{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/22078"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/22078","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Post Harvest Transmission of Salmonella enterica to the Roots and Leaves of Butterhead Lettuce Packaged With Intact Roots","abstract":"In the United States, illnesses associated with fresh produce are increasing in frequency. While contamination risks are present at every aspect of the farm to fork continuum, post-harvest practices holds the potential for cross-contamination of large amounts of product. Post-harvest contamination risks for hydroponically grown lettuce packaged with intact roots and sold as \"living lettuce\"\" are poorly understood. In this study, transmission of Salmonella enterica serotype Enteritidis to the roots and leaves of butterhead lettuce was studied when contamination was introduced during typical handling practices. The effectiveness of random sampling strategies for selection of Salmonella contaminated leaves was assessed by co-inoculating the Salmonella solution with Glo Germ™ and comparing recovery from blacklight selected leaves. The recovery of Salmonella was improved by only 0.5 log CFU/g when blacklight was used to select Glo Germ™ contaminated leaves (P=0.05). This suggests random leaf selection as described by current FDA protocols is adequate. In addition, this study showed rapid transfer of Salmonella from liquid to the roots and sub-sequentially to the leaves of living lettuce. Salmonella persisted but did not grow on leaves when stored at 4˚C for 18-days. Storage at 12˚C was associated with 2 log CFU/g increases in Salmonella on roots after 18-days storage (P=0.0002), while 4˚C storage was associated with a decrease of 0.4 log CFU/g Salmonella on roots (P=0.0001). Growth occurred only under temperature abuse conditions. This reinforces the need for maintaining temperature control and highlights the importance of identifying risks associated with post-harvest handling during hydroponic production and distribution.","abstract_html":"In the United States, illnesses associated with fresh produce are increasing in frequency. While contamination risks are present at every aspect of the farm to fork continuum, post-harvest practices holds the potential for cross-contamination of large amounts of product. Post-harvest contamination risks for hydroponically grown lettuce packaged with intact roots and sold as "living lettuce"" are poorly understood. In this study, transmission of Salmonella enterica serotype Enteritidis to the roots and leaves of butterhead lettuce was studied when contamination was introduced during typical handling practices. The effectiveness of random sampling strategies for selection of Salmonella contaminated leaves was assessed by co-inoculating the Salmonella solution with Glo Germ™ and comparing recovery from blacklight selected leaves. The recovery of Salmonella was improved by only 0.5 log CFU/g when blacklight was used to select Glo Germ™ contaminated leaves (P=0.05). This suggests random leaf selection as described by current FDA protocols is adequate. In addition, this study showed rapid transfer of Salmonella from liquid to the roots and sub-sequentially to the leaves of living lettuce. Salmonella persisted but did not grow on leaves when stored at 4˚C for 18-days. Storage at 12˚C was associated with 2 log CFU/g increases in Salmonella on roots after 18-days storage (P=0.0002), while 4˚C storage was associated with a decrease of 0.4 log CFU/g Salmonella on roots (P=0.0001). Growth occurred only under temperature abuse conditions. This reinforces the need for maintaining temperature control and highlights the importance of identifying risks associated with post-harvest handling during hydroponic production and distribution.","abstract_has_math":false,"creators":["Waitt, Jessie Anne"],"institution":"Virginia Tech","degree_name":"Master of Science in Life Sciences","degree_level":"masters","degree_discipline":"Food Science and Technology","degree_department":"Food Science and Technology","school":null,"contributors":[],"advisors":[],"committee_chairs":["Ponder, Monica A."],"committee_members":["Welbaum, Gregory E.","Kuhn, David D."],"year":2013,"date_issued":"2013-05-21","date_published":"2013-05-21","updated_at":"2026-07-22T22:19:13Z","subjects":["Living lettuce","Salmonella enterica","hydroponic production"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:859"],"render_values":[{"text":"vt_gsexam:859","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/22078","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Ponder, Monica A."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Welbaum, Gregory E.","Kuhn, David D."]},{"key":"dc:contributor.department","label":"Department","values":["Food Science and Technology"]},{"key":"dc:creator","label":"Author","values":["Waitt, Jessie Anne"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2013-05-22T08:00:10Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2013-05-22T08:00:10Z"]},{"key":"dc:date.issued","label":"Date","values":["2013-05-21"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Food Science and Technology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science in Life Sciences"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Living lettuce","Salmonella enterica","hydroponic production"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:859"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/22078"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["In the United States, illnesses associated with fresh produce are increasing in frequency. While contamination risks are present at every aspect of the farm to fork continuum, post-harvest practices holds the potential for cross-contamination of large amounts of product. Post-harvest contamination risks for hydroponically grown lettuce packaged with intact roots and sold as \"living lettuce\"\" are poorly understood. In this study, transmission of Salmonella enterica serotype Enteritidis to the roots and leaves of butterhead lettuce was studied when contamination was introduced during typical handling practices. The effectiveness of random sampling strategies for selection of Salmonella contaminated leaves was assessed by co-inoculating the Salmonella solution with Glo Germ™ and comparing recovery from blacklight selected leaves. The recovery of Salmonella was improved by only 0.5 log CFU/g when blacklight was used to select Glo Germ™ contaminated leaves (P=0.05). This suggests random leaf selection as described by current FDA protocols is adequate. In addition, this study showed rapid transfer of Salmonella from liquid to the roots and sub-sequentially to the leaves of living lettuce. Salmonella persisted but did not grow on leaves when stored at 4˚C for 18-days. Storage at 12˚C was associated with 2 log CFU/g increases in Salmonella on roots after 18-days storage (P=0.0002), while 4˚C storage was associated with a decrease of 0.4 log CFU/g Salmonella on roots (P=0.0001). Growth occurred only under temperature abuse conditions. This reinforces the need for maintaining temperature control and highlights the importance of identifying risks associated with post-harvest handling during hydroponic production and distribution."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science in Life Sciences"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["ETD"]},{"key":"dc:title","label":"Title","values":["Post Harvest Transmission of Salmonella enterica to the Roots and Leaves of Butterhead Lettuce Packaged With Intact Roots"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Ponder, Monica A."],"dc:contributor.committeemember":["Welbaum, Gregory E.","Kuhn, David D."],"dc:contributor.department":["Food Science and Technology"],"dc:creator":["Waitt, Jessie Anne"],"dc:date.accessioned":["2013-05-22T08:00:10Z"],"dc:date.available":["2013-05-22T08:00:10Z"],"dc:date.issued":["2013-05-21"],"dc:description.abstract":["In the United States, illnesses associated with fresh produce are increasing in frequency. While contamination risks are present at every aspect of the farm to fork continuum, post-harvest practices holds the potential for cross-contamination of large amounts of product. Post-harvest contamination risks for hydroponically grown lettuce packaged with intact roots and sold as \"living lettuce\"\" are poorly understood. In this study, transmission of Salmonella enterica serotype Enteritidis to the roots and leaves of butterhead lettuce was studied when contamination was introduced during typical handling practices. The effectiveness of random sampling strategies for selection of Salmonella contaminated leaves was assessed by co-inoculating the Salmonella solution with Glo Germ™ and comparing recovery from blacklight selected leaves. The recovery of Salmonella was improved by only 0.5 log CFU/g when blacklight was used to select Glo Germ™ contaminated leaves (P=0.05). This suggests random leaf selection as described by current FDA protocols is adequate. In addition, this study showed rapid transfer of Salmonella from liquid to the roots and sub-sequentially to the leaves of living lettuce. Salmonella persisted but did not grow on leaves when stored at 4˚C for 18-days. Storage at 12˚C was associated with 2 log CFU/g increases in Salmonella on roots after 18-days storage (P=0.0002), while 4˚C storage was associated with a decrease of 0.4 log CFU/g Salmonella on roots (P=0.0001). Growth occurred only under temperature abuse conditions. This reinforces the need for maintaining temperature control and highlights the importance of identifying risks associated with post-harvest handling during hydroponic production and distribution."],"dc:description.degree":["Master of Science in Life Sciences"],"dc:format.medium":["ETD"],"dc:identifier.other":["vt_gsexam:859"],"dc:identifier.uri":["http://hdl.handle.net/10919/22078"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["Living lettuce","Salmonella enterica","hydroponic production"],"dc:title":["Post Harvest Transmission of Salmonella enterica to the Roots and Leaves of Butterhead Lettuce Packaged With Intact Roots"],"dc:type":["Thesis"],"thesis:degree_discipline":["Food Science and Technology"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science in Life Sciences"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:13Z"}