Thermal Resistance of Bacillus stearothermophilus Spores Heated in Acidified Mushroom Extract

1994 ◽  
Vol 57 (1) ◽  
pp. 37-41 ◽  
Author(s):  
PABLO S. FERNANDEZ ◽  
MARIA J. OCIO ◽  
TOMAS SANCHEZ ◽  
ANTONIO MARTINEZ
Keyword(s):  
Citric Acid ◽  
Thermal Resistance ◽  
Heat Resistance ◽  
Bacillus Stearothermophilus ◽  
Ph Effect ◽  
Bidistilled Water ◽  
Mushroom Extract ◽  
Reference Medium ◽  
D Values

The thermal resistance of Bacillus stearothermophilus spores was studied in bidistilled water as the reference medium, mushroom extract and acidified mushroom extract. Citric acid and glucono-δ-lactone were used as acidulants. Results indicated that mushroom extract affects the heat resistance of spores; D values were lower than for those in bidistilled water. The pH effect was lower with higher treatment temperatures. Acidification reduced the thermal resistance of spores, the reduction being similar for both types of acidulants, and in general it also had the effect of increasing the z values. It has been confirmed that acidification of the canned mushrooms could actually help to control the thermophilic spoilage. This acidification could also be obtained by the use of glucono-δ-lactone, which has been shown to be as effective as citric acid in reducing the heat resistance of spores.

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.

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.

Thermal Resistance of Bacillus stearothermophilus Heated at High Temperatures in Different Substrates

1997 ◽  
Vol 60 (2) ◽  
pp. 144-147 ◽  
Author(s):  
F. RODRIGO ◽  
P. S. FERNÁNDEZ ◽  
M. RODRIGO ◽  
M. J. OCIO ◽  
A. MARTÍNEZ
Keyword(s):  
Heat Treatment ◽  
Thermal Resistance ◽  
Heat Resistance ◽  
Bacillus Stearothermophilus ◽  
Distilled Water ◽  
Water Acidification ◽  
Mushroom Extract ◽  
Overnight Incubation ◽  
High Temperature Short Time ◽  
Short Time

The effect of mushroom extract, with or without acidification with glucono-δ-lactone, and the overnight incubation of the spores in CaCl2, on the heat resistance of B. stearothermophilus ATCC 12980 spores was studied. The temperature range considered was 121 to 140°C for mushroom extract and CaCl2 and 121 to 145°C for double-distilled water as a reference substrate. The results indicated that mushroom extract without added acid significantly reduces the thermal resistance of the spores in comparison to the double-distilled water. Acidification of the mushroom extract reduces the heat resistance of spores of B. stearothermophilus at 121 °C. However, above 130°C lowering of the pH did not significantly reduce the thermal resistance of the spores, and so no generalizations should be made with regard to the effect of the pH when high temperature-short time (HTST) processes are being considered. Overnight incubation in CaCl2 and subsequent heat treatment lead to increased heat resistance at 121 °C compared to that observed in double-distilled water. However, at 130°C and above CaCl2 did not increase the apparent heat resistance of the spores.

Effect of Using Milk as a Heating Menstruum on the Apparent Heat Resistance of Bacillus stearothermophilus Spores1

1977 ◽  
Vol 40 (4) ◽  
pp. 228-231 ◽  
Author(s):  
J. L. MAYOU ◽  
J. J. JEZESKI
Keyword(s):  
Heat Resistance ◽  
Bacillus Stearothermophilus ◽  
Survival Curves ◽  
Ph Range ◽  
D Values ◽  
D Value

Heat resistance at 121.1 C (250 F) of Bacillus stearothermophilus spores was studied using two heating menstrua. D values of 3.8 and 3.5 min were obtained when spores were heated in 0.01 M PO4 buffer, pH 6.5, and in skimmilk, pH 6.5, respectively. With buffer as a heating menstruum. increasing the pH from 6.5 to 7.2 resulted in an increase in the D value from 3.8 to 4.1 min. When the pH of skimmilk was increased from 6.5 to 7.2, D values increased from 3.5 to 5.2 min. Skimmilk as a component of the enumeration medium inhibited germination and/or outgrowth of B. stearothermophilus spores; however, this inhibition was not influenced over the pH range of 6.0 to 7.2. Addition of 10% skimmilk, pH 6.5, to the medium for enumeration of spores heated in buffer at pH 6.5 or 7.2, in each instance reduced the number of spores that could be recovered but did not change the slopes of survival curves.

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.

scholarly journals Thermal Resistance of Spores of Two Species of the Genus Bacillus

1969 ◽  
Vol 70 (3) ◽  
pp. 189-196
Author(s):  
Fred Fernández-Coll ◽  
Wanda Rodríguez-Toro
Keyword(s):  
Thermal Resistance ◽  
Heat Resistance ◽  
Incubation Temperature ◽  
Bacillus Coagulans ◽  
Genus Bacillus ◽  
Ph Values ◽  
Solid Media ◽  
Different Temperatures ◽  
D Values ◽  
Acidified Foods

Parameters that increased the thermal resistance of spores of Bacillus coagulans and Bacillus macerans, two common spoilage organisms in canned acid and acidified foods, were studied. Spores of these organisms were produced on solid media with various concentrations of added manganese, calcium chloride, or both, and at different pH values, and incubated at different temperatures. They were then heated in boiling water and decimal reduction times (D values) calculated. Results indicated that growing the organisms in nutrient agar modified with 50 p/m of MnSO4, pH 6.8 and incubation temperature of 50° C produced spores with greatest heat resistance in both B. coagulans and B. macerans.

Effect of Sporulation Media on the Heat Resistance of Bacillus stearothermophilus Spores1

1977 ◽  
Vol 40 (4) ◽  
pp. 232-233 ◽  
Author(s):  
J. L. MAYOU ◽  
J. J. JEZESKI
Keyword(s):  
Heat Resistance ◽  
Bacillus Stearothermophilus ◽  
Nutrient Broth ◽  
Nutrient Agar ◽  
Heat Inactivation ◽  
Vegetative Cells ◽  
Temperature Range ◽  
Heat Treated ◽  
D Values

Based on D values obtained over the temperature range of 121.1 C (250 F) to 126.7 C (260 F), Bacillus stearothermophilus vegetative cells sporulated in the presence of milk were more resistant to heat inactivation than spores grown on nutrient agar fortified with MnSo4. Spores grown in the presence of milk and heat-treated at 121.1 and 126.7 C had D values of 4.7 and 0.8 min, respectively. Spores grown on fortified nutrient agar and beat-treated at 121.1 and 126.7 C had D values of 3. 7 and 0.55 min, respectively. No difference in heat resistance was observed between spores derived from vegetative cells grown in milk or nutrient broth when tested at 121.1 C.

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.

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.

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.

Sign in / Sign up

Export Citation Format

Share Document