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.

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.

Efficacy of Sanitizer Treatments on Survival and Growth Parameters of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes on Fresh-Cut Pieces of Cantaloupe during Storage†

2015 ◽  
Vol 78 (7) ◽  
pp. 1288-1295 ◽  
Author(s):  
DIKE O. UKUKU ◽  
LIHAN HUANG ◽  
CHRISTOPHER SOMMERS
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Storage Temperature ◽  
Growth Parameters ◽  
Bacterial Pathogens ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Mesophilic Bacteria ◽  
Survival And Growth ◽  
Fresh Cut

For health reasons, people are consuming fresh-cut fruits with or without minimal processing and, thereby, exposing themselves to the risk of foodborne illness if such fruits are contaminated with bacterial pathogens. This study investigated survival and growth parameters of Escherichia coli O157:H7, Salmonella, Listeria monocytogenes, and aerobic mesophilic bacteria transferred from cantaloupe rind surfaces to fresh-cut pieces during fresh-cut preparation. All human bacterial pathogens inoculated on cantaloupe rind surfaces averaged ~4.8 log CFU/cm2, and the populations transferred to fresh-cut pieces before washing treatments ranged from 3 to 3.5 log CFU/g for all pathogens. A nisin-based sanitizer developed in our laboratory and chlorinated water at 1,000 mg/liter were evaluated for effectiveness in minimizing transfer of bacterial populations from cantaloupe rind surface to fresh-cut pieces. Inoculated and uninoculated cantaloupes were washed for 5 min before fresh-cut preparation and storage of fresh-cut pieces at 5 and 10°C for 15 days and at 22°C for 24 h. In fresh-cut pieces from cantaloupe washed with chlorinated water, only Salmonella was found (0.9 log CFU/g), whereas E. coli O157:H7 and L. monocytogenes were positive only by enrichment. The nisin-based sanitizer prevented transfer of human bacteria from melon rind surfaces to fresh-cut pieces, and the populations in fresh-cut pieces were below detection even by enrichment. Storage temperature affected survival and the growth rate for each type of bacteria on fresh-cut cantaloupe. Specific growth rates of E. coli O157:H7, Salmonella, and L. monocytogenes in fresh-cut pieces were similar, whereas the aerobic mesophilic bacteria grew 60 to 80% faster and had shorter lag phases.

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 < 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 (>6%) at refrigerated and mild abuse temperatures (<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 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.

Pengaruh Suhu Penyimpanan terhadap Organoleptik, Derajat Keasaman dan Pertumbuhan Bakteri Coliform pada Susu Pasteurisasi

2016 ◽  
Vol 10 (1) ◽  
pp. 13-23 ◽  
Author(s):  
Agustina Arianita Cahyaningtyas ◽  
Wiwik Pudjiastuti ◽  
Ilham Ramdhan
Keyword(s):  
Storage Temperature ◽  
Total Coliform ◽  
Coliform Bacteria ◽  
Plate Count ◽  
Pasteurized Milk ◽  
Initial Analysis ◽  
Total Plate Count ◽  
Plate Count Method ◽  
Pathogenic Microbes ◽  
Total Coliform Bacteria

One attempt to reduce the number of pathogenic microbes in milk is through the pasteurization process. This research aims to determine the effect of storage temperature on the organoleptic, acidity (pH) and growth of coliform bacteria in pasteurized milk. Pasteurized milk is stored at the varies of temperature  4°C (observed for 14 days), 10°C-15°C (observed for 14 days) and 25°C-27°C (observed for 22 hours), as well as also conducted an initial analysis pasteurized milk. The parameters were observed among other organoleptic (smell, taste, color, texture), pH and total coliform bacteria. Testing acidity using pH paper, while the growth of coliform bacteria testing done using Total Plate Count method based on ISO 2897 in 2008. The results of this study indicate that storage at 4°C for 14 days, organoleptic pasteurized milk is still good until the day ke- 8, pH progressively decreases, and the growth of coliform bacteria obtained the highest score of 3100x101 CFU / ml. Storage at 10°C-15°C for 14 days, organoleptic pasteurized milk is still good until the 6th day, the pH progressively decreases, and the growth of coliform bacteria obtained the highest score of 5729x101 CFU / ml. Storage at 25°C-27°C for 22 days, organoleptic pasteurized milk is still good until the 9th, pH progressively decreases, and the growth of coliform bacteria obtained the highest score of 4.3 x106 CFU / ml.ABSTRAKSalah satu usaha untuk mengurangi jumlah mikroba patogen pada susu adalah melalui proses pasteurisasi. Penelitian ini bertujuan untuk mengetahui pengaruh suhu penyimpanan terhadap organoleptik, derajat keasaman (pH) dan pertumbuhan bakteri Coliform pada susu pasteurisasi. Susu pasteurisasi disimpan pada suhu yang bervariasi yaitu suhu 4°C (diamati selama 14 hari), suhu 10°C-15°C (diamati selama 14 hari) dan suhu 25°C-27°C (diamati selama 22 jam), serta dilakukan pula analisa awal susu pasteurisasi. Parameter yang diamati antara lain organoleptik (bau, rasa, warna, tekstur), pH dan jumlah bakteri Coliform. Pengujian derajat keasaman menggunakan kertas pH, sedangkan pengujian pertumbuhan bakteri Coliform dilakukan dengan menggunakan metode Total Plate Count berdasarkan SNI 2897 Tahun 2008. Hasil penelitian ini menunjukkan bahwa penyimpanan pada suhu 4°C selama 14 hari, organoleptik susu pasteurisasi masih baik sampai dengan hari ke-8, pH semakin lama semakin menurun, dan pertumbuhan bakteri Coliform didapatkan nilai tertinggi sebesar 3100x101 Cfu/ml. Penyimpanan pada suhu 10°C-15°C selama 14 hari, organoleptik susu pasteurisasi masih baik sampai hari ke-6, pH semakin lama semakin menurun, dan pertumbuhan bakteri Coliform didapatkan nilai tertinggi sebesar 5729x101 Cfu/ml. Penyimpanan pada suhu 25°C-27°C selama 22 hari, organoleptik susu pasteurisasi masih baik sampai jam ke-9, pH semakin lama semakin menurun, dan pertumbuhan bakteri Coliform didapatkan nilai tertinggi sebesar 4,3 x106 Cfu/ml.Kata kunci : bakteri coliform, derajat keasaman, suhu penyimpanan, organoleptik, susu pasteurisasi

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.

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