scholarly journals Modelling the Effect of Temperature on the Initial Decline during the Lag Phase of Geotrichum candidum

2021 ◽  
Vol 11 (16) ◽  
pp. 7344
Author(s):  
Ľubomír Valík ◽  
Petra Šipošová ◽  
Martina Koňuchová ◽  
Alžbeta Medveďová
Keyword(s):  
Death Rate ◽  
Goodness Of Fit ◽  
Practical Importance ◽  
Geotrichum Candidum ◽  
Effect Of Temperature ◽  
Coefficient Of Determination ◽  
Lag Phase ◽  
Square Root ◽  
Root Model ◽  
Square Root Model

The study of lag phase provides essential knowledge for food quality control. With respect to significance of Geotrichum candidum in the food context, the aim of this study was to quantitatively characterize the relationship between temperature (6–25 °C) and initial decline period during G. candidum lag phase. The decrease in G. candidum cells in the lag phase was primary modelled by Weibull’s model to define the first-decimal reduction time (δ). Subsequently, the lag death rate (LDR) values were recalculated from δ and further modelled by using Arrhenius equations, as well as a square root model, and the models’ suitability was proven by selected statistical indices. The square root model with the estimated parameters b = 0.016 °C−1 h−0.5 and Tmin = −0.72 °C showed better indices relating to goodness of fit based on a low root mean sum of square error (RMSE = 0.028 log CFU mL−1), a higher coefficient of determination (R2 = 0.978), and the lowest value of AIC (AIC = −38.65). The present study provides a solution to the possible application of secondary predictive models to the death rate dependence on temperature during the microbial lag phase. Despite limited practical importance, under specific conditions, it is possible to consider its use, for example, in exposure assessment.

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.

Optimal temperature input design for estimation of the Square Root model parameters: parameter accuracy and model validity restrictions

2002 ◽  
Vol 73 (2-3) ◽  
pp. 145-157 ◽  
Author(s):  
Kristel Bernaerts ◽  
Roos D. Servaes ◽  
Steven Kooyman ◽  
Karina J. Versyck ◽  
Jan F. Van Impe
Keyword(s):  
Model Parameters ◽  
Square Root ◽  
Optimal Temperature ◽  
Model Validity ◽  
Input Design ◽  
Root Model ◽  
Square Root Model

Application of a Predictive Growth Model of Pseudomonas spp. for Estimating Shelf Life of Fresh Agaricus bisporus

2017 ◽  
Vol 80 (10) ◽  
pp. 1676-1681 ◽  
Author(s):  
Jianming Wang ◽  
Junran Chen ◽  
Yunfeng Hu ◽  
Hanyan Hu ◽  
Guohua Liu ◽  
...  
Keyword(s):  
Shelf Life ◽  
Growth Curve ◽  
Agaricus Bisporus ◽  
Gompertz Model ◽  
Square Root ◽  
Pseudomonas Spp ◽  
Root Model ◽  
Spoilage Microorganisms ◽  
Square Root Model ◽  
Modified Gompertz Model

ABSTRACT For prediction of the shelf life of the mushroom Agaricus bisporus, the growth curve of the main spoilage microorganisms was studied under isothermal conditions at 2 to 22°C with a modified Gompertz model. The effect of temperature on the growth parameters for the main spoilage microorganisms was quantified and modeled using the square root model. Pseudomonas spp. were the main microorganisms causing A. bisporus decay, and the modified Gompertz model was useful for modelling the growth curve of Pseudomonas spp. All the bias factors values of the model were close to 1. By combining the modified Gompertz model with the square root model, a prediction model to estimate the shelf life of A. bisporus as a function of storage temperature was developed. The model was validated for A. bisporus stored at 6, 12, and 18°C, and adequate agreement was found between the experimental and predicted data.

Denitrification and ammonification at low soil temperatures

1991 ◽  
Vol 71 (3) ◽  
pp. 293-303 ◽  
Author(s):  
S. Dorland ◽  
E. G. Beauchamp
Keyword(s):  
Maximum Amount ◽  
Denitrification Rate ◽  
Threshold Temperature ◽  
Square Root ◽  
Organic C ◽  
Nitrite Production ◽  
Root Model ◽  
Incubation Periods ◽  
Soil Temperatures ◽  
Square Root Model

A laboratory study was conducted to determine the effects of temperatures from −2 to 25 °C on denitrification and ammonification in anaerobic soil treated with alfalfa or glucose. Organic C substrate as alfalfa or glucose increased denitrification rates at all temperatures within this range and lowered the threshold temperature at which denitrification occurred. The threshold temperature for denitrification was as low as −2 °C in unfrozen (supercooled) soil in contrast to most other studies where the threshold temperature was reported to be at or above 0 °C. When soil was frozen at −2 °C, the denitrification rate was much lower than in unfrozen soil at the same temperature. A square root model was employed which showed that the square root of the denitrification rate was linearly related to temperature from −2 to 25 °C. The maximum amount of [Formula: see text] produced during the incubation periods generally decreased from −2 to 25 °C and was greatest when glucose and especially alfalfa were added. The rate of ammonification increased with addition of alfalfa but the quantities of [Formula: see text] produced generally decreased from 25 to −2 °C. Key words: Threshold temperature, frozen vs. unfrozen soil, nitrite production, square root model

scholarly journals Isolation and Molecular Identification of the Native Microflora on Flammulina velutipes Fruiting Bodies and Modeling the Growth of Dominant Microbiota (Lactococcus lactis)

2021 ◽  
Vol 12 ◽  
Author(s):  
Qi Wei ◽  
Xinyuan Pan ◽  
Jie Li ◽  
Zhen Jia ◽  
Ting Fang ◽  
...  
Keyword(s):  
Mean Square Error ◽  
Lactococcus Lactis ◽  
Kinetic Models ◽  
Flammulina Velutipes ◽  
Square Root ◽  
Mean Square ◽  
Fruiting Bodies ◽  
Root Model ◽  
Native Microflora ◽  
Square Root Model

The objectives of this study were to isolate and identify the dominant microorganism in Flammulina velutipes fruiting bodies (FVFB) and to develop kinetic models for describing its growth. The native microflora community on FVFB was isolated and identified using morphological examination and high-throughput sequencing analysis. FVFB presented complex microbial communities with dominant microorganisms being Lactococcus lactis. Irradiated FVFB were inoculated with the isolated strain of L. lactis and cultivated at various temperatures (4, 10, 16, 20, 25, 32, and 37°C). Three primary models, namely the Huang, Baranyi and Roberts, and reparameterized Gompertz models, and three secondary models, namely the Huang square-root, Ratkowsky square-root, and Arrhenius-type models, were developed and evaluated. With the lowest values of mean square error (MSE, 0.023–0.161) and root mean square error (RMSE, 0.152–0.401) values, the reparameterized Gompertz model was more suitable to describe the growth of L. lactis on FVFB than both Huang and Baranyi and Roberts models. The Ratkowsky square-root model provided more accurate estimation for the effect of temperature on the specific growth rate of L. lactis. The minimum growth temperature predicted by the Ratkowsky square-root model was −7.1°C. The kinetic models developed in this study could be used to evaluate the growth behavior of L. lactis on FVFB and estimate the shelf-life of FVFB.

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