Thermal Resistance of Listeria monocytogenes in Milk

1985 ◽  
Vol 48 (9) ◽  
pp. 743-745 ◽  
Author(s):  
J. G. BRADSHAW ◽  
J. T. PEELER ◽  
J. J. CORWIN ◽  
J. M. HUNT ◽  
J. T. TIERNEY ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Resistance ◽  
Whole Milk ◽  
D Values ◽  
D Value

The thermal resistance of Listeria monocytogenes associated with a milkborne outbreak of listeriosis was determined in buffer and whole milk. Thermal resistance was stable over a 2-year period and could not be altered by selecting heat-stressed survivors. The rate of inactivation was linear and did not differ significantly between pH 5.5 and 9.0. When portions of whole milk containing 1 × 105 cells of L. monocytogenes/ml were heated at seven temperatures from 52.2 to 74.4°C, the D-values ranged from 1683.7 to 0.7 s, respectively. The zD-value was 6.3°C. The D-value at 71.7°C was 0.9 s. L. monocytogenes would not survive the pasteurization process.

Thermal Resistance of Salmonella spp. and Listeria monocytogenes in Liquid Egg Yolk and Egg Yolk Products†

1995 ◽  
Vol 58 (9) ◽  
pp. 960-966 ◽  
Author(s):  
MARY S. PALUMBO ◽  
SHARON M. BEERS ◽  
SAUMYA BHADURI ◽  
SAMUEL A. PALUMBO
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Resistance ◽  
Minimum Temperature ◽  
Salmonella Enteritidis ◽  
Egg Yolk ◽  
Salmonella Spp ◽  
Egg Products ◽  
D Values ◽  
Unit Reduction ◽  
D Value

The effectiveness of various pasteurization procedures in destroying Listeria monocytogenes and Salmonella enteritidis in liquid egg products was evaluated. Survivor studies were perfonned on individual strains of L. monocytogenes and L. innocua in commercially broken raw egg yolk samples after heating at 61.1, 63.3, and 64.4°C using submerged vials, and on Salmonella spp. at 60.0, 61.1, and 62.2°C. Surviving bacteria were enumerated on TSA and results expressed as D-values. The influence of aw -lowering ingredients such as salt and sugar on thermal resistance in yolk was investigated using a five-strain mixture of L. monocytogenes or a mixture of Salmonella spp. (four strains of S. enteritidis, one stain each of S. senftenberg and S. typhimurium) at 61.1°C to 66.7°C. At 61.1°C (present minimum temperature for pasteurization of plain egg yolk), a 7-log-unit reduction of Salmonella took 1.4 to 2.4 min, whereas a 7-log-unit reduction of L. monocytogenes took 4.9 to 16.1 min. The D-value for L. monocytogenes at 64.4°C increased from 0.44 min in plain yolk to 8.26 min after a 21.5-min lag (total time to achieve 1-log-unit reduction was 30.7 min) in yolk with 10% salt and 5% sugar, and 27.3 min after a 10.5-min lag (total time 37.8 min for 1-log-unit reduction) in yolk with 20% salt. The D-value for Salmonella in egg yolk at 64.4°C was < 0.2 min, but when 10% salt was added, the D-value was 6.4 min. Aw -lowering solutes in liquid egg yolk increased the thermal resistance of Salmonella and L. monocytogenes.

Thermal Resistance of Listeria monocytogenes Scott A in Ultrafiltered Milk as Related to the Effect of Different Milk Components

2010 ◽  
Vol 73 (11) ◽  
pp. 2110-2115 ◽  
Author(s):  
KINGA SZLACHTA ◽  
SUSANNE E. KELLER ◽  
ARLETTE SHAZER ◽  
STUART CHIRTEL
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Resistance ◽  
Milk Fat ◽  
Milk Powder ◽  
Skim Milk ◽  
Skim Milk Powder ◽  
Single Measure ◽  
Total Solids ◽  
Whole Milk ◽  
Milk Components

Pasteurization parameters for grade A milk are well established and set by regulation. However, as solids levels increase, an increased amount of heat is required to destroy any pathogens present. This effect is not well characterized. In this work, the effect of increased dairy solids levels on the thermal resistance of Listeria monocytogenes was examined through the use of ultrafiltered (UF) milk, reconstituted milk powder, and the milk components lactose and caseinate. From the results obtained, lactose and caseinate did not appear to affect thermal resistance. In addition, the level of milk fat, up to 10% of the total solids in UF whole milk, did not result in statistically significant changes to thermal resistance when compared with UF skim milk. Reconstituted skim milk powder at 27% total solids (D62-value = 1.16 ± 0.2 [SD] min, z = 5.7) did result in increased thermal resistance, as compared with reconstituted skim milk powder at 17.5% (D62-value = 0.86 ± 0.02 min, z = 5.57) and UF whole milk at 27% total solids (D62-value = 0.66 ± 0.07 min, z = 5.16). However, that increase appeared to be due to the increase in salt levels, not to increases in caseinate, fat, or lactose. Consequently, total solids, as a single measure, could not be used to predict increased thermal resistance of L. monocytogenes in concentrated milk.

Thermal Resistance of Disease-Associated Salmonella typhimurium in Milk

1987 ◽  
Vol 50 (2) ◽  
pp. 95-96 ◽  
Author(s):  
J. G. BRADSHAW ◽  
J. T. PEELER ◽  
J. J. CORWIN ◽  
J. E. BARNETT ◽  
R. M. TWEDT
Keyword(s):  
Thermal Resistance ◽  
Heat Resistance ◽  
Salmonella Typhimurium ◽  
Pasteurized Milk ◽  
Whole Milk ◽  
D Value

The thermal resistance of Salmonella typhimurium cultures that had been associated with a major milkborne oubreak of salmonellosis was determined in raw whole milk. Thirteen patient stool isolates and 24 implicated pasteurized milk isolates at concentrations of 1 × 105/ml were screened for heat resistance at 51.8°C. A representative milk strain was heated in replicate at four temperatures from 51.8 to 68.3°C. The zD value was calculated to be 5.3°C. Mean D-value estimates at 51.8°C were 24.0 and 22.8 min for patient and milk isolates, respectively. Extrapolated D71.7°C values were 0.24 and 0.22 s, and did not differ significantly (α = 0.05). These isolates would not survive proper pasteurization.

Thermal Resistance of Listeria monocytogenes, Salmonella Heidelberg, and Escherichia coli O157:H7 at Elevated Temperatures†

2004 ◽  
Vol 67 (8) ◽  
pp. 1666-1670 ◽  
Author(s):  
LIHAN HUANG
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Thermal Resistance ◽  
Continuous Flow ◽  
Elevated Temperatures ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Flow Apparatus ◽  
D Values ◽  
Salmonella Heidelberg

A continuous-flow apparatus was developed to measure thermal resistance (D- and z-values) of microorganisms at temperatures above 65°C. This apparatus was designed to test whether vegetative microorganisms exhibited unusually high thermal resistance that prevented them from being completely eliminated at temperatures applicable to vacuum-steam-vacuum processes (116 to 157°C). The apparatus was composed of a high-pressure liquid chromatography pump, a heating unit, and a cooling unit. It was designed to measure small D-values (<1 s). Three randomly selected organisms, Listeria monocytogenes, Salmonella Heidelberg, and Escherichia coli O157:H7 suspended in deionized water were tested in the continuous-flow apparatus at temperatures ranging from 60 to 80°C. Studies showed that the D-values of these organisms ranged from 0.05 to 20 s. Heating at 80°C was found to be basically the physical limit of the system. Experimental results showed that L. monocytogenes, Salmonella Heidelberg, and E. coli O157:H7 did not exhibit unusual heat resistance. The conditions used in the vacuum-steam-vacuum processes should have completely inactivated organisms such as L. monocytogenes, Salmonella Heidelberg, and E. coli O157:H7 if present on food surfaces. The complete destruction of bacteria during vacuum-steam-vacuum processes might not occur because the surface temperatures never reached those of the steam temperatures and because bacteria might be hidden beneath the surface and was thus never exposed to the destructive effects of the steam.

Effect of Sodium Lactate on Thermal Inactivation of Listeria monocytogenes and Salmonella in Ground Chicken Thigh and Leg Meat

2004 ◽  
Vol 67 (7) ◽  
pp. 1403-1407 ◽  
Author(s):  
R. Y. MURPHY ◽  
T. OSAILI ◽  
L. K. DUNCAN ◽  
J. A. MARCY
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Process ◽  
Thermal Inactivation ◽  
Meat Products ◽  
Sodium Lactate ◽  
Significant Difference ◽  
D Values ◽  
D Value

The effect of sodium lactate on thermal inactivation D- and z-values of Listeria monocytogenes and Salmonella was determined for chicken thigh and leg meat. At 55 to 70°C, the D-value of L. monocytogenes in ground chicken thigh and leg meat with the addition of 4.8% sodium lactate (4.8 g sodium lactate per 100 g of meat) was 53 to 75% higher than that in the meat without sodium lactate. No significant difference was found for the D-values of Salmonella at 55 to 70°C between the meat with and that without sodium lactate (4.8%, wt/wt). The z-values of both L. monocytogenes and Salmonella were not affected by sodium lactate (4.8%). The results from this study are useful for predicting thermal process lethality of L. monocytogenes and Salmonella in formulated chicken thigh and leg meat products.

Lethality of Heat to Listeria monocytogenes Scott A: D-Value and Z-Value Determinations in Ground Beef and Turkey

1991 ◽  
Vol 54 (10) ◽  
pp. 756-761 ◽  
Author(s):  
ALFRED R. FAIN ◽  
J. ERIC LINE ◽  
ALICE B. MORAN ◽  
L. MICHELE MARTIN ◽  
RICHARD V. LECHOWICH ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Ground Beef ◽  
Ground Meat ◽  
Circulating Water ◽  
Death Time ◽  
Lean Beef ◽  
Z Value ◽  
D Values ◽  
Thermal Death Time ◽  
D Value

D-Values and z-values for Listeria monocytogenes strain Scott A were determined in lean (2.0% fat) and fatty (30.5%) ground beef inoculated with approximately 107cells/g. Inoculated ground meat was sealed in glass thermal death time tubes which were completely immersed in a circulating water bath and held at prescribed temperatures for predetermined lengths of time. Survival was determined by enumeration on Columbia CNA agar base containing 1% sodium pyruvate with a CNA + 4% horse blood overlay (CBNA) and on Listeria Plating Medium (LPM). D-values for L. monocytogenes in lean and fatty ground beef at 125° were 81.3 and 71.1 min, respectively, as enumerated on CBNA plus pyruvate. D-values at 135°F were 2.6 and 5.8 min in lean and fatty beef. At 145°F, D-values were determined to be 0.6 and 1.2 min. D-values calculated from LPM recovery data from fatty ground beef at 125°F were 56.1 and 34.5 min, respectively. D-values at 135°F were 2.4 and 4.6 min in lean and fatty beef. At 145°F a D-value of 0.5 min was calculated in lean beef and a D-value of 1.1 min was determined in fatty beef. The z-values determined in lean beef and fatty beef using CBNA recovery data were 9.3 and 11.4°F, respectively. The z-value in lean beef using LPM recovery data was 9.8°F. The z-value in fatty beef using LPM recovery data was 13.2°F. A D-value for ground turkey meat at 160°F could not be determined under the conditions of this study. Problems encountered are discussed.

Predictive Thermal Inactivation Model for Listeria monocytogenes with Temperature, pH, NaCl, and Sodium Pyrophosphate as Controlling Factors†

1999 ◽  
Vol 62 (9) ◽  
pp. 986-993 ◽  
Author(s):  
VIJAY K. JUNEJA ◽  
BRIAN S. EBLEN
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Resistance ◽  
Predictive Model ◽  
Heating Temperature ◽  
Sodium Pyrophosphate ◽  
Effect Of Temperature ◽  
Plate Count ◽  
Heat Inactivation ◽  
Heat Sensitivity ◽  
D Values

The effects and interactions of heating temperature (55 to 65°C), pH (4 to 8), salt (NaCl; 0 to 6%, wt/vol), and sodium pyrophosphate (SPP; 0 to 0.3%, wt/vol) on the heat inactivation of a four-strain mixture of Listeria monocytogenes in beef gravy were examined. A factorial experimental design comparing 48 combinations of heating temperature, salt concentration, pH value, and SPP content was used. Heating was carried out using a submerged-coil heating apparatus. The recovery medium was plate count agar supplemented with 0.6% yeast extract and 1% sodium pyruvate. Decimal reduction times (D-values) were calculated by fitting a survival model to the data with a curve-fitting program. The D-values were analyzed by second-order response surface regression for temperature, pH, NaCl, and SPP levels. Whereas increasing the NaCl concentration protected L. monocytogenes against the lethal effect of heat, high SPP concentrations increased heat sensitivity. Also, low pH values increased heat sensitivity of L. monocytogenes. The four variables interacted to affect the inactivation of the pathogen. Thermal resistance of L. monocytogenes can be lowered by combining these intrinsic factors. A predictive model that described the combined effect of temperature, pH, NaCl, and SPP levels on thermal resistance of L. monocytogenes was developed. The model can predict D-values for any combination of temperature, pH, NaCl, and SPP that are within the range of those tested. Using this predictive model, food processors should be able to design adequate thermal regimes to eliminate L. monocytogenes in thermally processed foods.

Thermal Destruction of Listeria monocytogenes in Ground Pork Prepared with and without Soy Hulls

1995 ◽  
Vol 58 (5) ◽  
pp. 573-576 ◽  
Author(s):  
PATRICIA OLLINGER-SNYDER ◽  
FATHY EL-GAZZAR ◽  
M. EILEEN MATTHEWS ◽  
ELMER H. MARTH ◽  
NAN UNKLESBAY
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Destruction ◽  
Water Mixture ◽  
Soy Hull ◽  
Colony Forming Units ◽  
Ground Pork ◽  
Soy Hulls ◽  
D Values ◽  
D Value

D-values and z-values were determined for Listeria monocytogenes Scott A cells heated in raw ground pork prepared with and without soy hulls and in a soy hull/water mixture. Products inoculated with ca. 107 colony-forming units (CFU) per g were sealed in glass vials, immersed in a water bath, and held at 50, 55, 60, or 62°C for predetermined times. Survival was determined by testing heated samples with McBride listeria agar. The D-values for L. monocytogenes cells at 50, 55, and 60°C were 108.81, 9.80, and 1.14 min, respectively, when heating was in ground pork and 113.64, 10.19, and 1.70 min, respectively, when heating in ground pork with added soy hulls. At 62°C L. monocytogenes cells were inactivated too rapidly to permit determination of the D-value. The D-values for L. monocytogenes in the soy hull/water mixture at 50 and 55°C were 19.84 and 3.94 min, respectively. L. monocytogenes cells were inactivated too quickly to determine the D-value at 60°C. The z-values for L. monocytogenes in ground pork prepared with and without soy hulls were 5.45 and 5.05°C, respectively. If ground pork naturally contains 102 L. monocytogenes cells per g and if we want to assure safety with a 4-D Listeria cook (reducing the L. monocytogenes population by four orders of magniatude), then according to results of this study, ground pork must be heated to an internal temperature of 60°C for at least 4.6 min and ground pork with added soy hulls for at least 6.8 min.

Heat Resistance and Growth of Listeria monocytogenes in Liquid Whole Egg1,2

1990 ◽  
Vol 53 (1) ◽  
pp. 9-14 ◽  
Author(s):  
PEGGY M. FOEGEDING ◽  
SUSAN B. LEASOR
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Resistance ◽  
Heat Resistance ◽  
Growth Temperature ◽  
Generation Times ◽  
Liquid Whole Egg ◽  
D Values ◽  
Whole Egg

Listeria monocytogenes F5069, ATCC 19111, Scott A, and two L. monocytogenes strains isolated from egg were evaluated for growth and thermal resistance in liquid whole egg. Each strain grew in liquid whole egg at temperatures between 4 and 30°C, except Scott A which did not grow at 4 or 10°C. Generation times ranged from 24 h for F5069 to 51 h for ATCC 19111 at 4°C and from 7.8 h for one of the egg isolates to 31 h for ATCC 19111 at 10°C. Maximum populations for each strain increased with increasing growth temperature and were between 105 and 3 × 108 CFU/g. Decimal reduction times (D-values) of each L. monocytogenes strain in raw liquid whole egg were similar to D-values reported in milk. The heat resistance of all strains was similar. For L. monocytogenes F5069, D-values ranged from 22.6 min at 51°C to 0.20 min at 66°C. The zD-value for F5069 was 7.2°C. Minimal pasteurization parameters (60°C, 3.5 min) for liquid whole egg would result in 99 to 99.9% inactivation (populations reduced 2 to 3 log cycles) of the L. monocytogenes strains tested.

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