The Effect of Nisin on Growth Kinetics from Activated Bacillus cereus Spores in Cooked Rice and in Milk

2002 ◽  
Vol 65 (2) ◽  
pp. 419-422 ◽  
Author(s):  
THEREZA CHRISTINA VESSONI PENNA ◽  
DANTE AUGUSTO MORAES ◽  
DALETE NOGUEIRA FAJARDO
Keyword(s):  
Bacillus Cereus ◽  
Growth Kinetics ◽  
Lag Phase ◽  
White Rice ◽  
Decimal Reduction Time ◽  
Cooked Rice ◽  
Generation Times ◽  
Different Temperatures ◽  
D Values ◽  
Kinetics Of

The growth kinetics of germinated cells from activated spores of Bacillus cereus in cooked white rice and in milk were evaluated at different temperatures for control samples and for samples with 25 μg of nisin per ml added. Nisin was applied in the form of Nisaplin (106 IU/g), which contained 25,000 μg of nisin per g. The length of the lag phase for cooked white rice controls was 120 h at 10°C, 8 h at 25°C, and 2.5 h at 33°C. The generation times for cooked rice were 327.7 min at 10°C, 59.0 min at 25°C, and 42.3 min at 33°C; those for milk without nisin were 297.0 min at 20°C, 31.2 min at 30°C, 28.6 min at 35°C, and 33.7 min at 40°C; and those for milk with nisin added were 277.2 min at 20°C, 66.9 min at 30°C, and 66.4 min at 35°C. No development of B. cereus was observed for milk with nisin added at 40°C for 12 h, in which germinated cells decreased by a decimal reduction time (D) of 4.7 h. A temperature of 45°C was shown to be harmful to B. cereus, decreasing the germinated cells in both formulations with D-values of 4.3 to 4.6 h. Similar inhibition of cell growth at 40°C was not observed with lower nisin concentrations.

GROWTH OF OXIDE LAYER ON GERMANIUM (011) SUBSTRATE UNDER DRY AND WET ATMOSPHERES

1999 ◽  
Vol 06 (06) ◽  
pp. 1053-1060 ◽  
Author(s):  
N. TABET ◽  
J. AL-SADAH ◽  
M. SALIM
Keyword(s):  
Simple Model ◽  
Oxide Film ◽  
Growth Kinetics ◽  
Photoelectron Spectroscopy ◽  
Early Stage ◽  
X Ray ◽  
Apparent Thickness ◽  
Different Temperatures ◽  
Kinetics Of

X-ray Photoelectron Spectroscopy (XPS) has been used to investigate the oxidation of (011) Ge substrates. The sample surfaces were CP4-etched, then annealed in situ, at different temperatures, for various durations. Dry and wet atmospheres were used. The oxidation rate during the early stage was increased by the presence of moisture in the atmosphere. A simple model was used to define and determine an apparent thickness of the oxide film from XPS measurements. The time dependence of the apparent thickness is consistent with a partial coverage of the surface by oxide islands. The growth kinetics of the oxide islands obeys a nearly cubic law.

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.

Thermal Inactivation Kinetics of Sporolactobacillus nakayamae Spores, a Spoilage Bacterium Isolated from a Model Mashed Potato–Scallion Mixture

2016 ◽  
Vol 79 (9) ◽  
pp. 1482-1489
Author(s):  
HAYRIYE BOZKURT ◽  
JAIRUS R. D. DAVID ◽  
RYAN J. TALLEY ◽  
D. SCOTT LINEBACK ◽  
P. MICHAEL DAVIDSON
Keyword(s):  
Heat Resistance ◽  
Thermal Inactivation ◽  
Weibull Model ◽  
Inactivation Kinetics ◽  
Order Model ◽  
First Order ◽  
Different Temperatures ◽  
Spoilage Bacterium ◽  
D Values ◽  
Kinetics Of

ABSTRACT Sporolactobacillus species have been occasionally isolated from spoiled foods and environmental sources. Thus, food processors should be aware of their potential presence and characteristics. In this study, the heat resistance and influence of the growth and recovery media on apparent heat resistance of Sporolactobacillus nakayamae spores were studied and described mathematically. For each medium, survivor curves and thermal death curves were generated for different treatment times (0 to 25 min) at different temperatures (70, 75, and 80°C) and Weibull and first-order models were compared. Thermal inactivation data for S. nakayamae spores varied widely depending on the media formulations used, with glucose yeast peptone consistently yielding the highest D-values for the three temperatures tested. For this same medium, the D-values ranged from 25.24 ± 1.57 to 3.45 ± 0.27 min for the first-order model and from 24.18 ± 0.62 to 3.50 ± 0.24 min for the Weibull model at 70 and 80°C, respectively. The z-values determined for S. nakayamae spores were 11.91 ± 0.29°C for the Weibull model and 11.58 ± 0.43°C for the first-order model. The calculated activation energy was 200.5 ± 7.3 kJ/mol for the first-order model and 192.8 ± 22.1 kJ/mol for the Weibull model. The Weibull model consistently produced the best fit for all the survival curves. This study provides novel and precise information on thermal inactivation kinetics of S. nakayamae spores that will enable reliable thermal process calculations for eliminating this spoilage bacterium.

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.

scholarly journals Death kinetics of Escherichia coli in goat milk and Bacillus licheniformis in cloudberry jam treated by ohmic heating

2007 ◽  
Vol 61 (2) ◽  
Author(s):  
R. Pereira ◽  
J. Martins ◽  
C. Mateus ◽  
J. Teixeira ◽  
A. Vicente
Keyword(s):  
Escherichia Coli ◽  
Bacillus Licheniformis ◽  
Ohmic Heating ◽  
Goat Milk ◽  
Conventional Heating ◽  
Decimal Reduction Time ◽  
Fold Reduction ◽  
Death Kinetics ◽  
D Values ◽  
Kinetics Of

AbstractThe influence of ohmic heating on the death kinetic parameters of Escherichia coli ATCC® 25922 in goat milk and spores of Bacillus licheniformis ATCC® 14580 in cloudberry jam was investigated and compared with that of conventional heating. Ohmic treatment of goat milk shortened the decimal reduction time D in comparison with the D values obtained at conventional treatment. Similarly, the z value, increase of temperature required for a ten-fold reduction of D, was also lower at ohmic treatment. The death kinetics of Bacillus licheniformis ATCC® 14580 spores in cloudberry jam was also studied employing both types of heat treatment. Similar conclusions were obtained for the D values as in the case of goat milk. However, the differences between the z values obtained for ohmic and conventional heating were not significant.

Microstructures evolution and growth kinetics of intermetallic compounds in Cu/Sn/Cu system during ultrasonic soldering process

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xu Han ◽  
Xiaoyan Li ◽  
Peng Yao
Keyword(s):  
Grain Boundary ◽  
Microstructural Evolution ◽  
Growth Kinetics ◽  
Boundary Diffusion ◽  
Solder Joints ◽  
Content Type ◽  
Soldering Process ◽  
Different Temperatures ◽  
Ultrasonic Soldering ◽  
Kinetics Of

Purpose This study aims to investigate the effect of ultrasound on interfacial microstructures and growth kinetics of intermetallic compounds (IMCs) at different temperatures. Design/methodology/approach To investigate the effect of ultrasound on IMCs growth quantitatively, the cross-sectional area of IMCs layers over a confirmed length was obtained for calculating the thickness of the IMCs layer. Findings The generation of dimensional difference in normal direction between Cu6Sn5 and its adjacent Cu6Sn5, formation of bossed Cu6Sn5 and non-interfacial Cu6Sn5 in ultrasonic solder joints made the interfacial Cu6Sn5 layer present a non-scallop-like morphology different from that of traditional solder joints. At 260°C and 290°C, the Cu3Sn layer presented a wave-like shape. In contrast, at 320°C, the Cu3Sn in ultrasonic solder joints consisted of non-interfacial Cu3Sn and interfacial Cu3Sn with a branch-like shape. The Cu6Sn5/Cu3Sn boundary and Cu3Sn/Cu interface presented a sawtooth-like shape under the effect of ultrasound. The predominant mechanism of ultrasonic-assisted growth of Cu6Sn5 growth at 260°C, 290°C and 320°C involved the grain boundary diffusion accompanied by grain coarsening. The Cu3Sn growth was controlled by volume diffusion during the ultrasonic soldering process at 260°C and 290°C. The diffusion mechanism of Cu3Sn growth transformed to grain boundary diffusion accompanied by grain coarsening when the ultrasonic soldering temperature was increased to 320°C. Originality/value The microstructural evolution and growth kinetics of IMCs in ultrasonically prepared ultrasonic solder joints at different temperatures have rarely been reported in previous studies. In this study, the effect of ultrasound on microstructural evolution and growth kinetics of IMCs was systematically investigated.

Growth kinetics of chemically vapor deposited SiO2 films from silane oxidation

1998 ◽  
Vol 13 (8) ◽  
pp. 2308-2314 ◽  
Author(s):  
Fernando Ojeda ◽  
Alejandro Castro-García ◽  
Cristina Gómez-Aleixandre ◽  
José María Albella
Keyword(s):  
Gas Phase ◽  
Deposition Rate ◽  
Growth Kinetics ◽  
Film Growth ◽  
Chemical Vapor ◽  
Intermediate Species ◽  
Pressure Oxygen ◽  
Pressure Chemical ◽  
Different Temperatures ◽  
Kinetics Of

The growth kinetics of SiO2 thin films obtained by low-pressure chemical vapor deposition (CVD) from SiH4/O2/N2 gas mixtures has been determined at different temperatures and flow rates. The results show that the film growth is originated by some intermediate species (e.g., SiOxHy) produced in the gas phase. At low temperatures the deposition rate is limited by some homogeneous reaction with an apparent activation energy of 1.42 eV. Furthermore, the observation of critical limits when total pressure, oxygen/silane flow ratio, and temperature are decreased gives support to a branching-chain mechanism of deposition. Finally, we have observed that the deposition rate shows a hysteresis behavior when varying the temperature within the 300–400 °C range, which has been attributed to the inhibition of silane oxidation by the Si–OH surface groups of the films grown on the reactor walls.

Kinetics of Bacillus cereus Spore Inactivation in Cooked Rice by Combined Pressure–Heat Treatment

2013 ◽  
Vol 76 (4) ◽  
pp. 616-623 ◽  
Author(s):  
HOSSEIN DARYAEI ◽  
V. M. BALASUBRAMANIAM ◽  
J. DAVID LEGAN
Keyword(s):  
Heat Treatment ◽  
Bacillus Cereus ◽  
Treatment Time ◽  
Weibull Model ◽  
Process Temperature ◽  
Atmospheric Conditions ◽  
Undetectable Level ◽  
Decimal Reduction Time ◽  
Reduction Time ◽  
Cooked Rice

The efficacy of pressure–heat treatment was evaluated for the inactivation of Bacillus cereus spores in cooked rice. The spores of B. cereus ATCC 9818 were inoculated (1.1 × 108 CFU/g) in a parboiled rice product (pH 6.0, water activity of 0.95) and inactivated to an undetectable level (<10 CFU/g) by treatment of 600 MPa and process temperatures of 60 to 85°C or 0.1 MPa and 85°C. Kinetic inactivation parameters were estimated with linear and nonlinear models. The potential recovery of injured bacteria was also evaluated during storage of the treated product for 4 weeks at 4 and 25°C. Depending on the process temperature, a 600-MPa treatment inactivated spores by 2.2 to 3.4 log during the 30-s pressure come-up time, and to below the detection limit after 4- to 8-min pressure-holding times. In contrast, a 180-min treatment time was required to inactivate the spores to an undetectable level at 0.1 MPa and 85°C. The decimal reduction time of spores inactivated by combined pressure–heat treatment ranged from 1.08 to 2.36 min, while it was 34.6 min at 85°C under atmospheric conditions. The nonlinear Weibull model scale factor increased, and was inversely related to the decimal reduction time, and the shape factor decreased with increasing pressure or temperature. The recovery of injured spores was influenced by the extent of pressure-holding time and process temperature. This study suggests that combined pressure–heat treatment could be used as a viable alternative to inactivate B. cereus spores in cooked rice and extend the shelf life of the product.

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