Inactivation of Escherichia coli O157:H7 on inoculated alfalfa seeds with ozonated water under pressure

Ratna R. Sharma, Ali Demirci, Larry R. Beuchat, William F. Fett

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Alfalfa seeds inoculated with Escherichia coli O157:H7 (∼105 CFU/g) were subjected to low hydrostatic pressure. Seeds immersed in ozonated water at 4C were held at 8 and 12-psi ozone pressure for 2, 4, 8, 16, 32, and 64 min. Alternatively, seeds were continuously sparged with ozone for up to 64 min and then held at 12 psi for 5 min. Controls consisted of sparging and pressurization with air. Thirty-two minute treatments of continuous ozone sparging followed by pressurization of seeds at 12 psi for 5 min were repeated with the addition of four surfactants (Tween 20, Tween 80, SPAN 20, and SPAN 80) in the treatment water. Enumeration of E. coli O157:H7 on treated, untreated, and control seeds was done on tryptic soy agar supplemented with 50 μg/mL of nalidixic acid. The reduction in population of E. coli O157:H7 on seeds treated with the 8 and 12 psi hydrostatic pressure in ozonated water ranged from 0.74 - 1.56 log10 CFU/g and 0.72 - 1.62 log10 CFU/g, respectively. Control treatments carried out with air pressurization of seeds resulted in maximum population reductions of 1.55 log10 and 1.83 log10 CFU/g for 8 and 12 psi, respectively. For seeds treated with continuous ozone sparging (2 - 64 min) followed by pressurization at 12 psi for 5 min, the highest reduction was 2.03 log10 CFU/g. Reductions were, however, not significantly different (P > 0.05) from control treatment (with air) which reduced the populations by 0.57 - 2.19 log10 CFU/g. The presence of surfactants during continuous sparging of water followed by pressurization at 12 psi was not beneficial. None of the treatments adversely affected the germination of the seeds.

Original languageEnglish (US)
Pages (from-to)107-119
Number of pages13
JournalJournal of Food Safety
Issue number2
StatePublished - 2002

All Science Journal Classification (ASJC) codes

  • Parasitology
  • Food Science
  • Microbiology


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