Addition of Cocoa Powder, Cane Sugar, and Carrageenan to Milk Enhances Growth of Listeria monocytogenes

1987 ◽  
Vol 50 (9) ◽  
pp. 726-729 ◽  
Author(s):  
EILEEN M. ROSENOW ◽  
ELMER H. MARTH
Keyword(s):  
Listeria Monocytogenes ◽  
Growth Curves ◽  
Cane Sugar ◽  
Chocolate Milk ◽  
Added Sugar ◽  
Milk Sugar ◽  
Generation Times ◽  
Sugar Addition ◽  
Bacterium Strain ◽  
Cocoa Product

Previously we found that under similar conditions Listeria monocytogenes achieved populations in chocolate milk that were 10 times greater than those in other fluid milk products. The current studies were undertaken to determine why the bacterium grew so well in chocolate milk. Autoclaved samples of milk with 2% milkfat, 2% milk + sugar, 2% milk + cocoa, and 2% milk + sugar + cocoa were inoculated with one of two strains of L. monocytogenes and incubated at 13°C. Carrageenan was also added to one-half of all samples containing cocoa. Growth curves were derived and generation times and maximum populations were calculated for each combination of product and strain of the bacterium. Strain V7 grew faster than strain CA in all products, with most rapid growth occurring in samples containing cocoa (with or without added sugar). Addition of carrageenan further reduced the generation time of this strain. Overall, growth rates ranged from 3 h 55 min (V7 in 2% milk + sugar + cocoa + carrageenan) to 4 h 53 min (CA in 2% milk + cocoa). Product type was primarily responsible for differences in maximum populations achieved by L. monocytogenes. In each instance, final numbers reached were at least 108 cells/ml with highest levels in samples containing all ingredients. The data suggest that sugar, cocoa and carrageenan when added to milk contributed to enhancing growth of L. monocytogenes.

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).

Growth of Listeria monocytogenes in Skim, Whole and Chocolate Milk, and in Whipping Cream during Incubation at 4, 8, 13, 21 and 35°C

1987 ◽  
Vol 50 (6) ◽  
pp. 452-459 ◽  
Author(s):  
EILEEN M. ROSENOW ◽  
ELMER H. MARTH
Keyword(s):  
Listeria Monocytogenes ◽  
Low Temperatures ◽  
Incubation Temperature ◽  
Growth Curves ◽  
Interactive Effects ◽  
Chocolate Milk ◽  
Refrigerated Storage ◽  
Generation Times ◽  
Whole Milk ◽  
Doubling Times

Autoclaved samples of skim, whole, and chocolate milk and of whipping cream were inoculated with Listeria monocytogenes (one to four strains were tested individually, depending on the experiment) and incubated at 4, 8, 13, 21 or 35°C. Growth curves were then derived and generation times and maximum populations calculated for each combination of strain, product, and temperature. The growth rate of L. monocytogenes was similar in all four products at a given incubation temperature and increased with an increase in temperature. Doubling times over all products and strains were 41 min (35°C), 1 h 43 min-1 h 55 min (21°C), 4 h 27 min-6 h 55 min (13°C), 8 h 40 min-14 h 33 min (8°C), and 29 h 44 min-45 h 33 min (4°C). In each instance, maximum populations reached were at least 107 cells/ml, with highest numbers consistently produced in chocolate milk (at least 10 times greater than in skim or whole milk or cream at any temperature). Little decrease in final numbers occurred with extended storage at the incubation temperature being studied. All results were analyzed statistically to determine magnitude and source of variation. Observed differences in data resulted from interactive effects between strain, product, and temperature. Therefore, no single factor can be considered as the sole cause of a particular finding. That L. monocytogenes can attain such high populations at low temperatures should be of concern. Since refrigerated storage is no guarantee of protection against growth of L. monocytogenes, every precaution should be taken to prevent contamination of certain foods by this organism.

Low Temperature Growth and Thermal Inactivation of Listeria monocytogenes in Precooked Crawfish Tail Meat1

1993 ◽  
Vol 56 (2) ◽  
pp. 106-109 ◽  
Author(s):  
WARREN J. DORSA ◽  
DOUGLAS L. MARSHALL ◽  
MICHAEL W. MOODY ◽  
CAMERON R. HACKNEY
Keyword(s):  
Listeria Monocytogenes ◽  
Storage Time ◽  
Thermal Inactivation ◽  
Growth Curves ◽  
Lag Phase ◽  
Short Term ◽  
Temperature Growth ◽  
Generation Times ◽  
Thermal Death ◽  
D Values

Growth of Listeria monocytogenes in precooked crawfish tail meat at 0, 6, and 12°C was determined. Thermal death times were also determined. Growth curves for L. monocytogenes revealed that little multiplication was observable for the entire storage time of 20 d at 0°C. At 6 and 12°C, exponential growth began immediately with no observed lag phase. Generation times of 72.2, 17.0, and 6.9 h were calculated at 0, 6, and 12°C, respectively. Observed D values at 55, 60, and 65°C were 10.23, 1.98, and 0.19 min, respectively. The z value for L. monocytogenes in precooked crawfish tail meat was calculated to be 5.5°C. Results from this study indicate that a refrigeration temperature of 6°C (42.8°F) will support growth of L. monocytogenes and short-term temperature abuse at 12°C will induce very rapid growth of the organism on crawfish tail meat. Thermal treatment values from this study can be used to establish postpicking heat treatments that would eliminate L. monocytogenes from packaged crawfish tail meat prior to retail sale.

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<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.

Synthesis of Milk-Sugar and Cane-Sugar

1880 ◽  
Vol 9 (219supp) ◽  
pp. 3491-3491
Author(s):  
E. Demole
Keyword(s):  
Cane Sugar ◽  
Milk Sugar

Effect of Sodium Nitrite on Growth of Shigella flexneri

1991 ◽  
Vol 54 (6) ◽  
pp. 424-428 ◽  
Author(s):  
LAURA L. ZAIKA ◽  
ANNA H. KIM ◽  
LOUISE FORD
Keyword(s):  
Exponential Growth ◽  
Shigella Flexneri ◽  
Salt Content ◽  
Brain Heart Infusion ◽  
Growth Curves ◽  
Inhibitory Effect ◽  
Plate Count ◽  
Generation Times ◽  
High Salt Content ◽  
Lag Times

A partial factorial design study of the effect of NaNO2 (0, 100, 200, 1000 ppm) in combination with NaCl (0.5, 2.5, 4.0%), pH (7.5, 6.5, 5.5), and temperature (37, 28, 19°C) on growth of Shigella flexneri is reported. Experiments were done aerobically in brain-heart infusion medium, using an inoculum of 1 × 103 CFU/ml. Growth curves were fitted from plate count data by the Gompertz equation; exponential growth rates, lag times, generation times, and maximum populations were derived for all variable combinations. In the absence of nitrite, the organism grew well under all test conditions at 37 and 28°C but did not grow at 19°C at pH 5.5 nor at pH 7.5 with 4% NaCl. Nitrite did not affect growth in media of pH 7.5 at 37 and 28°C. At pH 6.5 growth was inhibited by 1000 ppm NaNO2. The organism failed to grow at 19°C at all nitrite levels in the presence of 2.5 or 4.0% NaCl. The inhibitory effect of nitrite was much greater in media of pH 5.5 and increased with increasing salt levels. More inhibition was apparent at 28 than at 37°C. While lack of growth was used as a paradigm of the effect of nitrite on S. flexneri, nitrite also increased the lag and generation times and decreased the exponential growth rate. Results indicated that NaNO2 in combinations with low temperature, low pH, and high salt content can effectively inhibit the growth of S. flexneri.

scholarly journals Studies on enzyme action. IV.—The sucroclastic action of acids as contrasted with that of enzymes.

1904 ◽  
Vol 73 (488-496) ◽  
pp. 526-537 ◽  
Author(s):  
Edward Frankland Armstrong ◽  
Robert John Caldwell ◽  
Henry Edward Armstrong
Keyword(s):  
Cane Sugar ◽  
Enzyme Action ◽  
Milk Sugar ◽  
New Instrument ◽  
Hydrolysis Of

Not only are the various bioses hydrolysed at very different rates by enzymes but they are also known to differ in their behaviour towards acids: cane sugar being hydrolysed with the greatest facility, whilst maltose is acted upon but slowly. The experiments described in this communication were instituted primarily with the object of ascertaining the behaviour of milk sugar, of which nothing was known. The hydrolysis of cane sugar under the influence of acid was carefully investigated by Wilhelmy as far back as 1850, with the aid of the polariscope, then a new instrument.

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.

scholarly journals Growth Potential of Listeria monocytogenes on Refrigerated Spinach and Rocket Leaves in Modified Atmosphere Packaging

Foods ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 1211
Author(s):  
Paul Culliney ◽  
Achim Schmalenberger
Keyword(s):  
Listeria Monocytogenes ◽  
Modified Atmosphere Packaging ◽  
Growth Curves ◽  
High Growth ◽  
Food Product ◽  
Growth Potential ◽  
Modified Atmosphere ◽  
Visual Appearance ◽  
Iceberg Lettuce ◽  
Duration Of Storage

Minimally processed ready-to-eat (RTE) vegetables are increasingly consumed for their health benefits. However, they also pose a risk of being ingested with food-borne pathogens. The present study investigated the ability of RTE spinach and rocket to support the growth of Listeria monocytogenes as previous studies provided contradicting evidence. Findings were compared to growth on iceberg lettuce that has repeatedly been shown to support growth. Products were inoculated with a three-strain mix of L. monocytogenes at 10 and 100 cfu g−1 and stored in modified atmosphere (4 kPa O2, 8 kPa CO2) at 8 °C over 7–9 days. Spinach demonstrated the highest growth potential rate of 2 to 3 log10 cfu g−1 over a 9-day period with only marginal deterioration in its visual appearance. Growth potential on rocket was around 2 log10 cfu g−1 over 9 days with considerable deterioration in visual appearance. Growth potential of iceberg lettuce was similar to that of rocket over a 7-day period. Growth curves fitted closely to a linear growth model, indicating none to limited restrictions of growth over the duration of storage. The high growth potentials of L. monocytogenes on spinach alongside the limited visual deterioration highlight the potential risks of consuming this raw RTE food product when contaminated.

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