Combining organic acid treatment with steam pasteurization to eliminate Listeria monocytogenes on fully cooked frankfurters.

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/cm2. 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.

Eradicating Listeria monocytogenes from fully cooked franks by using an integrated pasteurization-packaging system.

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.

Process control and sampling for Escherichia coli O157:H7 in beef trimmings.

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.

Thermal inactivation of Salmonella and Listeria monocytogenes in ground chicken thigh/leg meat and skin.

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 process validation for Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in ground turkey and beef products.

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.

Effect of sodium lactate on thermal inactivation of Listeria monocytogenes and Salmonella in ground chicken thigh and leg meat.

The effect of sodium lactate on thermal inactivation D- and z-values of Listeria monocytogenes and Salmonella was determined for chicken thigh and leg meat. At 55 to 70 degrees C, the D-value of L. monocytogenes in ground chicken thigh and leg meat with the addition of 4.8% sodium lactate (4.8 g sodium lactate per 100 g of meat) was 53 to 75% higher than that in the meat without sodium lactate. No significant difference was found for the D-values of Salmonella at 55 to 70 degrees C between the meat with and that without sodium lactate (4.8%. wt/wt). The z-values of both L. monocytogenes and Salmonella were not affected by sodium lactate (4.8%). The results from this study are useful for predicting thermal process lethality of L. montocytogenes and Salmonella in formulated chicken thigh and leg meat products.

Thermal lethality of salmonella in chicken leg quarters processed via an air/steam impingement oven.

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.

Thermal inactivation of Listeria monocytogenes on ready-to-eat turkey breast meat products during postcook in-package pasteurization with hot water.

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.

Determination of thermal lethality of Listeria monocytogenes in fully cooked chicken breast fillets and strips during postcook in-package pasteurization.

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.

Lethality of Salmonella and Listeria innocua in fully cooked chicken breast meat products during postcook in-package pasteurization.

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.

Thermal inactivation D- and Z-values of Salmonella and Listeria innocua in fully cooked and vacuum packaged chicken breast meat during postcook heat treatment.

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.

Thermal lethality of Salmonella senftenberg and Listeria innocua on fully cooked and vacuum packaged chicken breast strips during hot water pasteurization.

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.

Thermal inactivation D- and z-values of Salmonella serotypes and listeria innocua in chicken patties, chicken tenders, franks, beef patties, and blended beef and turkey patties.

Commercially formulated meat products, including chicken patties, chicken tenders, franks, beef patties, and blended beef and turkey patties, were obtained from processors. Each product was inoculated with 7 to 8 logs of Salmonella (Senftenberg, Typhimurium, Heidelberg, Mission, Montevideo, and California) or Listeria innocua. The inoculated meat samples were heat treated at 55 to 70 degrees C. At each temperature, the decimal reduction time (D) was obtained by linear regression of survival curves. Values of D and the temperature difference required for the thermal inactivation curve to drop a logarithmic cycle (z) were determined for the Salmonella serotypes and L. innocua in each product. At 55 to 70 degrees C. for the five tested products, the D-values for the Salmonella serotypes and L. innocua were 26.97 to 0.25 min and 191.94 to 0.18 min, respectively, and their z-values were 7.60 to 9.83 degrees C and 4.86 to 8.67 degrees C, respectively. Significant differences were found for the D- and z-values among the five products. This study will better enable processors to determine the process lethality of pathogens in commercial meat products.

Process lethality and product yield for chicken patties processed in a pilot-scale air-steam impingement oven.

Chicken breast patties were processed in a pilot-scale air-steam impingement oven to a patty center temperature of 55 to 80 degrees C. Thermal processing was conducted at an air temperature of 149 degrees C, an air velocity of 7 to 13 m3/min, and a wet bulb temperature of 39 to 98 degrees C. From thermal histories, the total process lethality of the patties was calculated for Salmonella spp. and Listeria innocua using the previously published z-values. The effect of product temperature, wet bulb temperature, and air velocity on process lethality was analyzed using a regression model. The process lethality of Salmonella spp. and L. innocua in the cooked chicken patties was correlated to the patty center temperatures and cooking conditions. The process lethality was strongly correlated to product temperature and was affected by cooking conditions. Process lethality started to increase rapidly at the product temperature around 67 degrees C. Regression analysis was used to correlate the product yield with cooking conditions. Depending on air velocity, product yield decreased 10 to 14% with increasing endpoint temperature from 55 to 80 degrees C and increased 2 to 9% with increasing wet bulb temperature from 39 to 98 degrees C. The effect of air velocity on the yield interacted with product temperature and wet bulb temperature.

Heat transfer properties, moisture loss, product yield, and soluble proteins in chicken breast patties during air convection cooking.

Chicken breast patties were processed in an air convection oven at air temperatures of 149 to 218 C, air velocities of 7.1 to 12.7 m3/min, and air relative humidities of 40 to 95%. The air humidity was controlled via introducing steam into the oven. The patties were processed to a final center temperature of 50 to 80 C. Heat flux, heat transfer coefficient, moisture loss in the cooked chicken patties, the product yield, and the changes of soluble proteins in the product were evaluated for the cooking system. During cooking, heat flux varied with the processing time. Heat flux increased with increasing air humidity. The effective heat transfer coefficient was obtained for different cooking conditions. Air humidity in the oven affected the heat transfer coefficient. The moisture loss in the cooked products increased with increasing the final product temperature and the oven air temperature. The soluble proteins in the cooked patties decreased with increasing the final product temperature. Increasing humidity increased heat transfer coefficient and therefore reduced cooking time. Reducing oven temperature, reducing internal temperature, and increasing air humidity increased the product yield. Soluble proteins might be used as an indicator for the degree of cooking. The results from this study are important for evaluating commercial thermal processes and improving product yields.

Thermal inactivation of Salmonella senftenberg and Listeria innocua in ground chicken breast patties processed in an air convection oven.

Ground chicken breast patties were thermally processed in a lab-scale air convection oven at air temperatures of 163, 177, 190, 204, or 218 C to final patty center temperatures of 50, 55, 60, 65, 70, 75, or 80 C. The cooking time increased with increasing product temperature and decreased with increasing oven air temperature. Prior to thermal processing, approximately 7 log10(cfu/g) of Salmonella senftenberg and Listeria innocua were inoculated into the chicken patties. Survival of S. senftenberg and L. innocua decreased with increasing patty temperature. After the patties were processed to a final center temperature of 70 to 80 C, 1 to 4 log10 (cfu/g) of S. senftenberg and 3 to 5 log10(cfu/g) of L. innocua were detected in the cooked patties. A significant difference in the thermal inactivation of S. senftenberg and L. innocua was obtained between the chicken patties cooked in an air convection oven and the patties cooked in a water bath. More surviving S. senftenberg and L. innocua were found in the patties cooked in an air convection oven than in the patties cooked in a water bath.

Survival and growth of Salmonella and Listeria in the chicken breast patties subjected to time and temperature abuse under varying conditions.

Chicken breast patties were inoculated with a mixture of Salmonella Senftenberg, Salmonella Typhimurium, Salmonella Heidelberg, Salmonella Mission, Salmonella Montevideo, Salmonella California, and Listeria innocua. The initial inoculation of bacteria was approximately 10(7) log10 CFU/g. The inoculated patties were processed in a pilot-scale air convection oven at an air temperature of 177 degrees C, an air velocity of 9.9 m3/min, and a low (a wet bulb temperature of 48 degrees C) or high (a wet bulb temperature of 93 degrees C) humidity condition. The patties were processed to a final center temperature of 65 to 75 degrees C. The survivors of Salmonella and Listeria in the processed patties were evaluated. Processing humidity affected the survivors of bacteria. More survivors of Salmonella and Listeria (>2 logs) were obtained for the patties cooked at low humidity than at high humidity. After thermal processing, the patties were stored under air, vacuum, or CO2 at refrigerated (4 degrees C) or thermally abused (8 to 15 degrees C) temperatures. Storage temperature, time, and gas environment affected the bacteria growth. Higher storage temperature and longer storage time correlated to an increased growth of bacteria in the cooked chicken patties. Less Salmonella (2 logs) and Listeria (0.5 to 1 log) cells were obtained in the patties stored under vacuum than in air. Storing the patties in 30% CO2 reduced the growth of Salmonella more than 2 log10 CFU/g. At a CO2 level of 15%, 1 log10 CFU/g of reduction was obtained for Listeria in cooked chicken patties.

Thermal lethality of Salmonella Senftenberg and Listeria innocua in fully cooked and packaged chicken breast strips via steam pasteurization.

Fully cooked chicken breast strips were surface inoculated to contain 9 log10 (CFU/g) Salmonella Senftenberg or Listeria innocua. The inoculated products were vacuum packaged in 0.2-mm-thick barrier bags (241 by 114 mm), then steam pasteurized at 88 degrees C in a continuous process for 26 to 40 min or in a batch process for 33 to 41 min. After the treatments, the products were analyzed for the survivors of Salmonella or Listeria. The models were developed to correlate the surviving rate of Salmonella and Listeria with cooking time for both continuous and batch processes. A cooking time of 34 min was needed to achieve 7 logs of the reduction in a batch process. To achieve the same log reduction, a longer (6 min) cooking time was needed in a batch process than in a continuous process. The results from this study will be useful for processors to evaluate postcooking treatment procedures for ready-to-eat meat products.

Effect of meat temperature on proteins, texture, and cook loss for ground chicken breast patties.

Soluble proteins, myofibrillar proteins, collagen, texture, and cook loss were evaluated at different meat temperatures by heating ground and formed chicken breast meat in brass containers in a water bath to temperatures of 40, 50, 60, 70, or 80 C. The soluble proteins decreased by approximately 90% as meat temperature increased from 23 to 80 C. The myofibrillar protein subunits of molecular weight greater than 43 kDa decreased with increasing temperature from 23 to 80 C as analyzed via SDS-PAGE. Amount of soluble collagen more than doubled when meat temperature was increased from 50 to 70 C. The maximum peak shear force was obtained, via Warner-Bratzler shear test, at 60 C for ground chicken breast patties. The weight of patties decreased approximately 10.3% when meat temperatures were increased from 23 to 80 C. Overall, heating temperature affected the texture of the meat and caused changes in proteins and cook loss.

Inactivation of Salmonella and Listeria in ground chicken breast meat during thermal processing.

Thermal inactivation of six Salmonella spp. and Listeria innocua was evaluated in ground chicken breast and liquid medium. Survival of Salmonella and Listeria was affected by the medium composition. Under the same thermal process condition, significantly more Salmonella and Listeria survived in chicken breast meat than in 0.1% peptone-agar solution. The thermal lethality of six tested Salmonella spp. was additive in chicken meat. Survival of Listeria in chicken meat during thermal processing was not affected by the presence of the six Salmonella spp. Sample size and shape affected the inactivation of Salmonella and Listeria in chicken meat during thermal processing.