Increase in heat resistance of Listeria monocytogenes Scott A by sublethal heat shock

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dc.contributor.authorLinton, Richard Howarden
dc.contributor.committeechairPierson, Merle D.en
dc.contributor.committeememberBishop, J. Russellen
dc.contributor.committeememberBunce, George Edwinen
dc.contributor.departmentFood Science and Technologyen
dc.date.accessioned2014-03-14T21:47:58Zen
dc.date.adate2009-10-22en
dc.date.available2014-03-14T21:47:58Zen
dc.date.issued1991-02-05en
dc.date.rdate2009-10-22en
dc.date.sdate2009-10-22en
dc.description.abstractLog phase cells of Listeria monocytogenes Scott A were heat shocked in Trypticase Soy + 0.6% Yeast Extract broth at 40, 44, and 45°C for 3, 10 and 20 min at each temperature, followed by heating at 55â C for 50 minutes in order to determine an optimum heat shock response. Most heat shock temperatures significantly increased thermal resistance (p < 0.05). Increasing heat shock temperature and time allowed the organism to survive much longer at 50 to 65°C than nonheat shocked cells. The optimal heat shock condition was 45°C for 20 min where D-values at 55°C increased 2.3 fold in non-selective agar and 1.6 fold in selective agar in comparison to non-heat shocked cells. However, cells heat shocked at 48°C for 10 min gave more consistent results; these cells were heated at 50, 55, 60, and 65°C to determine a z-value. Although D-values notably increased due to heat shocking, z-values remained constant regardless of the plating medium. When aerobically heat shocked cells (45°C for 10 min) were plated on a non-selective or a selective medium, a 1.4x increase in D-value was observed when enumerated under strictly anaerobic conditions. Aerobically heat shocked cells (48°C for 10 min) added to shrimp samples retained the increased heat resistance at 55°C when enumerated on a nonselective medium compared to the non-heat shocked cells. Heat shocking conditions may be created in pasteurization or minimal thermal processing of foods allowing increased heat resistance of pathogenic and spoilage microorganisms.en
dc.description.degreeMaster of Scienceen
dc.format.extentix, 106 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-10222009-124928en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-10222009-124928/en
dc.identifier.urihttp://hdl.handle.net/10919/45234en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V855_1991.L568.pdfen
dc.relation.isformatofOCLC# 23830693en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V855 1991.L568en
dc.subject.lcshListeria monocytogenes -- Researchen
dc.titleIncrease in heat resistance of <u>Listeria monocytogenes</u> Scott A by sublethal heat shocken
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineFood Science and Technologyen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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