Thermal Inactivation of Conidia From Aspergillus flavus and Aspergillus parasiticus

1975 ◽  
Vol 38 (11) ◽  
pp. 678-682 ◽  
Author(s):  
M. P. DOYLE ◽  
E. H. MARTH
Keyword(s):  
Thermal Resistance ◽  
Heat Resistance ◽  
Aspergillus Flavus ◽  
Positive Relationship ◽  
Thermal Inactivation ◽  
Aspergillus Parasiticus ◽  
Moist Heat ◽  
Heat Resistant ◽  
D Values ◽  
Strain Dependent

Thermal resistance at 45, 50, 55, and 60 C of conidia from various strains of Aspergillus flavus and Aspergillus parasiticus was determined using a heating menstruum buffered at pH 7.0 with KH2PO4-NaOH. Heat resistance of conidia from both molds was strain-dependent. With moist heat at 45 C, D-values for conidia from various strains ranged from 14 to >161 h, whereas at 60 C the range was from 8 to 59 sec. At 50 and 55 C, D values ranged from 16 to 987 and 3 to 29 min, respectively. There appeared to be a positive relationship between the degree of heat resistance of conidia and the amount of aflatoxin produced by the different aspergilli. Conidia that were 15 and 20 days old were less resistant to heat than when they were 7 or 10 days old. Conidia that were produced on a substrate low in protein and high in glucose were more heat resistant than were those produced on a more proteinaceous substrate that contained little glucose.

Heat Resistance of Fungi Isolated from Frozen Blueberries

2008 ◽  
Vol 71 (10) ◽  
pp. 2030-2035 ◽  
Author(s):  
YUTAKA KIKOKU ◽  
NOBUHIRO TAGASHIRA ◽  
HIROYUKI NAKANO
Keyword(s):  
Thermal Resistance ◽  
Heat Resistance ◽  
Thermal Inactivation ◽  
Heat Resistant ◽  
Death Time ◽  
Naturally Occurring ◽  
Thermal Death ◽  
D Values ◽  
Thermal Death Time

This study dealt with the isolation, characterization, and identification of the fungal microflora of frozen blueberries imported from Canada. The thermal inactivation rates of the rarely studied isolated heat-resistant molds, Devriesia spp. and Hamigera striata, in naturally and artificially contaminated blueberry slurries were also determined. The D-values of naturally contaminating Devriesia spp. at 70, 80, 85, and 90°C were 714, 114, 44.4, and 14.1 min, respectively. The D-values of H. striata at 70, 80, 85, and 90°C were 909, 286, 42.6, and 10.3 min, respectively. The z-values calculated from the thermal death time curves were 11.0 and 6.9°C for Devriesia spp. and H. striata, respectively. Results also showed that in both test mold species, the naturally occurring molds had significantly higher thermal resistance than did the artificially contaminated counterparts. The results established by this study may be used by blueberry processors to prevent losses due to spoilage caused by the heat-resistant microorganisms.

Thermal Inactivation of Conidia from Aspergillus flavus and Aspergillus parasiticus

1975 ◽  
Vol 38 (12) ◽  
pp. 750-758 ◽  
Author(s):  
M. P. DOYLE ◽  
E. H. MARTH
Keyword(s):  
Acetic Acid ◽  
Sodium Chloride ◽  
Citric Acid ◽  
Thermal Resistance ◽  
Aspergillus Flavus ◽  
Sodium Acetate ◽  
Thermal Inactivation ◽  
Aspergillus Parasiticus ◽  
Ph Values ◽  
Strain Dependent

Conidiospores from one strain of Aspergillus flavus and two of Aspergillus parasiticus were thermally inactivated in menstrua at pH values of 3.5, 4.5, 5.5, and 6.0. These values were obtained with the following buffering systems: sodium acetate and acetic acid, citric acid and Na2HPO4, potassium acid phthalate (KHP)-HCl and KHP-NaOH, and KH2PO4 and NaOH. Heating of conidia in a menstruum adjusted to pH 7.0 with KH2PO4 and NaOH served as the control. Use of the sodium acetate and acetic acid buffering system resulted in an increase in the rate at which conidia were inactivated when the pH was decreased. Use of the citric acid and Na2HPO4 buffering system resulted in increased thermal resistance for the conidia as the pH was decreased; however, the degree of increased thermal resistance was strain dependent. When the KHP-HCl and KHP-NaOH buffers were used, conidia were inactivated more rapidly than in the control at the higher pH values and more slowly than in the control at the lower pH values. An increase in amount of sodium chloride, sucrose, or glucose in the menstruum was accompanied by a decrease in the rate at which conidia were inactivated. Generally, sodium chloride was markedly protective to conidia at aw values of less than 0.94, whereas the sugars were markedly protective at values below 0.95. Greatest protection at these values was afforded by sucrose.

scholarly journals Spore age and its effect on thermal resistance of Bacillus coagulans and Bacillus macerans in acid ripe plantain puree

1969 ◽  
Vol 75 (3) ◽  
pp. 205-211
Author(s):  
Fred Fernández-Coll ◽  
Luis Silva-Negrón
Keyword(s):  
Thermal Resistance ◽  
Heat Resistance ◽  
Thermal Process ◽  
Bacillus Coagulans ◽  
Thermal Processes ◽  
Bacillus Macerans ◽  
Heat Resistant ◽  
D Values ◽  
Acidified Foods

Decimal reduction times (D values) at 100° C in sterile acid ripe plantain puree were calculated for 2-, 10- and 16-month old spores of Bacillus coagulans and Bacillus macerans. Results indicated that the D100° C values obtained were, respectively, 8.4, 13.2 and 9.2 mm for B. coagulans and 9.7, 9.7 and 9.7 min for B. macerans. According to these data, spore age has no effect on heat resistance for B. macerans. For B. coagulans, however, spore age appears to have an effect on thermal resistance. When 10-month old B. coagulans spores were used, the D100° C values obtained were significantly higher (P<0.01) than the ones for either 2- or 16-month old spores. This possible fluctuation in heat resistance with age of spore may introduce an element of variability that should not be overlooked when B. coagulans is used to determine the adequacy of a thermal process in acid or acidified foods. Since under certain conditions the spores of B. macerans could be more, or at least equally, heat resistant than those of B. coagulans, the question arises whether B. macerans could or should be used in lieu of B. coagulans in determining the adequacy of thermal processes in acid or acidified foods.

scholarly journals Effect of Physical Structures of Food Matrices on Heat Resistance of Enterococcus faecium NRRL-2356 in Wheat Kernels, Flour and Dough

Foods ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1890
Author(s):  
Biying Lin ◽  
Yufei Zhu ◽  
Lihui Zhang ◽  
Ruzhen Xu ◽  
Xiangyu Guan ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Heat Resistance ◽  
Enterococcus Faecium ◽  
Thermal Inactivation ◽  
Distribution Model ◽  
Heat Resistant ◽  
Wheat Kernel ◽  
First Order Kinetics ◽  
Food Matrices ◽  
Wheat Kernels

Nonpathogenic surrogate microorganisms, with a similar or slightly higher thermal resistance of the target pathogens, are usually recommended for validating practical pasteurization processes. The aim of this study was to explore a surrogate microorganism in wheat products by comparing the thermal resistance of three common bacteria in wheat kernels and flour. The most heat-resistant Enterococcus faecium NRRL-2356 rather than Salmonella cocktail and Escherichia coli ATCC 25922 was determined when heating at different temperature–time combinations at a fixed heating rate of 5 °C/min in a heating block system. The most heat-resistant pathogen was selected to investigate the influences of physical structures of food matrices. The results indicated that the heat resistance of E. faecium was influenced by physical structures of food matrices and reduced at wheat kernel structural conditions. The inactivation of E. faecium was better fitted in the Weibull distribution model for wheat dough structural conditions while in first-order kinetics for wheat kernel and flour structural conditions due to the changes of physical structures during heating. A better pasteurization effect could be achieved in wheat kernel structure in this study, which may provide technical support for thermal inactivation of pathogens in wheat-based food processing.

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.

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.

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.

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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