Date of Award


Degree Name

MS in Agriculture - Food Science and Nutrition


Food Science and Nutrition


College of Agriculture, Food, and Environmental Sciences


Amanda Lathrop

Advisor Department

Food Science and Nutrition

Advisor College

College of Agriculture, Food, and Environmental Sciences


The FSMA Produce Safety Rule (PSR) requires citrus packers to more closely assess, manage, and monitor food safety risks. Although there have been no foodborne illness outbreaks and only one recall in fresh citrus, the risk of pathogens coming in on the fruit and cross contamination during washing still exists. Packhouses have dynamic washing systems and in-plant validations may be the only way to demonstrate compliance with the PSR. In-plant validations use surrogates in place of pathogens, and none have been identified or validated for citrus. The aim of this research was to identify a surrogate for use in fresh citrus packhouses.

Potential surrogates were screened for free chlorine resistance, survival under commercial storage conditions, and shedding and attachment characteristics during simulated washing. E. faecium NRRL B-2354 and P. pentosaceus NRRL B-14009 were selected for further study. Resistance to chlorine was not significantly different between E. faecium and L. monocytogenes FSL J1-031 when exposed to 3 ppm free chlorine for 30, 60, 90, and 120 s at 20 and 100 ppm TSB (pE. faecium and P. pentosaceus behavior was significantly different than L. monocytogenes (p=0.05), indicating that neither is a suitable surrogate. In shedding and attachment, either the fruit (shedding) or water (attachment) was inoculated, washing was simulated, and organisms were enumerated from the water (shedding) or fruit (attachment). Both potential surrogates were statistically different than L. monocytogenes (pE. faecium can be used for L. monocytogenes shedding estimates and E. faecium and P. pentosaceus can be used for attachment estimates. Overall, this research suggests that E. faecium NRRL B-2354 can be considered as a surrogate for L. monocytogenes in whole, fresh citrus validation studies on chlorinated washes and – with appropriate adjustments – on shedding and attachment characteristics.