Behavior of Listeria monocytogenes at 4 and 22°C in Whey and Skim Milk Containing 6 or 12% Sodium Chloride

1989 ◽  
Vol 52 (9) ◽  
pp. 625-630 ◽  
Author(s):  
DEMETRIOS K. PAPAGEORGIOU ◽  
ELMER H. MARTH
Keyword(s):  
Listeria Monocytogenes ◽  
Sodium Chloride ◽  
Skim Milk ◽  
Salt Tolerant ◽  
Ph Values ◽  
Generation Times ◽  
Order Of Magnitude ◽  
Entire Experiment

Autoclaved samples of skim milk and deproteinated whey were fortified with 6 or 12% NaCl, inoculated with Listeria monocytogenes strains Scott A or California (CA), to contain ca. 1.0 × 103 cfu/ml (in the products with 6% salt) or ca. 5.0 × 103 cfu/ml (in the products with 12% salt) and incubated at 4 and 22°C. The pH values of the 6% salted whey, 6% salted skim milk, 12% salted whey, and 12% salted skim milk were 5.65, 6.20, 5.50, and 6.00 respectively. These values remained relatively constant during the entire experiment. Listeria counts were obtained by surface-plating appropriate dilutions and/or undiluted samples on Trypticase Agar (TA). Samples in which L. monocytogenes was not detected, were re-examined after 2, 4, 6 and 8 weeks of cold-enrichment. Generation times of L. monocytogenes in 6% salted whey at 22°C (3.67 h and 3.56 h for strains Scott A and CA, respectively) were significantly shorter than those in 6% salted skim milk at 22°C (4.31 and 4.42 h for the two strains, respectively). Generation times in 6% salted products at 4°C ranged between 37.49 h and 49.43 h. Maximum populations reached at 22 and 4°C ranged from 7.58 to 8.10 Log10 cfu/ml, and were significantly higher in 6% salted whey than in 6% salted skim milk. In 12% salted whey and skim milk incubated at 22°C, L. monocytogenes gradually decreased in numbers. Strain CA was inactivated within 85 d in 12% salted skim milk or within 110 d in 12% salted whey, and was significantly less salt tolerant than strain Scott A which survived for more than 130 d under the same conditions. Loss of viability by both strains was similar in 12% salted whey and skim milk after 130 d of storage at 4°C, and the decreases in population were less than 0.7 order of magnitude.

Behavior of Listeria monocytogenes in the Presence of Cocoa, Carrageenan, and Sugar in a Milk Medium Incubated With and Without Agitation

1990 ◽  
Vol 53 (1) ◽  
pp. 30-37 ◽  
Author(s):  
LAURA J. PEARSON ◽  
ELMER H. MARTH
Keyword(s):  
Listeria Monocytogenes ◽  
Linear Relationship ◽  
Skim Milk ◽  
Type A ◽  
Cane Sugar ◽  
Sugar Concentration ◽  
Chocolate Milk ◽  
Type B ◽  
Cocoa Powder ◽  
Generation Times

Enhanced growth of Listeria monocytogenes strain V7 in chocolate milk rather than skim milk was further investigated by testing various concentrations of cocoa powder (two types of Dutch-process, designated A and B), cane sugar, and sodium carrageenan in skim milk at 13 and 30°C with and without agitated incubation. Increasing sugar concentrations (0, 6.5, and 12.0%) were marginally significant (p = 0.06) in shortening generation times (5.17, 5.07, and 5.05 h, respectively) of the pathogen. Maximum populations attained by the pathogen were greater when cocoa (0.75% type A or B) and sugar (6.5 or 12.0%) were present. Sugar concentration affected growth of L. monocytogenes in an approximately linear relationship (8.41, 8.67, 8.82 log10 CFU/ml for 0, 6.5, and 12.0% sugar, respectively) except in samples containing only carrageenan. In this instance, presence of 6.5 and 12.0% sugar resulted in equivalent maximum populations (8.54 and 8.52 log10 CFU/ml). Three factors enhanced growth of the pathogen at 30°C: addition of cocoa, addition of sugar, and agitated rather than quiescent incubation. Without cocoa, generation times of L. monocytogenes were longer (1.04 h) compared to presence of type A (0.87 h) or B (0.90 h) cocoa. L. monocytogenes in agitated samples had shorter (0.82 h) generation times than in quiescent cultures (0.95 h). Highest populations were attained in agitated samples containing sugar and type A (9.21 log10 CFU/ml) or type B (9.22 log10 CFU/ml) cocoa compared to lowest populations in quiescent samples of skim milk (8.56 log10 CFU/ml).

Validation of Predictive Mathematical Models Describing the Growth of Listeria monocytogenes

1997 ◽  
Vol 60 (9) ◽  
pp. 1142-1145 ◽  
Author(s):  
ISABEL WALLS ◽  
VIRGINIA N. SCOTT
Keyword(s):  
Listeria Monocytogenes ◽  
Growth Rates ◽  
Microbial Growth ◽  
Lag Phase ◽  
Growth Data ◽  
Ph Values ◽  
Gompertz Equation ◽  
Generation Times ◽  
Different Temperatures ◽  
Good Agreement

Growth of Listeria monocytogenes and Listeria innocua in commercially available sterile homogeneous foods was investigated at different temperatures, pH values, and NaCl concentrations. Growth data were fitted to the Gompertz equation and the resulting growth kinetics were compared with predictions from the Pathogen Modeling Program and Food MicroModel. In general, good agreement was obtained when comparing growth rates and generation times for both models. Differences were observed when comparing lag phases, which ranged from 117 h shorter to 4.9 h longer than predicted for L. monocytogenes. Despite differences in lag phase, under most conditions, the models gave good predictions of microbial growth. Predictive modeling appears to be a useful tool in determining growth rates of Listeria in foods.

Growth of Listeria monocytogenes at different pH values in uncultured whey or whey cultured with Penicillium camemberti

1988 ◽  
Vol 34 (6) ◽  
pp. 730-734 ◽  
Author(s):  
Elliot T. Ryser ◽  
Elmer H. Marth
Keyword(s):  
Listeria Monocytogenes ◽  
Penicillium Camemberti ◽  
Ph Values ◽  
Generation Times ◽  
Camembert Cheese

Wheys from making Camembert cheese were either uncultured or cultured with Penicillium camemberti, adjusted to pH 5.0, 5.2, 5.4, 5.6, 6.2, and 6.8, and filter sterilized. Whey samples were inoculated to contain 100 to 500 Listeria monocytogenes (strains Scott A, V7, CA, or OH) cfu/mL and incubated at 6 °C. Counts of L. monocytogenes were obtained by surface plating appropriate dilutions on Tryptose Agar. Listeria monocytogenes failed to grow at or below pH 5.4; except for strains Scott A and OH which grew in cultured whey at pH 5.4 and attained populations of 7.8 × 103 and 5.4 × 104 cfu/mL, respectively, after 35 d of storage. In uncultured whey at pH 5.6, 6.2, and 6.8, populations of L. monocytogenes increased from 7.20 to 7.81, 7.51 to 8.23, and 7.48 to 8.08 log10 cfu/mL, respectively, after 35 d of storage at 6 °C. In cultured whey at pH 5.6, 6.2, and 6.8, numbers of L. monocytogenes increased from 7.53 to 8.13, 7.82 to 8.55, and 7.95 to 8.80 log10 cfu/mL, respectively, after 35 d of storage. Generation times for L. monocytogenes at 6 °C in uncultured whey at pH 5.6, 6.2, and 6.8 ranged between 25.3 and 31.6 h, 14.8 and 21.1 h, and 14.0 and 19.4 h, respectively, depending on the Listeria strain. In contrast, generation times were significantly (p < 0.05) shorter in cultured whey and ranged between 16.6 and 27.4 h, 10.3 and 16.6 h, and 17.4 and 16.3 h at pH values of 5.6, 6.2, and 6.8, respectively.

scholarly journals Antimicrobial activity of the Nisin Z producer Lactococcus lactis subsp. lactis Lc08 against Listeria monocytogenes in skim milk

2013 ◽  
Vol 65 (5) ◽  
pp. 1554-1560 ◽  
Author(s):  
L.M. Perin ◽  
R.O. Miranda ◽  
A.C. Camargo ◽  
M. Colombo ◽  
A.F. Carvalho ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Listeria Monocytogenes ◽  
Lactococcus Lactis ◽  
Food Systems ◽  
Skim Milk ◽  
In Vitro Tests ◽  
Lactococcus Lactis Subsp ◽  
Ph Values ◽  
Nisin Z

The presented study aimed to verify the effect of different pH values, enzyme solutions and heat treatments on the antimicrobial activity of the bacteriocinogenic strain Lactococcus lactis subsp. lactis Lc08 and to test their antimicrobial activity against Listeria monocytogenes in reconstituted skim milk at refrigeration temperatures. This strain was previously described as a nisin Z producer and capable of inhibiting L. monocytogenes growth in in vitro tests. The antimicrobial activity of the bacteriocin cell-free supernatant of Lc08 was sensitive to enzyme treatments (except papain). The pH values and heating (65ºC for 30min, 75ºC for 15s) had no apparent effect on the antimicrobial activity of the bacteriocin produced by Lc08. Only treatment at autoclave conditions result in loss of their antimicrobial activity. Lc08 presented antimicrobial activity against L. monocytogenes in the milk system after 12h at 25ºC. No effect was found at 7ºC. The results show the application viability of the Lc08 in food systems as a biopreservative against L. monocytogenes.

Behavior of Listeria monocytogenes in Skim Milk and in Yogurt Mix during Fermentation by Thermophilic Lactic Acid Bacteria

1988 ◽  
Vol 51 (8) ◽  
pp. 607-614 ◽  
Author(s):  
MICHELLE M. SCHAACK ◽  
ELMER H. MARTH
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Lactic Acid Bacteria ◽  
Skim Milk ◽  
Streptococcus Thermophilus ◽  
Lactobacillus Bulgaricus ◽  
Inhibition Of Growth ◽  
Order Of Magnitude ◽  
Thermophilic Lactic Acid Bacteria

Behavior of Listeria monocytogenes in skim milk and in yogurt mix during fermentation with thermophilic lactic starters was determined. Sterile skim milk was inoculated with ca. 103 L. monocytogenes cells/ml and with 5.0, 1.0 or 0.1% of a milk culture of Streptococcus thermophilus, Lactobacillus bulgaricus or a mixture of the two species. The milk was incubated at 37 or 42°C for 15 h, followed by refrigeration at 4°C. Yogurt mix was inoculated with ca. 5 × 103 L. monocytogenes cells/ml of mix and then was incubated at 45°C for 5 h, followed by refrigeration at 4°C. L. monocytogenes survived the 15-h fermentation with S. thermophilus in all combinations of level of inoculum and temperature of incubation, but inhibition of growth ranged from 96 to 100%. When incubated with L. bulgaricus, L. monocytogenes survived only between 9 and 15 h of incubation; a decrease in pH to below 4.0 was accompanied by rapid death of the pathogen. The combination of the two species was more inhibitory to L. monocytogenes than was S. thermophilus alone but less inhibitory than was L. bulgaricus alone. In yogurt mix, L. monocytogenes grew during the fermentation and increased in number by about one order of magnitude.

scholarly journals Preliminary Study of Sodium Chloride Tolerance of Rudbeckia fulgida var. speciosa ‘Goldsturm’, Heuchera americana ‘Dale's Variety’ and Aquilegia × cultorum ‘Crimson Star’ Grown in Greenhouse Conditions

2011 ◽  
Vol 29 (4) ◽  
pp. 223-228
Author(s):  
Carri Gerber ◽  
Laura Deeter ◽  
Kelsey Hylton ◽  
Bryce Stilwill
Keyword(s):  
Sodium Chloride ◽  
Digital Images ◽  
Symptom Development ◽  
Salt Tolerant ◽  
Ph Values ◽  
Visual Damage ◽  
Preliminary Study ◽  
Chloride Concentrations ◽  
Over Time

Abstract Heuchera americana ‘Dale's Variety’, Aquilegia × cultorum ‘Crimson Star’ and Rudbeckia fulgida var. speciosa ‘Goldsturm’ were grown in a soilless medium and watered weekly with either 0.00 (control), 0.05, 0.15 or 0.25 M NaCl solutions for 6 weeks. Foliage and leachate were analyzed for pH, Na+ and Cl−, and digital images were taken of all plants. Sodium and chloride concentrations in the leachate increased over time, while pH values remained unchanged. Aquilegia and Rudbeckia took up both Na+ and Cl−in increasing amounts over time. Heuchera took up large quantities of Cl−initially, but lesser amounts over time, and minimal Na+ into the foliage until the last week. At the highest treatment levels of NaCl, all plants showed significant visual damage. Aquilegia was the first to show visual damage at 0.05 M NaCl. Heuchera was intermediate in terms of symptom development. Based on the results of this study, Rudbeckia and Heuchera are listed as salt tolerant, and Aquilegia is listed as salt intolerant.

Growth of Listeria monocytogenes at 10°C in Milk Preincubated with Selected Pseudomonads1

1988 ◽  
Vol 51 (4) ◽  
pp. 277-282 ◽  
Author(s):  
DOUGLAS L. MARSHALL ◽  
RONALD H. SCHMIDT
Keyword(s):  
Listeria Monocytogenes ◽  
Skim Milk ◽  
Growth Curves ◽  
Milk Composition ◽  
Pseudomonas Fragi ◽  
Pseudomonas Spp ◽  
Generation Times ◽  
Whole Milk ◽  
Dry Milk ◽  
Stimulation Of

Preliminary studies involving co-inoculation of Listeria monocytogenes with Pseudomonas fragi into whole or skim milk demonstrated that neither inhibition nor stimulation of growth occurred for either organism. Additional investigations involved preincubation of whole milk, skim milk, and 10% reconstituted nonfat dry milk (NDM) for 3 d at 10°C with P. fragi, Pseudomonas fluorescens P26, P. fluorescens T25, or P. fluorescens B52, followed by inoculation with L. monocytogenes and further incubation at 10°C. Growth curves of L. monocytogenes were constructed for each treatment combination and generation times were statistically compared for differences. Results indicated that L. monocytogenes did not affect growth or survival of the preincubated Pseudomonas spp. However, growth rates of L. monocytogenes were significantly (P&lt;0.05) enhanced in milks preincubated with pseudomonads. Doubling times of L. monocytogenes were reduced by up to 3 h when grown in milk preincubated with Pseudomonas spp. Three strains of P. fluorescens showed more stimulation of the growth rate of L. monocytogenes compared to P. fragi in preincubated whole or skim milk but not in preincubated NDM. Milk composition had little effect on growth of either genus when incubated alone. Results of this study indicate that L. monocytogenes can grow in the presence of Pseudomonas spp. either as a co-inoculant or following preincubation in milk at 10°C. Furthermore, data suggest that the presence of the pseudomonads may enhance growth of L. monocytogenes in milk.

Growth of Listeria monocytogenes at 4, 32, and 40°C in Skim Milk and in Retentate and Permeate from Ultrafiltered Skim Milk

1991 ◽  
Vol 54 (5) ◽  
pp. 338-342 ◽  
Author(s):  
FATHY E. EL-GAZZAR ◽  
HANS F. BOHNER ◽  
ELMER H. MARTH
Keyword(s):  
Listeria Monocytogenes ◽  
Skim Milk ◽  
Growth Curves ◽  
Generation Times

Pasteurized skim milk and retentate (concentrated fivefold or twofold by volume) and permeate from ultrafiltered skim milk were inoculated with Listeria monocytogenes strains California or V7 and incubated at 4, 32, or 40°C. Changes in populations of the pathogen were determined, growth curves were derived, and generation times and maximum populations calculated for each combination of strain, product, and temperature. Both strains grew faster and achieved higher (ca. 1 to 2 orders of magnitude) populations at 4°C in retentate of either concentration than in skim milk. The pathogen grew in permeate at 4°C and attained maximum populations of ca. 106 to 107/ml. Tyndallized samples of skim milk and retentate and permeate from ultrafiltered skim milk were inoculated with the same strains of L. monocytogenes and incubated at 32 or 40°C. Populations achieved by the pathogen at these temperatures, ca. 107 to 108/ml, were similar in skim milk, retentate, and permeate.

Growth of Listeria monocytogenes in the Presence of Pseudomonas fluorescens at 7 or 13°C in Skim Milk

1989 ◽  
Vol 52 (12) ◽  
pp. 852-855 ◽  
Author(s):  
SEHAM A. FARRAG ◽  
ELMER H. MARTH
Keyword(s):  
Listeria Monocytogenes ◽  
Pseudomonas Fluorescens ◽  
Incubation Period ◽  
Skim Milk

Autoclaved samples of skim milk were inoculated with Listeria monocytogenes (strain Scott A, California or V7), Pseudomonas fluorescens (strain P26 or B52), or a combination of L. monocytogenes plus P. fluorescens, and incubated at 7 or 13°C for 8 weeks. McBride Listeria Agar was used to determine populations of L. monocytogenes (at 0, 7, 14, 28, 42, or 56 d), and Pseudomonas isolation agar to enumerate P. fluorescens. Growth of L. monocytogenes was somewhat enhanced after 7 d of incubation at 7 but not at 13°C in the presence of pseudomonads. However, after 14 d and until the end of the incubation period (56 d), slight inactivation of L. monocytogenes in the presence of P. fluorescens was observed. L. monocytogenes did not affect growth or survival of P. fluorescens; also, no marked changes in pH of the milk were caused either by L. monocytogenes alone or by L. monocytogenes plus P. fluorescens.

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.

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