scholarly journals Comparison of Primary Models to Predict Microbial Growth by the Plate Count and Absorbance Methods

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
María-Leonor Pla ◽  
Sandra Oltra ◽  
María-Dolores Esteban ◽  
Santiago Andreu ◽  
Alfredo Palop
Keyword(s):  
Growth Rate ◽  
Goodness Of Fit ◽  
Microbial Growth ◽  
Growth Parameters ◽  
Growth Curves ◽  
Food Microbiology ◽  
Plate Count ◽  
Three Phase ◽  
Primary Model ◽  
Almost All

The selection of a primary model to describe microbial growth in predictive food microbiology often appears to be subjective. The objective of this research was to check the performance of different mathematical models in predicting growth parameters, both by absorbance and plate count methods. For this purpose, growth curves of three different microorganisms (Bacillus cereus, Listeria monocytogenes, andEscherichia coli) grown under the same conditions, but with different initial concentrations each, were analysed. When measuring the microbial growth of each microorganism by optical density, almost all models provided quite high goodness of fit (r2>0.93) for all growth curves. The growth rate remained approximately constant for all growth curves of each microorganism, when considering one growth model, but differences were found among models. Three-phase linear model provided the lowest variation for growth rate values for all three microorganisms. Baranyi model gave a variation marginally higher, despite a much better overall fitting. When measuring the microbial growth by plate count, similar results were obtained. These results provide insight into predictive microbiology and will help food microbiologists and researchers to choose the proper primary growth predictive model.

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.

Predictive Model for the Effect of Environmental Conditions on the Postharvest Development of Colletotrichum gloeosporioides Strains Isolated from Papaya (Carica papaya L.)

2020 ◽  
Vol 83 (9) ◽  
pp. 1495-1504
Author(s):  
TERESA SANDOVAL-CONTRERAS ◽  
MARICARMEN IÑIGUEZ-MORENO ◽  
LUIS GARRIDO-SÁNCHEZ ◽  
JUAN ARTURO RAGAZZO-SÁNCHEZ ◽  
JOSÉ ALBERTO NARVÁEZ-ZAPATA ◽  
...  
Keyword(s):  
Growth Rate ◽  
Supply Chain ◽  
Relative Humidity ◽  
Colletotrichum Gloeosporioides ◽  
Growth Models ◽  
External Validation ◽  
Food Microbiology ◽  
Effect Of Temperature ◽  
Primary Model

ABSTRACT Colletotrichum species are the most important postharvest spoilage fungi of papaya fruit. The objective of this research was to evaluate the effect of temperature and relative humidity on growth rate and time for growth to become visible of five strains of Colletotrichum gloeosporioides isolated from papaya fruit in a complex medium. As a primary model, the radial growth rates were estimated using the Baranyi and Roberts model in papaya agar. The Solver MS Excel function was used to obtain the time to visible mycelium (tv). Secondary models obtained with the Rosso et al. cardinal model of inflection were applied to describe the effect of temperature on the growth rate (μ). The Arrhenius-Davey model was used to model tv. The obtained models seem to be satisfactory for describing both μ and tv. The relative humidity had an effect on μ and tv for all tested C. gloeosporioides isolates, but no model accurately described the behavior of the fungus. External validation of models was performed with papaya fruit. Growth models were developed with the same models used in vitro. The bias and the accuracy factors as indices for performance evaluation of predictive models in food microbiology as a function of temperature and RH were 1.22 and 1.33, respectively, for μ and 1.18 and 1.62, respectively, for tv, indicating accurate predictions. The supply chain of papaya is complex and requires constant conditions, and poor conditions can result in damage to the fruit. Knowledge of the behavior of C. gloeosporioides on papaya fruit and application of the developed models in the supply chain will help to establish transport control strategies to combat these fungi. This research has contributed to development of the first models of growth for C. gloeosporioides in Mexico. HIGHLIGHTS

scholarly journals Growth Rate and Histamine Production of Citrobacter freundii CK01 in Various Incubation Temperatures

2020 ◽  
Vol 147 ◽  
pp. 03018
Author(s):  
Grace Margareta ◽  
Susana Endah Ratnawati ◽  
Indun Dewi Puspita
Keyword(s):  
Growth Rate ◽  
Bacterial Growth ◽  
Temperature Stability ◽  
Plate Count ◽  
Citrobacter Freundii ◽  
Tuna Fish ◽  
Histamine Production ◽  
Primary Model ◽  
Root Model ◽  
Incubation Temperatures

Improper handling and temperature fluctuations during postharvest of fish commonly allow the growth of histamine-forming bacteria (HFB) that may cause histamine poisoning. Citrobacter freundii CK01 is one of the HFB isolated from Skipjack landed on Sadeng, Yogyakarta. This study aimed to determine the temperature effect on the growth rate and histamine production by C. freundii CK01. Bacterial growth and histamine production was tested in tuna fish infusion broth (TFIB) at 5, 15, 30 and 40°C. The bacterial growth was tested using Total Plate Count method, while histamine was determined using Thin Layer Chromatography and densitometry method. The primary model for bacterial growth was plotted with incubation time using DMFit referred to Baranyi & Roberts model. The secondary model was converted from growth rate and modeled using Ratkowsky Square Root Model. The equation for growth rate of C. freundii CK01 was μmax=[0.0105 (T + 13.886)]2 (Root Mean Square Error <10%). Histamine production reached the highest concentration at 15°C in 96 hours up to 117,13 ppm. This study shows that temperature affected the growth rate and histamine production of C. freundii, indicating the importance of maintaining the low temperature stability during handling of skipjack.

An analysis of the growth of silver maple and eastern cottonwood seedlings exposed to ozone

1982 ◽  
Vol 12 (2) ◽  
pp. 420-424 ◽  
Author(s):  
K. F. Jensen
Keyword(s):  
Growth Rate ◽  
Leaf Area ◽  
Growth Parameters ◽  
Growth Curves ◽  
Relative Growth ◽  
Eastern Cottonwood ◽  
Silver Maple ◽  
Leaf Weight ◽  
Net Assimilation ◽  
Species Specific

Silver maple (Acersaccharinum L.) and eastern cottonwood (Populusdeltoides Bartr.) seedlings were treated with either 0.0, 0.1, 0.2, or 0.3 ppm ozone for 12 h/day for up to 60 consecutive days. Six seedlings were harvested from each treatment at 10-day intervals to construct growth curves for leaf area, leaf weight, and stem plus leaf weight. Relative growth parameters were calculated from these curves. Relative growth rate, relative leaf-area growth rate, and relative leaf-weight growth rate declined with an increase in time and ozone concentration. Net assimilation rate declined with time in both species. Specific leaf area and leaf-area ratio had no consistent trends.

scholarly journals Historical analysis of somatic growth of Chilean hake (Merluccius gayi gayi) off central coast of Chile

2017 ◽  
Vol 41 (3) ◽  
pp. 558-569
Author(s):  
Francisco Cerna ◽  
Luis A. Cubillos ◽  
Guido Plaza
Keyword(s):  
Growth Rate ◽  
Growth Parameters ◽  
Historical Analysis ◽  
Somatic Growth ◽  
Growth Curves ◽  
Individual Growth ◽  
Linear Mixed Effect Model ◽  
Central Coast ◽  
Mixed Effect ◽  
Average Growth

Somatic growth was studied in the Chilean hake stock off central coast of Chile, through the application of Von Bertalanffy equation (vB) as a non-linear mixed effect model (NLME) on length-at-agedata derived from otolith readings made at Instituto de Fomento Pesquero since 1972. Average growth rates for each year from 1972 to 2009 were estimated. Growth parameters of vB curves were analyzed for three major periods regarding changes in stock biomass (1972-1990, 1991-2003 and 2004-2009). Results indicated that the average growth rate showed inter-annual variations that did not exceed ±15 cm of total length around the historical average of males and females, showing no persistent tendency towards sustained increase or decrease in somatic growth rate. Growth curves obtained with the vB parameters, estimated for the three periods, showed a similar trajectories until age 7 and 8 years, in both male and females. Changes after this age may be a result of a decrease of larger fish removed by the selective effect of fishing, which triggered variations in the fitted curves, but not necessarily changes in somatic growth of these ages in the population. The results demonstrated that the individual growth of hake has not changed significantly since 1972, without observing a density-dependent effect with decreasing abundance.

scholarly journals Modelling the growth rate of Listeria monocytogenes in cooked ham stored at different temperatures

2017 ◽  
Vol 61 (1) ◽  
pp. 45-51 ◽  
Author(s):  
Jacek Szczawiński ◽  
Małgorzata Ewa Szczawińska ◽  
Adriana Łobacz ◽  
Michał Tracz ◽  
Agnieszka Jackowska-Tracz
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Goodness Of Fit ◽  
Storage Temperature ◽  
Growth Curves ◽  
Information Criterion ◽  
Model Fit ◽  
Bacteria Growth ◽  
Cooked Ham ◽  
Different Temperatures

AbstractIntroduction:The purpose of the study was to determine and model the growth rates ofL. monocytogenesin cooked cured ham stored at various temperatures.Material and Methods:Samples of cured ham were artificially contaminated with a mixture of threeL. monocytogenesstrains and stored at 3, 6, 9, 12, or 15°C for 16 days. The number of listeriae was determined after 0, 1, 2, 3, 5, 7, 9, 12, 14, and 16 days. A series of decimal dilutions were prepared from each sample and plated onto ALOA agar, after which the plates were incubated at 37°C for 48 h under aerobic conditions. The bacterial counts were logarithmised and analysed statistically. Five repetitions of the experiment were performed.Results:Both storage temperature and time were found to significantly influence the growth rate of listeriae (P < 0.01). The test bacteria growth curves were fitted to three primary models: the Gompertz, Baranyi, and logistic. The mean square error (MSE) and Akaike’s information criterion (AIC) were calculated to evaluate the goodness of fit. It transpired that the logistic model fit the experimental data best. The natural logarithms ofL. monocytogenes’mean growth rates from this model were fitted to two secondary models: the square root and polynomial.Conclusion:Modelling in both secondary types can predict the growth rates ofL. monocytogenesin cooked cured ham stored at each studied temperature, but mathematical validation showed the polynomial model to be more accurate.

scholarly journals Growth of Staphylococcus aureus 2064 described by predictive microbiology: From primary to secondary models

2019 ◽  
Vol 12 (2) ◽  
pp. 175-181
Author(s):  
Alžbeta Medveďová ◽  
Adriana Havlíková ◽  
Ľubomír Valík
Keyword(s):  
Staphylococcus Aureus ◽  
Growth Rate ◽  
Specific Growth Rate ◽  
Water Activity ◽  
Goodness Of Fit ◽  
Specific Growth ◽  
Growth Curves ◽  
Extended Model ◽  
Predictive Microbiology ◽  
Temperature Range

Abstract The growth of Staphylococcus aureus 2064 isolate in model nutrient broth was studied as affected by temperature and water activity using principles and models of predictive microbiology. Specific rates resulting from growth curves fitted by the Baranyi model were modelled by the secondary Ratkowsky model for suboptimal temperature range (RTKsub) as well as the Ratkowsky extended model (RTKext) and cardinal model (CM) in the whole temperature range. With the biological background of the RTKext model, cardinal values of temperature Tmin = 6.06 °C and Tmax = 47.9 °C and water activity aw min = 0.859 were calculated and validated with cardinal values estimated by CM (Tmin = 7.72 °C, Tmax = 46.73 °C, aw min = 0.808). CM also provided other cardinal values, Topt = 40.63 °C, aw opt = 0.994, as well as optimal specific growth rate of 1.97 h–1 (at Topt and aw opt). To evaluate the goodness of fit of all models, mathematical and graphical validation was performed and the statistical indices proved appropriateness of all the secondary models used.

scholarly journals AMiGA: software for automated Analysis of Microbial Growth Assays

2020 ◽  
Author(s):  
Firas S. Midani ◽  
James Collins ◽  
Robert A. Britton
Keyword(s):  
Microbial Growth ◽  
Growth Parameters ◽  
Growth Curves ◽  
Growth Dynamics ◽  
Automated Analysis ◽  
Growth Conditions ◽  
Differential Growth ◽  
Experimental Conditions ◽  
Simple Method ◽  
Organization Analysis

ABSTRACTThe analysis of microbial growth is one of the central methods in the field of microbiology. Microbial growth dynamics can be characterized by growth parameters including carrying capacity, exponential growth rate, and growth lag. However, growth assays with clinical isolates, fastidious organisms, or microbes under stress often produce atypical growth shapes that do not follow the classical microbial growth pattern. Here, we introduce the Analysis of Microbial Growth Assays (AMiGA) software which streamlines the analysis of growth curves without any assumptions about their shapes. AMiGA can pool replicates of growth curves and infer summary statistics for biologically meaningful growth parameters. In addition, AMiGA can quantify death phases and characterize diauxic shifts. It can also statistically test for differential growth under distinct experimental conditions. Altogether, AMiGA streamlines the organization, analysis, and visualization of microbial growth assays.IMPORTANCEOur current understanding of microbial physiology relies on the simple method of measuring microbial populations’ size over time and under different conditions. Many advances have increased the throughput of those assays and enabled the study of non-lab adapted microbes under diverse conditions that widely affect their growth dynamics. Our software provides an all-in-one tool for estimating the growth parameters of microbial cultures and testing for differential growth in a high-throughput and user-friendly fashion without any underlying assumptions about how microbes respond to their growth conditions.

scholarly journals Modelling the Radial Growth of Geotrichum candidum: Effects of Temperature and Water Activity

2021 ◽  
Vol 9 (3) ◽  
pp. 532
Author(s):  
Martina Koňuchová ◽  
Ľubomír Valík
Keyword(s):  
Water Activity ◽  
Radial Growth ◽  
Goodness Of Fit ◽  
Growth Parameters ◽  
Growth Curves ◽  
Geotrichum Candidum ◽  
Coefficient Of Determination ◽  
Lag Phase ◽  
Growth Modelling ◽  
Effects Of Temperature

Modelling the growth of microorganisms in relation to environmental factors provides quantitative knowledge that can be used to predict their behaviour in foods. For this reason, the effects of temperature and water activity (aw) adjusted with NaCl on the surface growth of two isolates and one culture strain of Geotrichum candidum were studied. A dataset of growth parameters obtained from almost 600 growth curves was employed for secondary modelling with cardinal models (CMs). The theoretical minimal temperature resulting from the modelling of the mycelium proliferation rate ranged from −5.2 to −0.4 °C. Optimal and maximal temperatures were calculated and found to have narrow ranges of 25.4 to 28.0 °C and 34.2 to 37.6 °C, respectively. Cardinal aw values associated with radial growth (awmin from 0.948–0.960 and awopt from 0.992–0.993) confirmed the salt sensitivity of the species. Model goodness-of-fit was evaluated by the coefficient of determination R2, which ranged from 0.954 to 0.985, and RMSE, which ranged from 0.28 to 0.42. Substantially higher variability accompanied the lag time for growth modelling than the radial growth rate modelling despite the square root transformation of the reciprocal lag phase data (R2 = 0.685 to 0.808). Nevertheless, the findings demonstrate that the outputs of growth modelling can be applied to the quantitative evaluation of the roles of G. candidum in fresh cheese spoilage as well as the ripening of Camembert-type cheeses or various artisanal cheeses. Along with validation, the interactions with lactic acid bacteria can be included to improve the predictions of G. candidum in the future.

PENGARUH REDESTILASI CUKA KAYU GALAM (Melaleuca leucadendron Linn) TERHADAP PENGAWETAN IKAN

2014 ◽  
Vol 6 (2) ◽  
pp. 13 ◽  
Author(s):  
Evy Setiawati
Keyword(s):  
Temperature Variation ◽  
Room Temperature ◽  
Microbial Growth ◽  
Plate Count ◽  
Microbiological Analysis ◽  
Total Acid ◽  
Food Preservative ◽  
Wood Vinegar ◽  
Total Plate Count ◽  
Almost All

To overcome the reduction of fish quality, almost all people preserve fish by formaldehyde. Therefore, it is necessary to find a substitute for food preservative that safe for health. One of the natural preservative is wood vinegar. The research aim was to investigate the effect of wood vinegar from wood Galam on fish preservation. Purification of wood vinegar used in this research was used redistilled based on boiling point. The making of Galam wood vinegar used temperature variation ≤100°C and 100 <x <200°C. The purification used temperature variation x≤1000C, 100<x≤1100C, and 110<x≤ 1200C. Fish preservation used redistilled vinegar by concentration of 2.5%, 5%, 7.5%, and 10%. Microbiological analysis included Total Plate Count and Fungus. Redistilled wood vinegar product were colorless clear, transparent, weak, pH from 2.52 to 2.73,  specific gravity from 1.001 to 1.004, total acid from 16.75 to 42.34%. Fish preservation using 7.5% wood vinegar equal to 10%, but with different from 2.5% and 5%. Wood vinegar that had 7.5% concentration has the same effect to 10%, on the other hand, there is the greatest microbial growth treatment on 2.5% wood vinegar concentration. Based on the TPC, it can be said that the fish preservation could last up to 3 days at room temperature, and there was a significant microbial growth on the fifth day. Keywords: fish preservatives, redistilled, wood vinegar, galam wood

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