Semester

Summer

Date of Graduation

2020

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Jacek Jaczynski

Committee Member

Kristen Matak

Committee Member

Cangliang Shen

Committee Member

Michael Gutensohn

Abstract

Food borne illness has the potential to impact every point of production from producers to consumers. Food product recalls are common due to the presence of food borne illness causing bacteria. Detection of volatile organic compounds (VOC) have the potential to reduce the number of illnesses and recalls through application of additional monitoring of food products like those most commonly recalled. The objective of this research was to 1) explore the use of closed-loop headspace analysis coupled with gas chromatography-mass spectrometry (GC-MS) on food borne illness causing bacteria and 2) examine the VOC profile of Escherichia coli serotype O157:H7 in both tryptic soy broth (TSB) and ground beef. Escherichia coli JM109, Escherichia coli DH5α, and Salmonella enterica serotype Enteritidis ATCC 13076 were chosen to determine potential of bacteria to produce compounds not observed in their controls. A closed-loop headspace analysis was utilized to collect headspace VOCs through the use of glass absorbent filters filled with Alltech HaySep-Q™ PoraPak-Q™ that were then eluted with dichloromethane. Eluted VOC samples were analyzed by GC-MS. Results of analysis were evaluated for peak differences. Both E. coli strains grown in TSB produced typical indole peaks during 2 different lengths (24 hours and 5 hours) of VOC collection in addition to four and five peaks from E. coli JM109 and E. coli DH5α, respectively, that were not observed in their controls. S. Enteritidis grown under optimal conditions in liquid egg produced a profile in which seven compounds were detected in the inoculated liquid egg, but not observed in control after a 6-hour VOC collection. A 2-hour collection series produced inconsistent results suggesting that a collection of 2 hours may require a more sensitive GC-MS analysis or headspace collection. Escherichia coli serotype O157:H7 ATCC 43985 grown in TSB and ground beef were subjected to headspace VOC collection utilizing the closed-loop system for analysis. E. coli O157:H7 VOC analysis displayed 34 peaks of interest with 4 of these peaks not being detected in the control of sterile TSB at retention times of 8.722, 9.402, 20.919, and 30.777. Ground beef inoculated with E. coli O157:H7 displayed 48 peaks of interest with 22 compounds only appearing in the bacteria inoculated ground beef and not the control of uninoculated ground beef. This study has contributed to the foundation of VOC application within food safety and can be used to guide future research utilizing this methodology.

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