Thermal Resistance of Francisella tularensis in Infant Formula and Fruit Juices

2008 ◽  
Vol 71 (11) ◽  
pp. 2208-2212 ◽  
Author(s):  
J. B. DAY ◽  
S. TRUJILLO ◽  
Y.-Y. D. HAO ◽  
R. C. WHITING
Keyword(s):  
Thermal Resistance ◽  
Infant Formula ◽  
Francisella Tularensis ◽  
Orange Juice ◽  
Apple Juice ◽  
Thermal Inactivation ◽  
Live Vaccine Strain ◽  
Z Value ◽  
Mango Juice ◽  
D Values

Francisella tularensis is a gram-negative bacterium that can cause gastrointestinal or oropharyngeal tularemia from ingestion of contaminated food or water. Despite the potential for accidental or intentional contamination of foods with F. tularensis, little information exists on the thermal stability of this organism in food matrices. In the present study, the thermal resistance of the live vaccine strain of F. tularensis in four food products (liquid infant formula, apple juice, mango juice, and orange juice) was investigated. D-values ranged from 12 s (57.5°C) to 580 s (50°C) in infant formula with a z-value of 4.37°C. D-values in apple juice ranged from 8 s (57.5°C) to 59 s (50°C) with a z-value of 9.17°C. The live vaccine strain did not survive at temperatures above 55°C in mango juice and orange juice (>6-log inactivation). D-values at 55 to 47.5°C were 15 to 59 s in mango juice and 16 to 105 s in orange juice with z-values of 9.28 and 12.30°C, respectively. These results indicate that current pasteurization parameters used for destroying common foodborne bacterial pathogens are adequate for eliminating F. tularensis in the four foods tested. This study is the first to determine thermal inactivation of F. tularensis in specific foods and will permit comparisons with the thermal inactivation data of other more traditional foodborne pathogens.

Thermal Inactivation of H5N1 High Pathogenicity Avian Influenza Virus in Naturally Infected Chicken Meat

2007 ◽  
Vol 70 (3) ◽  
pp. 674-680 ◽  
Author(s):  
COLLEEN THOMAS ◽  
DAVID E. SWAYNE
Keyword(s):  
Linear Regression ◽  
Avian Influenza ◽  
Thermal Inactivation ◽  
Chicken Meat ◽  
Meat Sample ◽  
Breast Meat ◽  
Infectious Dose ◽  
High Pathogenicity ◽  
Z Value ◽  
D Values

Thermal inactivation of the H5N1 high pathogenicity avian influenza (HPAI) virus strain A/chicken/Korea/ES/2003 (Korea/03) was quantitatively measured in thigh and breast meat harvested from infected chickens. The Korea/03 titers were recorded as the mean embryo infectious dose (EID50) and were 108.0 EID50/g in uncooked thigh samples and 107.5 EID50/g in uncooked breast samples. Survival curves were constructed for Korea/03 in chicken thigh and breast meat at 1°C intervals for temperatures of 57 to 61°C. Although some curves had a slightly biphasic shape, a linear model provided a fair-to-good fit at all temperatures, with R2 values of 0.85 to 0.93. Stepwise linear regression revealed that meat type did not contribute significantly to the regression model and generated a single linear regression equation for z-value calculations and D-value predictions for Korea/03 in both meat types. The z-value and the upper limit of the 95% confidence interval for the z-value were 4.64 and 5.32°C, respectively. From the lowest temperature to the highest, the predicted D-values and the upper limits of their 95% prediction intervals (conservative D-values) for 57 to 61°C were 241.2 and 321.1 s, 146.8 and 195.4 s, 89.3 and 118.9 s, 54.4 and 72.4 s, and 33.1 and 44.0 s. D-values and conservative D-values predicted for higher temperatures were 0.28 and 0.50 s for 70°C and 0.041 and 0.073 s for 73.9°C. Calculations with the conservative D-values predicted that cooking chicken meat according to current U.S. Department of Agriculture Food Safety and Inspection Service time-temperature guidelines will inactivate Korea/03 in a heavily contaminated meat sample, such as those tested in this study, with a large margin of safety.

Thermal Inactivation of Escherichia coli O157: H7, Salmonella senftenberg, and Enzymes with Potential as Time-Temperature Indicators in Ground Beef

1997 ◽  
Vol 60 (5) ◽  
pp. 471-475 ◽  
Author(s):  
ALICIA ORTA-RAMIREZ ◽  
JAMES F. PRICE ◽  
YIH-CHIH HSU ◽  
GIRIDARAN J. VEERAMUTHU ◽  
JAMIE S. CHERRY-MERRITT ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Thermal Inactivation ◽  
Ground Beef ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Triose Phosphate ◽  
Beef Products ◽  
Z Value ◽  
D Values ◽  
Salmonella Senftenberg

The USDA has established processing schedules for beef products based on the destruction of pathogens. Several enzymes have been suggested as potential indicators of heat processing. However, no relationship between the inactivation rates of these enzymes and those of pathogenic microorganisms has been determined. Our objective was to compare the thermal inactivation of Escherichia coli O157:H7 and Salmonella senftenberg to those of endogenous muscle proteins. Inoculated and noninoculated ground beef samples were heated at four temperatures for predetermined intervals of time in thermal-death-time studies. Bacterial counts were determined and enzymes were assayed for residual activity. The D values for E. coli O157:H7 were 46.10, 6.44, 0.43, and 0.12 min at 53, 58, 63, and 68°C, respectively, with a z value of 5.60°C. The D values for S. senftenberg were 53.00, 15.17, 2.08, and 0.22 min at 53, 58, 63, and 68°C, respectively, with a z value of 6.24°C. Apparent D values at 53, 58, 63, and 68°C were 352.93, 26.31, 5.56, and 3.33 min for acid phosphatase; 6968.64, 543.48, 19.61, and 1.40 min for lactate dehydrogenase; and 3870.97, 2678.59, 769.23, and 42.92 min for peroxidase; with z values of 7.41,3.99, and 7.80°C, respectively. Apparent D values at 53, 58, 63, and 66°C were 325.03, 60.07, 3.07, and 1.34 min for phosphoglycerate mutase; 606.72, 89.86, 4.40, and 1.28 min for glyceraldehyde-3-phosphate dehydrogenase; and 153.06, 20.13, 2.25, and 0.74 min for triose phosphate isomerase; with z values of 5.18, 4.71, and 5.56°C, respectively. The temperature dependence of triose phosphate isomerase was similar to those of both E. coli O157 :H7 and S. senftenberg, suggesting that this enzyme could be used as an endogenous time-temperature indicator in beef products.

scholarly journals Antibiogram Profiling and Thermal Inactivation of Staphylococcus aureus and Escherichia coli Isolated from Milk of Dharan, Nepal

2020 ◽  
pp. 81-87
Author(s):  
Susmita Phattepuri ◽  
Prince Subba ◽  
Arjun Ghimire ◽  
Shiv Nandan Sah
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Thermal Inactivation ◽  
Total Coliform ◽  
Plate Count ◽  
Diffusion Method ◽  
E Coli ◽  
Coliform Count ◽  
Z Value ◽  
D Values

Milk is an excellent medium for the growth of many bacteria. This study aimed to determine antibiotic profiling and thermal inactivation of Staphylococcus aureus and Escherichia coli isolated from raw milk of Dharan. Total viable count, total Staphylococcal count, and total coliform count were carried out by conventional microbiological methods. Identification was done on the basis of Gram staining and biochemical tests. The antibiotic susceptibility test of the isolates carried out by the modified Kirby-Baur disc diffusion method. Thermal inactivation of S. aureus and E. coli were carried out by subjecting to thermal treatment in a water bath. Total plate count ranged from 204×104 CFU/mL to 332×105 CFU/mL. Total staphylococcal count and total coliform count ranged from 14×105 CFU/mL to 8×106 CFU/mL and 11×104 CFU/mL to 3×106 CFU/mL respectively. S. aureus showed an increasing resistance patterns towards Ampicillin, Cefotixin, Carbenicillin and Cefotaxime. Ciprofloxacin, Erythromycin, Amikacin, Gentamycin, Azithromycin, and Chloramphenicol were found to be effective against S. aureus. All the E. coli isolates were resistant to Ampicillin and least resistant to Cefotixin. Chloramphenicol, Amikacin, Azithromycin, and Nalidixic acid were found highly effective to E. coli. The D-values for S. aureus at 56°C, 58°C and 60°C were 1.36 min, 1.19 min, and 1.09 min respectively. The Z-value was 14.92°C. While D-values were obtained as 0.98 min, 0.75 min, and 0.57 min for E. coli at 56° C, 58° C and 60° C respectively, and Z-value was 9.75° C. Hence, S. aureus was found to be more heat resistant than E. coli.

Thermal Inactivation of Listeria monocytogenes in Chicken Gravy

1992 ◽  
Vol 55 (7) ◽  
pp. 492-496 ◽  
Author(s):  
I-PING D. HUANG ◽  
AHMED E. YOUSEF ◽  
ELMER H. MARTH ◽  
M. EILEEN MATTHEWS
Keyword(s):  
Heat Treatment ◽  
Listeria Monocytogenes ◽  
Heat Resistance ◽  
Thermal Inactivation ◽  
Refrigerated Storage ◽  
Department Of Agriculture ◽  
Large Numbers ◽  
Z Value ◽  
D Values ◽  
The U.S

Heat resistance of Listeria monocytogenes strains V7 and Scott A in chicken gravy and changes in heat resistance during refrigerated storage were studied. After chicken gravy was made, it was cooled to 40°C, inoculated with 105 CFU L. monocytogenes per ml of gravy, and then stored at 7°C for 10 d. Gravy was heated at 50, 55, 60, and 65°C immediately after inoculation and after 1, 3, 5, and 10 d of refrigerated storage. The D values for strains Scott A and V7 in gravy heated at 50°C at day 0 were 119 and 195 min and at day 10 they were 115 and 119 min, respectively, whereas at 65°C comparable values at day 0 were 0.48 and 0.19 min and at day 10 they were 0.014 and 0.007 min. Heat resistance (expressed as D values) was greater at day 0 than at the end of refrigerated storage. The z values ranged from 3.41 to 6.10°C and were highest at the early stages of chill storage and then decreased at the later stages. Strain V7 was more heat resistant than Scott A at 50°C. Strain Scott A always had a higher z value than did strain V7 at the same storage interval. A heat treatment greater than the 4-D process recommended by the U.S. Department of Agriculture was required to inactivate the large numbers of L. monocytogenes that developed in chicken gravy during refrigerated storage.

Spoilage of Pasteurized Crabmeat by a Nontoxigenic Psychrotrophic Anaerobic Sporeformer

1992 ◽  
Vol 55 (3) ◽  
pp. 176-181 ◽  
Author(s):  
WAYNE P. SEGNER
Keyword(s):  
Thermal Resistance ◽  
Blue Crab ◽  
Phosphate Buffer ◽  
Resistance Curve ◽  
Microbial Spoilage ◽  
Z Value ◽  
Endpoint Data ◽  
D Values ◽  
The Relationship ◽  
Hurricane Hugo

Microbial spoilage occurred in machine picked, pasteurized crabmeat of the Blue Crab that had been canned in Maryland in the fall of 1989 and later in 1990. Spoilage in 1989 was first detected after hurricane Hugo, although the relationship between the onset of spoilage and the hurricane, if any, is unclear. The sole spoilage organism was identified as a nontoxigenic psychrotrophic anaerobic sporeformer. The pattern of spoilage suggested a build-up of this organism in machine picking operations. Spoilage was noticeably absent from hand picked pasteurized crabmeat from the same plant. While the psychrotrophic anererobic sporeformer, in some respects, culturally resembles the psychrotroph Clostridium arcticum, the crabmeat spoilage organism may be an unrecognized species. Spores of the crabmeat isolate heated in neutral phosphate buffer gave a thermal resistance curve from survivor data characterized by a D185 (85°C) equal to 15.6 min and a z-value equal to 17.8°F (9.9°C). In crabmeat, D-values calculated from fractional survivor endpoint data gave a thermal resistance curve characterized by an extrapolated D185 equal to 35 min and a z-value equal to 11.6°F (6.5°C). From these data, a process equivalent to = = 31 was incapable of destroying even a reasonably low number of spores of the psychrotrophic anaerobe in pasteurized crabmeat.

scholarly journals Supercritical Carbon Dioxide Applied to Citrus Processing

1991 ◽  
Author(s):  
Murat O. Balaban ◽  
Ana G. Arreola
Keyword(s):  
Atmospheric Pressure ◽  
Orange Juice ◽  
Thermal Inactivation ◽  
Oil Extraction ◽  
Overall Acceptability ◽  
Plate Counts ◽  
Lemon Oil ◽  
Oil Fractionation ◽  
Sensory Evaluations ◽  
D Values

Uses of supercritical (SC) fluids in citrus processing in conventional applications such as citrus oil fractionation, lemon oil extraction, and orange juice debittering are reviewed. In a non-conventional application, single strength orange juice was treated with SC CO2. Effect of pressure (7–34 MPa), temperature (35–60°C), and time (15–180 min) on pectinesterase (PE) activity, cloud stability, microorganisms, and sensory attributes were investigated. SC CO2 inactivated PE below thermal inactivation temperatures. (Activation energy at 31 MPa = 97.4 KJ/mole; at atmospheric pressure = 166.6 KJ/mole.) SC treatment did not change pH and °Brix; but stabilized and enhanced cloud and color. Ascorbic acid was better preserved. Sensory evaluations of color and cloudiness of treated juice were better. Flavor, aroma and overall acceptability were not different. Aerobic total plate counts showed that D value of treated juice decreased as pressure increased. D values at 35, 45 and 60°C of SC treated juice at 33.1 MPa were 28, 22.6 and 12.7 min, respectively. Paper published with permission.

Desiccation and Thermal Resistance of Escherichia coli O121 in Wheat Flour

2019 ◽  
Vol 82 (8) ◽  
pp. 1308-1313 ◽  
Author(s):  
QUINCY J. SUEHR ◽  
NATHAN M. ANDERSON ◽  
SUSANNE E. KELLER
Keyword(s):  
Escherichia Coli ◽  
Thermal Resistance ◽  
Wheat Flour ◽  
Shiga Toxin ◽  
Salmonella Enteritidis ◽  
Thermal Inactivation ◽  
The United States ◽  
Inactivation Kinetics ◽  
E Coli ◽  
D Values

ABSTRACT Non-O157 Shiga toxin–producing Escherichia coli infections have recently been associated with wheat flour on two separate accounts in the United States and Canada. However, there is little information regarding the thermal resistance and longevity of non-O157 Shiga toxin–producing Escherichia coli during storage in low-moisture environments. The objectives of this study were to determine the thermal inactivation kinetics of E. coli O121 in wheat flour and to compare the thermal inactivation rates with those of other pathogens. Wheat flour, inoculated with E. coli O121, was equilibrated at 25°C to a water activity of 0.45 in a humidity-controlled conditioning chamber. Inoculated samples were treated isothermally at 70, 75, and 80°C, and posttreatment population survivor ratios were determined by plate counting. D- and z-values calculated with a log-linear model, were compared with those obtained in other studies. At 70, 75, and 80°C, the D-values for E. coli O121 were 18.16 ± 0.96, 6.47 ± 0.50, and 4.58 ± 0.40 min, respectively, and the z-value was 14.57 ± 2.21°C. Overall, E. coli O121 was observed to be slightly less thermally resistant than what has been previously reported for Salmonella Enteritidis PT30 in wheat flour as measured under the same conditions with the same methods.

Heat Resistance of Escherichia coli O157:H7 in Apple Juice

1996 ◽  
Vol 59 (3) ◽  
pp. 226-229 ◽  
Author(s):  
D. F. SPLITTSTOESSER ◽  
M. R. MCLELLAN ◽  
J. J. CHUREY
Keyword(s):  
Escherichia Coli ◽  
Benzoic Acid ◽  
Thermal Resistance ◽  
Heat Resistance ◽  
Malic Acid ◽  
Apple Juice ◽  
Sorbic Acid ◽  
Escherichia Coli O157 ◽  
Z Value

The objective was to determine the effect of cider composition on the heat resistance of Escherichia coli O157:H7. The average D52 value in a model Empire apple juice was 18 min with a z value of 4.8°C. Increasing the Brix from 11.8 to 16.5° had no effect on thermal resistance, while increasing L-malic acid from 0.2 to 0.8%, or reducing the pH from 4.4 to 3.6 sensitized the cells to heat. The greatest effect on heat resistance was afforded by the preservatives benzoic and sorbic acids: D50 values in ciders containing 1,000 mg/l were 5.2 min in the presence of sorbic acid and only 0.64 min in the presence of benzoic acid. Commercial apple juice concentrates yielded lower numbers of survivors than single-strength juices even though their higher sugar concentrations of about 46° Brix increased heat resistance.

Appendix

1988 ◽  
Vol 9 (11) ◽  
pp. 506-507
Keyword(s):  
Thermal Resistance ◽  
High Resistance ◽  
Bacillus Stearothermophilus ◽  
Biological Indicator ◽  
False Positives ◽  
Paper Strip ◽  
Resistance Curve ◽  
End User ◽  
Z Value ◽  
D Values

The performance of a biological indicator (BI) over a range of sterilization temperatures is known as a z value and, as defined by Roberts, is “the number of degrees change in temperature to achieve a tenfold change in the D value.” A plot of the D values versus exposure temperatures will reveal the z value as the negative reciprocal of the slope of the resulting thermal resistance curve. Historically, paper strip carriers of Bacillus stearothermophilus spores have been found to possess a z value in the range of l7°-2O°F, whereas self-contained BIs tested in our laboratories have exhibited z values as high as 64°F (Figure I), which reflects their excessively high resistance at flash sterilization temperatures. In general, such matters are not of concern to the end user until such time as false positives are encountered during flash sterilization.

Effects of Inoculation Procedures on Variability and Repeatability of Salmonella Thermal Resistance in Wheat Flour

2016 ◽  
Vol 79 (11) ◽  
pp. 1833-1839 ◽  
Author(s):  
IAN M. HILDEBRANDT ◽  
BRADLEY P. MARKS ◽  
ELLIOT T. RYSER ◽  
ROSSANA VILLA-ROJAS ◽  
JUMING TANG ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Water Activity ◽  
Wheat Flour ◽  
Thermal Inactivation ◽  
Culture Method ◽  
Isothermal Treatment ◽  
Inactivation Kinetics ◽  
Inoculation Methods ◽  
Low Moisture Foods ◽  
D Values

ABSTRACT Limited prior research has shown that inoculation methods affect thermal resistance of Salmonella in low-moisture foods; however, these effects and their repeatability have not been systematically quantified. Consequently, method variability across studies limits utility of individual data sets and cross-study comparisons. Therefore, the objective was to evaluate the effects of inoculation methodologies on stability and thermal resistance of Salmonella in a low-moisture food (wheat flour), and the repeatability of those results, based on data generated by two independent laboratories. The experimental design consisted of a cross-laboratory comparison, both conducting isothermal Salmonella inactivation studies in wheat flour (~0.45 water activity, 80°C), utilizing five different inoculation methods: (i) broth-based liquid inoculum, (ii) lawn-based liquid inoculum, (iii) lawn-based pelletized inoculum, (iv) direct harvest of lawn culture with wheat flour, and (v) fomite transfer of a lawn culture. Inoculated wheat flour was equilibrated ~5 days to ~0.45 water activity and then was subjected to isothermal treatment (80°C) in aluminum test cells. Results indicated that inoculation method impacted repeatability, population stability, and inactivation kinetics (α = 0.05), regardless of laboratory. Salmonella inoculated with the broth-based liquid inoculum method and the fomite transfer of a lawn culture method exhibited instability during equilibration. Lawn-based cultures resulted in stable populations prior to thermal treatment; however, the method using direct harvest of lawn culture with wheat flour yielded different D-values across the laboratories (α = 0.05), which was attributed to larger potential impact of operator variability. The lawn-based liquid inoculum and the lawn-based pelletized inoculum methods yielded stable inoculation levels and repeatable D-values (~250 and ~285 s, respectively). Also, inoculation level (3 to 8 log CFU/g) did not affect D-values (using the lawn-based liquid inoculum method). Overall, the results demonstrate that inoculation methods significantly affect Salmonella population kinetics and subsequent interpretation of thermal inactivation data for low-moisture foods.

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