Inactivation of Escherichia coli O157:H7 in Orange Juice Using a Combination of High Pressure and Mild Heat

1999 ◽  
Vol 62 (3) ◽  
pp. 277-279 ◽  
Author(s):  
M. LINTON ◽  
J. M. J. McCLEMENTS ◽  
M. F. PATTERSON
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Resistant Strain ◽  
Orange Juice ◽  
Escherichia Coli O157 ◽  
Pressure Treatment ◽  
Processing Conditions ◽  
E Coli ◽  
Mild Heat ◽  
Ph Range

The effect of high pressure on the survival of a pressure-resistant strain of Escherichia coli O157:H7 (NCTC 12079) in orange juice was investigated over the pH range 3.4 to 5.0. The pH of commercial, sterile orange juice was adjusted to 3.4, 3.6, 3.9, 4.5, or 5.0. The juice was then inoculated with 108 CFU ml−1 of E. coli O157:H7. The inoculated orange juice was subjected to pressure treatments of 400, 500, or 550 MPa at 20°C or 30°C to determine the conditions that would give a 6-log10 inactivation of E. coli O157:H7. A pressure treatment of 550 MPa for 5 min at 20°C produced this level of kill at pH 3.4, 3.6, 3.9, and 4.5 but not at pH 5.0. Combining pressure treatment with mild heat (30°C) did result in a 6-log10 inactivation at pH 5.0. Thus, the processing conditions (temperature and time) must be considered when pressure-treating orange juice to ensure microbiological safety.

Survival of Escherichia coli O157:H7 during Storage in Pressure-Treated Orange Juice

1999 ◽  
Vol 62 (9) ◽  
pp. 1038-1040 ◽  
Author(s):  
M. LINTON ◽  
J. M. J. McCLEMENTS ◽  
M. F. PATTERSON
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Orange Juice ◽  
Ambient Pressure ◽  
Storage Period ◽  
High Pressure Processing ◽  
Escherichia Coli O157 ◽  
Pressure Treatment ◽  
E Coli ◽  
Time Required

The effect of a high-pressure treatment on the survival of a pressure-resistant strain of Escherichia coli O157:H7 (NCTC 12079) in orange juice during storage at 3°C was investigated over the pH range of 3.4 to 5.0. The pH of shelf-stable orange juice was adjusted to 3.4, 3.6, 3.9, 4.5, and 5.0 and inoculated with 108 CFU ml−1 of E. coli O157:H7. The orange juice was then pressure treated at 400 MPa for 1 min at 10°C or was held at ambient pressure (as a control). Surviving E. coli O157: H7 cells were enumerated at 1-day intervals during a storage period of 25 days at 3°C. Survival of E. coli O157:H7 during storage was dependent on the pH of the orange juice. The application of high pressure prior to storage significantly increased the susceptibility of E. coli O157:H7 to high acidity. For example, after pressure treatment, the time required for a 5-log decrease in cell numbers was reduced from 13 to 3 days at pH 3.4, from 16 to 6 days at pH 3.6, and from >25 to 8 days at pH 3.9. It is evident that the use of high-pressure processing of orange juice in order to increase the juice's shelf-life and to inactivate pathogens has the added advantage that it sensitizes E. coli O157:H7 to the high acid conditions found in orange juice, which results in the survival of significantly fewer E. coli O157:H7 during subsequent refrigerated storage.

High-Pressure Resistance Variation of Escherichia coli O157:H7 Strains and Salmonella Serovars in Tryptic Soy Broth, Distilled Water, and Fruit Juice

2007 ◽  
Vol 70 (9) ◽  
pp. 2078-2083 ◽  
Author(s):  
BROOKE M. WHITNEY ◽  
ROBERT C. WILLIAMS ◽  
JOSEPH EIFERT ◽  
JOSEPH MARCY
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Orange Juice ◽  
High Pressure Processing ◽  
Distilled Water ◽  
Escherichia Coli O157 ◽  
Bacterial Populations ◽  
E Coli ◽  
Log Reduction ◽  
Salmonella Serovars

The effect of high pressure on the log reduction of six strains of Escherichia coli O157:H7 and five serovars of Salmonella enterica was investigated in tryptic soy broth, sterile distilled water, and commercially sterile orange juice (for Salmonella) and apple cider (for E. coli). Samples were subjected to high-pressure processing treatment at 300 and 550 MPa for 2 min at 6°C. Samples were plated onto tryptic soy agar directly after pressurization and after being held for 24 h at 4°C. At 300 MPa, little effect was seen on E. coli O157:H7 strains, while Salmonella serovars varied in resistance, showing reductions between 0.26 and 3.95 log CFU/ml. At 550 MPa, E. coli O157:H7 strains exhibited a range of reductions (0.28 to 4.39 log CFU/ml), while most Salmonella populations decreased beyond the detection limit (>5-log CFU/ml reduction). The most resistant strains tested were E. coli E009 and Salmonella Agona. Generally, bacterial populations in fruit juices showed larger decreases than did populations in tryptic soy broth and distilled water. E. coli O157:H7 cultures held for 24 h at 4°C after treatment at 550 MPa showed a significant log decrease as compared with cultures directly after treatment (P ≤ 0.05), while Salmonella serovars did not show this significant decrease (P > 0.05). All Salmonella serovars tested in orange juice treated at 550 MPa for 2 min at 6°C and held for 24 h showed a >5-log decrease, while E. coli O157:H7 strains require a higher pressure, higher temperature, longer pressurization, or a chemical additive to achieve a 5-log decrease.

Effect of Low-Temperature, High-Pressure Treatment on the Survival of Escherichia coli O157:H7 and Salmonella in Unpasteurized Fruit Juices

2001 ◽  
Vol 64 (8) ◽  
pp. 1122-1127 ◽  
Author(s):  
ALEX YEOW-LIM TEO ◽  
SADHANA RAVISHANKAR ◽  
CHARLES E. SIZER
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Low Temperature ◽  
Apple Juice ◽  
Fruit Juices ◽  
Escherichia Coli O157 ◽  
Pressure Treatment ◽  
Salmonella Spp ◽  
High Pressure Treatment ◽  
E Coli

The destructive effect of high pressure (615 MPa) combined with low temperature (15°C) on various strains of Escherichia coli O157:H7 and various serovars of Salmonella in grapefruit, orange, apple, and carrot juices was investigated. The three-strain cocktail of E. coli O157:H7 (SEA13B88, ATCC 43895, and 932) was found to be most sensitive in grapefruit juice (8.34-log reduction) and least in apple juice (0.41-log reductions) when pressurized at 615 MPa for 2 min at 15°C. Correspondingly, no injured survivor was detected in grapefruit and carrot juices under similar treatment conditions. No Salmonella spp. were detected in a 2-min pressure treatment (615 MPa, 15°C) of grapefruit and orange fruit juices. Except for Enteritidis, all four serovars tested in the present study have viability loss of between 3.92- and 5.07-log reductions when pressurized in apple juice at 615 MPa for 2 min at 15°C. No injured cells were recovered from grapefruit and orange juices, whereas the same treatment demonstrated reduction in numbers of Salmonella serovars Agona and Muenchen in apple juices and to a lesser extent with Typhimurium, Agona, and Muenchen in carrot juice. The present study demonstrated that low-temperature, high-pressure treatment has the potential to inactivate E. coli O157:H7 strains and different Salmonella spp. in different fruit juices.

High-Pressure Transient Sensitization of Escherichia coli to Lysozyme and Nisin by Disruption of Outer-Membrane Permeability

1996 ◽  
Vol 59 (4) ◽  
pp. 350-355 ◽  
Author(s):  
KRISTEL J. A. HAUBEN ◽  
ELKE Y. WUYTACK ◽  
CARINE C. F. SOONTJENS ◽  
CHRIS W. MICHIELS
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Outer Membrane ◽  
High Pressures ◽  
Ethylenediaminetetraacetic Acid ◽  
Viable Count ◽  
Water Soluble ◽  
Pressure Treatment ◽  
E Coli ◽  
Glucose Agar

Escherichia coli MG1655 suspensions in 10 mM phosphate buffer (pH 7.0) were subjected to high pressures in the range of 180 to 320 MPa for 15 min. Cell death was evident at 220 MPa and increased exponentially with pressure. Surviving populations were sublethally injured, as demonstrated by their reduced ability to form colonies on violet red bile glucose agar, a selective growth medium containing crystal violet and bile salts. During exposure to high pressure (> 180 MPa), cells were sensitive to lysozyme, nisin, and ethylenediaminetetraacetic acid (EDTA), as was apparent from an increased lethality of pressure in the presence of these agents. Sublethal injury in the surviving population was lower in the presence of nisin and lysozyme, but higher in the presence of EDTA. Combinations of EDTA with nisin or lysozyme present during pressure treatment increased lethality in an additive manner. However, the addition of lysozyme, nisin and/or EDTA to pressurized cell suspensions immediately after pressure treatment did not cause any viable count reduction. Finally, we observed leakage of the periplasmic enzyme β-lactamase from an ampicillin-resistant recombinant E. coli MG1655 under high pressure. These results suggest that high pressure transiently disrupts the permeability of the E. coli outer membrane for water-soluble proteins.

Inactivation of Escherichia coli O157:H7 in Ground Beef by Single-Cycle and Multiple-Cycle High-Pressure Treatments

2008 ◽  
Vol 71 (4) ◽  
pp. 811-815 ◽  
Author(s):  
PILAR MORALES ◽  
JAVIER CALZADA ◽  
MARTA ÁVILA ◽  
MANUEL NUÑEZ
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Shear Force ◽  
Ground Beef ◽  
Escherichia Coli O157 ◽  
Single Cycle ◽  
E Coli ◽  
Beef Patties ◽  
Texture Parameters ◽  
Multiple Cycle

The effect of single- and multiple-cycle high-pressure treatments on the survival of Escherichia coli CECT 4972, a strain belonging to the O157:H7 serotype, in ground beef was investigated. Beef patties were inoculated with 107 CFU/g E. coli O157:H7, and held at 4°C for 20 h before high-pressure treatments. Reduction of the E. coli O157:H7 population by single-cycle treatments at 400 MPa and 12°C ranged from 0.82 log CFU/g for a 1-min cycle to 4.39 log CFU/g for a 20-min cycle. Multiple-cycle treatments were very effective, with four 1-min cycles at 400 MPa and 12°C reducing the E. coli O157:H7 population by 4.38 log CFU/g, and three 5-min cycles by 4.96 log CFU/g. The color parameter L* increased significantly with high-pressure treatments in the interior and the exterior of beef patties, whereas a* decreased in the interior, and b* increased in the exterior—changes that might diminish consumer acceptance of the product. Kramer shear force and energy were generally higher in pressurized than in control ground beef. Maximum values for these texture parameters, which corresponded to tougher patties, were reached after one 10-min cycle in the case of single-cycle treatments or two 5-min cycles in the case of multiple-cycle treatments. High-pressure treatments had no significant effect on Warner-Bratzler shear force.

Survival of Escherichia coli O157:H7 and Salmonella in Apple Cider and Orange Juice as Affected by Ozone and Treatment Temperature

2004 ◽  
Vol 67 (11) ◽  
pp. 2381-2386 ◽  
Author(s):  
ROBERT C. WILLIAMS ◽  
SUSAN S. SUMNER ◽  
DAVID A. GOLDEN
Keyword(s):  
Escherichia Coli ◽  
Ambient Temperature ◽  
Orange Juice ◽  
Treatment Temperature ◽  
Ozone Treatment ◽  
Escherichia Coli O157 ◽  
Apple Cider ◽  
E Coli ◽  
Peptone Water ◽  
Thermal Pasteurization

Inactivation of Escherichia coli O157:H7 and Salmonella in apple cider and orange juice treated with ozone was evaluated. A five-strain mixture of E. coli O157:H7 or a five-serovar mixture of Salmonella was inoculated (7 log CFU/ml) into apple cider and orange juice. Ozone (0.9 g/h) was pumped into juices maintained at 4°C, ambient temperature (approximately 20°C), and 50°C for up to 240 min, depending on organism, juice, and treatment temperature. Samples were withdrawn, diluted in 0.1% peptone water, and surface plated onto recovery media. Recovery of E. coli O157:H7 was compared on tryptic soy agar (TSA), sorbitol MacConkey agar, hemorrhagic coli agar, and modified eosin methylene blue agar; recovery of Salmonella was compared on TSA, bismuth sulfite agar, and xylose lysine tergitol 4 (XLT4) agar. After treatment at 50°C, E. coli O157:H7 populations were undetectable (limit of 1.0 log CFU/ml; a minimum 6.0-log CFU/ml reduction) after 45 min in apple cider and 75 min in orange juice. At 50°C, Salmonella was reduced by 4.8 log CFU/ml (apple cider) and was undetectable in orange juice after 15 min. E. coli O157:H7 at 4°C was reduced by 4.8 log CFU/ml in apple cider and by 5.4 log CFU/ml in orange juice. Salmonella was reduced by 4.5 log CFU/ml (apple cider) and 4.2 log CFU/ml (orange juice) at 4°C. Treatment at ambient temperature resulted in population reductions of less than 5.0 log CFU/ml. Recovery of E. coli O157:H7 and Salmonella on selective media was substantially lower than recovery on TSA, indicating development of sublethal injury. Ozone treatment of apple cider and orange juice at 4°C or in combination with mild heating (50°C) may provide an alternative to thermal pasteurization for reduction of E. coli O157:H7 and Salmonella in apple cider and orange juice.

scholarly journals Inactivation of Escherichia coli andListeria innocua in Milk by Combined Treatment with High Hydrostatic Pressure and the Lactoperoxidase System

2000 ◽  
Vol 66 (10) ◽  
pp. 4173-4179 ◽  
Author(s):  
Cristina García-Graells ◽  
Caroline Valckx ◽  
Chris W. Michiels
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
Combined Treatment ◽  
Food Preservation ◽  
Pressure Treatment ◽  
E Coli ◽  
Preservation Method ◽  
Lactoperoxidase System

ABSTRACT We have studied inactivation of four strains each ofEscherichia coli and Listeria innocua in milk by the combined use of high hydrostatic pressure and the lactoperoxidase-thiocyanate-hydrogen peroxide system as a potential mild food preservation method. The lactoperoxidase system alone exerted a bacteriostatic effect on both species for at least 24 h at room temperature, but none of the strains was inactivated. Upon high-pressure treatment in the presence of the lactoperoxidase system, different results were obtained for E. coli and L. innocua. For none of the E. coli strains did the lactoperoxidase system increase the inactivation compared to a treatment with high pressure alone. However, a strong synergistic interaction of both treatments was observed for L. innocua. Inactivation exceeding 7 decades was achieved for all strains with a mild treatment (400 MPa, 15 min, 20°C), which in the absence of the lactoperoxidase system caused only 2 to 5 decades of inactivation depending on the strain. Milk as a substrate was found to have a considerable effect protecting E. coli and L. innocua against pressure inactivation and reducing the effectiveness of the lactoperoxidase system under pressure on L. innocua. Time course experiments showed that L. innocua counts continued to decrease in the first hours after pressure treatment in the presence of the lactoperoxidase system.E. coli counts remained constant for at least 24 h, except after treatment at the highest pressure level (600 MPa, 15 min, 20°C), in which case, in the presence of the lactoperoxidase system, a transient decrease was observed, indicating sublethal injury rather than true inactivation.

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