Factors affecting the efficacy of pressure inactivation of Escherichia coli O157:H7 on alfalfa seeds and seed viability

In this study, the effectiveness of dry-heat treatment in combination with chemical treatments (electrolyzed oxidizing [EO] water, califresh-S, 200 ppm of active chlorinated water) with and without sonication in eliminating Escherichia coli O157:H7 on laboratory-inoculated alfalfa, radish, and mung bean seeds was compared with that of dry-heat treatment in combination with irradiation treatment. The treatment of mung bean seeds with EO water in combination with sonication followed by a rinse with sterile distilled water resulted in reductions of approximately 4.0 log10 CFU of E. coli O157:H7 per g, whereas reductions of ca. 1.52 and 2.64 log10 CFU/g were obtained for radish and alfalfa seeds. The maximum reduction (3.70 log10 CFU/g) for mung bean seeds was achieved by treatment with califresh-S and chlorinated water (200 ppm) in combination with sonication and a rinse. The combination of dry heat, hot EO water treatment, and sonication was able to eliminate pathogen populations on mung bean seeds but was unable to eliminate the pathogen on radish and alfalfa seeds. Other chemical treatments used were effective in greatly reducing pathogen populations on radish and alfalfa seeds without compromising the quality of the sprouts, but these treatments did not result in the elimination of pathogens from radish and alfalfa seeds. Moreover, a combination of dry-heat and irradiation treatments was effective in eliminating E. coli O157:H7 on laboratory-inoculated alfalfa, radish, and mung bean seeds. An irradiation dose of 2.0 kGy in combination with dry heat eliminated E. coli O157:H7 completely from alfalfa and mung bean seeds, whereas a 2.5-kGy dose of irradiation was required to eliminate the pathogen completely from radish seeds. Dry heat in combination with irradiation doses of up to 2.0 kGy did not unacceptably decrease the germination percentage for alfalfa seeds or the length of alfalfa sprouts but did decrease the lengths of radish and mung bean sprouts.

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Efficacy of Chemical Treatments in Eliminating Salmonella and Escherichia coli O157:H7 on Scarified and Polished Alfalfa Seeds

Journal of Food Protection ◽

10.4315/0362-028x-64.10.1489 ◽

2001 ◽

Vol 64 (10) ◽

pp. 1489-1495 ◽

Cited By ~ 48

Author(s):

SARAH L. HOLLIDAY ◽

ALAN J. SCOUTEN ◽

LARRY R. BEUCHAT

Keyword(s):

Escherichia Coli ◽

Chemical Treatment ◽

Organic Material ◽

Pathogenic Bacteria ◽

Escherichia Coli O157 ◽

E Coli ◽

Mechanical Abrasion ◽

Chemical Treatments ◽

The Impact ◽

Alfalfa Seeds

Alfalfa seeds are sometimes subjected to a scarification treatment to enhance water uptake, which results in more rapid and uniform germination during sprout production. It has been hypothesized that this mechanical abrasion treatment diminishes the efficacy of chemical treatments used to kill or remove pathogenic bacteria from seeds. A study was done to compare the effectiveness of chlorine (20,000 ppm), H2O2 (8%), Ca(OH)2 (1%), Ca(OH)2 (1%) plus Tween 80 (1%), and Ca(OH)2 (1%) plus Span 20 (1%) treatments in killing Salmonella and Escherichia coli O157:H7 inoculated onto control, scarified, and polished alfalfa seeds obtained from two suppliers. The influence of the presence of organic material in the inoculum carrier on the efficacy of sanitizers was investigated. Overall, treatment with 1% Ca(OH)2 was the most effective in reducing populations of the pathogens. Reduction in populations of pathogens on seeds obtained from supplier 1 indicate that chemical treatments are less efficacious in eliminating the pathogens on scarified seeds compared to control seeds. However, the effectiveness of chemical treatment in removing Salmonella and E. coli O157:H7 from seeds obtained from supplier 2 was not markedly affected by scarification or polishing. The presence of organic material in the inoculum carrier did not have a marked influence on the efficacy of chemicals in reducing populations of test pathogens. Additional lots of control, scarified, and polished alfalfa seeds of additional varieties need to be tested before conclusions can be drawn concerning the impact of mechanical abrasion on the efficacy of chemical treatment in removing or killing Salmonella and E. coli O157:H7.

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Elimination of Escherichia coli O157:H7 from Alfalfa Seeds through a Combination of High Hydrostatic Pressure and Mild Heat

Applied and Environmental Microbiology ◽

10.1128/aem.02531-08 ◽

2009 ◽

Vol 75 (7) ◽

pp. 1901-1907 ◽

Cited By ~ 27

Author(s):

Hudaa Neetoo ◽

Thompson Pizzolato ◽

Haiqiang Chen

Keyword(s):

Escherichia Coli ◽

Pathogenic Bacteria ◽

Elevated Temperatures ◽

Treatment Time ◽

Seed Viability ◽

Treatment Temperature ◽

Reduced Pressure ◽

Unique Challenge ◽

Produce Safety ◽

Alfalfa Seeds

ABSTRACT Escherichia coli O157:H7 has been associated with contaminated seed sprout outbreaks. The majority of these outbreaks have been traced to sprout seeds contaminated with low levels of pathogens. Sanitizing sprout seeds presents a unique challenge in the arena of produce safety in that even a low residual pathogen population remaining on contaminated seed after treatments appears capable of growing to very high levels during sprouting. In this study, the effectiveness of high-pressure treatment in combination with low and elevated temperatures was assessed for its ability to eliminate E. coli O157:H7 on artificially contaminated alfalfa seeds. Inoculated seed samples were treated at 600 MPa for 2 min at 4, 20, 25, 30, 35, 40, 45, and 50°C. The pressure sensitivity of the pathogenic bacteria was strongly dependent on the treatment temperature. At 40°C, the process was adequate in eliminating a 5-log-unit population on the seeds with no adverse effect on seed viability. Three treatments carried out at reduced pressure levels and/or extended treatment time, 550 MPa for 2 min at 40°C, 300 MPa for 2 min at 50°C, and 400 MPa for 5 min at 45°C, were equally lethal to the pathogen. When all three treatments were compared in terms of their impact on seed viability, the process of 550 MPa for 2 min at 40°C was the most desirable, achieving final germination percentages and sprout sizes statistically similar to those of control untreated seeds (P > 0.05).

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Inactivation of Escherichia coli O157:H7 and Salmonella spp. on alfalfa seeds by caprylic acid and monocaprylin

International Journal of Food Microbiology ◽

10.1016/j.ijfoodmicro.2010.09.011 ◽

2010 ◽

Vol 144 (1) ◽

pp. 141-146 ◽

Cited By ~ 30

Author(s):

Su-sen Chang ◽

Mauricio Redondo-Solano ◽

Harshavardhan Thippareddi

Keyword(s):

Escherichia Coli ◽

Caprylic Acid ◽

Escherichia Coli O157 ◽

Salmonella Spp ◽

Alfalfa Seeds

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Factors Impacting the Regrowth of Escherichia coli O157:H7 in Dairy Manure Compost

Journal of Food Protection ◽

10.4315/0362-028x-72.7.1576 ◽

2009 ◽

Vol 72 (7) ◽

pp. 1576-1584 ◽

Cited By ~ 23

Author(s):

JINKYUNG KIM ◽

FENG LUO ◽

XIUPING JIANG

Keyword(s):

Escherichia Coli ◽

Moisture Content ◽

Room Temperature ◽

Dairy Manure ◽

Population Increase ◽

Escherichia Coli O157 ◽

Inoculum Level ◽

Factors Affecting ◽

E Coli ◽

Manure Compost

The environmental variables affecting Escherichia coli O157:H7 regrowth in dairy manure compost were investigated. Factors evaluated were moisture content, strain variation, growth medium of inoculum, level of background microflora and inoculum, different days of composting, and acclimation at room temperature. A mathematical model was applied to describe E. coli O157 regrowth potential in compost. Repopulation occurred in autoclaved compost with a moisture content as low as 20% (water activity of 0.986) in the presence of background microflora of 2.3 to 3.9 log CFU/g. The population of all three E. coli O157 strains increased from ca. 1 to 4.85 log CFU/g in autoclaved compost, with the highest increase in the spinach-outbreak strain. However, E. coli O157 regrowth was suppressed by background microflora at ca. 6.5 log CFU/g. By eliminating acclimation at room temperature and increasing the inoculum level to ca. 3 log CFU/g, E. coli O157:H7 could regrow in the presence of high levels of background microflora. E. coli O157:H7 regrowth in the autoclaved compost collected from the field study was evident at all sampling days, with the population increase ranging from 3.49 to 6.54 log CFU/g. The fate of E. coli O157:H7 in compost was well described by a Whiting and Cygnarowicz-Provost model, with R2 greater than 0.9. The level of background microflora was a significant factor for both growth and death parameters. Our results reveal that a small number of E. coli O157 cells can regrow in compost, and both background microflora and moisture content were major factors affecting E. coli O157:H7 growth.

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Inactivation of Escherichia coli O157:H7, Salmonella Typhimurium DT104, and Listeria monocytogenes on Inoculated Alfalfa Seeds with a Fatty Acid–Based Sanitizer

Journal of Food Protection ◽

10.4315/0362-028x-69.3.582 ◽

2006 ◽

Vol 69 (3) ◽

pp. 582-590 ◽

Cited By ~ 15

Author(s):

PASCALE M. PIERRE ◽

ELLIOT T. RYSER

Keyword(s):

Escherichia Coli ◽

Lactic Acid ◽

Fatty Acid ◽

Listeria Monocytogenes ◽

Salmonella Typhimurium ◽

Escherichia Coli O157 ◽

E Coli ◽

Reference Concentration ◽

Glycerol Monolaurate ◽

Alfalfa Seeds

Alfalfa seeds were inoculated with a three-strain cocktail of Escherichia coli O157:H7, Salmonella enterica subsp. enterica serovar Typhimurium DT104, or Listeria monocytogenes by immersion to contain ∼6 to 8 log CFU/g and then treated with a fatty acid–based sanitizer containing 250 ppm of peroxyacid, 1,000 ppm of caprylic and capric acids (Emery 658), 1,000 ppm of lactic acid, and 500 ppm of glycerol monolaurate at a reference concentration of 1×. Inoculated seeds were immersed at sanitizer concentrations of 5×, 10×, and 15× for 1, 3, 5, and 10 min and then assessed for pathogen survivors by direct plating. The lowest concentration that decreased all three pathogens by >5 log was 15×. After a 3-min exposure to the 15× concentration, populations of E. coli O157:H7, Salmonella Typhimurium DT104, and L. monocytogenes decreased by >5.45, >5.62, and >6.92 log, respectively, with no sublethal injury and no significant loss in seed germination rate or final sprout yield. The components of this 15× concentration (treatment A) were assessed independently and in various combinations to optimize antimicrobial activity. With inoculated seeds, treatment C (15,000 ppm of Emery 658, 15,000 ppm of lactic acid, and 7,500 ppm of glycerol monolaurate) decreased Salmonella Typhimurium, E. coli O157:H7, and L. monocytogenes by 6.23 and 5.57 log, 4.77 and 6.29 log, and 3.86 and 4.21 log after 3 and 5 min of exposure, respectively. Treatment D (15,000 ppm of Emery 658 and 15,000 ppm of lactic acid) reduced Salmonella Typhimurium by >6.90 log regardless of exposure time and E. coli O157:H7 and L. monocytogenes by 4.60 and >5.18 log and 3.55 and 3.14 log after 3 and 5 min, respectively. No significant differences (P > 0.05) were found between treatments A, C, and D. Overall, treatment D, which contained Emery 658 and lactic acid as active ingredients, reduced E. coli O157:H7, Salmonella Typhimurium, and L. monocytogenes populations by 3.55 to >6.90 log and may provide a viable alternative to the recommended 20,000 ppm of chlorine for sanitizing alfalfa seeds.

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