Estimating the Survival of Clostridium botulinum Spores during Heat Treatments

2000 ◽  
Vol 63 (2) ◽  
pp. 190-195 ◽  
Author(s):  
M. PELEG ◽  
M. B. COLE
Keyword(s):  
Clostridium Botulinum ◽  
Heat Inactivation ◽  
Survival Ratio ◽  
Survival Curves ◽  
First Order Kinetics ◽  
Individual Survival ◽  
D Values ◽  
The Individual ◽  
Increasing Temperature ◽  
Limiting Case

A recently published study of the inactivation of Clostridium botulinum spores at various temperatures in the range of 101 to 121°C and neutral pH revealed that their semilogarithmic survival curves all had considerable upward concavity. This finding indicated that heat inactivation of the spores under these conditions did not follow a first-order kinetics and that meaningful D values could not be calculated. The individual survival curves could be described by the cumulative form of the Weibull distribution, i.e., by log S =−b(T)tn(T), where S is the survival ratio and b(T) and n(T) are temperature-dependent coefficients. The fact that at all temperatures in the above range n(T) was smaller than 1 suggested that as time increases sensitive members of the population parish and survivors with increasing resistance remain. If damage accumulation is not a main factor, and the inactivation is path independent, then survival curves under monotonously increasing temperature can be constructed using a relatively simple model, which can be used to calculate the spores' survival in a limiting case. This is demonstrated with computer-simulated heating curves and the experimental constants of the C. botulinum spores, setting the number of decades reduction to 8, 10, and 12 (the current criterion for commercial sterility).

Modeling Penicillium expansum Resistance to Thermal and Chlorine Treatments

2009 ◽  
Vol 72 (12) ◽  
pp. 2618-2622 ◽  
Author(s):  
BEATRIZ C. M. SALOMÃO ◽  
JOHN J. CHUREY ◽  
GLÁUCIA M. F. ARAGÃO ◽  
RANDY W. WOROBO
Keyword(s):  
Apple Juice ◽  
Weibull Model ◽  
Superior Performance ◽  
Penicillium Expansum ◽  
Heat Inactivation ◽  
Survival Curves ◽  
Biphasic Model ◽  
Log Reduction ◽  
Weibull Models ◽  
D Values

Apples and apple products are excellent substrates for Penicillium expansum to produce patulin. In an attempt to avoid excessive levels of patulin, limiting or reducing P. expansum contamination levels on apples designated for storage in packinghouses and/or during apple juice processing is critical. The aim of this work was (i) to determine the thermal resistance of P. expansum spores in apple juice, comparing the abilities of the Bigelow and Weibull models to describe the survival curves and (ii) to determine the inactivation of P. expansum spores in aqueous chlorine solutions at varying concentrations of chlorine solutions, comparing the abilities of the biphasic and Weibull models to fit the survival curves. The results showed that the Bigelow and Weibull models were similar for describing the heat inactivation data, because the survival curves were almost linear. In this case, the concept of D- and z-values could be used, and the D-values obtained were 10.68, 6.64, 3.32, 1.14, and 0.61 min at 50, 52, 54, 56, and 60°C, respectively, while the z-value was determined to be 7.57°C. For the chlorine treatments, although the biphasic model gave a slightly superior performance, the Weibull model was selected, considering the parsimony principle, because it has fewer parameters than the biphasic model has. In conclusion, the typical pasteurization regimen used for refrigerated apple juice (71°C for 6 s) is capable of achieving a 6-log reduction of P. expansum spores.

Comparative Radiation Death Kinetics of Clostridium botulinum Spores at Low-Temperature Gamma Irradiation

1977 ◽  
Vol 40 (5) ◽  
pp. 313-316 ◽  
Author(s):  
ABE ANELLIS ◽  
D. BERKOWITZ ◽  
D. KEMPER
Keyword(s):  
Clostridium Botulinum ◽  
Model System ◽  
Radiation Temperature ◽  
60Co Gamma Rays ◽  
Death Kinetics ◽  
D Values ◽  
Increasing Temperature ◽  
Relationship Of ◽  
Kinetics Of ◽  
D Value

Spores of Clostridium botulinum 33A were irradiated with 60Co gamma rays in 0.067 M Sorensen phosphate buffer (pH 7.0) at −196, −140, −80, −30, or 5 C and incubated in recovery broth for 30 days at 30 C, thus simulating an inoculated pack and eliciting “partial spoilage” data. Resistance of the spores decreased linearly with increasing temperature. A simple empirical equation was derived to predict D values for any desired temperature. An Arrhenius plot of the D value—radiation temperature profile indicated that the death kinetics is not first order. Comparison of the data in this model system with those previously observed in beef indicates a similar radiation death pattern, except that resistance of the spores was somewhat more (1.6-fold) temperature dependent, although significantly more resistant, in the beef. A comparison of the D value-temperature relationship of Streptoccus faecium a21, obtained earlier, with strain 33A in the same model system indicated that the spores were considerably less resistant below −20 C and much more resistant above this radiation temperature.

Effect of irradiation temperature in the range −196 to 95C on the resistance of spores of Clostridium botulinum 33A in cooked beef

1971 ◽  
Vol 17 (2) ◽  
pp. 135-142 ◽  
Author(s):  
N. Grecz ◽  
A. A. Walker ◽  
Abe Anellis ◽  
D. Berkowitz
Keyword(s):  
Clostridium Botulinum ◽  
Inoculum Level ◽  
Spore Resistance ◽  
Thermodynamic Effect ◽  
Linear Plot ◽  
Radiation Processes ◽  
D Values ◽  
Increasing Temperature ◽  
Best Fit ◽  
Arrhenius Analysis

Cans of ground cooked beef, inoculated with 106 or 108 spores per can of Clostridium botulinum 33A, were irradiated with 60Co gamma rays at a series of 14 temperatures ranging from −196 to 95C. The higher inoculum level required higher sterilizing doses. The D values, computed on the basis of recoverable C. botulinum, were independent of the inoculum level, and showed that spore resistance progressively decreased with increasing temperature. A statistical analysis of these data disclosed that the change in D values from −196 to 65C followed equally well a quadratic, exponential, or linear best-fit plot; above 65C radiation death was much more rapid. An equation was derived from the linear plot to predict D values for any desired temperature between −196 and 65C. Calculations of Ea and Q10 values, based on the linear curve, indicated a very small thermodynamic effect on radiation kill. An Arrhenius analysis of the temperature effect suggested that there was no simple physicochemical mechanism occurring in the inoculated beef pack which might explain the change in spore kill as a function of temperature. Theoretical commercial radiation processes for beef, based on the 12D concept and strain 33A spores, are presented for several easily controlled irradiation temperatures.

On the Response of Modulated Doublet Modes to Traveling Wave Excitation

2000 ◽  
Author(s):  
J. Y. Chang ◽  
J. A. Wickert
Keyword(s):  
Periodic Structure ◽  
Traveling Wave ◽  
Illustrative Case ◽  
Wave Excitation ◽  
State Response ◽  
The Individual ◽  
Limiting Case ◽  
Backward Propagation ◽  
Fourier Harmonics ◽  
Split Frequency

Abstract The forced vibration of arotationally periodic structure when subjected to traveling wave excitation is discussed, with emphasis placed on the steady-state response of doublet modes having either repeated or split frequencies. Such vibration modes have spatially modulated shapes defined by (i) the numbers of nodal diameters present in the limiting case of axisymmetry, and (ii) certain additional, superposed, contaminating Fourier harmonics which distort their appearances. The natural frequency and mode structure of a model periodic structure is discussed in the context of an otherwise axisymmetric disk having evenly-spaced, sector-shaped, line distributions of stiffness and inertia. Through a perturbation analysis, the contamination wavenumbers present in a doublet having repeated frequency are shown to comprise two subsets, the members of which have sine and cosine coefficients of the same, or of differing, signs for each wavenumber present in the mode shape’s Fourier expansion. That structure for the wavenumber content is explored further with respect to the response of repeated and split doublets to a harmonic traveling wave excitation. The individual Fourier components comprising a modulated doublet mode shape can propagate in the same direction as the excitation, or opposite to it, depending on the wavenumber of the excitation and the subset to which the contamination wavenumber belongs. The response of the split frequency doublets and the circumstances under which traveling or standing wave responses, or a blend of the two, can occur in the structure’s reference frame are examined and discussed in the context of the model periodic structure. The qualitative character of the response, the forward or backward propagation direction of each mode’s constituent wavenumber components, and the phase speeds of those components are discussed in illustrative case studies.

Calculating Salmonella Inactivation in Nonisothermal Heat Treatments from Isothermal Nonlinear Survival Curves

2001 ◽  
Vol 64 (5) ◽  
pp. 606-613 ◽  
Author(s):  
K. L. MATTICK ◽  
J. D. LEGAN ◽  
T. J. HUMPHREY ◽  
M. PELEG
Keyword(s):  
Differential Equation ◽  
Heat Treatment ◽  
Mathematical Models ◽  
Survival Curve ◽  
Survival Ratio ◽  
Survival Curves ◽  
Time Intervals ◽  
Heat Treated ◽  
Rich Media ◽  
Nonisothermal Conditions

Salmonella cells in two sugar-rich media were heat treated at various constant temperatures in the range of 55 to 80°C and their survival ratios determined at various time intervals. The resulting nonlinear semilogarithmic survival curves are described by the model log10S(t) = −b(T)tn(T), where S(t) is the momentary survival ratio N(t)/N0, and b(T) and n(T) are coefficients whose temperature dependence is described by two empirical mathematical models. When the temperature profile, T(t), of a nonisothermal heat treatment can also be expressed algebraically, b(T) and n(T) can be transformed into a function of time, i.e., b[T(t)] and n[T(t)]. If the momentary inactivation rate primarily depends on the momentary temperature and survival ratio, then the survival curve under nonisothermal conditions can be constructed by solving a differential equation, previously suggested by Peleg and Penchina, whose coefficients are expressions that contain the corresponding b[T(t)] and n[T(t)] terms. The applicability of the model and its underlying assumptions was tested with a series of eight experiments in which the Salmonella cells, in the same media, were heated at various rates to selected temperatures in the range of 65 to 80°C and then cooled. In all the experiments, there was an agreement between the predicted and observed survival curves. This suggests that, at least in the case of Salmonella in the tested media, survival during nonisothermal inactivation can be estimated without assuming any mortality kinetics.

scholarly journals EFFECT OF CHEMICAL AND THERMAL TREATMENTS ON INHIBITION OF PEROXIDASE ACTIVITIE OF PURPLE SKIN EGGPLANT (SOLANUMMELONGENA L.)

2021 ◽  
Vol 9 (04) ◽  
pp. 304-313
Author(s):  
Jocelyn Constant Yapi ◽  
◽  
Jean Bedel Fagbohoun ◽  
Zranseu Ange Benedicte Deffan ◽  
Elvis Gbocho Serge Ekissi ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Thermal Inactivation ◽  
Solanum Melongena ◽  
Thermal Treatments ◽  
Optimal Temperature ◽  
Spectrophotometric Methods ◽  
Acid Effect ◽  
Fresh Cut ◽  
D Values ◽  
Increasing Temperature

Peroxidase (POD) associated with the browning of fresh-cut fruits and vegetableswas extracted from purple skin eggplant(Solanum melongena L.) and characterised using reliable spectrophotometric methods. Maximal POD activity was found at 35 °C and pH 6.0 with guaiacol as the substrate. The enzyme was stable at his optimal temperature (35 °C) and hisat pH stability was in the range of 5.6 - 6.6.Peroxidase retained its full activity in the presence of ion K+, Cu2+, Na+, Pb2+ and Ba2+ but were inhibited strongly by the ion Fe2+ and Mg2+ and the reducing agents as sodium thiosulfateand ascorbic acid. Effect of heattreatment on eggplant peroxidase showed that D-values decreased with increasing temperature, indicating faster peroxidase inactivation at higher temperatures.At 60 °C, the D-values ranged from 20.42 to 54.24 min. Hence, heat treatment at 60 °C for 30 min reduced browning of eggplant fruit.These data can be used to predict prevention of browning in the purple skin eggplantby thermal inactivation and the use of chimical agents onthe enzyme.

Transport kinetics of methanol in hydroxyethyl methacrylate homopolymer and its copolymers

2004 ◽  
Vol 19 (11) ◽  
pp. 3359-3363 ◽  
Author(s):  
C-S. Tsai ◽  
Sanboh Lee ◽  
Tinh Nguyen
Keyword(s):  
Continuous Phase ◽  
Transport Processes ◽  
Hydroxyethyl Methacrylate ◽  
Nominal Thickness ◽  
Methacrylate Copolymers ◽  
Different Temperatures ◽  
Free Energy Of Mixing ◽  
D Values ◽  
Increasing Temperature ◽  
Kinetics Of

The kinetics of methanol transport in 2-hydroxyethyl methacrylate (HEMA) homopolymer and 75/25 and 50/50 mol fraction HEMA/DHPMA (2,3-dihydroxypropyl methacrylate) copolymers at five different temperatures has been investigated using the sorption experiment technique. A combined case I and case II diffusion model was used to describe the transport processes. Four replicates for each temperature of each material having a nominal thickness of 0.1 mm were immersed in methanol maintained at 35, 40, 45, 50, and 55 °C, and the mass uptake as a function of time was measured gravimetrically. Experimental results are found to be in good agreement with model prediction at all temperatures and for all three materials. Both the diffusion coefficients of case I transport and velocity of case II transport increase with increasing temperature. D values at low temperatures (35 and 40 °C), which are in the 10−9 cm2/s range, of the HEMA homopolymer are less than those of the copolymers. On the other hand, the activation energies of case I transport of the copolymers are substantially higher than those of the HEMA homopolymer; however, the level of DHPMA loading in the copolymer does not seem to affect the activation energy. In addition, thermodynamic heat and free energy of mixing values indicate heat is released when HEMA/DHPMA copolymers are exposed to methanol and that the solvent/copolymer systems exist as a continuous phase. In contrast, the methanol/HEMA homopolymer system exists as separate phases.

Demonstration of the Applicability of the Weibull–Log-Logistic Survival Model to the Isothermal and Nonisothermal Inactivation of Escherichia coli K-12 MG1655†

2004 ◽  
Vol 67 (11) ◽  
pp. 2617-2621 ◽  
Author(s):  
MARIA G. CORRADINI ◽  
MICHA PELEG
Keyword(s):  
Escherichia Coli ◽  
Logistic Model ◽  
Survival Ratio ◽  
Model Combination ◽  
Survival Curves ◽  
Dependent Rate ◽  
Nonisothermal Heating ◽  
Survival Patterns ◽  
K 12 ◽  
Heating Profiles

Published isothermal semilogarithmic survival curves of Escherichia coli K-12 MG1655, in the range of 49.8 to 60.6°C, all had noticeable downward concavity. They could be described by the model log S(t) = −b(T)tn, where S(t) = N(t)/N0, N(t) and N0 being the momentary and initial number of organisms, respectively; b(T) is a temperature-dependent rate parameter; and n is a constant found to be about 1.5. The temperature dependence of b(T) could be described by the log-logistic model, b(T) = ln{1 + exp[k(T − Tc)]}, which had an almost perfect fit, with k = 0.88°C−1 and Tc = 60.5°C. The constants, n, k, and Tc were considered the organism's survival parameters in the particular medium. They were incorporated into a rate equation on the assumption that in nonisothermal heating, the momentary inactivation rate is the isothermal rate at the momentary temperature at a time that corresponds to the momentary survival ratio. This model's estimates matched the actual survival curves obtained in the same work under two different nonisothermal heating profiles, lending support to the notion that the Weibull–log-logistic model combination can be used not only to describe isothermal inactivation mathematically, but also to predict survival patterns under nonisothermal conditions.

Effect of Using Milk as a Heating Menstruum on the Apparent Heat Resistance of Bacillus stearothermophilus Spores1

1977 ◽  
Vol 40 (4) ◽  
pp. 228-231 ◽  
Author(s):  
J. L. MAYOU ◽  
J. J. JEZESKI
Keyword(s):  
Heat Resistance ◽  
Bacillus Stearothermophilus ◽  
Survival Curves ◽  
Ph Range ◽  
D Values ◽  
D Value

Heat resistance at 121.1 C (250 F) of Bacillus stearothermophilus spores was studied using two heating menstrua. D values of 3.8 and 3.5 min were obtained when spores were heated in 0.01 M PO4 buffer, pH 6.5, and in skimmilk, pH 6.5, respectively. With buffer as a heating menstruum. increasing the pH from 6.5 to 7.2 resulted in an increase in the D value from 3.8 to 4.1 min. When the pH of skimmilk was increased from 6.5 to 7.2, D values increased from 3.5 to 5.2 min. Skimmilk as a component of the enumeration medium inhibited germination and/or outgrowth of B. stearothermophilus spores; however, this inhibition was not influenced over the pH range of 6.0 to 7.2. Addition of 10% skimmilk, pH 6.5, to the medium for enumeration of spores heated in buffer at pH 6.5 or 7.2, in each instance reduced the number of spores that could be recovered but did not change the slopes of survival curves.

Inactivation Kinetics of Three Listeria monocytogenes Strains under High Hydrostatic Pressure

2008 ◽  
Vol 71 (10) ◽  
pp. 2007-2013 ◽  
Author(s):  
INEKE K. H. VAN BOEIJEN ◽  
ROY MOEZELAAR ◽  
TJAKKO ABEE ◽  
MARCEL H. ZWIETERING
Keyword(s):  
Listeria Monocytogenes ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
Inactivation Kinetics ◽  
Wild Type ◽  
First Order Kinetics ◽  
Survival Capacity ◽  
D Values ◽  
Kinetics Of ◽  
Stable Feature

High hydrostatic pressure (HHP) inactivation of three Listeria monocytogenes strains (EGDe, LO28, and Scott A) subjected to 350 MPa at 20°C in ACES buffer resulted in survival curves with significant tailing for all three strains. A biphasic linear model could be fitted to the inactivation data, indicating the presence of an HHP-sensitive and an HHP-resistant fraction, which both showed inactivation according to first-order kinetics. Inactivation parameters of these subpopulations of the three strains were quantified in detail. EGDe showed the highest D-values for the sensitive and resistant fraction, whereas LO28 and Scott A showed lower HHP resistance for both fractions. Survivors isolated from the tail of LO28 and EGDe were analyzed, and it was revealed that the higher resistance of LO28 was a stable feature for 24% (24 of 102) of the resistant fraction. These HHP-resistant variants were 10 to 600,000 times more resistant than wild type when exposed to 350 MPa at 20°C for 20 min. Contrary to these results, no stable HHP-resistant isolates were found for EGDe (0 of 102). The possible effect of HHP survival capacity of stress-resistant genotypic and phenotypic variants of L. monocytogenes on the safety of HHP-processed foods is discussed.

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