Thermal Inactivation of Staphylococcus aureus in Retentates from Ultrafiltered Milk

1989 ◽  
Vol 52 (9) ◽  
pp. 631-637 ◽  
Author(s):  
JEFFREY L. KORNACKI ◽  
ELMER H. MARTH
Keyword(s):  
Staphylococcus Aureus ◽  
Heat Resistance ◽  
Thermal Inactivation ◽  
Thermal Protection ◽  
Skim Milk ◽  
Stationary Growth Phase ◽  
Plate Count ◽  
Mannitol Salt Agar ◽  
Whole Milk ◽  
D Values

Cells of Staphylococcus aureus strains 196E, 481, and 425 were thermally stressed at 56°C for 10 min in milk and enumerated on Plate Count Agar (PCA), Mannitol Salt Agar (MSA), and PCA with an overlay of MSA. PCA recovered more S. aureus 196E and 481 than did PCA/MSA, which recovered more than MSA. PCA/MSA recovered slightly more S. aureus 425 than did PCA, which recovered more than MSA. At 58°C, in order of decreasing heat resistance, the four strains of S. aureus originally isolated from food were 425 > 100 and 481 > 196E. Their D-values were 26,14,13, and 3.0 min, respectively. S. aureus 425 was more heat resistant in the stationary than in the log phase when heated at 58°C in whole milk. Heat resistance at 58°C increased overall during the stationary growth phase, but was fairly stable when the culture was from 17 to 25 h or from 41 to 49 h old. S. aureus 425 exhibited no consistent differences in heat resistance in concentrated (4X by volume) and unconcentrated skim or whole milk. Adjustments of protein (3.5–4.0% to 12.6–16%), milkfat (0.28–1.12% to 10%), and lactose (ca. 4.5–5.0% to ca. 14.5–15%) contents of milk and 4X (volume concentration) UF milk retentates afforded no significant thermal protection to S. aureus 425. Diafiltration of 4X skim milk reduced thermal protection of S. aureus 425 in the retentate over that of unconcentrated skim milk of the same lot when tested at 63 and 74°C. S. aureus 425 had greatest D-values (min) in skim milk (0.36 ± 0.05) and permeate (0.30 ± 0.14) followed by permeate from diafiltration (0.28 ± 0.06) when tested at 63°C.

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.

Destruction de Microbacterium lacticum, Escherichia coli et Staphylococcus aureus au cours du séchage du lait par atomisation. I. Dénombrement sélectif des bactéries survivantes

1977 ◽  
Vol 23 (6) ◽  
pp. 716-720
Author(s):  
A. Chopin ◽  
G. Mocquot ◽  
Y. Le Graet
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Spray Drying ◽  
Skim Milk ◽  
Resistant Mutant ◽  
Plate Count ◽  
Mannitol Salt Agar ◽  
E Coli ◽  
Plate Count Agar ◽  
Plate Counts

In this paper a method which allows the measure of microbial death rate during spray-drying by means of a streptomycin-resistant mutant that can be grown on a streptomycin-containing agar is described. Plate counts of Microbacterium lacticum, Escherichia coli, and Staphylococcus aureus recovered from skim milk powders were done on plate count agar in the presence and absence of streptomycin and on various selective media. The powders were produced from evaporated milk previously inoculated with those organisms.Our results showed that the proposed method allows the recovery of 78% of M. lacticum, 61% of E. coli, and 100% of S. aureus that survived spray-drying. Recoveries of surviving E. coli on violet bile agar and brilliant green bile 2% were 34% and 29% respectively. Baird-Parker and mannitol salt agar media allow the recovery of all surviving S. aureus, thus showing that S. aureus cells did not lose their ability to grow in media containing 7.5% NaCl. Our results show that physiological injury of the cells during spray-drying differs from injury due to heating only. [Traduit par le journal]

Modeling the Effects of Temperature, Sodium Chloride, and Green Tea and Their Interactions on the Thermal Inactivation of Listeria monocytogenes in Turkey†

2014 ◽  
Vol 77 (10) ◽  
pp. 1696-1702 ◽  
Author(s):  
VIJAY K. JUNEJA ◽  
JIMENA GARCIA-DÁVILA ◽  
JULIO CESAR LOPEZ-ROMERO ◽  
ETNA AIDA PENA-RAMOS ◽  
JUAN PEDRO CAMOU ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Sodium Chloride ◽  
Protective Effect ◽  
Heat Resistance ◽  
Green Tea ◽  
Thermal Inactivation ◽  
Heating Temperature ◽  
Lethal Effect ◽  
Interactive Effects ◽  
D Values

The interactive effects of heating temperature (55 to 65°C), sodium chloride (NaCl; 0 to 2%), and green tea 60% polyphenol extract (GTPE; 0 to 3%) on the heat resistance of a five-strain mixture of Listeria monocytogenes in ground turkey were determined. Thermal death times were quantified in bags that were submerged in a circulating water bath set at 55, 57, 60, 63, and 65°C. The recovery medium was tryptic soy agar supplemented with 0.6% yeast extract and 1% sodium pyruvate. D-values were analyzed by second-order response surface regression for temperature, NaCl, and GTPE. The data indicated that all three factors interacted to affect the inactivation of the pathogen. The D-values for turkey with no NaCl or GTPE at 55, 57, 60, 63, and 65°C were 36.3, 20.8, 13.2, 4.1, and 2.9 min, respectively. Although NaCl exhibited a concentration-dependent protective effect against heat lethality on L. monocytogenes in turkey, addition of GTPE rendered the pathogen more sensitive to the lethal effect of heat. GTPE levels up to 1.5% interacted with NaCl and reduced the protective effect of NaCl on heat resistance of the pathogen. Food processors can use the predictive model to design an appropriate heat treatment that would inactivate L. monocytogenes in cooked turkey products without adversely affecting the quality of the product.

Survival of Borrelia burgdorferi in Whole Milk, Low Fat Milk, and Skim Milk at 34°C and in Skim Milk at 5°C

1991 ◽  
Vol 54 (7) ◽  
pp. 532-536 ◽  
Author(s):  
GERALDINE M. FARRELL ◽  
AHMED E. YOUSEF ◽  
ELMER H. MARTH
Keyword(s):  
Borrelia Burgdorferi ◽  
Milk Protein ◽  
Skim Milk ◽  
Storage Period ◽  
Most Probable Number ◽  
Low Fat ◽  
Probable Number ◽  
Whole Milk ◽  
The Mean ◽  
D Values

Autoclaved whole milk, low-fat milk, protein-fortified skim milk and regular skim milk were inoculated to contain ca. 105 to 106 Borrelia burgdorferi strains 35210, 35211, or EBNI/ml and stored at 34°C for 16 d. Similarly inoculated skim milk also was held at 5°C for 46 d. Numbers of survivors were estimated by the Most Probable Number (MPN) technique. In all instances, numbers of B. burgdorferi decreased over the storage period. At 34°C, no strain of B. burgdorferi was detected after day 12. The mean D-values, at 34°C, for strains 35210, 35211, and EBNI were 2.2, 2.4, and 2.2 d, respectively. The mean D-values, at 34°C, for all strains in whole milk, low-fat milk, protein-fortified skim milk, and regular skim milk were 2.4, 2.3, 1.9, and 2.4 d, respectively. At 5°C, spirochete numbers in regular skim milk decreased, but all three strains remained at a detectable level for 46 d. The mean D-values, at 5°C, for strains 35210, 35211, and EBNI were 12, 15, and 12 d, respectively.

Heat Resistance of Escherichia coli in Cow and Buffalo Milk

1980 ◽  
Vol 43 (5) ◽  
pp. 376-380 ◽  
Author(s):  
R. S. SINGH ◽  
B. RANGANATHAN
Keyword(s):  
Escherichia Coli ◽  
Heat Treatment ◽  
Heat Resistance ◽  
Skim Milk ◽  
Buffalo Milk ◽  
Time Interval ◽  
E Coli ◽  
Heat Resistant ◽  
Whole Milk

Three Escherichia coli cultures (0111:B4, 0127:B8 and NP) were selected to study their heat-resistant characteristics when in cow skim, cow whole and buffalo whole milk. The temperatures of heat-treatment included in this study were 50, 55, 60 and 63 C. The time interval during heat-treatment was 10 min at 50 and 55 C and 5 min at 60 and 63 C. Marked differences in heat-resistance were observed in the three E. coli cultures. The z-values obtained for strain 0111:B4 were 8.3, 9.0 and 10.2 when tested in cow skim milk, cow whole milk and buffalo milk, respectively. The z-values for 0127:B8 and NP were 17.5, 18.0 and 19.2 and 18.8, 19.0 and 20.3, respectively, for the three types of milk.

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.

Evaluation of Microbiological Safety of Shrimp Cooked in a Microwave Oven

1995 ◽  
Vol 58 (7) ◽  
pp. 742-747 ◽  
Author(s):  
SRIKANTH GUNDAVARAPU ◽  
YEN-CON HUNG ◽  
ROBERT E. BRACKETT ◽  
P. MALLIKARJUNAN
Keyword(s):  
Mathematical Model ◽  
Listeria Monocytogenes ◽  
Heat Resistance ◽  
Constant Temperature ◽  
Microwave Power ◽  
Thermal Inactivation ◽  
Microwave Oven ◽  
D Values ◽  
Cooking Times ◽  
Temperature Water

The effect of different microwave power levels (240, 400, 560, and 800 W) on the survival of Listeria monocytogenes in inoculated shrimp was investigated. Thermal inactivation rates (D-values) of L. monocytogenes were determined using constant temperature water baths to establish the heat resistance of L. monocytogenes in shrimp. Shrimp were inoculated with approximately 5 × 105 CFU/g of a five-strain mixture of L. monocytogenes. One hundred grams of shrimp were cooked in the microwave oven at different power levels using cooking times predicted by a mathematical model as well as 20% longer times than those obtained from the model. No viable L. monocytogenes were detected in uninoculated shrimp after microwave cooking, but at least one replication of inoculated shrimp tested positive for the presence of Listeria. No viable L. monocytogenes were detected in shrimp cooked at 120% of predicted times.

Increased Heat Resistance of Salmonellae in Beef with Added Soy Proteins

1983 ◽  
Vol 46 (5) ◽  
pp. 380-384 ◽  
Author(s):  
S. E. CRAVEN ◽  
L. C. BLANKENSHIP
Keyword(s):  
Heat Resistance ◽  
Soy Protein ◽  
Soy Proteins ◽  
Plate Count ◽  
Maximum Heat ◽  
Plate Count Agar ◽  
Isolated Soy Protein ◽  
Soy Isolate ◽  
Ph Range ◽  
D Values

Raw beef inoculated with cells of a composite of five Salmonella strains was heated at 54 or 60°C. Survivors were enumerated by plating samples in plate count agar (PCA), XL agar or PCA followed by an XL agar overlay. Best differential recoveries of salmonellae were effected by incubation of PCA plates for 4 h at 37°C followed by overlay with XL agar and incubation for an additional 44 h. D-values of salmonellae at 54 and 60°C were increased significantly when ground beef was supplemented with 30% textured soy protein, soy protein concentrate or isolated soy protein. Increased heat resistance appeared to be caused by an increase in the pH of beef from 5.8–5.9 to 6.1 upon addition of the soy proteins. After adjusting the pH of mixtures of beef and soy proteins with hydrochloric or lactic acid to 5.8 to 5.9, survival of salmonellae to heat was reduced to the level of survival in beef alone. The pH of beef with added structured soy isolate was the same as beef, and heat resistance of salmonellae was not increased in this product. In the pH range 5.9 to 7.1, the maximum heat resistance of salmonellae in beef containing textured soy protein occurred at pH values of 6.5 to 6.8.

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.

Thermal Inactivation D- and z-Values of Multidrug-Resistant and Non–Multidrug-Resistant Salmonella Serotypes and Survival in Ground Beef Exposed to Consumer-Style Cooking

2008 ◽  
Vol 71 (3) ◽  
pp. 509-515 ◽  
Author(s):  
J. D. STOPFORTH ◽  
R. SUHALIM ◽  
B. KOTTAPALLI ◽  
W. E. HILL ◽  
M. SAMADPOUR
Keyword(s):  
Heat Resistance ◽  
Thermal Inactivation ◽  
Ground Beef ◽  
Antibiotic Use ◽  
Multidrug Resistant ◽  
Significant Difference ◽  
Salmonella Serotypes ◽  
D Values ◽  
Food Processes ◽  
Best Fit

There has been speculation that multidrug-resistant (MDR) strains are generated by subtherapeutic antibiotic use in food animals and that such strains result in increased resistance to lethality by food processes such as heat and irradiation. The objective of this study was to evaluate the heat resistance of 20 strains, namely an MDR and a non–multidrug-resistant (NMDR) strain of each of 10 Salmonella serotypes isolated from cattle or cattle environments. MDR and NMDR Salmonella serotypes studied included Montevideo, Typhimurium, Anatum, Muenster, Newport, Mbandaka, Dublin, Reading, Agona, and Give. For phase I, stationary-phase cultures of the strains were aliquoted into sterile capillary tubes and immersed in a temperature-controlled water bath at 55, 60, 65, and 70°C for appropriate times. Survivor curves were plotted for each temperature, and a best-fit linear regression was derived for each temperature. D-values (decimal reduction times) and z-values (changes in temperature required to change the D-values) were calculated for each strain. Although there was no overall significant difference in the heat resistance of MDR and NMDR serotypes, NMDR serotypes generally appeared to have slightly higher heat resistance than NMDR serotypes, especially at 55 and 60°C. The highest relative heat resistance (highest z-values) was exhibited by Salmonella Anatum. Notably, the relative heat resistance of NMDR Salmonella Agona was similar to that of NMDR Salmonella Anatum and had the highest D-values at all four temperatures. For phase II, three serotypes (regardless of resistance profile) with the highest relative heat resistance and their drug-resistant counterparts were selected for thermal inactivation in ground beef patties cooked to endpoint temperatures. Salmonella Agona was able to survive in ground beef cooked to an internal temperature of 71°C. Results of these studies suggest drug resistance does not affect the heat resistance of Salmonella and that serotype or strain is an important consideration in risk assessment of the pathogen with regard to survival at cooking temperatures.

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