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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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AN ASSESSMENT OF THE EFFECT OF WEATHER ON THE MOOD AND ENERGY OF PEOPLE WITH WINTER DEPRESSIVE SYMPTOMS: AN EXPERIENCE SAMPLING METHOD
Title
AN ASSESSMENT OF THE EFFECT OF WEATHER ON THE MOOD AND ENERGY OF PEOPLE WITH WINTER DEPRESSIVE SYMPTOMS: AN EXPERIENCE SAMPLING METHOD
Creator
Mosqueda, Andrea I.
Date
2016, 2016-05
Description
Seasonal Affective Disorder (SAD) is a depressive disorder characterized by recurrent episodes most often beginning in the fall and remitting...
Show moreSeasonal Affective Disorder (SAD) is a depressive disorder characterized by recurrent episodes most often beginning in the fall and remitting in spring and summer. Individuals with SAD experience both vegetative symptoms (e.g., fatigue, increased appetite and weight gain, and an increased need for sleep) and psychological symptoms (e.g., sadness, difficulty concentrating, and feelings of worthlessness or hopelessness. In addition to the seasonal variations in vegetative and psychological functioning in SAD, daily weather also can potentially affect these phenomena. Symptoms such as mood, cognition, and energy can vary between and within days as a function of weather variables in a population experiencing seasonal symptoms. Using experience sampling method (ESM), which allows for less reliance on participant memory, we examined the impact of weather on day-to-day variability of mood and fatigue, and specifically in individuals with seasonal symptoms. To our knowledge, this is the first study to use ESM to examine the impact of weather on this symptomatology. Results failed to find evidence of a relationship between variability in daily weather and either daily mood or fatigue in this sample of seasonal individuals. This was the case for both same day weather and weather aggregated over the previous six days. Future studies would benefit from a longer data collection period in order to determine if there are long-term effects of weather variables on mood or fatigue. ESM would be useful in studying the effect of various time-varying variables on a variety of time-related aspects of SAD symptomatology.
M.S. in Psychology, May 2016
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HIGH PRESSURE PROCESSING CONDITIONS FOR INACTIVATION OF HUMAN NOROVIRUS SURROGATE IN OYSTERS
Title
HIGH PRESSURE PROCESSING CONDITIONS FOR INACTIVATION OF HUMAN NOROVIRUS SURROGATE IN OYSTERS
Creator
Agarwal, Sagar
Date
2015, 2015-07
Description
Noroviruses are the leading cause of acute nonbacterial gastroenteritis in humans. Bivalve mollusks bio-accumulate norovirus as they feed....
Show moreNoroviruses are the leading cause of acute nonbacterial gastroenteritis in humans. Bivalve mollusks bio-accumulate norovirus as they feed. High pressure processing (HPP), a non-thermal processing technology, can inactivate microorganisms in foods while preserving flavor, appearance, nutritional value, and extending shelf-life. In the present study, we have systematically investigated the effect of parameters such as temperature, salinity and product composition on the efficacy of HPP for inactivation of human norovirus surrogate. For temperature analysis MNV-1 suspended in aqueous media, oyster homogenate, and bio-accumulated in whole oysters were treated with pressures varying from 200-500 MPa at 4, 10, and 20oC with a hold time of 1 minute. In media, a 4-log10 reduction was observed upon treatment at 300 MPa for 1 minute at 4oC, whereas pressures of 400 and 500 MPa were required for a comparable reduction at initial processing temperatures of 10 and 20oC. Colder temperature promoted higher reduction in virus titer at a given pressure. Addition of 1, 2 and 3% (w/v) sea salt to aqueous media provided significant baroprotective effect at colder temperatures. While pressure of 300 MPa for 1 min at 4oC was sufficient to achieve 3-log10 reduction for MNV-1 suspended in 1% (w/v) sea salt media, the same conditions resulted in only 1.4-log10 reduction for MNV-1 suspended in 3% (w/v) sea salt media. However increasing processing temperature the minimized the baroprotective effects. Similar results were observed for the effect of food matrix on virus survival, with significant baroprotective effect at colder temperatures and a minimal impact of matrix on increasing processing temperature. For initial processing temperature of 4oC a 300 MPa treatment with a hold time of 1 min resulted in a 4-log10 reduction for MNV-1 suspended in aqueous media, 3.35-log10 reduction in oyster homogenate, and <1-log10 reduction in whole oysters. Whereas at higher initial processing temperatures of 10 and 20oC the difference in reduction between matrices was insignificant. A comparison of temperature v/s salinity and temperature v/s composition revealed that effects of temperature far outweighed the impact of product properties (salinity and composition).Whole oysters seeded with MNV-1 treated at 350 MPa for 1 min at 4oC was found to have a 4-log10 reduction, while MNV-1 suspended in aqueous media at 20oC on similar treatment had a 0.5-log10 reduction. Similarly MNV-1 suspended in aqueous media with 3% salt when treated with 400 MPa for 1 min at 4oC resulted in a 5-log10 reduction, whereas MNV-1 suspended in aqueous media at 20oC on similar treatment had a 1.9-log10 reduction. Oyster processors should use refrigerated temperature to achieve higher reduction in virus titer at lower pressures.
M.S. in Food Safety and Technology, July 2015
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Evaluation of Salmonella Proliferation on Alfalfa Sprouts during Storage at Different Temperatures
Title
Evaluation of Salmonella Proliferation on Alfalfa Sprouts during Storage at Different Temperatures
Creator
Lin, Chih Tso
Date
2020
Description
Sprouts, a low-calorie vegetable rich in nutrition, have been a popular ingredient in many meals in the USA. They are grown either at...
Show moreSprouts, a low-calorie vegetable rich in nutrition, have been a popular ingredient in many meals in the USA. They are grown either at commercial sprout farms or at home and served raw or lightly cooked. However, sprouts are also known as a source of foodborne illness outbreaks. FDA Food Code identifies raw sprouts as a time/temperature control for safety food. However, little information is known about the growth profile of foodborne pathogens in sprouts stored at different temperatures. This study aimed at evaluating the proliferation of Salmonella in alfalfa sprouts during storage at 4, 10, and 25℃ under two different contamination routes: 1) sprouts that were inoculated with Salmonella after harvest and 2) sprouts that were grown from contaminated seeds. Alfalfa sprouts grown from uninoculated seeds and harvested after 5 days of sprouting were divided into 25-g portions. Each portion was inoculated with a cocktail of five Salmonella serovars at levels of 10^1, 10^3 or 10^5 CFU/g prior to storage at 4, 10, or 25℃. Alternatively, sprouts grown for five days from seeds spiked with 1% of seeds previously inoculated with the Salmonella cocktail were divided into 25-g portions and stored at 4, 10, or 25℃. At defined time points (Days 0, 2, 4, 7, 14, and 21), levels of Salmonella and background microflora in stored sprouts were determined by plate count. Alfalfa sprouts appeared fresh during the 21 days of storage at 4 or 10℃ but started to show signs of spoilage after 4 days of storage at 25℃. The total plate counts maintained at a level above 9 log CFU/g throughout 21 d of storage at 4 and 10℃ or during the first 7 d of storage at 25℃. Storing sprouts at 4 or 10℃ could inhibit the proliferation of Salmonella. After 21 d of storage, the Salmonella counts in inoculated sprouts decreased slightly, by 0.88 or 0.93 log units, respectively. For sprouts stored at 25℃, the Salmonella growth profile differed depending on the route of contamination and the level of Salmonella at the start of storage. In sprouts inoculated at levels of 1.41, 2.83, and 4.75 log CFU/g, the Salmonella counts increased to 6.62, 6.86, and 6.68 log units, respectively, during the first 4-7 days of storage. For alfalfa sprouts grown from contaminated seeds, the Salmonella counts remained at a level similar to that in the harvested sprouts (8.16 log CFU/g) during the first 7 d. Results from this study further the understanding of pathogen growth in sprouts and will aid in the development of guidelines for proper storage of sprouts.
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Population Dynamics of Listeria monocytogenes in Nut, Seed and Legume Butters
Title
Population Dynamics of Listeria monocytogenes in Nut, Seed and Legume Butters
Creator
Zhang, Xinyuan
Date
2020
Description
Nut, seed, and legume butters are low water activity foods and do not support the growth of foodborne pathogens. Research has determined that...
Show moreNut, seed, and legume butters are low water activity foods and do not support the growth of foodborne pathogens. Research has determined that some pathogens, such as Listeria monocytogenes, can survive for long periods of time in butters, such as almond butter. However, information on the persistence of L. monocytogenes in butters is lacking. The purpose of this study was to determine the population dynamics of L. monocytogenes in butters stored at 5 and 25°C. Nut (almond, hazelnut, pecan), seed (pumpkin, sesame, sunflower), legume (peanut and soy) and butters containing chocolate (hazelnut and peanut) were inoculated with a 4-strain cocktail of rifampicin-resistant L. monocytogenes at 4 (high inoculation) or 1 log CFU/g (low inoculation). High inoculation butters were mixed by hand for 15 min and 100-g portions were weighed into deli-style containers with lids and stored at 5 or 25°C for 12 mo (370 d). Low inoculation butters were stored in 25- g portions in stomacher bags at 25°C for 6 mo (180 d). During storage, 25 g from the 100- g high inoculation portion or 25 g from the low inoculation samples, in triplicate, were homogenized with 225 mL BPB (or BLEB for FDA BAM enrichments when necessary) and serial dilutions of the homogenate were plated onto BHIA with rifampicin for enumeration of L. monocytogenes. Data were statistically analyzed using Student’s t-test (α=0.05). The average initial population of L. monocytogenes in the butters was 3.58±0.25 log CFU/g for the high inoculation butters; L. monocytogenes was detected through enrichments for all low inoculation butters. After 12 mo storage at 5°C, the population of L. monocytogenes decreased by 1.34, 1.27, 1.72, 2.04 and 0.93 log CFU/g in almond, hazelnut, peanut with chocolate, hazelnut with chocolate and pecan butter, respectively, when inoculated at the higher level. Significantly less population reduction was observed in pumpkin, sesame, soy, peanut and sunflower butters (1.08, 0.61, 0.84, 0.05 and 0.40 log CFU/g, respectively). After 12 mo storage at 25°C, the L. monocytogenes population in all butters, with the exception of sunflower butter, decreased to below the limit of enumeration (1.67 log CFU/g), but the pathogen was still present via enrichment. For low inoculation butters, L. monocytogenes was present as determined by enrichment in all butters in at least one of two trials after 6 mo. The results of this study provide information on the survival of L. monocytogenes in different butter types when stored at different temperatures.
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