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PULSED LIGHT INACTIVATION OF MURINE NOROVIRUS ON VARIOUS FOOD CONTACT SURFACES
Title
PULSED LIGHT INACTIVATION OF MURINE NOROVIRUS ON VARIOUS FOOD CONTACT SURFACES
Creator
Zhou, Zijin
Date
2015, 2015-07
Description
Norovirus is one of the leading causes for foodborne illness. Transmission of virus from surface to food has been known to cause a number of...
Show moreNorovirus is one of the leading causes for foodborne illness. Transmission of virus from surface to food has been known to cause a number of outbreaks. Studies of norovirus have been conducted using Murine Norovirus to simulate the behaviors. Pulsed light (PL) is a promising surface decontamination technology, which has the potential to be applied in a food service setting. PL uses intense pulses of short duration and a broad spectrum to accomplish microbial inactivation. This study evaluates the effect of PL on MNV-1, artificially inoculated onto various food contact surfaces including 304 stainless steel, glazed tile, polypropylene, and ultra-high molecular weight (UHMW) polyethylene. The virus was allowed to inoculate on the coupons for 20mins and treated with PL in a Xenon Steripulse XL-3000TM pulsed light treatment system for up to 60 s, at a distance of 8.3 cm 10.8 cm or 13.3cm from the central axis of the lamp. An infrared (IR) camera was used to record surface temperatures, in 1-s increments. After PL treatments, remaining viruses were recovered from surfaces and quantified by plaque assay. At a distance of 10.8cm, MNV-1 was reduced by 2.22-, 2.27- 2.75- and 3.12-log, after 20s treatment on inoculated stainless steel, glazed tile, UHMW polyethylene and polypropylene, respectively. After 50s treatment, MNV-1 was reduced by 4.86- and 5.93- log on glazed tile and stainless steel surface respectively. The surface temperature on tile and stainless steel increased at the rate of 1.08±0.20 and 1.28±0.32°C /s respectively. A relatively short treatment using pulsed light is sufficient to inactivate MNV-1 on the surface of materials commonly used in food preparation. The results suggest that the technology has the potential to reduce surface viral contamination in a food preparation setting.
M.S. in Food Safety and Technology, July 2015
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DEVELOPING METHODS TO IDENTIFY SURROGATES FOR ESCHERICHIA COLI O157:H7 IN VALIDATION OF FRESH PRODUCE WASHING PROCESSES
Title
DEVELOPING METHODS TO IDENTIFY SURROGATES FOR ESCHERICHIA COLI O157:H7 IN VALIDATION OF FRESH PRODUCE WASHING PROCESSES
Creator
Rolfe, Catherine
Date
2016, 2016-07
Description
Cross-contamination during fresh produce washing is commonly prevented using chlorine treatment. Surrogate microorganisms have been widely...
Show moreCross-contamination during fresh produce washing is commonly prevented using chlorine treatment. Surrogate microorganisms have been widely used in process validation and to assess microbial cross-contamination. Fresh produce washing incorporates physical, chemical, biological and kinetic factors which create an intricate process for which little is known regarding surrogate selection. The purpose of this study was to identify the important elements relevant to produce washing processes and identify methods that will be used in surrogate selection. The behavior of three (3) non-pathogenic microorganisms (generic E. coli Nissle 1917 EcN, Pediococcus pentosaceus and lettuce isolate 813-F1) were examined in comparison to E. coli O157:H7 based on phenotypic similarities. Chlorine inactivation kinetics of E. coli O157:H7 and the non-pathogenic strains were evaluated with varying pH levels (6.5 and 8.0) and exposure times (3-30 seconds). Detachment of leaf-bound E. coli O157:H7 and non-pathogenic strains at different inoculation levels (approximately 2 and 6 log CFU/mL) and drying conditions (aging time, temperature) in wash water was examined. Chlorine inactivation at pH 6.5 resulted in a range of viability corresponding to E. coli O157:H7 and the non-pathogenic strains; demonstrating a sharp inactivation curve for E. coli O157:H7, EcN and P. pentosaceus. Whereas, inactivation at pH 8.0 allowed more survival relating to exposure time for all microorganisms. Detachment from inoculated leaves at 2 and 6 log CFU/mL inoculation showed steady survival levels in wash water at 0 ppm and lower survival at 1 ppm for all strains excluding 813-F1; 813-F1 was consistently less chlorine-sensitive in chlorine inactivation assays and more cross-contamination to wash water was observed for this strain. Aging time of inoculated bacteria on leaves was not seen to have remarkable effects on bacterial transfer during washing. These results suggest assay methods of chlorine inactivation at pH 6.5 and detachment with 6 log CFU/mL initial inoculation may be useful in selecting appropriate surrogates for fresh produce washing.
M.S. in Food Safety and Technology, July 2016
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