INACTIVATION OF ESCHERICHIA COLI O157:H7 ON INOCULATED ALFALFA SEEDS WITH OZONATED WATER UNDER PRESSURE

Alfalfa seeds inoculated with a five-strain mixture of Escherichia coli O157:H7 were immersed in water containing 4, 8, 10, and 21 ppm of ozone for 2, 4, 8, 16, 32, and 64 min at 4°C. Direct ozone sparging of seeds in water was used as an alternative mode of ozone treatment. Ozone-sparged seeds were also subsequently exposed to heat treatment at 40, 50, and 60°C for 3 h. Populations of E. coli O157:H7 on untreated and treated seeds were determined by spread plating diluted samples on tryptic soy agar supplemented with 50 μg/ml of nalidixic acid. Since E. coli O157:H7 was released from inoculated seeds during treatment with ozone, the rate of release of cells from inoculated seeds soaked in 0.1% peptone water for up to 64 min was also determined. The overall reduction of E. coli O157:H7 on seeds treated with ozonated water without continuous sparging ranged from 0.40 to 1.75 log10 CFU/g (59.6 to 98.2%), whereas reductions for control seeds were 0.32 to 1.03 log10 CFU/g (51.7 to 90.5%). Treatment with higher ozone concentrations enhanced inactivation, but contact time longer than 8 min did not result in significantly higher reductions (P > 0.05). For seeds treated by ozone sparging, a 1.12-log10 CFU/g (92.1%) reduction was achieved using a 2-min contact time, and a 2.21-log10 CFU/g (99.4%) reduction was achieved with a 64-min contact time. The corresponding reductions for control seeds were 0.71 log10 CFU/g (79.5%) and 2.21 log10 CFU/g (99.4%), respectively. Treatment of ozone-sparged seeds at 60°C for 3 h reduced the population to an undetectable level by direct plating (4 to 4.8 log10 CFU/g), although survivors were detected by enrichment. Ozone did not have a detrimental effect on seed germination percentage.

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Chemical and Irradiation Treatments for Killing Escherichia coli O157:H7 on Alfalfa, Radish, and Mung Bean Seeds

Journal of Food Protection ◽

10.4315/0362-028x-66.5.767 ◽

2003 ◽

Vol 66 (5) ◽

pp. 767-774 ◽

Cited By ~ 63

Author(s):

M. L. BARI ◽

E. NAZUKA ◽

Y. SABINA ◽

S. TODORIKI ◽

K. ISSHIKI

Keyword(s):

Escherichia Coli ◽

Heat Treatment ◽

Mung Bean ◽

Escherichia Coli O157 ◽

E Coli ◽

Chemical Treatments ◽

Dry Heat ◽

Pathogen Populations ◽

Dry Heat Treatment ◽

Alfalfa Seeds

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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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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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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