scholarly journals Modeling the Growth/No-Growth Boundaries of Postprocessing Listeria monocytogenes Contamination on Frankfurters and Bologna Treated with Lactic Acid

2008 ◽  
Vol 75 (2) ◽  
pp. 353-358 ◽  
Author(s):  
Yohan Yoon ◽  
Patricia A. Kendall ◽  
Keith E. Belk ◽  
John A. Scanga ◽  
Gary C. Smith ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Storage Temperature ◽  
Model Performance ◽  
Bacterial Populations ◽  
Response Data ◽  
Acceptable Model ◽  
And Storage ◽  
Storage Temperatures ◽  
Dipping Time

ABSTRACT This study developed models to predict lactic acid concentration, dipping time, and storage temperature combinations determining growth/no-growth interfaces of Listeria monocytogenes at desired probabilities on bologna and frankfurters. L. monocytogenes was inoculated on bologna and frankfurters, and 75 combinations of lactic acid concentrations, dipping times, and storage temperatures were tested. Samples were stored in vacuum packages for up to 60 days, and bacterial populations were enumerated on tryptic soy agar plus 0.6% yeast extract and Palcam agar on day zero and at the end point of storage. The combinations that allowed L. monocytogenes increases of ≥1 log CFU/cm2 were assigned the value of 1 (growth), and the combinations that had increases of <l log CFU/cm2 were given the value of 0 (no growth). These binary growth response data were fitted to logistic regression to develop a model predicting probabilities of growth. Validation with existing data and various indices showed acceptable model performance. Thus, the models developed in this study may be useful in determining probabilities of growth and in selecting lactic acid concentrations and dipping times to control L. monocytogenes growth on bologna and frankfurters, while the procedures followed may also be used to develop models for other products, conditions, or pathogens.

Effect of Native Microflora, Waiting Period, and Storage Temperature on Listeria monocytogenes Serovars Transferred from Cantaloupe Rind to Fresh-Cut Pieces during Preparation†

2012 ◽  
Vol 75 (11) ◽  
pp. 1912-1919 ◽  
Author(s):  
DIKE O. UKUKU ◽  
MODESTO OLANYA ◽  
DAVID J. GEVEKE ◽  
CHRISTOPHER H. SOMMERS
Keyword(s):  
Listeria Monocytogenes ◽  
Storage Temperature ◽  
Plate Count ◽  
Mesophilic Bacteria ◽  
Recent Outbreak ◽  
Plate Count Method ◽  
Fresh Cut ◽  
Native Microflora ◽  
And Storage ◽  
Storage Temperatures

The most recent outbreak of listeriosis linked to consumption of fresh-cut cantaloupes indicates the need to investigate the behavior of Listeria monocytogenes in the presence of native microflora of cantaloupe pieces during storage. Whole cantaloupes were inoculated with L. monocytogenes (108-CFU/ml suspension) for 10 min and air dried in a biosafety cabinet for 1 h and then treated (unwashed, water washed, and 2.5% hydrogen peroxide washed). Fresh-cut pieces (~3 cm) prepared from these melons were left at 5 and 10°C for 72 h and room temperature (20°C) for 48 h. Some fresh-cut pieces were left at 20°C for 2 and 4 h and then refrigerated at 5°C. Microbial populations of fresh-cut pieces were determined by the plate count method or enrichment method immediately after preparation. Aerobic mesophilic bacteria, yeast and mold of whole melon, and inoculated populations of L. monocytogenes on cantaloupe rind surfaces averaged 6.4, 3.3, and 4.6 log CFU/cm2, respectively. Only H2O2 (2.5%) treatment reduced the aerobic mesophilic bacteria, yeast and mold, and L. monocytogenes populations to 3.8, 0.9, and 1.8 log CFU/cm2, respectively. The populations of L. monocytogenes transferred from melon rinds to fresh-cut pieces were below detection but were present by enrichment. Increased storage temperatures enhanced the lag phases and growth of L. monocytogenes. The results of this study confirmed the need to store fresh-cut cantaloupes at 5°C immediately after preparation to enhance the microbial safety of the fruit.

Control of Natural Microbial Flora and Listeria monocytogenes in Vacuum-Packaged Trout at 4 and 10° C Using Irradiation

2002 ◽  
Vol 65 (3) ◽  
pp. 515-522 ◽  
Author(s):  
IOANNIS N. SAVVAIDIS ◽  
PANAGIOTIS SKANDAMIS ◽  
KYRIAKOS A. RIGANAKOS ◽  
NIKOLAOS PANAGIOTAKIS ◽  
MICHAEL G. KONTOMINAS
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Gamma Irradiation ◽  
Shelf Life ◽  
Unirradiated Sample ◽  
Bacterial Populations ◽  
Natural Microflora ◽  
Lower Temperature ◽  
And Storage ◽  
Higher Sensitivity

The effect of gamma irradiation on the natural microflora of whole salted vacuum-packaged trout at 4 and 10°C was studied. In addition, the effectiveness of gamma irradiation in controlling Listeria monocytogenes inoculated into trout was investigated. Irradiation at doses of 0.5 and 2 kGy affected populations of bacteria, namely, Pseudomonas spp., Brochothrix thermosfacta, lactic acid bacteria, H2S-producing bacteria typical of Shewanella putrefaciens, and Enterobacteriaceae, at both 4 and 10°C. This effect was more pronounced at the higher dose (2 kGy) and the lower temperature (4°C). Pseudomonads, H2S-producing bacteria typical of S. putrefaciens, and Enterobacteriaceae showed higher sensitivity to gamma irradiation than did the rest of the microbial species. Sensory evaluation did not show a good correlation with bacterial populations. On the basis of sensory odor scores, a shelf life of 28 days (2 kGy, 4°C) was obtained for salted vacuum-packaged freshwater trout, compared with a shelf life of 7 days for the unirradiated sample. Under the same conditions, the growth of L. monocytogenes inoculated into the samples was suppressed by 2 log cycles after irradiation (2 kGy) and storage for up to 18 days at 4°C.

Modeling the Growth of Listeria monocytogenes in Pasteurized White Asparagus

2007 ◽  
Vol 70 (3) ◽  
pp. 753-757 ◽  
Author(s):  
A. VALERO ◽  
E. CARRASCO ◽  
F. PÉREZ-RODRÍGUEZ ◽  
R. M. GARCÍA-GIMENO ◽  
G. ZURERA
Keyword(s):  
Listeria Monocytogenes ◽  
Food Processing ◽  
Goodness Of Fit ◽  
Microbial Population ◽  
Storage Temperature ◽  
Arrhenius Model ◽  
Microbial Risks ◽  
The Relationship ◽  
And Storage ◽  
Storage Temperatures

Growth of Listeria monocytogenes in pasteurized white asparagus was monitored at different storage temperatures (4, 10, 20, and 30°C). Among the main microbial kinetic parameters, growth rate (μ) per hour was calculated at each temperature using the Baranyi-Roberts model. L. monocytogenes was able to grow at all temperatures, although at 4°C only a slight increment of the microbial population was observed (∼1 log CFU/g) after 300 h of storage. Subsequently, two different secondary modeling approaches were proposed to study the relationship between μ and storage temperature: the Arrhenius and Ratkowsky models. Although both models properly described the data observed, smaller values of root mean square error (RMSE) and standard error of prediction (SEP) were obtained with the Ratkowsky model, providing a better goodness of fit (Ratkowsky model: RMSE = 0.010, SEP = 21.23%; Arrhenius model: RMSE = 0.026, SEP = 54.37%). The maximum population density (MPD) was calculated at each temperature studied. A clear dependence between MPD and temperature was found; lower temperatures produced lower values of MPD. This finding confirmed the Jameson effect, indicating that multiple hurdles in the food-processing chain plus lower temperatures reduced L. monocytogenes growth. Predicting the growth of L. monocytogenes along the food chain will help to reduce microbial risks associated with consumption of pasteurized white asparagus.

Effect of Salt, Smoke Compound, and Storage Temperature on the Growth of Listeria monocytogenes in Simulated Smoked Salmon†

2007 ◽  
Vol 70 (10) ◽  
pp. 2321-2328 ◽  
Author(s):  
CHENG-AN HWANG
Keyword(s):  
Listeria Monocytogenes ◽  
Storage Temperature ◽  
Control Measures ◽  
Lag Phase ◽  
Phase Duration ◽  
Liquid Smoke ◽  
Smoked Salmon ◽  
And Storage ◽  
Storage Temperatures ◽  
Maximum Population Density

Smoked salmon can be contaminated with Listeria monocytogenes. It is important to identify the factors that are capable of controlling the growth of L. monocytogenes in smoked salmon so that control measures can be developed. The objective of this study was to determine the effect of salt, a smoke compound, storage temperature, and their interactions on L. monocytogenes in simulated smoked salmon. A six-strain mixture of L. monocytogenes (102 to 103 CFU/g) was inoculated into minced, cooked salmon containing 0 to 10% NaCl and 0 to 0.4% liquid smoke (0 to 34 ppm of phenol), and the samples were stored at temperatures from 0 to 25°C. Lag-phase duration (LPD; hour), growth rate (GR; log CFU per hour), and maximum population density (MPD; log CFU per gram) of L. monocytogenes in salmon, as affected by the concentrations of salt and phenol, storage temperature, and their interactions, were analyzed. Results showed that L. monocytogenes was able to grow in salmon containing the concentrations of salt and phenol commonly found in smoked salmon at the prevailing storage temperatures. The growth of L. monocytogenes was affected significantly (P &lt; 0.05) by salt, phenol, storage temperature, and their interactions. As expected, higher concentrations of salt or lower storage temperatures extended the LPD and reduced the GR. Higher concentrations of phenol extended the LPD of L. monocytogenes, particularly at lower storage temperatures. However, its effect on reducing the GR of L. monocytogenes was observed only at higher salt concentrations (&gt;6%) at refrigerated and mild abuse temperatures (&lt;10°C). The MPD, which generally reached 7 to 8 log CFU/g in salmon that supported L. monocytogenes growth, was not affected by the salt, phenol, and storage temperature. Two models were developed to describe the LPD and GR of L. monocytogenes in salmon containing 0 to 8% salt, 0 to 34 ppm of phenol, and storage temperatures of 4 to 25°C. The data and models obtained from this study would be useful for estimating the behavior of L. monocytogenes in smoked salmon.

Effect of Mayonnaise pH and Storage Temperature on the Behavior of Listeria monocytogenes in Ham Salad and Potato Salad†

2005 ◽  
Vol 68 (8) ◽  
pp. 1628-1634 ◽  
Author(s):  
CHENG-AN HWANG
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Storage Temperature ◽  
Inactivation Rate ◽  
Consistent Effect ◽  
Cell Counts ◽  
Cooked Ham ◽  
Mathematical Equations ◽  
And Storage ◽  
Storage Temperatures

This study examined and modeled the behavior of Listeria monocytogenes in ham salad and potato salad as affected by the pH of mayonnaise and storage temperature. An eight-strain cocktail of L. monocytogenes was inoculated on the surface of diced cooked ham or potato. The inoculated ham or potato was then mixed with regular mayonnaise (pH 3.8) or mayonnaise that was adjusted with NaOH to pH 4.2 or 4.6. The cell counts of L. monocytogenes in the salads during storage at 4, 8, or 12°C were enumerated and used to model the behavior of L. monocytogenes in ham salad or potato salad. At each of the storage temperatures, L. monocytogenes was able to grow in ham salad, whereas L. monocytogenes was inactivated in potato salad. The growth rate (log CFU per hour) in ham salad or the inactivation rate (log CFU per hour) in potato salad increased as the storage temperature increased. The duration before growth in ham salad or inactivation in potato salad increased as storage temperature decreased. The mayonnaise pH showed no consistent effect on the growth rate or inactivation rate and duration before growth or inactivation occurred. Mathematical equations that described the growth rate or inactivation rate of L. monocytogenes in both salads as a function of mayonnaise pH and storage temperature were generated and shown to be satisfactory in describing the growth rate or inactivation rate of L. monocytogenes in the ham salad or potato salad.

scholarly journals Growth potential of Listeria monocytogenes in six different RTE fruit products: impact of food matrix, storage temperature and shelf life

2018 ◽  
Vol 7 (3) ◽  
Author(s):  
Matthias Ziegler ◽  
Simon Rüegg ◽  
Roger Stephan ◽  
Claudia Guldimann
Keyword(s):  
Listeria Monocytogenes ◽  
Shelf Life ◽  
Storage Temperature ◽  
Growth Potential ◽  
Food Matrix ◽  
Significant Growth ◽  
C Storage ◽  
Fresh Cut ◽  
And Storage ◽  
Storage Temperatures

We tested the growth potential of Listeria monocytogenes on six RTE fruit products at low (4°C at the factory followed by 8°C retail/home storage) and abusive (4°C followed by 12°C) storage temperatures. Sliced coconut and fresh cut cantaloupe, as well as a fruit mix containing diced pineapple, cantaloupe, apples and grapes supported the growth of L. monocytogenes with a growth potential d>0.5 log CFU/g over six days. Mangoes, a mix of diced kiwi, cantaloupe and pineapple as well as a mix of diced pineapple, mango, grapefruit, kiwi and pomegranate did not support a growth potential that exceeded 0.5 log CFU/g over six days. The growth potential of L. monocytogenes correlated significantly with the pH; no product with a pH below 4 showed a significant growth potential of L. monocytogenes. Time after inoculation was also a significant predictor of the growth potential, while the fruit type and storage temperature were not.

Modeling the Effect of Water Activity, pH, and Temperature on the Probability of Enterotoxin A Production by Staphylococcus aureus

2016 ◽  
Vol 79 (1) ◽  
pp. 148-152 ◽  
Author(s):  
TIAN DING ◽  
YAN-YAN YU ◽  
CHENG-AN HWANG ◽  
QING-LI DONG ◽  
SHI-GUO CHEN ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Water Activity ◽  
Storage Temperature ◽  
Probability Model ◽  
Toxin Production ◽  
Factors Affecting ◽  
Model Predictions ◽  
And Storage ◽  
Storage Temperatures ◽  
Good Agreement

ABSTRACT The objectives of this study were to develop a probability model of Staphylococcus aureus enterotoxin A (SEA) production as affected by water activity (aw), pH, and temperature in broth and assess its applicability for milk. The probability of SEA production was assessed in tryptic soy broth using 24 combinations of aw (0.86 to 0.99), pH (5.0 to 7.0), and storage temperature (10 to 30°C). The observed probabilities were fitted with a logistic regression to develop a probability model. The model had a concordant value of 97.5% and concordant index of 0.98, indicating that the model satisfactorily describes the probability of SEA production. The model showed that aw, pH, and temperature were significant factors affecting the probability of toxin production. The model predictions were in good agreement with the observed values obtained from milk. The model may help manufacturers in selecting product pH and aw and storage temperatures to prevent SEA production.

Growth Modeling of Listeria monocytogenes in Pasteurized Liquid Egg

2013 ◽  
Vol 76 (9) ◽  
pp. 1549-1556 ◽  
Author(s):  
MIHO OHKOCHI ◽  
SHIGENOBU KOSEKI ◽  
MASAAKI KUNOU ◽  
KATSUAKI SUGIURA ◽  
HIROKAZU TSUBONE
Keyword(s):  
Listeria Monocytogenes ◽  
Specific Growth ◽  
Storage Temperature ◽  
Growth Parameters ◽  
Root Model ◽  
Natural Flora ◽  
Mean Square Errors ◽  
Kinetics Of ◽  
Storage Temperatures ◽  
Maximum Population Density

The growth kinetics of Listeria monocytogenes and natural flora in commercially produced pasteurized liquid egg was examined at 4.1 to 19.4°C, and a growth simulation model that can estimate the range of the number of L. monocytogenes bacteria was developed. The experimental kinetic data were fitted to the Baranyi model, and growth parameters, such as maximum specific growth rate (μmax), maximum population density (Nmax), and lag time (λ), were estimated. As a result of estimating these parameters, we found that L. monocytogenes can grow without spoilage below 12.2°C, and we then focused on storage temperatures below 12.2°C in developing our secondary models. The temperature dependency of the μmax was described by Ratkowsky's square root model. The Nmax of L. monocytogenes was modeled as a function of temperature, because the Nmax of L. monocytogenes decreased as storage temperature increased. A tertiary model of L. monocytogenes was developed using the Baranyi model and μmax and Nmax secondary models. The ranges of the numbers of L. monocytogenes bacteria were simulated using Monte Carlo simulations with an assumption that these parameters have variations that follow a normal distribution. Predictive simulations under both constant and fluctuating temperature conditions demonstrated a high accuracy, represented by root mean square errors of 0.44 and 0.34, respectively. The predicted ranges also seemed to show a reasonably good estimation, with 55.8 and 51.5% of observed values falling into the prediction range of the 25th to 75th percentile, respectively. These results suggest that the model developed here can be used to estimate the kinetics and range of L. monocytogenes growth in pasteurized liquid egg under refrigerated temperature.

scholarly journals Effect of Potassium Lactate and a Potassium Lactate–Sodium Diacetate Blend on Listeria monocytogenes Growth in Modified Atmosphere Packaged Sliced Ham

2007 ◽  
Vol 70 (10) ◽  
pp. 2297-2305 ◽  
Author(s):  
L. A. MELLEFONT ◽  
T. ROSS
Keyword(s):  
Listeria Monocytogenes ◽  
Organic Acid ◽  
Shelf Life ◽  
Storage Temperature ◽  
Modified Atmosphere ◽  
Acid Salt ◽  
Potassium Lactate ◽  
Sodium Diacetate ◽  
Potential Inhibitors ◽  
And Storage

Two commercially available organic acid salts, potassium lactate (PURASAL HiPure P) and a potassium lactate–sodium diacetate blend (PURASAL Opti.Form PD 4), were assessed as potential inhibitors of Listeria monocytogenes growth in modified atmosphere packaged (MAP) sliced ham in challenge studies. The influence of the initial inoculation level of L. monocytogenes (101 or 103 CFU g−1) and storage temperature (4 or 8°C) was also examined. The addition of either organic acid salt to MAP sliced ham strongly inhibited the growth of L. monocytogenes during the normal shelf life of the product under ideal refrigeration conditions (4°C) and even under abusive temperature conditions (i.e., 8°C). During the challenge studies and in the absence of either organic acid salt, L. monocytogenes numbers increased by 1,000-fold after 20 days at 8°C and 10-fold after 42 days at 4°C. Both organic acid salt treatments were found to be listeriostatic rather than listericidal. The addition of either organic acid salt to the MAP ham also reduced the growth of indigenous microflora, i.e., aerobic microflora and lactic acid bacteria. The influence of these compounds on the risk of listeriosis in relation to product shelf life is discussed.

Control of Listeria monocytogenes on Frankfurters with Antimicrobials in the Formulation and by Dipping in Organic Acid Solutions

2004 ◽  
Vol 67 (11) ◽  
pp. 2456-2464 ◽  
Author(s):  
I. M. BARMPALIA ◽  
I. GEORNARAS ◽  
K. E. BELK ◽  
J. A. SCANGA ◽  
P. A. KENDALL ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Organic Acid ◽  
The United States ◽  
Acid Solutions ◽  
Overall Acceptability ◽  
Bactericidal Effects ◽  
Yeasts And Molds ◽  
And Storage

The antilisterial activity of sodium lactate (SL) and sodium diacetate (SD) was evaluated in a frankfurter formulation and in combination with a dipping treatment into solutions of lactic acid or acetic acid after processing and inoculation. Pork frankfurters were formulated with 1.8% SL or 0.25% SD or combinations of 1.8% SL with 0.25 or 0.125% SD. After processing, frankfurters were inoculated (2 to 3 log CFU/cm2) with a 10-strain composite of Listeria monocytogenes and left undipped or were dipped (2 min) in 2.5% solutions of lactic acid or acetic acid (23 ± 2°C) before vacuum packaging and storage at 10°C for 40 days. Total microbial populations and L. monocytogenes, lactic acid bacteria, and yeasts and molds were enumerated during storage. Sensory evaluations also were carried out on frankfurters treated and/or formulated with effective antimicrobials. The combination of 1.8% SL with 0.25% SD provided complete inhibition of L. monocytogenes growth throughout storage. Dipping in lactic acid or acetic acid reduced initial populations by 0.7 to 2.1 log CFU/cm2, but log CFU/cm2. For samples containing single antimicrobials and dipped in lactic acid or acetic acid, L. monocytogenes growth was completely inhibited or reduced over 12 and 28 days, respectively, whereas final populations were lower (P &lt; 0.05) than those in undipped samples of the same formulations. Bactericidal effects during storage (reductions of 0.6 to 1.0 log CFU/cm2 over 28 to 40 days) were observed in frankfurters containing combinations of SL and SD that were dipped in organic acid solutions. Inclusion of antimicrobials in the formulation and/or dipping the product into organic acid solutions did not affect (P &gt; 0.05) the flavor and overall acceptability of products compared with controls. The results of this study may be valuable to meat processors as they seek approaches for meeting new regulatory requirements in the United States.

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