Spread of Escherichia coli O157:H7 during flume washing and drying of fresh-cut romaine lettuce
ABSTRACTSPREAD OF ESCHERICHIA COLI O157:H7 DURING FLUME WASHING AND DRYING OF FRESH-CUT ROMAINE LETTUCE By Siyi WangThe microbiological safety of leafy greens remains a concern as evidenced from recent outbreaks. This study assessed the spread of E. coli O157:H7 during washing and drying of fresh-cut romaine lettuce. Radicchio was spot-inoculated at 10-1, 101 and 103 CFU/leaf and mixed with uninoculated romaine lettuce to obtain 5 kg batches with inoculated vs uninoculated ratios of 0.5:100, 1:100, 5:100 and 10:100. After 90 s of sanitizer-free flume washing followed by shaker table and centrifugal dryer, the radicchio was removed and the lettuce was divided into 225 g samples to test presence/absence of E. coli O157:H7 using a GeneQuence assay. Based on triplicate trials, lower inoculation levels led to decreased E. coli O157:H7 transfer to romaine lettuce (P < 0.05). All lettuce samples yielded E. coli O157:H7 when radicchio was inoculated at 103 CFU/leaf. At 101 CFU/leaf, the percentage of positive samples decreased from 96.8% to 93.7%, 81.0% and 63.5% while at 10-1 CFU/leaf, 22.2%, 6.3%, 4.8% and 6.3% were positive at 10:100, 5:100, 1:100 and 0.5:100 ratios. Within each inoculation level, there were no significant differences (P>0.05) among four product ratios. These findings are critical to predict the extent of cross-contamination under realistic conditions and will provide important data for improving exposure assessment in risk assessments for leafy greens.
Read
- In Collections
-
Electronic Theses & Dissertations
- Copyright Status
- In Copyright
- Material Type
-
Theses
- Thesis Advisors
-
Ryser, Elliot
- Committee Members
-
Linz, John
Barry, Cornelius
- Date Published
-
2016
- Subjects
-
Escherichia coli O157:H7
Food--Safety measures
Microbial contamination--Prevention
Lettuce
Microbiology
- Program of Study
-
Food Science - Master of Science
- Degree Level
-
Masters
- Language
-
English
- Pages
- xi, 77 pages
- ISBN
-
9781339702346
1339702347
- Permalink
- https://doi.org/doi:10.25335/59b7-n902