Heat Tolerances of Salmonella, Cronobacter sakazakii, and Pediococcus acidilactici Inoculated into Galactooligosaccharide

2017 ◽  
Vol 80 (7) ◽  
pp. 1123-1127 ◽  
Author(s):  
Jihyun Bang ◽  
Moonkak Choi ◽  
Haeseok Jeong ◽  
Sangseob Lee ◽  
Yoonbin Kim ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Microbial Population ◽  
Heating Time ◽  
Pathogenic Microorganisms ◽  
Pediococcus Acidilactici ◽  
Cronobacter Sakazakii ◽  
Decimal Reduction Time ◽  
Treatment Conditions ◽  
Heat Treated ◽  
D Values

ABSTRACT Food-grade galactooligosaccharide (GOS) with low water activity (aw of ca. 0.7) is used as an ingredient in various foods. We evaluated heat tolerances of Salmonella, Cronobacter sakazakii, and Pediococcus acidilactici at temperatures (70 to 85°C) used during the saturation process of GOS by comparing decimal reduction time (D-values) and thermal resistance constants (z-values). To determine the D- and z-values, GOS containing Salmonella (5.1 to 5.8 log CFU/g) or C. sakazakii (5.3 to 5.9 log CFU/g) was heat treated at 70, 77.5, or 85°C for up to 40, 25, or 15 s, respectively, and GOS containing P. acidilactici (6.1 to 6.5 log CFU/g) was heat treated at 70, 77.5, or 85°C for up to 150, 75, or 40 s, respectively. The D-values were calculated using a linear model for heating time versus microbial population for each bacterium. When the D-values for Salmonella, C. sakazakii, and P. acidilactici in GOS were compared, the thermal resistance of all bacteria decreased as the temperature increased. Among the three bacteria, P. acidilactici had higher D-values than did Salmonella and C. sakazakii. The z-values of Salmonella, C. sakazakii, and P. acidilactici were 30.10, 33.18, and 13.04°C, respectively. Overall order of thermal resistance was P. acidilactici > Salmonella ≈ C. sakazakii. These results will be useful for selecting appropriate heat treatment conditions for the decontamination of pathogenic microorganisms during GOS manufacturing.

Thermal Resistance of Aeromonas hydrophila in Liquid Whole Egg†

1997 ◽  
Vol 60 (3) ◽  
pp. 231-236 ◽  
Author(s):  
JAMES D. SCHUMAN ◽  
BRIAN W. SHELDON ◽  
PEGGY M. FOEGEDING
Keyword(s):  
Thermal Resistance ◽  
Aeromonas Hydrophila ◽  
Animal Origin ◽  
Inactivation Kinetics ◽  
Processing Plant ◽  
Decimal Reduction Time ◽  
Heat Resistant ◽  
Liquid Whole Egg ◽  
D Values ◽  
Whole Egg

Aeromonas hydrophila (AH) is a psychrotrophic spoilage bacterium and potential pathogen which has been isolated from a variety of refrigerated foods of animal origin, including raw milk, red meat, poultry, and commercially broken raw liquid whole egg (LWE). Decimal reduction times (D values) of 4 strains of AH (1 egg isolate, 2 egg processing plant isolates, 1 ATCC type strain) were determined in LWE using an immersed sealed capillary tube (ISCT) procedure. Initial populations (7.0 to 8.3 log CFU/tube in 0.05 ml LWE) were heated at 48, 51, 54, 57, and 60°C, and survivors were plated onto starch ampicillin agar (48 h at 28°C). D values ranged from 3.62 to 9.43 min (at 48°C) to 0.026 to 0.040 min (at 60°C). Both processing plant isolates were more heat resistant than the ATCC strain. Decimal reduction time curves (r2 ≤ 0.98) yielded ZD values of 5.02 to 5.59°C, similar to those for other non-spore-forming bacteria. D values of the most heat resistant AH strain were also determined in LWE at 48, 51, and 54°C using a conventional capped test tube procedure (10 ml/tube). Cells heated in test tubes yielded nonlinear (tailing) survivor curves and larger (P ≤ 0.05) apparent D values at each temperature than those obtained using the ISCT method. This study provides the first thermal resistance data for AH in LWE and the first evidence that straight-line semilogarithmic thermal inactivation kinetics may be demonstrated for Aeromonas using the ISCT procedure.

D Values of Bacillus stearothermophilus Spores as a Function of pH and Recovery Medium Acidulant

1995 ◽  
Vol 58 (6) ◽  
pp. 628-632 ◽  
Author(s):  
P. S. FERNÁNDEZ ◽  
F. J. GÓMEZ ◽  
M. J. OCIO ◽  
M. RODRIGO ◽  
T. SÁNCHEZ ◽  
...  
Keyword(s):  
Citric Acid ◽  
Thermal Resistance ◽  
Bacillus Stearothermophilus ◽  
Great Influence ◽  
Bidistilled Water ◽  
Mushroom Extract ◽  
Heat Treated ◽  
Reference Medium ◽  
D Values ◽  
Recovery Medium

The effect of the pH and the type of acidulant (citric acid or glucono-δ-lactone) of the recovery medium on the thermal resistance of Bacillus stearothermophilus ATCC 12980 was studied. The spores were heated in bidistilled water as a reference substrate and in acidified mushroom extract using citric acid or glucono-δ-lactone as acidulants (pH 6.2) and subcultured in reference (pH 7) and acidified (pH 6.2) media. A period of treatment-dependent pH sensitization was observed in heat-treated spores. In all cases, D values were lower in the acidified recovery medium than those obtained in the reference medium, but the type of acidulant used in the recovery medium had no influence on the D values. No influence on z values was observed as a consequence of the different recovery media, but they changed within a range of 7 to 10°C as a function of the different heating substrates. Glucono-δ-lactone proved to be as effective as citric acid in controlling the microbiological spoilage of foods. The pH has a great influence on decreasing the D values, mainly when acidification of the substrate and acidification of the recovery medium are combined. Consequently, it would be appropriate to take this effect into account in process calculations or validation.

Effect of copper incorporation on phase transformation behavior of electroless nickel–phosphorous coating and its effect on the tribological behavior

2020 ◽  
pp. 146442072098160
Author(s):  
Abhijit Biswas ◽  
Suman Kalyan Das ◽  
Prasanta Sahoo
Keyword(s):  
Heat Treatment ◽  
Phase Transformation ◽  
Tribological Behavior ◽  
Electroless Nickel ◽  
Two Phase ◽  
Microstructural Changes ◽  
Treatment Conditions ◽  
Heat Treated ◽  
Higher Temperature ◽  
Effect Of Copper

The microstructural changes of electroless Ni–P–Cu coating at various heat-treatment conditions are investigated to understand its implications on the tribological behavior of the coating. Coatings are heat-treated at temperatures ranging between 200°C and 800 °C and for 1–4 h duration. Ni–P–Cu coatings exhibit two-phase transformations in the temperature range of 350–450 °C and the resulting microstructural changes are found to significantly affect their thermal stability and tribological attributes. Hardness of the coating doubles when heat-treated at 452 °C, due to the formation of harder Ni3P phase and crystalline NiCu. Better friction and wear performance are also noted upon heat treatment of the coating at the phase transformation regime, particularly at 400 °C. Wear mechanism is characterized by a mixed adhesive cum abrasive wear phenomena. Heat treatment at higher temperature (600 °C and above) and longer duration (4 h) results in grain coarsening phenomenon, which negatively influences the hardness and tribological characteristics of the coating. Besides, diffusion of iron from the ferrous substrate as well as greater oxide formation are noticed when the coating is heat-treated at higher temperatures and for longer durations (4 h).

Changes in Microstructure of Biomedical Co-Cr-Mo-C Alloys with Solution Treating and Aging

2010 ◽  
Vol 89-91 ◽  
pp. 377-382 ◽  
Author(s):  
S. Mineta ◽  
Shigenobu Namba ◽  
Takashi Yoneda ◽  
Kyosuke Ueda ◽  
Takayuki Narushima
Keyword(s):  
Solution Treatment ◽  
Heating Time ◽  
Treatment Temperature ◽  
Vacuum Furnace ◽  
Solution Treatment Temperature ◽  
Precipitate Dissolution ◽  
Heat Treated ◽  
M23c6 Type ◽  
Type Carbide ◽  
Time Required

Microstructural changes occurring in biomedical Co-Cr-Mo alloys with three carbon levels due to solution treatment and aging were investigated. Ingots of Co-Cr-Mo alloys with three different carbon levels were prepared by vacuum furnace melting; their chemical composition was Co-28Cr-6Mo-xC (x = 0.12, 0.25 and 0.35 mass%). Precipitates were electrolytically extracted from as-cast and heat-treated alloys. An M23C6 type carbide and a phase were detected as precipitates in as-cast Co-28Cr-6Mo-0.12C alloy, and an M23C6 type carbide and an  phase (M6C-M12C type carbide) were detected in as-cast Co-28Cr-6Mo-0.25C and Co-28Cr-6Mo-0.35C alloys. Only the M23C6 type carbide was detected during solution treatment. Complete precipitate dissolution occurred in all the three alloys after solution treatment. The holding time required for complete precipitate dissolution increased with increasing carbon content and decreasing solution treatment temperature. Complete precipitate dissolution occurred in the Co-Cr-Mo-C alloys solution treated at 1523 K for 43.2 ks; they were then subjected to aging from 873 to 1473 K for a heating time up to 44.1 ks after complete precipitate dissolution in solution treatment at 1523 K for 43.2 ks. The M23C6 type carbide with a grain size of 0.1–3 m was observed after aging. A time-temperature-precipitation diagram of the M23C6 type carbide formed in the Co-28Cr-6Mo-0.25C alloy was plotted.

Creation of Patterned Gold Nanostructures via Electron-Beam-Induced Deposition

2013 ◽  
Vol 1546 ◽  
Author(s):  
Anastasia V. Riazanova ◽  
Johannes J. L. Mulders ◽  
Lyubov M. Belova
Keyword(s):  
Electron Beam ◽  
Three Dimensional ◽  
Area Ratio ◽  
Ex Situ ◽  
Geometrical Shape ◽  
Local Electron ◽  
Post Annealing ◽  
Treatment Conditions ◽  
Heat Treated ◽  
Electron Beam Induced Deposition

ABSTRACTOne of the methods to grow nanoscale three-dimensional (3D) Au patterns is to perform local electron-beam-induced deposition (EBID) using the Me2Au(acac) precursor inside the chamber of a scanning electron microscope (SEM). However, due to the organometallic nature of the chemical, the concentration of the metallic constituent in the as-deposited structure is dramatically low, at around 10 at. % of Au. Ex-situ post-annealing of Me2Au(acac) EBIDs is a very promising purification approach, resulting in an Au content of > 92 at. % after annealing at 600 °C. However, in most of the cases it also distorts the geometrical shape of the heat-treated structure, preserving of which is essential for the application. In this paper we present a systematic study of the dependence between the annealing parameters and resulting purity in combination with the shape of the Au structure. Optimized heat treatment conditions for the creation of well-purified high aspect ratio Au pillar array are presented; and for planar continuous structures, the importance of the parameter height to area ratio is identified.

Mechanical Behavior of Friction Stir Welded AA-6061 Thick Plates in Different Heat Treatment Conditions

2021 ◽  
Vol 875 ◽  
pp. 203-210
Author(s):  
Talha Ahmed ◽  
Wali Muhammad ◽  
Zaheer Mushtaq ◽  
Mustasim Billah Bhatty ◽  
Hamid Zaigham
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Aging Treatment ◽  
Travel Speed ◽  
Butt Joint ◽  
Tensile Fracture ◽  
Friction Stir ◽  
Treatment Conditions ◽  
Heat Treated ◽  
Joint Form

In this study, mechanical properties of friction stir welded Aluminum Alloy (AA) 6061 in three different heat treatment conditions i.e. Annealed (O), Artificially aged (T6) and Post Weld Heat Treated (PWHT) were compared. Plates were welded in a butt joint form. Parameters were optimized and joints were fabricated using tool rotational speed and travel speed of 500 rpm and 350 mm/min respectively. Two sets of plates were welded in O condition and out of which one was, later, subjected to post weld artificial aging treatment. Third set was welded in T6 condition. The welds were characterized by macro and microstructure analysis, microhardness measurement and mechanical testing. SEM fractography of the tensile fracture surfaces was also performed. Comparatively better mechanical properties were achieved in the plate with PWHT condition.

Thermal Inactivation of Borrelia burgdorferi, the Cause of Lyme Disease

1990 ◽  
Vol 53 (4) ◽  
pp. 296-299 ◽  
Author(s):  
SI K. LEE ◽  
AHMED E. YOUSEF ◽  
ELMER H. MARTH
Keyword(s):  
Borrelia Burgdorferi ◽  
Thermal Inactivation ◽  
Treatment Time ◽  
Treatment Temperature ◽  
Most Probable Number ◽  
Lag Phase ◽  
Probable Number ◽  
Heat Treated ◽  
Thermal Death ◽  
D Values

Borrelia burgdorferi strain EBNI was cultivated in BSK-II medium at 34°C, then cultures at different physiological states were heat-treated at temperatures in the range of 50 to 70°C. Numbers of survivors were estimated by the Most Probable Number technique. Log MPN was plotted against treatment time, and resulting survivor curves were linear. Estimated D-values for cultures incubated at 34°C for 7 d before heat-treatment were 5.5, 4.3, 2.7, .47, and .14 min at 50, 55, 60, 65, and 70°C, respectively. Spirochetes in the lag phase had greater resistance to heat than those in the stationary phase, with the latter being more resistant to heat than spirochetes in the same phase of growth but refrigerated at 4°C for 3 d. D-values for B. burgdorferi are generally less at 50°C, and greater at 70°C than those reported for other nonsporeforming pathogens. When log10 MPN was plotted against treatment temperature, two linear segments for each thermal death curve were obtained. Our data show the spirochete had higher z-values than most nonsporeforming pathogens. The pH of the medium, in the range of 5.0 to 7.6, did not affect resistance of B. burgdorferi to heat.

scholarly journals Choice of sterilizing/disinfecting agent: determination of the Decimal ReductionTime (D-Value)

2009 ◽  
Vol 45 (4) ◽  
pp. 701-708 ◽  
Author(s):  
Priscila Gava Mazzola ◽  
Angela Faustino Jozala ◽  
Letícia Célia de Lencastre Novaes ◽  
Patricia Moriel ◽  
Thereza Christina Vessoni Penna
Keyword(s):  
Medical Devices ◽  
Cross Contamination ◽  
Decimal Reduction Time ◽  
E Coli ◽  
Health Care Unit ◽  
Sodium Dichloroisocyanurate ◽  
D Values ◽  
Spread Of Infection ◽  
Disinfectant Efficacy

Efforts to diminish the transmission of infections include programs in which disinfectants play a crucial role. Hospital surfaces and medical devices are potential sources of cross contamination, and each instrument, surface or area in a health care unit can be responsible for spread of infection. The decimal reduction time was used to study and compare the behavior of selected strains of microorganisms. The highest D-values for various bacteria were obtained for the following solutions: (i) 0.1% sodium dichloroisocyanurate (pH 7.0) - E. coli and A. calcoaceticus (D = 5.9 min); (ii) sodium hypochlorite (pH 7.0) at 0.025% for B. stearothermophilus (D = 24 min), E. coli and E. cloacae (D = 7.5 min); at 0.05% for B. stearothermophilus (D = 9.4 min) and E. coli (D = 6.1 min). The suspension studies were an indication of the disinfectant efficacy on a surface. The data in this study reflect the formulations used and may vary from product to product. The expected effectiveness from the studied formulations shows that the tested agents can be recommended for surface disinfection as stated in present guidelines and emphasize the importance and need to develop routine and novel programs to evaluate product utility.

scholarly journals Heat-Treated Wood as a Substrate for Coatings, Weathering of Heat-Treated Wood, and Coating Performance on Heat-Treated Wood

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Vlatka Jirouš-Rajković ◽  
Josip Miklečić
Keyword(s):  
Heat Treatment ◽  
Wood Species ◽  
Treated Wood ◽  
Wood Properties ◽  
Treatment Method ◽  
Coating Performance ◽  
Treatment Processes ◽  
Treatment Conditions ◽  
Heat Treated ◽  
Trade Names

Heat treatment is a method of wood modification with increasing market acceptance in Europe. The major patented European commercial heat treatment processes have trade names ThermoWood, Platowood, Retiwood, Le Bois Perdure, and Oil-Heat-Treated Wood (OHT). To what extent modification of wood affects the resistance of wood to weathering is also an important aspect for wood applications, especially where appearance is important. Unfortunately, heat-treated wood has poor resistance to weathering, and surface treatment with coatings is required for both protection and aesthetic reasons. As a substrate for coating, heat-treated wood has altered characteristics such as lower hygroscopicity and liquid water uptake and changed acidity, wettability, surface free energy, and anatomical microstructure. Various wood species, heat treatment method, treatment intensity, and treatment conditions exhibited a different extent of changes in wood properties. These altered properties could affect coating performance on heat-treated wood. The reported changes in acidity and in surface energy due to heat treatments are inconsistent with one another depending on wood species and temperature of the treatments. This paper gives an overview of the research results with regards to properties of heat-treated wood that can affect coating performance and weathering of uncoated and coated heat-treated wood.

The Heat Resistance of Spores of Clostridium botulinum 213B Heated at 121–130°C in Acidified Mushroom Extract

1992 ◽  
Vol 55 (11) ◽  
pp. 913-915 ◽  
Author(s):  
K. L. BROWN ◽  
A. MARTINEZ
Keyword(s):  
Citric Acid ◽  
Thermal Resistance ◽  
Heat Resistance ◽  
High Temperatures ◽  
Clostridium Botulinum ◽  
Mushroom Extract ◽  
D Values

Spores of Clostridium botulinum 213B were heated in mushroom extract acidified to pH 6 with citric acid or glucono-deltalactone at temperatures of 121.1, 125, and 130°C using a thermoresistometer. Decimal reduction times were similar in acidified and natural pH (6.7) mushroom extract. At 121.1, 125, and 130°C, D values were in the range 2.44 – 2.55 s, 0.91–1.45 s, and 0.51–0.75 s, respectively. There was no evidence that mild acidification reduced thermal resistance at high temperatures.

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