Impact of vacuum cooling on Escherichia coli O157: H7 infiltration into lettuce tissue

Haiping Li, Mehrdad Tajkarimi, Bennie Osburn

Research output: Contribution to journalArticlepeer-review

64 Scopus citations


Vacuum cooling is a common practice in the California leafy green industry. This study addressed the impact of vacuum cooling on the infiltration of Escherichia coli O157:H7 into lettuce as part of the risk assessment responding to the E. coli O157:H7 outbreaks associated with leafy green produce from California. Vacuum cooling significantly increased the infiltration of E. coli O157:H7 into the lettuce tissue (2.65E+06 CFU/g) compared to the nonvacuumed condition (1.98E+05 CFU/g). A stringent surface sterilization and quadruple washing could not eliminate the internalized bacteria from lettuce. It appeared that vacuuming forcibly changed the structure of lettuce tissue such as the stomata, suggesting a possible mechanism of E. coli O157:H7 internalization. Vacuuming also caused a lower reduction rate of E. coli O157:H7 in stored lettuce leaves than that for the nonvacuumed condition.

Original languageEnglish (US)
Pages (from-to)3138-3142
Number of pages5
JournalApplied and Environmental Microbiology
Issue number10
StatePublished - May 1 2008

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology


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