Growth ofListeria monocytogenesin Camembert and other soft cheeses at refrigeration temperatures

1993 ◽  
Vol 60 (3) ◽  
pp. 421-429 ◽  
Author(s):  
Jonathan P. Back ◽  
Sarah A. Langford ◽  
Rohan G. Kroll
Keyword(s):  
Listeria Monocytogenes ◽  
Temperature Dependent ◽  
Ripening Process ◽  
Significant Growth ◽  
Soft Cheese ◽  
French And English ◽  
Dependent Growth ◽  
Rates Of Growth ◽  
Storage Temperatures

SummaryListeria monocytogenessurvived and, under most conditions, multiplied when inoculated directly into the cheese milk of laboratory made Camembert cheeses. The rate and extent of growth was reduced at lower storage temperatures. Significantly higher rates of growth occurred at the surface compared with the centre of the cheeses, and these were probably associated with increased pH and proteolysis at the cheese surface due to the mould ripening process. Similar results were obtained with Camembert cheeses surface inoculated after manufacture. There was also temperature-dependent growth of List, monocytogenes on a range of inoculated commercially manufactured soft cheeses. Significant growth occurred in Cambazola, French and English Brie, blue and white Lymeswold, French Camembert and Brie with garlic. Little if any growth occurred in blue and white Stilton, Mycella, Chaume and full fat soft cheese with garlic and herbs at the temperatures examined.

scholarly journals Differential Listeria monocytogenes Strain Survival and Growth in Katiki, a Traditional Greek Soft Cheese, at Different Storage Temperatures

2009 ◽  
Vol 75 (11) ◽  
pp. 3621-3626 ◽  
Author(s):  
Dafni-Maria Kagkli ◽  
Vassilios Iliopoulos ◽  
Virginia Stergiou ◽  
Anna Lazaridou ◽  
George-John Nychas
Keyword(s):  
Listeria Monocytogenes ◽  
Pulsed Field Gel Electrophoresis ◽  
Temperature Dependent ◽  
Protected Designation Of Origin ◽  
Soft Cheese ◽  
Different Temperatures ◽  
The Subject ◽  
Survival And Growth ◽  
Different Strains ◽  
Storage Temperatures

ABSTRACT Katiki Domokou is a traditional Greek cheese, which has received the Protected Designation of Origin recognition since 1994. Its microfloras have not been studied although its structure and composition may enable (or even favor) the survival and growth of several pathogens, including Listeria monocytogenes. The persistence of L. monocytogenes during storage at different temperatures has been the subject of many studies since temperature abuse of food products is often encountered. In the present study, five strains of L. monocytogenes were aseptically inoculated individually and as a cocktail in Katiki Domokou cheese, which was then stored at 5, 10, 15, and 20°C. Pulsed-field gel electrophoresis was used to monitor strain evolution or persistence during storage at different temperatures in the case of the cocktail inoculum. The results suggested that strain survival of L. monocytogenes was temperature dependent since different strains predominated at different temperatures. Such information is of great importance in risk assessment studies, which typically consider only the presence or absence of the pathogen.

Comparison of Media and Sampling Locations for Isolation of Listeria monocytogenes in Queso Fresco Cheese

2006 ◽  
Vol 69 (9) ◽  
pp. 2151-2156 ◽  
Author(s):  
CHIA-MIN LIN ◽  
LEI ZHANG ◽  
MICHAEL P. DOYLE ◽  
BALA SWAMINATHAN
Keyword(s):  
Listeria Monocytogenes ◽  
Storage Temperature ◽  
Epidemiologic Studies ◽  
Detection Methods ◽  
Health Concern ◽  
Public Health Concern ◽  
Sampling Locations ◽  
Soft Cheese ◽  
Regulatory Analysis ◽  
Storage Temperatures

Listeriosis associated with Hispanic-style soft cheese is an ongoing public health concern. Although rapid detection methods based on molecular and immunological technologies have been applied successfully for detecting Listeria monocytogenes in foods, obtaining isolates of the pathogen is a critical procedure for epidemiologic studies and regulatory analysis. Oxford agar, a medium recommended by the U.S. Food and Drug Administration Bacteriological Analytical Manual (BAM) to isolate L. monocytogenes from cheese, is unable to differentiate L. monocytogenes from other Listeria species. Hence, two selective isolation media, L. monocytogenes blood agar (LMBA) and Rapid 'L. mono agar (RLMA), were compared with Oxford agar for isolating L. monocytogenes from cheese. Queso fresco cheese was inoculated at 100 or 101 CFU/g with a five-strain mixture of L. monocytogenes or with the five-strain L. monocytogenes mixture and Listeria innocua. Cheese samples were stored at 21, 12, and 4°C and Listeria counts were determined at 3, 7, and 10 days; 7, 10, 14, 21 days; and 2, 4, 8, and 12 weeks postinoculation, respectively. Surface and interior cheese samples as well as liquid exudate produced during storage were assayed individually to determine differences in Listeria contamination at different sampling locations. L. monocytogenes was more easily differentiated from L. innocua on RLMA than LMBA and Oxford agar. Similar L. monocytogenes counts (ca. 104 CFU/g) were obtained on the last sampling day on the surface and interior of cheese samples (P > 0.05) for all storage temperatures and both initial inoculation levels, but smaller cell numbers were detected in the exudate produced during storage. In addition, simultaneous inoculation of L. innocua with L. monocytogenes did not affect the final L. monocytogenes counts in the cheese. The amount of exudate released from the cheese and decrease of pH correlated with storage temperature. More exudate was produced and a greater decrease of pH occurred at 21°C than at 12 or 4°C. Our results indicate that RLMA is a suitable medium for isolating L. monocytogenes from queso fresco cheese. Higher counts of L. monocytogenes were obtained from surface and interior samples of cheese than from the exudate of the cheese during storage. In addition, pH may be a useful indicator of improperly stored queso fresco cheese.

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.

Inhibition of Listeria monocytogenes in a Smear-Surface Soft Cheese by Lactobacillus plantarum WHE 92, a Pediocin AcH Producer

1998 ◽  
Vol 61 (2) ◽  
pp. 186-191 ◽  
Author(s):  
SAÏD ENNAHAR ◽  
OMAR ASSOBHEI ◽  
CLAUDE HASSELMANN
Keyword(s):  
Listeria Monocytogenes ◽  
Cell Suspension ◽  
Lactobacillus Plantarum ◽  
Ripening Process ◽  
Ripening Period ◽  
Soft Cheese ◽  
A Cell ◽  
Low Levels ◽  
Control Samples

The anti-Listeria monocytogenes activity of Lactobacillus plantarum WHE 92, a pediocin AcH producer, was investigated in Munster cheese, a smear-surface soft cheese. The appearance of L. monocytogenes in the cheese, which naturally occurs solely in the crust and never before 1 week of ripening, could be prevented by spraying a cell suspension of L. plantarum WHE 92 (ca. 105 CFU/ml) on the cheese surface at the beginning of the ripening period. L. monocytogenes was sometimes detected at low levels (<5.0 × 101 CFU/g) after 7 to 11 days of ripening. However, this pathogen was not able to grow, nor did it survive the presence of L. plantarum WHE 92 in any of the samples examined until the end of ripening (21 days), whereas it often reached counts higher than 104 CFU/g in control samples. In other respects, L. plantarum WHE 92, which exists naturally in Munster cheese, did not adversely affect the evolution of the ripening process. This procedure has allowed manufacturers to successfully put an antilisterial treatment into practice in their ripening rooms.

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.

KEX2 mutations suppress RNA polymerase II mutants and alter the temperature range of yeast cell growth

1989 ◽  
Vol 9 (6) ◽  
pp. 2341-2349
Author(s):  
C Martin ◽  
R A Young
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Single Gene ◽  
Yeast Cells ◽  
Temperature Sensitive ◽  
Temperature Dependent ◽  
Growth Properties ◽  
Cold Sensitive ◽  
Dependent Growth ◽  
Kex2 Protease

Suppressors of a temperature-sensitive RNA polymerase II mutation were isolated to identify proteins that interact with RNA polymerase II in yeast cells. Ten independently isolated extragenic mutations that suppressed the temperature-sensitive mutation rpb1-1 and produced a cold-sensitive phenotype were all found to be alleles of a single gene, SRB1. An SRB1 partial deletion mutant was further investigated and found to exhibit several pleiotropic phenotypes. These included suppression of numerous temperature-sensitive RNA polymerase II mutations, alteration of the temperature growth range of cells containing wild-type RNA polymerase, and sterility of cells of alpha mating type. The ability of SRB1 mutations to suppress the temperature-sensitive phenotype of RNA polymerase II mutants did not extend to other temperature-sensitive mutants investigated. Isolation of the SRB1 gene revealed that SRB1 is KEX2. These results indicate that the KEX2 protease, whose only known substrates are hormone precursors, can have an important influence on RNA polymerase II and the temperature-dependent growth properties of yeast cells.

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