beef patties cooked in an air impingement oven and confirmed by inoculation studies for a 7-log (CFU/g) reduction of E. coli O157:H7, Salmonella, and L. monocytogenes.

Raw beef producers currently face the problem of Escherichia coli O157:H7 surface contamination of beef carcasses that can lead to product adulteration. Although carcass interventions are in place, elimination of E. coli O157:H7 from every potential hiding place on the surfaces of a beef carcass is not technologically feasible. Therefore, E. coli O157:H7 on beef carcasses might further contaminate the surfaces of beef trimmings. With the use of case scenarios from nine commercial processing facilities, we present a process control and statistical sampling approach for monitoring beef trimmings to divert contaminated lots of the trimmings from the raw ground beef supply chain.

The pathogen thermal lethality in ground and formulated beef/turkey was evaluated for a cocktail of E. coli O157:H7, Salmonella, and Listeria monocytogenes, respectively. At a temperature range of 55–70°C, the heat resistance of L. monocytogenes was not significantly (at α=0.05) different from those of Salmonella. The heat resistance of L. monocytogenes at 55–70°C was 45–81% higher than that of E. coli O157:H7. In this study, a practical approach was developed to predict log10(CFU/g) reduction of E. coli O157:H7, Salmonella, or L. monocytogenes in ground, formulated, and formed beef/turkey links that were cooked in an air impingement oven. The predictions of pathogen thermal kills in the links were verified via the inoculation studies for at least a 7log10(CFU/g) reduction of E. coli O157:H7, Salmonella, and L. monocytogenes.

Chicken leg quarters were injected with 0.1 ml of the cocktail culture per cm2 of the product surface area to contain about 7 log(CFU/g) of Salmonella. The inoculated leg quarters were processed in an air/steam impingement oven at an air temperature of 232 degrees C, an air velocity of 1.4 m/s, and a relative humidity of 43%. The endpoint product temperatures were correlated with the cooking times. A model was developed for pathogen thermal lethality up to 7 log(CFU/g) reductions of Salmonella in correlation to the product mass (140 to 540 g) and cooking time (5 to 35 min). The results from this study are useful for validating thermal lethality of pathogens in poultry products that are cooked via impingement ovens.

Chicken leg quarters (180–230g) were processed for 4min in steam at 99°C and then in an air impingement oven for 24min at an oven temperature of 232°C, an air velocity of 2m/s, and a humidity of 60%. The cooked chicken leg quarters were sampled to measure for the end-point internal temperatures. Sampling size in each subgroup for the internal temperature measurements was determined based on a normal distribution at a confidence level of 95%. The process mean, range, and standard deviation at 95% confidence level were 73.9°C, 1.8°C, and 0.9°C, respectively, for the internal temperatures of the cooked chicken leg quarters. The process lethality was validated for up to 7 log10cfu/g reductions of Listeria monocytogenes in the cooked chicken leg quarters and verified by an inoculation study in which the chicken leg quarters were injected with 0.1ml of the culture per cm2 of the product surface area to contain 7–8log10cfu/g of L. monocytogenes. This paper provided an approach for process control, sampling, and validation to reduce pathogens in fully cooked poultry products.

Thermal inactivation of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in ground pork was compared. The D (decimal reduction time at a certain heating temperature) values of E. coli 015707, Salmonella, and L. monocytogenes at 55 to 70 degreesC were 33.44 to 0.048 min, 45.87 to 0.083 min, and 47.17 to 0.085 min, respectively. The z (temperature rise for 1 log(10) reduction of D) value of E. coli O157:H7, Salmonella, and L. monocytogenes in ground pork was 4.94 degreesC, 5.89 degreesC, and 5.92 degreesC, respectively. Significant difference was found on the D and z values between E. coli O157:H7 and Salmonella or between E. coli O157:H7 and L. monocytogenes. The D and z values of Salmonella in ground pork were not significantly different from L. monocytogenes.

Thermal inactivation D and z values of Salmonella and Listeria monocytogenes were obtained for chicken thigh and leg meat and skin. The D values of Salmonella at 55 to 70 degrees C were 43.33 to 0.07 min in the meat and 43.76 to 0.09 min in the skin. The D values of L. monocytogenes at 55 to 70 degrees C were 38.94 to 0.04 min in the meat and 34.05 to 0.05 min in the skin. The z value of Salmonella was 5.34 degrees C in the meat and 5.56 degrees C in the skin. The z value of L. monocytogenes was 5.08 degrees C in the meat and 5.27 degrees C in the skin. For Salmonella or L. monocytogenes, the z value of the meat was not different from that of skin. However, the z value of Salmonella in meat or skin was different from that of L. monocytogenes in meat or skin. The z value of Salmonella or L. monocytogenes in chicken thigh and leg meat was different from that in the skin. The results from this study are useful for predicting process lethality of Salmonella and L. monocytogenes in products that contain chicken thigh and leg meat or skin.

Thermal inactivation D (decimal reduction time at a certain heating temperature) values of Escherichia coli O157:H7 at 55 degreesC to 70 degreesC were 21.36 to 0.031 min in raw franks and 24.91 to 0.038 min in fully cooked franks. Although statistically significant differences were found on the D values of E. coli O157:H7 between raw and fully cooked franks, the z value of E. coli O157:H7 in raw franks (5.07 degreesC) and fully cooked franks (5.08 degreesC) was not significantly different. The obtained D and z values were used to validate the process lethality of the pathogen in the raw franks that were processed according to a multistage cooking/cooling schedule or in the fully cooked franks that were pasteurized in-packages via steam. In this study, the calculated process lethality for both the cooking (process lethality = 254 min) and post-cook pasteurization (process lethality = 39 min) processes was far greater than the processing time that was needed for achieving a 7D reduction of E. coli O157:H7 during cooking and post-cook pasteurization of the franks.

ABSTRACT: The D and z values of Salmonella, Listeria innocua, and Listeria monocytogenes were obtained for different ready‐to‐eat poultry products, including chicken, turkey, and duck. The D values of Salmonella, L. innocua, and L. monocytogenes were 151.5 to 0.1 min at 55 to 70°C, and the z values of Salmonella, L. innocua, and L. monocytogenes were 4.9 to 7.0 °C. Significant differences were found for the heat resistance of Salmonella, L. innocua, and L. monocytogenes among turkey, duck, and chicken products, indicating that the kinetic values of a certain pathogen in a specific product should be used for determining process lethality in fully cooked and vacuum‐packaged poultry products during post‐cook heat treatments.

Fully cooked chicken breast fillets and strips were surface inoculated with a cocktail of Listeria monocytogenes culture. The inoculation level was 10(7) to 10(8) CFU/g meat. The inoculated products were vacuum packaged and pasteurized at 90 degrees C with a pilot-scale steam or hot water cooker. After heat treatment, the survivors of L. monocytogenes were enumerated. No significant difference was found on survivors of L. monocytogenes between steam- and hot water-treated products. To achieve a 7-log10 (CFU/g) reduction, approximately 5, 25, and 35 min were needed for single-packaged fillets, 227-g package strips, and 454-g strips, respectively. The results from this study were subsequently verified by a computer model that could predict the thermal lethality of pathogens in fully cooked meat and poultry products during postcook in-package pasteurization.

ABSTRACT Fully cooked chicken leg quarters (160 g to 300 g) were injected to contain 107 to 108 colony‐forming units (CFU)/g of a 5‐strain Listeria monocytogenes culture. The inoculated leg quarters were vacuum‐packaged in 0.08‐mm‐thick packaging films and then pasteurized at 96°C via steam. The heat transfer coefficient was about 760 W/m2 K in the steam cooker. Seven log10 (CFU/g) reduction of L. monocytogenes was achieved in about 22 min of steam treatment. Results from the inoculation tests agreed with the process lethality model prediction using the kinetic values that were obtained for the same product. This information helps industry to validate the lethality of L. monocytogenes in similar products during postcook pasteurization.

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.

The process lethality model was used to predict the thermal kill of Salmonella and Listeria innocua in fully cooked and vacuum-packaged chicken breast meat during hot-water postprocess pasteurization. Time-temperature profiles of the meat samples during treatment and D-values (decimal reduction times) and z-values (change in temperature required to change the D-value) for Salmonella and L. innocua in the same meat product were used in the prediction of lethality. The results of the model prediction were compared with those of the inoculation study for the same meat product at a 95% confidence level of up to 10(7) CFU/g for Salmonella and L. innocua. The thermal lethality predictions obtained with the process lethality model for Salmonella and L. innocua were within the 95% confidence level for the experimental data from the inoculation study, suggesting that the process lethality model was a useful tool for the determination of the kill of Salmonella or L. innocua at up to 10(7) CFU/g in fully cooked chicken breast meat products during postprocess pasteurization with hot water.

Seven log10 CFU of Salmonella Senftenberg or Listeria innocua were surface inoculated on fully cooked chicken breast strips. The inoculated strips (227 or 454 g) were vacuum packaged in 0.2-mm-thick pouches (114 by 114 mm and 241 by 114 mm, respectively). The products were then heat treated in a hot water cooker at 88 degrees C for 0 to 40 min. After heat treatment, Salmonella Senftenberg and L. innocua survivors were enumerated. Increasing treatment time increased the thermal lethality for Salmonella Senftenberg and L. innocua. The effect of treatment time interacted with product size. To achieve a 7-log10 reduction for Salmonella Senftenberg and L. innocua, the 454-g packages needed to be heat treated for 34 min and the 227-g packages needed to be treated for 20 min. Models were developed to correlate treatment time with bacterial survival rate and could be used to predict up to a 7-log10 reduction of Salmonella Senftenberg or L. innocua for similar products.

Studies were conducted to determine thermal inactivation D- and z-values of Salmonella and Listeria innocua in fully cooked and vacuum-packaged chicken breast meat. Fully cooked chicken breast meat products that were obtained from three different sources with differing formulations were uniformly inoculated with a cocktail of Salmonella (including Senftenberg, Typhimurium, Heidelberg, Mission, Montevideo, and California) or L. innocua at approximately 10(7) cfu/g. The inoculated meat samples were vacuum-packaged and then heat-treated at a temperature of 55 to 70 C for 5 to 90 min. After heat treatment, the samples were immediately cooled in an ice-water bath. Survivors of Salmonella and L. innocua were enumerated for each sample. D- and z-values of Salmonella and L. innocua were determined for each product and compared among the products. Source and formulation did not cause significant differences in the D- and z-values of Salmonella or L. innocua among the three fully cooked and vacuum-packaged chicken breast meat products.

ABSTRACT: The study was conducted to determine the effect of packaging‐film thicknesses on thermal inactivation of Salmonella and Listeria innocua in cooked chicken breast meat. The meat was inoculated to contain 107 CFU/g of Salmonella or L. innocua and vacuum‐packaged in a thickness of 0.0762‐ or 0.2032‐mm film. The packaged meat was heat‐treated in a water bath at 68°C for 10 to 120 s and then cooled in an ice‐water bath. The survivors of Salmonella or L. innocua were enumerated. This study revealed that packaging‐film thicknesses affected thermal inactivation of Salmonella and L. innocua. The results are useful for surface pasteurization of fully cooked and vacuum‐packaged meat and poultry products.