Growth kinetics ofStaphylococcus aureuson Brie and Camembert cheeses

2014 ◽  
Vol 81 (2) ◽  
pp. 252-256 ◽  
Author(s):  
Heeyoung Lee ◽  
Kyungmi Kim ◽  
Soomin Lee ◽  
Minkyung Han ◽  
Yohan Yoon
Keyword(s):  
Growth Kinetics ◽  
Storage Temperature ◽  
Model Performance ◽  
Lag Phase ◽  
Square Root ◽  
Growth Data ◽  
Phase Duration ◽  
Mannitol Salt Agar ◽  
Staph Aureus ◽  
Kinetics Of

In this study, we developed mathematical models to describe the growth kinetics ofStaphylococcus aureuson natural cheeses. A five-strain mixture ofStaph. aureuswas inoculated onto 15 g of Brie and Camembert cheeses at 4 log CFU/g. The samples were then stored at 4, 10, 15, 25, and 30 °C for 2–60 d, with a different storage time being used for each temperature. Total bacterial andStaph. aureuscells were enumerated on tryptic soy agar and mannitol salt agar, respectively. The Baranyi model was fitted to the growth data ofStaph. aureusto calculate kinetic parameters such as the maximum growth rate in log CFU units (rmax; log CFU/g/h) and the lag phase duration (λ; h). The effects of temperature on the square root ofrmaxand on the natural logarithm of λ were modelled in the second stage (secondary model). Independent experimental data (observed data) were compared with prediction and the respective root mean square error compared with theRMSEof the fit on the original data, as a measure of model performance. The total growth of bacteria was observed at 10, 15, 25, and 30 °C on both cheeses. Thermaxvalues increased with storage temperature (P<0·05), but a significant effect of storage temperature on λ values was only observed between 4 and 15 °C (P<0·05). The square root model and linear equation were found to be appropriate for description of the effect of storage temperature on growth kinetics (R2=0·894–0·983). Our results indicate that the models developed in this study should be useful for describing the growth kinetics ofStaph. aureuson Brie and Camembert cheeses.

Kinetic behaviour ofStaphylococcus aureuson cheese as a function of water activity and temperature

2014 ◽  
Vol 82 (1) ◽  
pp. 64-69 ◽  
Author(s):  
Heeyoung Lee ◽  
Kyungmi Kim ◽  
Soomin Lee ◽  
Yohan Yoon
Keyword(s):  
Water Activity ◽  
Storage Temperature ◽  
Model Performance ◽  
Effect Of Temperature ◽  
Lag Phase ◽  
Growth Data ◽  
Mannitol Salt Agar ◽  
Staph Aureus ◽  
Kinetic Behaviour ◽  
Cell Counts

This study developed mathematical models in order to evaluate the effect ofAw(Water activity) and growth temperature onStaphylococcus aureuskinetic behaviour. TheAwlevels (0·970, 0·975, 0·983, and 0·991) of cheese were adjusted by NaCl; then,Staph. aureuswas inoculated on the cheese, followed by storage at 7–30 °C for 72–720 h. Total bacterial andStaph. aureuscell counts were enumerated on tryptic soy agar and mannitol salt agar, respectively. The Baranyi model was fitted to theStaph. aureusgrowth data in order to calculate the maximum specific growth rate (μmax; log CFU/g/h), lag phase duration (λ; h), lower asymptote (N0; log CFU/g) and upper asymptote (Nmax; log CFU/g). The effects of storage temperature andAwon the kinetic parameters (μmaxand λ) were then further analysed with the Ratkowsky-type model and a polynomial equation, respectively. The root mean square error (RMSE) and relative error (RE) were calculated in order to estimate the model performance. No significant effect ofAwonStaph. aureusgrowth was observed at 7 °C; thus, the Baranyi model was fitted to the growth data from 15, 25 and 30 °C. The μmaxvalues (0·011–0·303 log CFU/g/h) increased (P<0·05) as the storage temperature andAwincreased. In addition, λ values (2·42–63·48 h) decreased (P<0·05) as storage temperature andAwincreased; yet, the effect ofAwon λ was observed only at 15 °C. The theoretical minimum storage temperature andAwwere 10·15 °C and 0·882, respectively.RMSE(0·010–1·544) andREvalues (−0·131 to 0·187) from validation indicated that model performance was appropriate. Hence, these results suggest that the developed models in this study should be useful in describing the effect of temperature andAwon the growth kinetic behaviour ofStaph. aureusin cheese along with the exposure assessment ofStaph. aureusin cheese as well.

Interactive Effects of Temperature, Initial pH, Sodium Chloride, and Sodium Pyrophosphate on the Growth Kinetics of Clostridium perfringens†

1996 ◽  
Vol 59 (9) ◽  
pp. 963-968 ◽  
Author(s):  
VIJAY K. JUNEJA ◽  
BENNE S. MARMER ◽  
JOHN G. PHILLIPS ◽  
SAMUEL A. PALUMBO
Keyword(s):  
Sodium Chloride ◽  
Growth Kinetics ◽  
Generation Time ◽  
Interactive Effects ◽  
Sodium Pyrophosphate ◽  
Lag Phase ◽  
Phase Duration ◽  
Initial Ph ◽  
Effects Of Temperature ◽  
Kinetics Of

The interactive effects of temperature (12 to 42°C), initial pH (5.5 to 7), sodium chloride (0 to 3%) and sodium pyrophosphate concentrations (0 to 0.3%) on the growth in Trypticase-peptone-glucose-yeast extract broth of a three-strain mixture of Clostridium perfringens vegetative cells were determined. The number of viable C. perfringens cells was determined at appropriate intervals by plating on tryptose-sulfite-cycloserine agar. Growth data were analyzed by the Gompertz equation; the gompertz B and M parameters were then used to calculate lag-phase duration, exponential growth rate, generation time, and maximum population-density values. The data indicated that the growth kinetics of C. perfringens were dependent on the interaction of the four variables, particularly in regard to exponential growth rates and lag-phase durations. Cubic models based on the natural logarithm transformation of lag-phase duration and generation time were evaluated and appeared to adequately fit the data. The data suggest that sodium pyrophosphate can have significant bacteriostatic activity against C. perfringens and may provide processed meats with a degree of protection against this microorganism, particularly if employed in conjunction with a combination of acidic pH, high salt concentrations, and adequate refrigeration.

scholarly journals Growth of Listeria monocytogenes in Thawed Frozen Foods

2017 ◽  
Vol 80 (3) ◽  
pp. 447-453 ◽  
Author(s):  
Ai Kataoka ◽  
Hua Wang ◽  
Philip H. Elliott ◽  
Richard C. Whiting ◽  
Melinda M. Hayman
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Growth Rates ◽  
Storage Temperature ◽  
Growth Parameters ◽  
Quadratic Model ◽  
Lag Phase ◽  
Frozen Foods ◽  
Phase Duration ◽  
Primary Model

ABSTRACT The growth characteristics of Listeria monocytogenes inoculated onto frozen foods (corn, green peas, crabmeat, and shrimp) and thawed by being stored at 4, 8, 12, and 20°C were investigated. The growth parameters, lag-phase duration (LPD) and exponential growth rate (EGR), were determined by using a two-phase linear growth model as a primary model and a square root model for EGR and a quadratic model for LPD as secondary models, based on the growth data. The EGR model predictions were compared with growth rates obtained from the USDA Pathogen Modeling Program, calculated with similar pH, salt percentage, and NaNO2 parameters, at all storage temperatures. The results showed that L. monocytogenes grew well in all food types, with the growth rate increasing with storage temperature. Predicted EGRs for all food types demonstrated the significance of storage temperature and similar growth rates among four food types. The predicted EGRs showed slightly slower rate compared with the values from the U.S. Department of Agriculture Pathogen Modeling Program. LPD could not be accurately predicted, possibly because there were not enough sampling points. These data established by using real food samples demonstrated that L. monocytogenes can initiate growth without a prolonged lag phase even at refrigeration temperature (4°C), and the predictive models derived from this study can be useful for developing proper handling guidelines for thawed frozen foods during production and storage.

scholarly journals Substantiation of the sell-by date of food products

2020 ◽  
Vol 52 (1) ◽  
pp. 59-63
Author(s):  
S.M. Kuzminskiy ◽  
T.V. Adamchuk ◽  
О.М. Holinko ◽  
N.P. Levytska
Keyword(s):  
Food Products ◽  
Storage Conditions ◽  
Lag Phase ◽  
Contamination Level ◽  
Second Phase ◽  
Phase Duration ◽  
Normative Documents ◽  
Culture Development ◽  
Storage Distribution ◽  
Kinetics Of

Objective of the Work. The overview of current methodical approaches for experimental substantiation of the sell-by date of food products. Methods and Materials. Data analysis of scientific literature and normative documents on methods of substantiation of the sell-by date of food products. Results and Discussion. Sell-by date is a period since product’s manufacture, during which it maintains its safety and quality (including nutritional value) within reasonably foreseeable conditions of storage, distribution and consumption. In the case of new products (recipes) introduction it is necessary to review the sell-by date, and its extending as the need arises. The main aspects of microbiological substantiation of the sell-by date of food products are considered. The identification of microbial hazard for particular product is the first phase of the work. The second phase of the work is to determine the kinetic parameters of precise microorganism’s accumulation to maximum permitted level within regulated and aggravated conditions of product’s storage. Conclusions. In the process of microbiological substantiation of the sell-by date of food products it should be taken into consideration the presence of leading pathogen and causative microorganisms of microbial spoilage, the initial contamination level, the lag phase duration of germ culture development, variations between strains, the kinetics of microorganisms’ accumulation within the product in real and aggravated storage conditions, the indetermination connected with biological nature of microorganisms and their inhomogeneous allocation within the product, the limitation for shortcut research methods (if applicable). The decision rule should be based on the consumer’s risk concept. Key Words: food products, sell-by date, substantiation, microbiological indicators.

scholarly journals Prediction of growth kinetics of Pseudomonas spp. in meat products under isothermal and non-isothermal storage conditions

2021 ◽  
Vol 7 (3) ◽  
pp. 194-202
Author(s):  
Fatih Tarlak
Keyword(s):  
Goodness Of Fit ◽  
Storage Temperature ◽  
Food Products ◽  
Storage Conditions ◽  
Chicken Meat ◽  
Lag Phase ◽  
Phase Duration ◽  
Pseudomonas Spp ◽  
Primary Model ◽  
One Step

The main objective of the present study was to develop and validate a new alternative modelling method to predict the shelf-life of food products under non-isothermal storage conditions. The bacterial growth data of the Pseudomonas spp. was extracted from published studies conducted for aerobically-stored fish, pork and chicken meat and described with two-step and one-step modelling approaches employing different primary models (the modified Gompertz, logistic, Baranyi and Huang models) under isothermal storage temperatures. Temperature dependent kinetic parameters (maximum specific growth rate ‘µmax’ and lag phase duration ‘λ’) were described as a function of storage temperature via the Ratkowsky model integrated with each primary model. The Huang model based on the one-step modelling approach yielded the best goodness of fit results (RMSE = 0.451 and adjusted-R2 = 0.942) for all food products at isothermal storage conditions, therefore, was also used to check it’s the prediction capability under non-isothermal storage conditions. The differential form of the Huang model provided satisfactorily statistical indexes (1.075 > Bf > 1.014 and 1.080 > Af > 1.047) indicating reliably being able to use to describe the growth behaviour of Pseudomonas spp. in fish, pork and chicken meat subjected to non-isothermal storage conditions.

scholarly journals Chemical Forms of Selenium in the Metal-Resistant Bacterium Ralstonia metallidurans CH34 Exposed to Selenite and Selenate

2005 ◽  
Vol 71 (5) ◽  
pp. 2331-2337 ◽  
Author(s):  
Géraldine Sarret ◽  
Laure Avoscan ◽  
Marie Carrière ◽  
Richard Collins ◽  
Nicolas Geoffroy ◽  
...  
Keyword(s):  
Transformation Product ◽  
Lag Phase ◽  
Elemental Selenium ◽  
Experimental Conditions ◽  
Phase Duration ◽  
Contact Exposure ◽  
Ralstonia Metallidurans ◽  
A Minor ◽  
X Ray Absorption ◽  
Kinetics Of

ABSTRACT Ralstonia metallidurans CH34, a soil bacterium resistant to a variety of metals, is known to reduce selenite to intracellular granules of elemental selenium (Se0). We have studied the kinetics of selenite (SeIV) and selenate (SeVI) accumulation and used X-ray absorption spectroscopy to identify the accumulated form of selenate, as well as possible chemical intermediates during the transformation of these two oxyanions. When introduced during the lag phase, the presence of selenite increased the duration of this phase, as previously observed. Selenite introduction was followed by a period of slow uptake, during which the bacteria contained Se0 and alkyl selenide in equivalent proportions. This suggests that two reactions with similar kinetics take place: an assimilatory pathway leading to alkyl selenide and a slow detoxification pathway leading to Se0. Subsequently, selenite uptake strongly increased (up to 340 mg Se per g of proteins) and Se0 was the predominant transformation product, suggesting an activation of selenite transport and reduction systems after several hours of contact. Exposure to selenate did not induce an increase in the lag phase duration, and the bacteria accumulated approximately 25-fold less Se than when exposed to selenite. SeIV was detected as a transient species in the first 12 h after selenate introduction, Se0 also occurred as a minor species, and the major accumulated form was alkyl selenide. Thus, in the present experimental conditions, selenate mostly follows an assimilatory pathway and the reduction pathway is not activated upon selenate exposure. These results show that R. metallidurans CH34 may be suitable for the remediation of selenite-, but not selenate-, contaminated environments.

Validation of Predictive Mathematical Models Describing Growth of Staphylococcus aureus

1996 ◽  
Vol 59 (1) ◽  
pp. 11-15 ◽  
Author(s):  
ISABEL WALLS ◽  
VIRGINIA N. SCOTT ◽  
DANE T. BERNARD
Keyword(s):  
Staphylococcus Aureus ◽  
Mathematical Models ◽  
Growth Kinetics ◽  
Growth Rates ◽  
Close Agreement ◽  
Growth Conditions ◽  
Lag Phase ◽  
Growth Data ◽  
Gompertz Equation ◽  
Ph Range

An investigation was performed on the growth of Staphylococcus aureus in a commercially available, sterile, homogeneous food at 12°C with 1.2 and 5.9% NaCl; at 25°C with 10.4% NaCl; and at 20 and 35°C with 1.2, 5.3, 12.5, and 15.8% NaCl; over a pH range of 5.5 to 7.5. Growth data were fitted to the Gompertz equation and the resulting growth kinetics were compared with predictions from the Pathogen Modeling Program (PMP) and Food MicroModel (FMM). For the PMP, predicted lag-phase durations varied from 0.5 to 130 h longer than the observed values. In general, close agreement with growth rates was obtained but there was a 10-fold difference in one case. For FMM, predicted lag-phase durations ranged from 27 h shorter to 47 h longer than the observed values. Again, close agreement with growth rates was obtained, but in one case a fivefold difference was observed. In general, for the sterile foods used under the growth conditions tested, the models underestimated the growth of S. aureus. This implies that while the models can be used as a guide to indicate growth rates in foods they should not be relied upon as the sole determinant of the product's safety.

Nucleation rates and the kinetics of particle growth I. The pure birth process

1964 ◽  
Vol 277 (1369) ◽  
pp. 155-166 ◽  
Keyword(s):  
Differential Equations ◽  
Chemical Reaction ◽  
Growth Kinetics ◽  
Particle Growth ◽  
Growth Data ◽  
Birth Process ◽  
Irreversible Chemical Reaction ◽  
Growth Laws ◽  
Infinite Set ◽  
Kinetics Of

A model of particle growth kinetics in a condensing system is investigated in which the mechanism is presumed to be an irreversible chemical reaction which proceeds at the particle-atm osphere interface. General growth laws for the assembly of particles are derived from the resulting infinite set of differential equations and tested against growth data on sulphur hydrosols. The relation between the model and the well-known pure birth process of mathematical statistics is emphasized.

The effect of inorganic and organic mercury on growth kinetics of Nitzschia acicularis W. Sm. and Tetraselmis suecica Butch.

1980 ◽  
Vol 26 (8) ◽  
pp. 930-937 ◽  
Author(s):  
B. Mora ◽  
J. Fábregas
Keyword(s):  
Growth Kinetics ◽  
Mercuric Acetate ◽  
Gradual Increase ◽  
Inorganic Mercury ◽  
Inoculum Size ◽  
Lag Phase ◽  
Tetraselmis Suecica ◽  
Initial Effect ◽  
Cellular Area ◽  
Kinetics Of

Studies have been made on the toxicities of three inorganic (HgCl2, HgSO4, and NH2HgCl) and two organic (CH3HgCl and phenyl mercuric acetate (PMA)) mercury derivatives on planktonic algae (Nitzschia acicularis W. Sm. and Tetraselmis suecica Butch.). Growth kinetics and fluorescence changes were used as criteria for assessing algal–metal responses.Methylmercury chloride was found to be the more toxic form, inhibiting growth of both species at levels of 0.025 ppm Hg. PMA inhibited Nitzschia at the same concentration. Inorganic forms prevent growth of the diatom at 0.15–0.20 ppm Hg. Addition of inorganic mercury at concentrations of 0.05 ppm Hg resulted in reduction of the lag phase, increase in exponential growth rate, or both. Increasing mercury concentrations caused a gradual increase in the lag phase in T. suecica and in N. acicularis only with mercuric sulphate. Populations recovered from this initial effect and started to grow. The effect of inoculum size on mercurial toxicity was tested. The higher concentrations of mercury that still permit growth restricted the chlorophyll fluorescence to the central cellular area and the cells appear slimmed. This effect is highest in concentrations that inhibit growth.

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