Fate of Listeria monocytogenes on Ready to Serve Lettuce1

1988 ◽  
Vol 51 (8) ◽  
pp. 596-599 ◽  
Author(s):  
E. G. STEINBRUEGGE ◽  
R. BURT MAXCY ◽  
MICHAEL B. LIEWEN
Keyword(s):  
Listeria Monocytogenes ◽  
Storage Conditions ◽  
Growth Patterns ◽  
Plate Count ◽  
Plastic Bags ◽  
Retail Outlets ◽  
Serotype 1 ◽  
Plate Counts ◽  
Storage Behavior ◽  
Aerobic Plate Count

The ability of Listeria monocytogenes to survive and grow on head lettuce obtained from a retail outlet over a period of 10 months was determined. Lettuce was torn into bite sized pieces, inoculated with L. monocytogenes ATCC 7644, placed into plastic bags, and held under a variety of storage conditions. Samples stored at 5°C and 12°C were subjected to aerobic plate count analysis, and levels of L. monocytogenes were determined immediately after inoculation and after 7 and 14 d of storage. Samples stored at 25°C were sampled after inoculation and after 4 and 8 h storage. Lettuce juice was inoculated, stored at 5°C and sampled as described for head lettuce. Aerobic plate counts on lettuce stored at 5°C and 12°C increased greatly during the 14 d of storage. Behavior of L. monocytogenes was variable. In most trials, numbers increased by several log cycles during 14 d of storage, but in several trials growth never occurred or did not persist for 14 d. The same general growth patterns were observed in lettuce held at 25°C. Aerobic plate counts increased by 1 or 2 log cycles and L. monocytogenes increased by 1 log cycle, except for occasional trials where the organisms did not grow or survive. Lettuce juice held at 5°C was also able to support growth of L. monocytogenes. L. monocytogenes serotype 1 was isolated from some uninoculated samples indicating that the organism was naturally present on some of the lettuce heads purchased from retail outlets.

Bacteriological Evaluation of Some Luncheon Meats in the Canadian Retail Market

1977 ◽  
Vol 40 (6) ◽  
pp. 382-384 ◽  
Author(s):  
C. L. DUITSCHAEVER
Keyword(s):  
Plate Count ◽  
Public Health Significance ◽  
High Incidence ◽  
Retail Outlets ◽  
Plate Counts ◽  
Health Significance ◽  
Aerobic Plate Count ◽  
Bacteriological Evaluation

Four types of luncheon meats, bologna, chicken loaf, ham, and macaroni cheese, each manufactured by four different companies, were purchased from four major retail outlets in Ontario over a period of 16 weeks during the summer of 1975. Bacterial evaluation included determination of total aerobic plate count, coliforms, Escherichia coli, Staphylococcus aureus, Clostridium perfringens, salmonellae, and enterococci. Bacteria of public health significance were not a problem except for a high incidence of enterococci in all samples. S. aureus counts exceeded 1000/g in 20% of 30 positive samples out of a total of 159 samples. Total aerobic plate counts exceeded 5,000,000/g in 46.5% of the samples. Wide variation in bacteriological quality of the products between manufacturers was found.

scholarly journals Efficacy of Cetylpyridinium Chloride against Listeria monocytogenes and Its Influence on Color and Texture of Cooked Roast Beef†

2005 ◽  
Vol 68 (11) ◽  
pp. 2349-2355 ◽  
Author(s):  
M. SINGH ◽  
H. THIPPAREDDI ◽  
R. K. PHEBUS ◽  
J. L. MARSDEN ◽  
T. J. HERALD ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Lactic Acid Bacteria ◽  
Cetylpyridinium Chloride ◽  
Meat Products ◽  
Plate Count ◽  
Bacterial Populations ◽  
Plate Counts ◽  
Roast Beef ◽  
Aerobic Plate Count

Sliced (cut) and exterior (intact) surfaces of restructured cooked roast beef were inoculated with Listeria monocytogenes, treated with cetylpyridinium chloride (CPC; immersion in 500 ml of 1% solution for 1 min), individually vacuum packaged, and stored for 42 days at 0 or 4°C. Noninoculated samples were similarly treated, packaged, and stored to determine effects on quality (color and firmness) and on naturally occurring bacterial populations, including aerobic plate counts and lactic acid bacteria. Immediately after CPC treatment, regardless of inoculation level, L. monocytogenes populations were reduced (P = 0.05) by about 2 log CFU/cm2 on sliced surfaces and by about 4 log CFU/cm2 on exterior surfaces. Throughout 42 days of refrigerated storage (at both 0 and 4°C), L. monocytogenes populations on CPC-treated samples remained lower (P = 0.05) than those of nontreated samples for both surface types. After 42 days of storage at both 0 and 4°C, aerobic plate count and lactic acid bacteria populations of treated samples were 1 to 1.5 log CFU/cm2 lower (P = 0.05) than those of nontreated samples for both surface types. CPC treatment resulted in negligible effects (P > 0.05) on the color (L*, a*, and b* values) of exterior and sliced roast beef surfaces during storage. For both sliced and exterior surfaces, CPC-treated samples were generally less firm than nontreated samples. CPC treatment effectively reduced L. monocytogenes populations on roast beef surfaces and resulted in relatively minor impacts on color and texture attributes. CPC treatment, especially when applied to products prior to slicing, may serve as an effective antimicrobial intervention for ready-to-eat meat products.

Chemical and Microbial Changes in Dehulled Confectionery Sunflower Kernels during Storage Under Controlled Conditions

1976 ◽  
Vol 39 (1) ◽  
pp. 18-23 ◽  
Author(s):  
J. A. ROBERTSON ◽  
J. K. THOMAS
Keyword(s):  
Storage Time ◽  
Storage Period ◽  
Plate Count ◽  
Enterobacter Agglomerans ◽  
High Moisture ◽  
Plastic Bags ◽  
Plate Counts ◽  
Aerobic Plate Count ◽  
And Storage ◽  
Microbiological Analyses

Samples of freshly dehulled, confectionery sunflower kernels were adjusted to moistures of 5.2, 10.5, and 14.7%, sealed in plastic bags and stored at 35, 75, and 95 F (1.7, 23.9, and 35 C) for 12 weeks. At 2-week intervals aliquots were removed for flavor, chemical, and microbiological analyses. Acid values of oil extracted from stored kernels increased with temperature, moisture content, and storage time. At acid values of 4 or higher, kernels had a sour flavor. In general, the peroxide value decreased with increased moisture at each temperature and storage period. The initial aerobic plate count of the sunflower kernels was log 6.83/g, the Enterobacteriaceae count was log 6.15/g, and the yeast and mold count was log 3.65/g. From countable plates randomly selected, about 80% of the Enterobacteriaceae were identified as Enterobacter agglomerans (Erwinia herbicola). At 35 F microbial counts generally changed little. At 75 F, however, counts decreased rapidly; and at 95 F, yeast and mold counts of 14.7% moisture kernels increased, Enterobacteriaceae counts decreased, and aerobic plate counts decreased except in high moisture samples. A microbiological survey of whole sunflower seed and dehulled kernels from three dehulling operations indicated that contamination of the dehulled kernels was primarily from sunflower hulls rather than from processing equipment.

Incidence and Survival of Listeria monocytogenes in Ready-To-Eat Seafood Products

1997 ◽  
Vol 60 (4) ◽  
pp. 372-376 ◽  
Author(s):  
SUSAN A. MCCARTHY
Keyword(s):  
Listeria Monocytogenes ◽  
Storage Time ◽  
Storage Temperature ◽  
Storage Conditions ◽  
Plate Count ◽  
Standard Plate Count ◽  
Smoked Salmon ◽  
Standard Plate ◽  
Seafood Products ◽  
Survival And Growth

The effects of processing and postprocess storage conditions on the incidence and survival of Listeria monocytogenes on crawfish (Procambaris sp.), crabmeat (Callinectus sapidus), and smoked salmon (Salmo salar) were evaluated. L. monocytogenes was recovered from 3% of whole boiled market crawfish samples and 17% of frozen vacuum-packaged partially cooked crawfish tail meat, but not from boiled crabmeat or smoked salmon. Contamination was most likely due to postprocess handling as commonly used methods of cooking (5 min boil or 20 min steep) reduced L. monocytogenes to nondetectable levels in laboratory-contaminated crawfish. In postprocess storage temperature abuse studies, cooked whole crawfish were inoculated internally and externally with 3.0 log CFU of L. monocytogenes per g and incubated at 22 or 30°C for 6 h. The greatest increase in numbers of cells, 1.9 log CFU/g (determined by standard plate count), occurred at 30°C on externally contaminated crawfish. There was little change in numbers of L. monocytogenes during cold storage (6°C, 5 days; −20°C, 15 days). There was little change in cell numbers associated with products stored at 22 or −20°C. At 6°C, numbers of cells associated with crabmeat increased by 3.8 log MPN/g after 6 days; however, there was no increase in numbers of cells associated with salmon. The results show that the survival and growth characteristics of L. monocytogenes are dependent on storage time and temperature and the nature of the seafood product.

Dry Rehydratable Film for Enumeration of Total Aerobic Bacteria in Foods: Collaborative Study

1990 ◽  
Vol 73 (2) ◽  
pp. 242-248
Author(s):  
Michael S Curiale ◽  
Therese Sons ◽  
J Sue Mcallister ◽  
Barbara Halsey ◽  
Terrance L Fox
Keyword(s):  
Collaborative Study ◽  
Agar Plate ◽  
Plate Count ◽  
Relative Standard ◽  
Plate Counts ◽  
Agar Method ◽  
Standard Deviations ◽  
Aerobic Plate Count ◽  
Film Method ◽  
Dry Film

Abstract A rehydratable dry-film plating procedure for aerobic plate counts has been compared to the standard agar plate method (966.23B and C, 15th ed.; 46.014-46.015, 14th ed.) in a collaborative study by 12 laboratories. Each laboratory analyzed the normal microflora of 3 samples in duplicate for 6 products. The aerobic plate counts ranged from 1.0 X 103 to 1.0 X 108 cfu/g. The products were flour, nuts, frozen raw shrimp, spice, frozen raw ground turkey, and frozen and refrigerated vegetables. Repeatability standard deviations of the 2 methods did not differ significantly for 13 of 18 test samples. For 1 shrimp and 2 turkey samples, the dry-film method had lower repeatability variances (P < 0.05) and for 1 spice sample the agar method had lower repeatability variances (P < 0.05). Relative standard deviations of repeatability were between 1.7 and 15.5% for the dry-film method and 1.2 and 16.0% for the agar method. Relative standard deviations of reproducibility ranged from 2.4 to 23.4 % for the dry-film method and 2.3 to 18.8% for the agar method. The dry rehydratable film method has been adopted official first action for determination of the aerobic plate count.

Use of Chemical Sanitizers To Reduce Microbial Populations and Maintain Quality of Whole and Fresh-Cut Cantaloupe†

2009 ◽  
Vol 72 (12) ◽  
pp. 2453-2460 ◽  
Author(s):  
XUETONG FAN ◽  
BASSAM A. ANNOUS ◽  
LINDSEY A. KESKINEN ◽  
JAMES P. MATTHEIS
Keyword(s):  
Bacterial Population ◽  
Soluble Solids ◽  
Plate Count ◽  
Sodium Chlorite ◽  
Log Reduction ◽  
Plate Counts ◽  
Fresh Cut ◽  
Aerobic Plate Count ◽  
Native Microflora

Whole cantaloupes either not inoculated or inoculated with Salmonella Poona were submerged in water, 180 ppm of chlorine, acidified calcium sulfate (ACS: 1.2% Safe2O-ACS50), 1,000 ppm of acidified sodium chlorite (ASC), 80 ppm of peroxyacetic acid (PAA), and a combination of ACS and PAA for 10 min. Although only ASC and the combination of ACS and PAA significantly reduced the aerobic plate count of samples taken from the surface of whole cantaloupe (compared with samples taken from cantaloupe submerged in water only), all treatments reduced yeast and mold counts on the whole cantaloupe. However, none of the treatments of whole cantaloupes consistently reduced yeast and mold counts for the samples of fresh-cut cantaloupes. The aerobic plate counts for fresh-cut cantaloupe were reduced by 1 to 2 log CFU/g by sanitization of whole fruit with ASC, ACS, and the combination of ACS and PAA. The low bacterial population on the fresh-cut fruit was maintained during 14 days of storage at 4°C. All treatments had a limited effect on the population of Salmonella, achieving no more than a 1.5-log reduction of the pathogen inoculated on the surface of the whole cantaloupes. Salmonella was nondetectable via direct plating (with a detection limit of 0.4 log CFU/g) in fresh-cut cantaloupes prepared from whole cantaloupes treated with any of the sanitizers. However, after enrichment, Salmonella often was detectable. Color, texture, soluble solids, pH, ascorbic acid, and drip loss of cut cantaloupes were not consistently affected by any of the whole-fruit treatments. Overall, treatments of whole cantaloupe with ASC, ACS, and the combination of ACS and PAA at the concentrations tested permitted a significant reduction in Salmonella and native microflora of whole and cut fruit; however, Salmonella still could be found in cut cantaloupes from all treatments.

Effect of Stored Pre-Poured Plates on Microbial Enumeration Using the Surface Plate Method1

1980 ◽  
Vol 43 (8) ◽  
pp. 592-594 ◽  
Author(s):  
J. E. KENNEDY ◽  
P. E. PHILLIPS ◽  
J. L. OBLINGER
Keyword(s):  
Correlation Coefficients ◽  
Storage Period ◽  
Regression Coefficients ◽  
Plate Count ◽  
Plate Method ◽  
Plate Count Agar ◽  
Plastic Bags ◽  
Plate Counts ◽  
Microbial Enumeration ◽  
Surface Plate

The surface plate method, using freshly pre-poured agar plates and/or stored pre-poured plates and the pour plate method were compared for enumeration of microorganisms in fresh bologna, fresh ground beef, frozen turkey pot pie and bacterial suspensions of Pseudomonas fluorescens and Streptococcus faecalis. Stored pre-poured Plate Count Agar (PCA) plates were packaged in plastic bags and held at 5 C for up to 6 weeks before use. Aerobic plate counts were derived from plates incubated at 35 C for 48 h, 20 C for 5 days and 7 C for 10 days. Differences in counts between methods for a given sample, incubation and pre-poured plate storage period were less than 0.5 log cycle in 97% of the comparisons. Regression and correlation coefficients between methods were highly significant; correlation coefficients varied from 0.987 to 0.999, and regression coefficients from 0.977 to 1.068 between any pair of methods. Storage of pre-poured plates for up to 6 weeks appeared to have no significant effect on recovery of microorganisms, using the surface plate technique.

Comparison of Brands of Media for Isolating Bacteria from Poultry, Beef and Shrimp

1984 ◽  
Vol 47 (5) ◽  
pp. 394-397 ◽  
Author(s):  
H. S. LILLARD ◽  
N. A. COX ◽  
J. S. BAILEY ◽  
J. E. THOMSON
Keyword(s):  
Escherichia Coli ◽  
Practical Significance ◽  
Plate Count ◽  
E Coli ◽  
Plate Counts ◽  
Aerobic Plate Count ◽  
Raw Shrimp

Five brands of media (BBL, Difco, Gibco, Oxoid and Scott) were evaluated for enumerating microorganisms by the aerobic plate count and by Enterobacteriaceae, Escherichia coli, and coliform counts, and for determining Salmonella incidence. Microbiological evaluations were done on raw chickens, raw beef and raw shrimp, except that Salmonella incidence was not determined on shrimp samples. There were statistically significant differences in total plate counts (with chicken, beef and shrimp), Enterobacteriaceae counts (with shrimp) coliforms (with chicken) and E. coli counts (with chicken) by the five brands of media, but these differences were too small to be of practical significance. It was concluded that no differences of practical significance were found among the five brands of media.

Bacteriological Profile of Raw, Frozen Chicken Nuggets

2008 ◽  
Vol 71 (3) ◽  
pp. 613-615 ◽  
Author(s):  
SOFRONI EGLEZOS ◽  
GARY A. DYKES ◽  
BIXING HUANG ◽  
NARELLE FEGAN ◽  
ED STUTTARD
Keyword(s):  
Plate Count ◽  
Chicken Nuggets ◽  
E Coli ◽  
Bacteriological Profile ◽  
Processing Facility ◽  
Plate Counts ◽  
The Mean ◽  
Aerobic Plate Count ◽  
Number Of Bacteria

The bacteriological profile of raw, frozen chicken nuggets manufactured at a chicken processing facility in Queensland, Australia, was determined. Chicken nuggets are manufactured by grinding poultry, adding premixes to incorporate spices, forming the meat to the desired size and shape, applying a batter and breading, freezing, and packaging. A total of 300 frozen batches were analyzed for aerobic plate count, Escherichia coli, and Salmonella over a period of 4 years. The mean of the aerobic plate count was 5.4 log CFU/g, and counts at the 90th, 95th, and 99th percentiles were 5.7, 5.9, and 6.5 log CFU/g, respectively. The maximum number of bacteria detected was 6.6 log CFU/g. E. coli prevalence was 47%, and of the positive samples, the mean was 1.9 log CFU/g; counts at the 90th, 95th, and 99th percentiles were 2.3, 2.4, and 2.8 log CFU/g, respectively. The maximum number of E. coli was 2.9 log CFU/g. The Salmonella prevalence was 8.7%, and 57.7% of these isolates were typed as Salmonella subspecies II 4,12,[27]:b:[e,n,x] (Sofia), a low-virulence serotype well adapted to Australian poultry flocks. There was a significant relationship (P < 0.05) between season and both aerobic plate counts and E. coli counts, and no correlation between E. coli counts and Salmonella prevalence. This study provides valuable data on the bacteriological quality of raw, frozen chicken nuggets.

Growth Potential of Individual Strains of Listeria monocytogenes in Fresh Vacuum-Packaged Refrigerated Ground Top Rounds of Beef

1995 ◽  
Vol 58 (4) ◽  
pp. 398-403 ◽  
Author(s):  
WERNER B. BARBOSA ◽  
JOHN N. SOFOS ◽  
GLENN R. SCHMIDT ◽  
GARY C. SMITH
Keyword(s):  
Listeria Monocytogenes ◽  
Ground Beef ◽  
Growth Potential ◽  
High Ph ◽  
Ph Values ◽  
Colony Forming Units ◽  
Serotype 1 ◽  
Plate Counts ◽  
Serotype 4B

Separate inocula of four strains of Listeria monocytogenes were prepared at 4°C and inoculated (3.58 to 4.67 log10 colony forming units [CFU]/g) in top round ground beef (< 4.0% fat) patties (78.8 ± 6.7 g) of normal (5.47 ± 0.03) or high (6.14 ± 0.08) pH, which were stored (4°C) vacuum-packaged for 56 days and analyzed for L. monocytogenes, total aerobic plate counts (APC) and pH. In normal-pH ground beef, strain N-7143 (serotype 3a), multiplied from 4.25 ± 0.71 log10 CFU/g at day of inoculation to 6.53 ± 0.34 log10 CFU/g at 35 days of storage (P < 0.05); a 2.3 log10 CFU/g increase. Populations of strain Na-19 (serotype 3b) increased 1.8 log10 CFU/g in 35 days of storage, while numbers of strain Na-16 (serotype 1/2a) did not change (P > 0.05) during the 56 days of storage. Strain Scott A (serotype 4b) decreased in numbers from 4.00 ± 1.21 log10 CFU/g at day-0 to 2.72 ± 0.98 log10 CFU/g at 56 days. Populations of strain Scott A were lower (P < 0.05) than other strains after 21 days of storage. In high-pH ground beef, populations of strains Na-19, N-7143 and Na-16 increased (P < 0.05) by 2.87, 2.64 and 2.24 log10 CFU/g, respectively, in 28 days. Populations of strain Scott A did not change significantly (P > 0.05), and they were lower (P< 0.05) than populations of other strains at 28 days. The results indicated that although growth of L. monocytogenes in vacuum-packaged, refrigerated ground beef was slow, it proceeded more rapidly in product of pH values above 6.0, and depended on strain of the pathogen tested.

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