ELISA Determination of Turkey Roll Endpoint Temperature: Effects of Formulation, Storage, and Processing

Effects of refrigerated and frozen storage, salt concentration, cooking schedule and product diameter were compared on determination of minimum endpoint cooking temperature of turkey breast rolls by measuring extractable protein (EP), lactate dehydrogenase (LDH) activity and LDH concentration by sandwich enzyme-linked immunosorbent assay. LDH concentration differed in rolls processed to 70.0°C and 71.1°C, whereas EP and LDH activity did not differ at these temperatures. Salt concentration, cooking schedule and product casing diameter did not markedly influence LDH concentration. LDH content of uncooked rolls decreased during frozen storage. A maximum concentration of 0.31 μg LDH/g meat indicated proper processing.     

Thermal Inactivation of Salmonella spp. in Chicken Broth, Beef, Pork, Turkey, and Chicken: Determination of D- and Z-values

ABSTRACT: The heat resistance of 35 Salmonella strains was determined at 55 to 65°C. No correlation between the heat resistance and the origin of the Salmonella spp. could be established. D-values in chicken broth, using a linear regression, of an 8 Salmonella serotype cocktail were 4.87, 2.72, 1.30, and 0.41 min at 55, 58, 60 and 62°C, respectively. Using a linear model, the D-values ranged from 4.86 min at 55°C to 0.38 min at 62°C. When the 8 Salmonella serotype cocktail was heated in meat, D-values at the common test temperatures of 58 and 60°C calculated by both approaches were significantly higher (p < 0.05) than those observed in chicken broth.     

Pink Color Development in Turkey Meat as Affected by Nicotinamide, Cooking Temperature, Chilling Rate, and Storage Time

Consumers associate pink color in cooked turkey with undercooking. “Pinking” has been attributed to several factors, but remains a problem in the poultry industry. Effects of temperature, chilling rate, and storage time were investigated relative to pink color intensity of turkey meat cooked in the presence of 2% nicotinamide. As final cook temperature increased, sensory pinkness increased as did CIE a* values. Slower chilling rate resulted in higher CIE a* values and lower CIE b* values. Increased storage time generally increased CIE a* values and decreased b* values while CIE L* values were not affected.     

Controlling Listeria monocytogenes and Leuconostoc mesenteroides in Uncured Deli‐style Turkey Breast Using a Clean Label Antimicrobial

Interest in natural/organic meat products has resulted in the need to validate the effectiveness of clean label antimicrobials to increase safety and shelf life of these products. A Response Surface Methodology (RSM) was used to investigate the effects of varying levels of moisture, pH, and a commercial “clean‐label” antimicrobial (cultured sugar‐vinegar blend; CSVB) on the growth rate of Listeria monocytogenes and Leuconostoc mesenteroides in uncured turkey stored at 4 °C for 16 wk. Twenty treatment combinations of moisture (60% to 80%), pH (5.8 to 6.4), and CSVB (2.5% to 5.0%) were evaluated during phase I to develop growth curves for both microbe types, whereas the interactive effects of pH (5.8 to 6.4) and CSVB (0.0 to 4.75) were tested in 16 treatment combinations during Phase II at a single moisture level using L. monocytogenes only. CSVB inhibited L. monocytogenes growth in 14 of the 20 treatments tested in Phase I and in 12 of the 16 treatments in Phase II through 16 and 8 wk, respectively. In contrast, CSVB had little effect on L. mesenteroides, with growth inhibited in only 4 of 20 treatments in Phase I and was therefore not tested further in Phase II. Significant interactions of the RSM design coefficients yielded a predictive model for L. mesenteroides growth rate, but due to lack of growth, no growth rate model was developed for L. monocytogenes. CSVB was found to be an effective antilisteral antimicrobial, while having little effect on a spoilage microorganism.     

Chemical and Cellular Antioxidant Activities of Chicken Breast Muscle Subjected to Various Thermal Treatments Followed by Simulated Gastrointestinal Digestion

The effect of thermal treatments on chemical and cellular antioxidant activities of chicken breasts subjected to in vitro gastrointestinal digestion was investigated. Breast of Korat crossbred chicken (KC) and commercial broiler (BR) were cooked under various conditions, namely heating at 70 °C for 30 min (H‐0.5) and 24 h (H‐24), autoclaving (AC) at 121°C for 15 min (AC‐15) and 60 min (AC‐60). Protein digestibility decreased upon the extreme thermal treatment of AC‐60. The H‐0.5 improved metal chelating activity of KC digesta, FRAP, and anti‐liposome oxidation of BR digesta. Digesta of BR/H‐0.5 and KC/AC‐15 at 50 μg/mL exhibited the highest cytoprotective effect against tert‐butyl hydroperoxide (TBHP)‐induced oxidative damage of HepG2 cells. In addition, the KC/AC‐15 digesta at a concentration as low as 12.5 μg/mL inhibited intracellular TBHP‐induced reactive oxyfen species (ROS) production (P < 0.05). Thus, the digesta of KC breasts subjected to AC‐15 provides not only nutritional value but also antioxidant activity at the cellular level.     

Thermal Inactivation of Salmonella spp. and Listeria innocua in the Chicken Breast Patties Processed in a Pilot-Scale Air-Convection Oven

ABSTRACT Salmonella spp. or Listeria innocua containing chicken patties were processed via a pilot-scale air-convection oven to a final temperature of 55 to 80 °C. Thermal processing was conducted at an air temperature of 149 °C, an air velocity of 7.1 to 12.7 m3/min, and a wet bulb temperature of 39 to 98 °C. The cooking time was correlated with cooking conditions using a standardized least square regression model. The models were developed to correlate cooking time and the thermal inactivation of Salmonella or Listeria with cooking conditions. The thermal lethality of Salmonella and Listeria increased with increasing product temperature and wet bulb temperature. This study bridged the gap between laboratory studies and commercial applications and will help commercial processors to evaluate and validate their thermal processes.     

Effect of Packaging-Film Thicknesses on Thermal Inactivation of Salmonella and Listeria innocua in Fully Cooked Chicken Breast Meat

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.     

In-package Pasteurization Combined with Biocide-impregnated Films to Inhibit Listeria monocytogenes and Salmonella Typhimurium in Turkey Bologna

ABSTRACT: The inhibitory effects of in-package pasteurization (3–5D, decimal reduction times) combined with a nisin (7%, w/w) containing wheat gluten film were tested over an 8-wk storage period against Listeria monocytogenes and Salmonella Typhimurium populations inoculated on refrigerated bologna. Bologna slices subjected to the in-package pasteurization process reducedL. monocytogenes populations 3.8- to 7.0-log colony-forming units (CFU)/g, and the remaining population fluctuated between 1.2- and 38-log CFU/g over the 2-mo storage period. S . Typhimurium was reduced 5.7- to 7.3-log CFU/g, and the remaining population progressively declined from 100 to <10 CFU/g over 2 mo of storage. The wheat gluten film containing nisin was effective in reducing the population of L. monocytogenes (2.75-log reduction with pasteurization; 1-log reduction without pasteurization), but was not effective against S . Typhimurium (<1-log reduction). Combining both treatments significantly reduced the L. monocytogenes populations and prevented outgrowth over the 2-mo storage period but provided no added inhibitory effect against S . Typhimurium compared with only pasteurization.     

Environmental conditions and serotype affect Listeria monocytogenes susceptibility to phage treatment in a laboratory cheese model

Listeria monocytogenes can survive and grow in a variety of environments, including refrigeration, making it difficult to control and highlighting the importance of optimizing control strategies against this pathogen. Listeria phages are attractive biocontrol agents because phages bind to specific wall teichoic acids (WTA) on the bacterial cell wall, inhibiting pathogens without disrupting the normal microbiota or structure of the food. Common stresses found on dairy products can affect cell wall composition and structure and subsequently affect the efficiency of control strategies that target the cell wall. The goal of this study was to determine the effect of a range of pH and temperatures on the effectiveness of a commercial phage cocktail treatment against several strains of L. monocytogenes in a cheese matrix. We developed a laboratory-scale cheese model that was made at different pH, treated with phage, and then inoculated with L. monocytogenes. Cheeses were incubated at 6, 14, or 22°C for 14 d, and bacterial counts were determined on d 1, 7, and 14. Our data show that phage treatment has a limited ability to reduce L. monocytogenes counts at each temperature tested; however, it was more effective on specific strains of L. monocytogenes when cheese was stored at higher temperatures. More specifically, the average counts of L. monocytogenes on phage-treated cheese stored at 22°C were significantly lower than those on phage-treated cheese stored at 6 or 14°C. Similarly, phage treatment was significantly more effective at inhibiting L. monocytogenes on cheese made at higher pH (6 and 6.5) compared with counts on cheese made at pH 5.5, where L. monocytogenes did not grow. Furthermore, serotype was found to affect the susceptibility of L. monocytogenes to phage treatment; serotype 1/2 strains showed significantly higher susceptibility to phage treatment than serotype 4b strains. Overall, our results suggest the importance of considering the efficacy of phage under conditions (i.e., temperature and pH) specific to a given food matrix when applying interventions against this important foodborne pathogen.     

Comparison of primary predictive models to study the growth of Listeria monocytogenes at low temperatures in liquid cultures and selection of fastest growing ribotypes in meat and turkey product slurries

This study compared the performance of four primary mathematical models to study the growth kinetics of Listeria monocytogenes ribotypes grown at low temperature so as to identify the best predictive model. The parameters of the best-fitting model were used to select the fastest growing strains with the shortest lag time and greatest growth rate. Nineteen food, human and animal L. monocytogenes isolates with distinct ribotype were grown at 4, 8, and 12 degrees C in tryptic soy broth and slurries prepared from cooked uncured sliced turkey breasts (with or without potassium lactate and sodium diacetate, PL/SD) and cooked cured frankfurters (with or without PL/SD). Separate regressions were performed on semi-logarithm growth curves to fit linear (based on Monod) and non-linear (Gompertz, Baranyi-Roberts, and Logistic) equations and performance of each model was evaluated using an F-test. No significant differences were found in the performance of linear and non-linear models, but the Baranyi model had the best fit for most growth curves. The maximum growth rate (MGR) of Listeria strains increased with the temperature. Similarly MGR was found significantly greater when no antimicrobials were present in the formulation of turkey or frankfurter products. The variability in lag times and MGRs in all media as determined by the Baranyi model was not consistent among strains. No single strain consistently had the fastest growth (shortest lag time, fastest MGR, or shortest time to increase 100-fold), but nine strains were identified as fastest growing strains under most growth conditions. The lack of association between serotype and fastest strain was also observed in the slurry media study. The fastest growing strains resulting from this study can be recommended for future use in L. monocytogenes challenge studies in delicatessen meat and poultry food matrices, so as to develop conservative pathogen growth predictions.