A technique for obtaining linear heat-survivor curves with Staphylococcus aureus and its application to the assay of sublethal heat injury

1975 ◽  
Vol 21 (11) ◽  
pp. 1880-1884
Author(s):  
Andre Hurst ◽  
Ashton Hughes ◽  
Georgia Whitfield
Keyword(s):  
Heat Treatment ◽  
Staphylococcus Aureus ◽  
Modified Technique ◽  
Heat Injury ◽  
Linear Heat ◽  
Heat Treated ◽  
Batch Technique ◽  
D Values

Staphylococcus aureus was grown in a complex (HK) medium either by a batch technique or by a modified batch technique after growth in a chemostat. These cultures were heat-treated at 52 °C, and counted on trypticase soy agar (TSA) or trypticase soy agar containing 7.5% NaCl (TSAS). When linear heat-survivor curves were obtained decimal reduction times (D52°C) could be calculated from the TSA counts and pseudodecimal reduction times (D′52°C) from the TSAS counts. The D or D′ values of batch-grown cells varied from 22 to 133 min and from 3 to 12 min, respectively. With cells grown by the modified technique the values were less variable (D was 22–51 min and D′ was 3–7 min). D and D′ values could be calculated from the same heat treatment in two of six estimations with batch-grown cells but in six of six estimations with cells grown by the modified technique.

The reliability of selective media for the enumeration of unheated and heated staphylococci

1974 ◽  
Vol 20 (12) ◽  
pp. 1735-1744 ◽  
Author(s):  
M. E. Stiles ◽  
P. C. Clark
Keyword(s):  
Heat Treatment ◽  
Staphylococcus Aureus ◽  
Relative Efficiency ◽  
Protective Action ◽  
Egg Yolk ◽  
Protective Agent ◽  
Selective Media ◽  
Heat Injury

The relative efficiency of 15 selective media for enumerating unheated and sublethally heated strains of Staphylococcus aureus was tested against tryptic soy agar (Difco). Baird-Parker's egg yolk tellurite glycine pyruvate agar was found to be the medium of choice for both unheated and sublethally heated cells. Tellurite polymyxin egg yolk agar and egg yolk azide agar also gave favorable results. For unheated cells, Vogel-Johnson agar and tellurite glycine agar gave satisfactory results, but after heat treatment, even after a 10-h enrichment in tryptic soy broth for resuscitation of the heat injury, these media gave unreliable counts. Egg yolk acted not only as a diagnostic, but also as a protective agent in selective media for staphylococci. The protective action of egg yolk was more effective in azide- and tellurite-containing selective media than in salt-containing selective media.

Survival of Methicillin-Resistant Staphylococcus aureus during Commercial Heat Treatment of Slab Bacon and Consumer Preparation of Sliced Bacon

2014 ◽  
Vol 77 (1) ◽  
pp. 83-86 ◽  
Author(s):  
JONATHAN A. CAMPBELL ◽  
JAMES S. DICKSON ◽  
JOSEPH C. CORDRAY ◽  
DENNIS OLSON ◽  
AUBREY F. MENDONCA ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Staphylococcus Aureus ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Methicillin Resistant ◽  
Processed Meats ◽  
Log Reduction ◽  
Pork Products ◽  
Heat Treated ◽  
Mrsa Infection ◽  
Commercial Process

With the knowledge that retail pork products may be contaminated with methicillin-resistant Staphylococcus aureus (MRSA), the risk of consumers contracting a MRSA infection or foodborne illness from processed meats, especially bacon, is uncertain. Therefore, a study was designed to investigate the survival of MRSA during heat treatment of slab bacon at a commercial process and during cooking of sliced bacon at the consumer level. Fresh pork bellies were injected with a curing solution, inoculated, and heat treated to an internal temperature of 52°C. Three commercial brands of sliced bacon with similar “sell by” dates and fat-to-lean ratios were also inoculated and cooked at a temperature of 177°C for 0, 2, and 5 min on each side. Heat-treated slab bacon showed a log reduction of 1.89, which was significant (P < 0.05) compared with an uncooked inoculated control. Cooked sliced bacon had a reduction of viable MRSA cells of >6.5 log CFU/cm2, and there was not a significant brand interaction (P > 0.05).

Synthesis of enterotoxin B by Staphylococcus aureus strain S6 after recovery from heat injury

1973 ◽  
Vol 19 (12) ◽  
pp. 1463-1468 ◽  
Author(s):  
D. L. Collins-Thompson ◽  
A. Hurst ◽  
H. Kruse
Keyword(s):  
Heat Treatment ◽  
Staphylococcus Aureus ◽  
Salt Tolerance ◽  
Sodium Phosphate ◽  
Potassium Phosphate ◽  
Aureus Strain ◽  
Heat Injury ◽  
K Cells ◽  
Enterotoxin B ◽  
And Control

After sublethal heat treatment of Staphylococcus aureus S6 at 52C for 15 min in either 0.1 M sodium phosphate (Na cells) or 0.1 M potassium phosphate (K cells), more than 99% of the cells were unable to grow on a medium containing 7.5% NaCl. When placed in H and K medium the survivors recovered their salt tolerance and grew after a lag of 3 h (Na cells) or 5 h (K cells). In the absence of glucose, the total amount of enterotoxin B synthesized by the Na and K cells was similar to the control cells. Addition of 0.1% glucose to the medium increased the total amount of toxin formed by Na, K, and control cells.

Effect of combined ultrasonic and heat treatment (thermoultrasonication) on the survival of a strain ofStaphylococcus aureus

1987 ◽  
Vol 54 (1) ◽  
pp. 61-67 ◽  
Author(s):  
Juan A. Ordoñez ◽  
M. Angeles Aguilera ◽  
M. Luisa Garcia ◽  
Bernabe Sanz
Keyword(s):  
Heat Treatment ◽  
Staphylococcus Aureus ◽  
Phosphate Buffer ◽  
Ultrasonic Waves ◽  
Combined Effect ◽  
Ofstaphylococcus Aureus ◽  
Combined Process ◽  
Two Agents ◽  
Heat Treated ◽  
Whole Milk

SummaryThe combined effect of ultrasonic waves (20 kHz, 150 W) and heat treatment applied simultaneously (thermoultrasonication) on the survival of a strain ofStaphylococcus aureuswas studied in 0·05 m-phosphate buffer pH 6·8 and ultra-heat-treated whole milk. This combined process decreased by 63% the decimal reduction times for the heat treatment when the organism was suspended in buffer and by 43% when suspended in milk. These effects were much greater than the additive effect of the two agents considered independently.

Bacteriological Survey of Freshly Formed Cheddar Cheese

1984 ◽  
Vol 47 (7) ◽  
pp. 546-548 ◽  
Author(s):  
MICHAEL H. BRODSKY
Keyword(s):  
Heat Treatment ◽  
Staphylococcus Aureus ◽  
Geometric Mean ◽  
Cheddar Cheese ◽  
Raw Milk ◽  
Fecal Coliforms ◽  
Salmonella Spp ◽  
Pasteurized Milk ◽  
Heat Treated ◽  
Raw Milk Cheese

Two hundred-fifty freshly formed cheese samples produced by 32 provincially inspected cheese plants were analyzed by 7 regional laboratories of the Ontario Ministry of Health. Coliforms were detected in 61 (25.8%) and fecal coliforms confirmed in 46 (19.5%) of the 236 samples tested, with geometric mean counts per g of 133 and 136, respectively. The incidence of coliforms was highest in Cheddar cheeses made from pasteurized milk (29.7%) compared with the incidence of raw milk cheese (22.0%) and cheese made from milk which had been subjected to sub-pasteurization heat treatment (28.2%). Conversely, the incidence of fecal coliforms was lowest in pasteurized milk cheese (17.8%), followed by raw milk cheese (22.0%) and highest in heat-treated milk cheeses (25.6%). Staphylococcus aureus above the screening level of 1000 per g was not found in any of the 237 samples analyzed. Salmonella spp. were not detected in any of the 250 samples. These results suggest that producers of Cheddar cheese should have no difficulty in meeting the microbiological standards adopted by the Health Protection Branch, Health and Welfare Canada.

Effect of a Complex Heat Treatment on the Structure of 300M Steel

1981 ◽  
Vol 39 ◽  
pp. 312-313
Author(s):  
R. Padmanabhan ◽  
W. E. Wood
Keyword(s):  
Heat Treatment ◽  
Metal Carbides ◽  
Austenite Grain Size ◽  
300M Steel ◽  
Heat Treated ◽  
Strain Fracture ◽  
Prior Austenite Grain Size ◽  
Short Time ◽  
Final Tempering ◽  
Similar Yield

Intermediate high temperature tempering prior to subsequent reaustenitization has been shown to double the plane strain fracture toughness as compared to conventionally heat treated UHSLA steels, at similar yield strength levels. The precipitation (during tempering) of metal carbides and their subsequent partial redissolution and refinement (during reaustenitization), in addition to the reduction in the prior austenite grain size during the cycling operation have all been suggested to contribute to the observed improvement in the mechanical properties. In this investigation, 300M steel was initially austenitized at 1143°K and then subjected to intermediate tempering at 923°K for 1 hr. before reaustenitizing at 1123°K for a short time and final tempering at 583°K. The changes in the microstructure responsible for the improvement in the properties have been studied and compared with conventionally heat treated steel. Fig. 1 shows interlath films of retained austenite produced during conventionally heat treatment.

“In vitro” and in Animal Model Studies on a Double Virus- Inactivated Factor VIII Concentrate

1995 ◽  
Vol 74 (03) ◽  
pp. 868-873 ◽  
Author(s):  
Silvana Arrighi ◽  
Roberta Rossi ◽  
Maria Giuseppina Borri ◽  
Vladimir Lesnikov ◽  
Marina Lesnikov ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Animal Model ◽  
Factor Viii ◽  
Hepatitis A ◽  
Hepatitis A Virus ◽  
Virus Inactivation ◽  
Enveloped Viruses ◽  
Model Studies ◽  
Heat Treated

SummaryTo improve the safety of plasma derived factor VIII (FVIII) concentrate, we introduced a final super heat treatment (100° C for 30 min) as additional virus inactivation step applied to a lyophilized, highly purified FVIII concentrate (100 IU/mg of proteins) already virus inactivated using the solvent/detergent (SID) method during the manufacturing process.The efficiency of the super heat treatment was demonstrated in inactivating two non-lipid enveloped viruses (Hepatitis A virus and Poliovirus 1). The loss of FVIII procoagulant activity during the super heat treatment was of about 15%, estimated both by clotting and chromogenic assays. No substantial changes were observed in physical, biochemical and immunological characteristics of the heat treated FVIII concentrate in comparison with those of the FVIII before heat treatment.

Vanadium Additions to a High-Cr White Iron and its Effects on the Abrasive Wear Behavior.

MRS Advances ◽  
2020 ◽  
Vol 5 (59-60) ◽  
pp. 3077-3089
Author(s):  
Alexeis Sánchez ◽  
Arnoldo Bedolla-Jacuinde ◽  
Francisco V. Guerra ◽  
I. Mejía
Keyword(s):  
Heat Treatment ◽  
Abrasive Wear ◽  
Volume Fraction ◽  
Wear Behavior ◽  
Wear Behaviour ◽  
White Iron ◽  
Heat Treated ◽  
Bulk Hardness ◽  
Abrasive Wear Behavior ◽  
Vanadium Carbides

AbstractFrom the present study, vanadium additions up to 6.4% were added to a 14%Cr-3%C white iron, and the effect on the microstructure, hardness and abrasive wear were analysed. The experimental irons were melted in an open induction furnace and cast into sand moulds to obtain bars of 18, 25, and 37 mm thickness. The alloys were characterized by optical and electronic microscopy, and X-ray diffraction. Bulk hardness was measured in the as-cast conditions and after a destabilization heat treatment at 900°C for 45 min. Abrasive wear resistance tests were undertaken for the different irons according to the ASTM G65 standard in both as-cast and heat-treated conditions under a load of 60 N for 1500 m. The results show that, vanadium additions caused a decrease in the carbon content in the alloy and that some carbon is also consumed by forming primary vanadium carbides; thus, decreasing the eutectic M7C3 carbide volume fraction (CVF) from 30% for the base iron to 20% for the iron with 6.4%V;but overall CVF content (M7C3 + VC) is constant at 30%. Wear behaviour was better for the heat-treated alloys and mainly for the 6.4%V iron. Such a behaviour is discussed in terms of the CVF, the amount of vanadium carbides, the amount of martensite/austenite in matrix and the amount of secondary carbides precipitated during the destabilization heat treatment.

Heat Treatment Influence on the Corrosion Resistance of a Cu-Al-Fe-Mn Bronze

2018 ◽  
Vol 69 (5) ◽  
pp. 1055-1059 ◽  
Author(s):  
Mariana Ciurdas ◽  
Ioana Arina Gherghescu ◽  
Sorin Ciuca ◽  
Alina Daniela Necsulescu ◽  
Cosmin Cotrut ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Structural Changes ◽  
Heating Temperature ◽  
Galvanic Corrosion ◽  
Cooling Water ◽  
Open Circuit ◽  
Water Quenching ◽  
Heat Treated ◽  
Different Temperatures

Aluminium bronzes are exhibiting good corrosion resistance in saline environments combined with high mechanical properties. Their corrosion resistance is obviously confered by the alloy chemical composition, but it can also be improved by heat treatment structural changes. In the present paper, five Cu-Al-Fe-Mn bronze samples were subjected to annealing heat treatments with furnace cooling, water quenching and water quenching followed by tempering at three different temperatures: 200, 400 and 550�C. The heating temperature on annealing and quenching was 900�C. The structure of the heat treated samples was studied by optical and scanning electron microscopy. Subsequently, the five samples were submitted to corrosion tests. The best resistance to galvanic corrosion was showed by the quenched sample, but it can be said that all samples are characterized by close values of open-circuit potentials and corrosion potentials. Concerning the susceptibility to other types of corrosion (selective leaching, pitting, crevice corrosion), the best corrosion resistant structure consists of a solid solution, g2 and k compounds, corresponding to the quenched and 550�C tempered sample.

scholarly journals Influence of Post Weld Heat Treatment on the Grain Size, and Mechanical Properties of the Alloy-800H Rotary Friction Weld Joints

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4366
Author(s):  
Saqib Anwar ◽  
Ateekh Ur Rehman ◽  
Yusuf Usmani ◽  
Ali M. Al-Samhan
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Heat Affected Zone ◽  
Tensile Testing ◽  
Weld Zone ◽  
Alloy 800H ◽  
Weld Joints ◽  
Heat Treated ◽  
Friction Weld

This study evaluated the microstructure, grain size, and mechanical properties of the alloy 800H rotary friction welds in as-welded and post-weld heat-treated conditions. The standards for the alloy 800H not only specify the composition and mechanical properties but also the minimum grain sizes. This is because these alloys are mostly used in creep resisting applications. The dynamic recrystallization of the highly strained and plasticized material during friction welding resulted in the fine grain structure (20 ± 2 µm) in the weld zone. However, a small increase in grain size was observed in the heat-affected zone of the weldment with a slight decrease in hardness compared to the base metal. Post-weld solution heat treatment (PWHT) of the friction weld joints increased the grain size (42 ± 4 µm) in the weld zone. Both as-welded and post-weld solution heat-treated friction weld joints failed in the heat-affected zone during the room temperature tensile testing and showed a lower yield strength and ultimate tensile strength than the base metal. A fracture analysis of the failed tensile samples revealed ductile fracture features. However, in high-temperature tensile testing, post-weld solution heat-treated joints exhibited superior elongation and strength compared to the as-welded joints due to the increase in the grain size of the weld metal. It was demonstrated in this study that the minimum grain size requirement of the alloy 800H friction weld joints could be successfully met by PWHT with improved strength and elongation, especially at high temperatures.

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