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Title: CHARACTERIZATION OF WILD BLUEBERRY POLYPHENOLS BIOAVAILABILITY AND KINETIC PROFILE OVER 24-HOUR PERIOD IN HUMAN SUBJECTS
Creator: Zhong, Siqiong
Date: 2016, 2016-12
Description: Diets abundant in phenolic compounds have been linked to decreased risk of cardiovascular disease, obesity and diabetes. Wild blueberries (WBB...
Show moreDiets abundant in phenolic compounds have been linked to decreased risk of cardiovascular disease, obesity and diabetes. Wild blueberries (WBB) are one of the richest sources of dietary phenolic compounds, particularly anthocyanin compounds. They also contain hydroxycinnamic acids, namely chlorogenic acids (CGA). Understanding their metabolic fate may provide insight to their health benefits and protection against chronic disease development. The purpose of this study was to (1) identify WBB anthocyanin and CGA metabolites in human plasma (2) assess bioavailability and biotransformation of WBB anthocyanin and CGA in human (3) measure the acute e↵ects of WBB consumption on glucose homeostasis and lipid metabolism. This was a pilot study with healthy male and female volunteers (n=12). Plasma samples were collected at baseline (t=0h), 0.25h, 0.5h, 1h, 2h, 4h, 6h, 8h, 10h and 24h after consuming a WBB drink (25 g freeze dried WBB powder) with a standard polyphenol free breakfast. The anthocyanins in the WBB drink and their metabolites in human plasma were identified using HPLC-ESI-Q-TOF and quantified by dynamic MRM transitions on HPLC-ESI-QQQ. A total of 30 anthocyanins were identified in the WBB drink. These included glycosides of cyanidin, delphinidin, malvidin, petunidin and peonidin, which were detected in positive mode. Glucose was the most abundant glycoside attachment followed by galactose, arabinose, acetylated glucose, acetylated galactose and xylose. CGAs were also found in the WBB drink in negative mode and confirmed with standards. All the anthocyanins in the WBB drink were found in plasma as well as 3-CGA. The bioavailability for delphinidin, cyandin, malvidin, peonidin, and petunidin were each less than 1% and total bioavailability of WBB anthocyanins was 1.09%. The bioavailability for 3-CGA was 0.22% after consuming 25g WBB powder. The Tmax (time of maximum concentration was achieved) of anthocyanins and 3-CGA was ⇠2h post ingestion. Tmax of phase II metabolites, including petunidin- glucuronide, peonidin-glucuronide, delphinidin-glucuronide and cyanidin-glucuronide was 8.8, 2.6, 6.3 and 7h, respectively. Phenolic acids metabolites, including vanillic acids, ferulic acids, 2,3-dihydroxybenzoic acid, phloroglucinaldehyde, syringic acid were also detected in human plasma during the 24 h period. These results suggest that anthocyanins and CGAs from a WBB drink can be partly absorbed in their intact form in humans and partly transformed to conjugated and degraded metabolites. The data also indicate that there are early phase and late phase appearing metabolites in the blood of humans, which could have important health promoting implications. Future studies will need to be conducted to determine how these pools of metabolites impact physiology and the most sensitive systems to their e↵ect. In the present study, no significant di↵erences on glucose homeostasis and lipid metabolism were apparent. This study provides a foundation for further understanding on health benefits of dietary anthocyanins and their metabolites.
M.S. in Food Safety and Technology, December 2016
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Title: SURVIVAL AND ATTACHMENT OF SALMONELLA ENTERICA ON ALMOND, HAZELNUT, AND BLACK PEPPER
Creator: Zhai, Yang
Date: 2016, 2016-05
Description: S. Enteritidis (SE) and S. Typhimurium (ST) are the two most common Salmonella enterica serovars that cause foodborne illnesses in U.S....
Show moreS. Enteritidis (SE) and S. Typhimurium (ST) are the two most common Salmonella enterica serovars that cause foodborne illnesses in U.S. Outbreaks of these serovars have been attributed to low moisture foods such as nuts and spices. However, little is known about the mechanisms of attachment on low moisture food surfaces. This study evaluated the associations between attachment and survival of Salmonella enterica serovars, storage temperatures, and surface characteristics of selected food samples. In the study, S. Enteritidis PT4 and S. Typhimurium LT2 were inoculated onto the surfaces of black peppercorns, almonds and hazelnuts at ~108 CFU/g. After 2 h air-drying, samples were stored at 4 and 25°C with 58 ± 2% relative humidity for up to 14 d. At specific time points, the food sample were washed two times in 1 × Phosphate Buffered Saline (PBS) to remove attached bacterial cells. The bacterial suspensions were serially diluted and plated on Brain Heart Infusion (BHI) and Xylose Lysine Deoxycholate (XLD) agar plates for enumeration. Significant differences (P<0.05) were found in the survival and attachment of SE and ST under all the conditions. ST can survive and attach better than SE at both 4 and 25°C. The decline rates on almonds, hazelnuts, and black peppercorns at 25°C were 0.348 ± 0.017, 0.273 ± 0.015, and 0.196 ± 0.017 log CFU/g per day for SE and 0.077 ± 0.008, 0.157 ± 0.008, and 0.048 ± 0.005 log CFU/g per day for ST, respectively. The attachment rates on almonds, hazelnuts and black peppercorns at 25°C were 18.71 ± 14.38, 1.56 ± 1.50, and 4.68 ± 0.76% for SE and 38.46 ± 11.32, 18.45 ± 7.73, and 56.30 ± 14.72% for ST, respectively. In addition, low temperature (i.e. 4°C) may contribute more to the survival of Salmonella than ambient temperature (i.e. 25°C). Certain surface characteristics (roughness & hydrophobicity) of hazelnut may probably result in weaker attachment of both Salmonella serovars. The results can be used to better understand the physiology of Salmonella enterica on low moisture foods and aid in developing effective control measures to reduce pathogen contamination.
M.S. in Food Safety and Technology, May 2016
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Title: IN-PACKAGE DECONTAMINATION OF SALMONELLA MONTEVIDEO ON BLACK PEPPER USING PULSED LIGHT TECHNOLOGY
Creator: Xu, Xinran
Date: 2016, 2016-07
Description: This study evaluated the efficacy of three pulsed light systems (1.8, 3 and 100 Hz) for inactivation of Salmonella Montevideo on the surface...
Show moreThis study evaluated the efficacy of three pulsed light systems (1.8, 3 and 100 Hz) for inactivation of Salmonella Montevideo on the surface of black pepper. The impact of frequency, treatment time and distance from the lamp on the rate of inactivation was studied. A reduction of 4.21 1og10 CFU/g was achieved with a 35 s treatment at 16.6-cm from lamp at 1.8 Hz. Similarly, reductions of 4.72 CFU/g and 4.70 CFU/g were obtained at 14.1-cm after 35 s treatment at 3 Hz and 100 Hz, respectively. Temperature measurement of packed and unpacked black pepper indicated that packaging material absorbed a small amount of energy. Measurement of surface and internal temperature suggested that temperature below the surface increased far less than surface temperature. For instance, temperature on the surface of the black pepper can go up to 200 °C as measured by the infrared camera within 30 to 40 s treatment. However, the temperature at 1 mm below the surface was up to 100 °C depending upon the distance from the lamp. The color of the black pepper did not change after pulsed light treatment (p>0.05). These results suggest that pulsed light can potentially be used to inactivate pathogens on black pepper surface without adversely affecting its quality.
M.S. in Food Safety and Technology, July 2016
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Title: USE OF AQUEOUS DISPERSIONS OF SDS MICELLES TO REMOVE BACTERIAL CONTAMINATION FROM FRESH PRODUCE AND FOOD CONTACT SURFACES
Creator: Han, Yibin
Date: 2013-04-30, 2013-05
Description: The current trend of increased consumption of fresh produce has coincided with an increase in foodborne illness resulting from fresh produce...
Show moreThe current trend of increased consumption of fresh produce has coincided with an increase in foodborne illness resulting from fresh produce consumption, which in turn has increased the amount of research directed at understanding the interactions between microbial pathogens and fresh produce. This dissertation examines the removal and inactivation of Escherichia coli O157:H7 and E. coli K12 from Romaine lettuce leaves and a model hydrophobic surface (polyvinyl chloride, PVC) using a nanofluid (a fluid containing nanometer-sized particles - in this case, sodium dodecyl sulfate, SDS) and its combinations with organic acids. A novel mechanism previously proposed by Wasan and Nikolov (D. T. Wasan & Nikolov, 2003) was used as the basis to explore the removal of bacteria from these surfaces by the aqueous dispersion of SDS micelles, and to explain how SDS plus levulinic acid at pH<3 improves inactivation of these bacteria. Examination of the bactericidal effect of levulinic acid, SDS, and their combination on E. coli O157:H7 attached to Romaine lettuce leaves revealed that using levulinic acid or SDS alone cannot effectively wash the bacterial cells from the surface or cause inactivation. However, combining them increased the effectiveness of the solution. The most effective combination of SDS plus acid for bacteria removal and inactivation among those we tested was found to be 0.06 mol/L SDS + 0.25 mol/L levulinic acid. This combination, which has a pH of 2.9, inactivated more than 5.2-log E. coli O157:H7 on a leaf surface, and similar results were achieved for E. coli K12 on a leaf surface, and for both E. coli O157:H7 and E. coli K12 on the surface of PVC. Surface and interface measurements, including x surface tension and contact angle, of washing solutions indicated that solutions containing SDS had a lower work of adhesion than those without the surfactant, which shows that a significant role of SDS in the inactivation mechanism is a weakening of the forces of attraction between the bacteria and the surface being cleaned. Our experiments also confirm that SDS likely plays a secondary role which depends on the solution pH. When the presence of an organic acid lowers the pH of the washing solution to below 2.6, the surface charge of E. coli O157:H7 changes from negative to positive (the pH is lower than the bacteria’s isoelectric point). In this case, we hypothesize that negatively-charged SDS molecules attach to the cells’ surfaces and inactivate the bacteria. This work provides additional insight into the complex nature of bacterial detachment from solid surfaces. Our work with aqueous dispersions of SDS micelles indicates how and why bacterial inactivation is increased through a combination treatment of SDS and an organic acid.
M.S. in Food Safety and Technology, May 2013
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Title: SURVIVAL AND ATTACHMENT OF SALMONELLA ENTERICA ON SELECT LOW MOISTURE NUT SURFACES
Creator: Zhang, Bo
Date: 2017, 2017-07
Description: Salmonella can contaminate various nuts and lead to human foodborne disease outbreaks and related product recalls in the United States. Nuts...
Show moreSalmonella can contaminate various nuts and lead to human foodborne disease outbreaks and related product recalls in the United States. Nuts have been identified as an increasingly common vector for human salmonellosis. The objective of this study was to evaluate the influence of environmental factors and Salmonella enterica serotypes on the survival and attachment of this pathogen on the surface of low moisture, raw in shell nuts. Two S. enterica strains (Enteritidis and Typhimurium) were individually tested on three different food samples (almonds, hazelnuts and black peppers) at 4°C or 25°C for up to 14 days. The storage relative humidity was maintained at 20±2% throughout the study. Nut samples were collected at 0, 1, 3, 7 and 14 days. The population of bacteria was calculated based on the plate count data. The results showed that S. Typhimurium attached and survived better than S. Enteritidis on almonds, hazelnuts and black peppers at both 4 and 25°C. A lower storage temperature led to a better survival of Salmonella on raw nuts during storage. The surface characteristics of hazelnuts resulted in the least Salmonella attachment compared to almond and black pepper.
M.S. in Food Safety and Technology, July 2017
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Title: GROWTH AND SURVIVAL OF SALMONELLA IN PARTIALLY SPROUTED PUMPKIN, SUNFLOWER, AND CHIA SEEDS SUBSEQUENTLY DRIED FOR DIRECT CONSUMPTION
Creator: Wang, Can
Date: 2017, 2017-05
Description: Products based on dried, partially sprouted seeds have been associated with foodborne salmonellosis. Typically, sprouted seeds have been a...
Show moreProducts based on dried, partially sprouted seeds have been associated with foodborne salmonellosis. Typically, sprouted seeds have been a major concern with respect to foodborne illness, but little is known about the risks associated with dried partial sprouted seed products. Previous studies suggest that low-temperature, highhumidity storage conditions may provide an alternative means to inactivate Salmonella for those processors opposed to traditional thermal processing. The objective of this study was to determine the growth of Salmonella during germination of pumpkin, sunflower, and chia seeds, and the survival of Salmonella during drying and storage under variable temperature and relative humidity (RH) conditions. Pumpkin, sunflower, and chia seeds were dry inoculated at 5 log CFU/g with 4 serotype mixture of Salmonella using a dry transfer method, and then soaked in sterile water at 25 and 37°C for 24 h. Salmonella and total aerobic mesophilic plate counts (APC) were determined on xylose lysine deoxycholate (XLD) and tryptic soy agar supplemented with 0.6% yeast extract (TSAYE), respectively. Seeds using this procedure were drained and dried at 25, 51 and 60°C. The water activity (aw) and microbial population of seeds were monitored during drying. Seeds soaked and dried at 25oC were utilized for subsequently storage studies. Portions of dried chia seeds were ground into powder, then pumpkin, sunflower and chia seeds and chia seeds powder were stored at either 37 or 45oC at three different RH levels. The aw and microbial population of seed samples were monitored during storage. During the seed soaking, Salmonella and APC increased approximately 3 log CFU/g. Some decreases were observed at the end of the growth period, as may be expected after stationary phase. Drying at 60oC to a aw of 0.1 resulted in over 6-log CFU/g loss in bacterial population in partially sprouted pumpkin and sunflower seeds, and 5-log CFU/g loss in partially sprouted chia seeds. However, seeds dried at 25oC bring the aw to 0.5 had only approximately a 1-log CFU/g loss in bacterial population. The highest temperature (45oC) and RH (76%) storage condition had the greatest inactivation effect. At 45oC and 76%RH, Salmonella in pumpkin and sunflower seeds were below detection limit after 4 d and 7 d respectively. Salmonella populations in chia seeds and chia seeds powder were still detectable after 7 d regardless of the treatment condition. Salmonella is capable of survival during the manufacture of partially sprouted seeds including both drying and storage steps. Mild thermal treatment coupled with high RH storage condition holds promise for Salmonella inactivation in pumpkin and sunflower seeds but is less effective for chia seeds and chia seeds powder. Dried, partially sprouted seeds that are used as ingredients or consumed directly without further processing are a high-risk food product. Such products must be treated to eliminate foodborne pathogens that may cause foodborne illness.
M.S. in Food Science, May 2017
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Title: EFFECT OF HIGH PRESSURE PROCESSING ON MIGRATION CHARACTERISTICS IN POLYPROPYLENE FILM
Creator: Zhao, Kun
Date: 2013-04-15, 2013-05
Description: High pressure processing (HPP) is readily gaining prominence worldwide as an alternative method of food preservation due to its benefits of...
Show moreHigh pressure processing (HPP) is readily gaining prominence worldwide as an alternative method of food preservation due to its benefits of improved quality, freshness and nutrient retention. The use of polymer-based flexible packaging materials has allowed application of HPP to prepackaged food products, without significant loss of physical and mechanical properties. However, there is limited data existing on migration properties in the materials before and/or after HPP. Therefore, it’s necessary to evaluate potential migration issues in pre-packed foods during HPP (Song and Koontz, 2012). This research was conducted to determine the migration properties in cast polypropylene (CPP) films during and after HPP (71°C and 700MPa) and a comparable thermal processing (TP, 71°C and 0.1MPa), using headspace (HS) gas chromatography (GC) coupled with mass spectrometer (MS) technique to quantify selected surrogate compounds (chloroform (CF), toluene (TOL), methyl salicylate (MS) and phenyl cyclohexane (PC)) in FDA-suggested food simulants (Miglyol and 10% Ethanol), and using dynamic mechanical analyser (DMA) to test glass transition temperature (Tg) of films. In general, HPP significantly decreased the migration of selected surrogates from CPP film into Miglyol or 10% Ethanol when compared to TP. For Miglyol, after 5min-HPP migration recoveries of CF, TOL, MS and PC were 53, 61, 24, and 16% respectively, while all compounds reached 100% after 5min-TP. For 10% Ethanol, recoveries of four compounds were 22.6, 12.6, 11.2, and 8.4% after HPP treatment, but were 51.0, 25.5, 21.2, and 9.2% with TP treatment. During storage at room temperature after processing, migration recoveries increased for both HPP/TP treated and non- xii processed samples; however, concentration of surrogated in HPP treated films were near or lower than those from non-processed and/or TP treated films. This research will help the U.S Food and Drug Administration (FDA) and the food industry to determine whether any safety issues related to chemical migration should be addressed concerning the use of HPP in production of prepackaged foods. The results may be used in the food contact notification and petition review processes of approving new packaging materials and components for use in HPP applications (Song and Koontz, 2011).
M.S. in Food Safety and Technology, May 2013
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Title: IMPACT OF THERMAL AND HIGH PRESSURE PROCESSING ON THE ANTIGENICITY AND DETECTABILITY OF EGG AND MILK ALLERGENS
Creator: Yang, Shuopeng
Date: 2013, 2013-12
Description: Cow’s milk allergy and egg allergy are the two most prevalent food allergies in the United States. Enzyme-linked immunosorbent assay (ELISA),...
Show moreCow’s milk allergy and egg allergy are the two most prevalent food allergies in the United States. Enzyme-linked immunosorbent assay (ELISA), based on antigen-antibody reactions, is the most popular method used by the food industry to detect allergen residues. Thermal treatments are the traditional food processing methods, while high pressure processing (HPP) has increasingly been applied as an alternative food processing technology. This research examined how thermal and high pressure processing may affect the antigenicity and detectability of milk and egg allergens. The first part of this study examined the performance of four ELISA test kits (Veratox for Total Milk Allergen, Biokits BLG Assay Kit, ELISA Systems Casein and BLG Residue Assays) for quantitation of milk residues in packaged foods that have been subjected to different degrees of processing. Whether standard reference materials (SRM) can be used to compare the relative performance of these test kits was also examined. Commercial food products including ice creams, cookies, fried fish sticks, and canned soups were chosen to represent foods that have been pasteurized, baked, fried, and autoclaved, respectively. Calcium caseinate, NIST non-fat dry milk (NFDM) SRM #1549 and USDA certified whey protein were used as reference standards. Veratox and ELISA Systems Casein kits, both of which use NFDM as the calibrator, showed similar readings for ice cream. However, the Casein kit tended to register a lower level of milk residues in other thermal processed products, especially for canned soup where the test kit showed a 50-fold lower level of milk residue than that reported by the Veratox kit. Using whey protein as a reference standard, the two BLG test kits showed a similar level of whey protein equivalent in ice cream, but for fish stick, cookie, and canned soup samples, the x ELISA Systems BLG kit registered values about 4-, 39-, and 17-fold lower than the values obtained by the Biokits BLG test kit, suggesting that the ELISA Systems kit has a greatly reduced sensitivity for foods that have received heat treatments. When using NIST NFDM as the reference standard, the Veratox and Biokits registered the same level of NFDM equivalent in ice cream, but the Biokits gave a higher level for the fish, cookies, and soup samples, indicating that this kit has a better sensitivity for heat processed food. Overall, different test kits registered different levels of milk even for the same commercial sample. The use of common reference materials provides a means for comparison, but the quantitation of milk residues is still complicated by the different heat sensitivity of each test kit. The second part of this study evaluated the impact of thermal processing on the solubility and antigenicity of egg allergens. Solutions (5 mg/ml sample in PBS) of Henningsen dehydrated whole egg, ovalbumin (OVA), and ovomucoid (OVO) were subjected to three different thermal processing conditions (heated in water at 60℃, 100℃, and autoclaved) for 10 minutes. The solubility of the unheated and heat-treated samples was determined by the BCA total protein assay. Changes in the antigenicity (IC50 value) of egg proteins after thermal treatments were determined by inhibition ELISA. Differences in the antigenicity determined as affected by the use of different target protein, coating antigen, and primary antibody were determined. At 60℃, the solubility and antigenicity of heat treated samples showed similar results as those of untreated sample. For sample treated under other conditions, different heat treatments affect the solubility of egg protein samples differently. Different heat processes, different antigen-antibody combinations, and different extraction methods could affect the IC50 values xi differently, which means the antigenicity changed differently due to different influence factors (e.g. IC50 values of OVO always increased after boiling or autoclaving treatment no matter which coating antigen and primary antibody chose, however OVA and whole egg powder showed uncertain changes). The last part of this study evaluated the impact of high pressure processing on the solubility, antigenicity, and the detectability of egg allergens. Solutions of dehydrated whole egg, OVA, OVO, and Egg Beater (ConAgra Foods) were subjected to high pressure treatments for 3 min under 4 conditions (400MPa 20℃, 400MPa 60℃, 600MPa 20℃, and 600MPa 60℃). The amount of protein in the high pressure treated samples was determined by BCA assay and the Veratox egg allergen test kits. Changes in protein antigenicity were determined by inhibition ELISA assay. The results showed that high pressure treatments under all 4 conditions did not affect the solubility and antigenicity of the egg proteins in the treated samples. HPP did not affect the detectability of these proteins by Veratox test either.
M.S. in Food Safety and Technology, December 2013
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Title: MAXIMIZING THE ANTI-INFLAMMATORY EFFECTS OF STRAWBERRY ANTHOCYANINS: UNDERSTANDING THE INFLUENCE OF CONSUMPTION TIMING VARIABLE
Creator: Huang, Yancui
Date: 2015, 2015-05
Description: Chronic low-grade inflammation is an emerging risk factor for chronic disease development and complication. Strawberries, rich in anthocyanins...
Show moreChronic low-grade inflammation is an emerging risk factor for chronic disease development and complication. Strawberries, rich in anthocyanins, attenuate meal-induced postprandial increases in inflammation and oxidative stress as well as improved post-meal insulin responses. Anthocyanins are considered to be responsible in part, for their health benefits. The bioavailability of anthocyanins is low and short-lived. The relationship between strawberry intake timing of consumption relative to a meal and the metabolic-, inflammatory- and oxidative stress responses that ensue are not known. Therefore, this study aimed to determine if the strawberry consumption timing would influence meal-induced oxidative-immuno-metabolic outcomes. Fourteen overweight (BMI 26 ± 2 kg/m2) healthy adults (aged 25 ± 4 years) participated in a 3-arm, placebo-controlled, crossover clinical trial. Subjects came to the research clinical on 3 different occasions for 10 hours (h) and received 3 study drinks: 2 hours before a meal, with the meal, and 2 hours after the meal. A strawberry drink was given at 1 of the 3 time points and control drinks at the alternative time points. Plasma analytes of glucose, insulin and triglycerides were measured over the 10 h along with oxidized low density lipoprotein, a marker of oxidative damage, and interleukin-6, a marker of inflammation. Results were compared between strawberry “timing” groups and with a demographically matched reference group (n=10, BMI 27 ± 2 kg/m2and aged 27 ± 4 years) that was provided only control drinks (no strawberry). Study result showed a significant reduction in postprandial blood glucose when strawberry was consumed before the meal compared to having the strawberry drink with or after the meal, p < 0.05. Compared to the reference group, eating strawberries, regardless of the consumption time, attenuated postprandial blood glucose without additional insulin, suggesting improved sensitivity. Interleukin-6was significantly lower after consuming the strawberry drink before the meal (p=0.048) and modestly lower after consuming the strawberry drink with (p=0.116) or after the meal (p=0.098) compared to the reference group. This study provides data suggesting that strawberries have a role in glycemic control and attenuating the pro-inflammatory effect of a modern diet. There may be particular advantages when consumed before a meal.
M.S. in Food Safety and Technology, May 2015
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Title: THE RECIPROCAL INTERACTIONS BETWEEN RED RASPBERRY POLYPHENOLS AND GUT MICROBIOME COMPOSITION: PRELIMINARY FINDINGS
Creator: Zhang, Xuhuiqun
Date: 2017, 2017-07
Description: Red raspberry (Rubus idaeus L.) contains a variety of polyphenols including anthocyanins and ellagitannins. Red raspberry polyphenols absorbed...
Show moreRed raspberry (Rubus idaeus L.) contains a variety of polyphenols including anthocyanins and ellagitannins. Red raspberry polyphenols absorbed in different forms (parent compounds, degradant or microbial metabolite molecules) are subject to xenobiotic metabolism in the intestine, liver, and/or kidney, forming methylate, glucuronide, and sulfate conjugated metabolites. Consistent exposure of certain polyphenols to the gut microbiota may act as prebiotic-like substances feeding the beneficial gut bacteria and changing the gut microbiome composition and function. The dichotomy between the biotransformation of polyphenols into their metabolites by gut microbiota and the modulation of gut microbiome composition by polyphenols is hypothesized to contribute to positive health outcomes. The present study examined the regular consumption of red raspberry purée (RRB) and/or fructo-oligosaccharide (FOS) on gut microbiome composition and subsequent bioavailability of red raspberry polyphenols in healthy volunteers. An 8-week pilot study, including two 4-week chronic treatments and 3 postprandial days, served as a feasibility study and mechanism to collect multiple biological specimens for method development. An ultra high-performance liquid chromatography (HPLC) coupled with electrospray ionization quadrupole time of flight (QTOF) and triple quadrupole (QQQ) mass spectrometer were used to identify and quantify the phenolic compounds in red raspberry purée, plasma and urine samples. Fecal samples were used for the metagenomic study. The sequencing of the 16S ribosomal RNA gene was utilized to study the gut microbiome composition. The red raspberry purée contained 148.55 ± 5.43 mg/100 g fresh weight (FW) polyphenols. Chronic RRB and/or FOS exposure influenced gut microbiome composition: at the phylum level, 4-week FOS (8 g/d), RRB (125 g/d), or FOS plus RRB (8 and 125 g/d, respectively) exposures all decreased Firmicutes and increased Bacteroidetes; at the genus level, 4-week FOS, RRB, or FOS plus RRB exposures all boosted Bacteroides and diminished Blautia; and the increased Akkermansia was only observed after RRB exposure. Chronic RRB and/or FOS exposure also altered the observed RRB polyphenol metabolites: the parent anthocyanins, such as cyanidin 3-O-sophoroside, were lower in plasma and urine after adaptation to RRB, while the production of urolithin A glucuronide (the main microbial-derived metabolite of ellagitannins) increased after FOS, RRB and FOS plus RRB exposure; an effect hypothesized to be related to the altered composition and metabolic activity of the gut microbiota. Overall, these data suggest chronic RRB and/or FOS exposure influenced gut microbiome composition and subsequently increased gut microbial metabolites.
M.S. in Food Safety and Technology, July 2017
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Title: EFFECT OF NOVEL SANITIZERS IN COMBINATION WITH HIGH-POWER-ULTRASOUND ON MNV-ION ROMAINE LETTUCE
Creator: Zeng, Jin
Date: 2016, 2016-05
Description: Human norovirus is a leading cause of foodborne outbreaks around the world especially in fresh-cut products like romaine lettuce. Traditional...
Show moreHuman norovirus is a leading cause of foodborne outbreaks around the world especially in fresh-cut products like romaine lettuce. Traditional sanitizers such as sodium hypochlorite have been used in food industry to prevent contamination; however there are certain issues such as residuals and toxicity. Novel organic sanitizers have been developed and most of them have been proved not effective on human norovirus. High- Power-Ultrasound (HPU) has a potential to improve effectiveness of sanitizers for washing of fresh-cut produce. As a novel technology, HPU is a non-thermal processing that can enhance inactivating microorganisms in food. In the present study, we have systematically investigated the effect of sanitizers, Chico-wash, ProduceShield, Tsunami 100, EatCleaner and chlorine on human norovirus surrogate and the effect of HPU to enhance viral inactivation. For washing study, romaine lettuce leaves were cut into 5x5 cm2 pieces and spotinoculated with approximately 7 log PFU/ml of MNV-1. The leaves were washed for 60s, 90s, and 120s using various sanitizer concentrations. After washing, leaves were transferred into a stomach bag that contained 20ml of Dulbecco's modified eagle medium (DMEM) or phosphate buffer solution (PBS) containing 0.5M sodium thiosulfate to neutralize the sanitizers. Viruses were extracted by stomaching and recovered from the samples and quantified by viral plaque assay. Water wash without sanitizer was used as a negative control. For water wash, 1.1± 0.1 log PFU/g, 1.3 ± 0.1 log PFU/g and 1.3 ± 0.1 log PFU/g reduction were observed respectively under 60s, 90s and 120s washing.For 20% Chico-wash, under three different time intervals, MNV-1 reductions of 1.2 ± 0.1 log PFU/g, 1.1± 0.1 log PFU/g and 1.2 ± 0.2 log10 PFU/g were observed respectively. While for ProduceShield, at 20% concentration level, 1.5 log PFU/g, 1.6 log PFU/g and 1.6 log PFU/g reduction were observed respectively. For Tsunami 100, leaves were washed for 60s at different concentrations of 20, 40, 60, 80 and 100 ppm, the reduction of MNV-1 was 2.1 ± 0.2, 2.9 ± 0.3, 3.2 ± 0.3, 3.7 ± 0.2 and 3.7 ± 0.2 log PFU/g, respectively, on the surface of lettuce leaves. In HPU study, a high power ultrasound was introduced into washing step in combination with Tsunami 100 at concentrations of 20, 40, 60, 80, 100 ppm. The reduction of MNV-1 was 2.7 ± 0.3, 2.9 ± 0.5, 3.3 ± 0.7, 3.6 ± 0.7 and 3.8 ± 0.5 log10 PFU/g, respectively. For EatCleaner, lettuce leaves were washed for 60s and the reduction of MNV-1 was 1.9 ± 0.1 log10 PFU/g.The results suggest that Chico-wash and ProduceShield were not effective on removing MNV-1 from romaine lettuce while EatCleaner was effective. Tsunami 100 was effective on MNV-1. One-way ANOVA shows that introducing HPU could enhance MNV-1 inactivation at low Tsunami 100 concentration.
M.S. in Food Safety and Technology, May 2016
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Title: INVESTIGATION AND CONTROL OF NOROVIRUS TRANSFER DURING PREPARATION OF FRESH PRODUCE IN A FOOD SERVICE SETTING
Creator: Zhao, Heng
Date: 2013-04-24, 2013-05
Description: Outbreaks of human norovirus are commonly attributed to fresh produce and multi-ingredient foods that have received significant handling...
Show moreOutbreaks of human norovirus are commonly attributed to fresh produce and multi-ingredient foods that have received significant handling immediately prior to consumption. The objective of this study was to evaluate the effect of gloved and ungloved hands on norovirus transfer during fresh produce preparation. The palm and fingers of bare or gloved (polyvinyl, vinyl or nitrile) hands were inoculated with approximately 7-log PFU/hand murine norovirus (MNV-1). Freshly chopped Romaine lettuce was handled by the contaminated hands, and then sampled to determine the transfer coefficient. MNV-1 transfer was also measured from chopped contaminated lettuce to clean bare or gloved hands. In addition, pulsed light was investigated, in a preliminary study, for its ability to inactivate MNV-1 on the surface of food contact surfaces including the various glove types and Romaine lettuce, and thus prevent the spread of contamination. Transfer of MNV-1 occurred more readily to (up to 45%) Romaine lettuce than from (less than 12%) it. Transfer to Romaine lettuce was greater (p<0.05) from vinyl gloves than bare hands and the other glove types tested, while no significant difference (p>0.05) in transfer from lettuce to the different glove types was observed. The results indicate that norovirus transfer can occur readily in a food service setting, and that transfer coefficients are affected by the type of surfaces involved. MNV-1 was reduced by pulsed light by >4-log within 30 sec on all surfaces except nitrile gloves, indicating the potential for this technology to be employed in a food service setting to control the spread of noroviruses during food preparation.
M.S. in Food Safety and Technology, May 2013
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Title: EFFICACY OF PULSED LIGHT TECHNOLOGY FOR THE INACTIVATION OF SALMONELLA ENTERITIDIS PT 30 ON ALMOND KERNEL SURFACE
Creator: Harguindeguy, Maite
Date: 2016, 2016-05
Description: Almond surfaces can be contaminated with pathogens such as Salmonella. Traditional thermal processing technologies used for inactivation of...
Show moreAlmond surfaces can be contaminated with pathogens such as Salmonella. Traditional thermal processing technologies used for inactivation of Salmonella on almonds can adversely impact the quality. Therefore, there is a need to investigate the efficacy of alternative technologies for inactivation of Salmonella on almonds without adversely affecting the quality. Pulsed light, a novel technology, can potentially be used to achieve this. Therefore, this study evaluated the efficacy of three pulsed light systems (operating at 1.8, 3, or 100 Hz) under various electrical input powers (1000, 1250 and 1500 W) and treatment times for inactivation of Salmonella Enteritidis PT 30 on almond surfaces. More than 4-log reduction was achieved at different treatment conditions for each of the control units. For instance, a 160 s treatment at 1500 W (100 Hz system) resulted in a 4.3 log CFU/almond reduction. Whereas, similar reductions were achieved in a shorter time with the lower frequency systems (1.8 or 3 Hz). Reductions of 4.6 and 5.9 log CFU/almond were achieved after 80 and 100 s treatment, respectively with the 1.8 Hz system (1250 W). Similarly, a 100 s treatment with the 3 Hz system (1000 W) resulted in a reduction of 4.7 log CFU/almond. Statistical analysis showed that the effect of equipment, treatment time, and electrical power input were significant (p<0.05). The D-values of 1.8, 3, and 100 Hz systems were 0.24, 0.53 and 0.73 min, respectively at 1500 W. In general, lower frequencies resulted in increased inactivation in shorter time. This can be attributed to the higher instantaneous power at lower frequencies. Similar trends were observed at other electrical input powers. The D-values found using pulsed light treatment are lower than the conventional dry heat treatment ones. Also, minimal color change was observed for treated almonds. These results indicate that pulsed light is efficacious for decontaminating almond surfaces within a relatively short time.
M.S. in Food Process Engineering, May 2016
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Title: SALMONELLA SURVIVAL DURING INOCULATION AND STORAGE OF DRIED SPICES CONTAINING ANTIMICROBIAL COMPONENTS
Creator: Hu, Chuxuan
Date: 2016, 2016-05
Description: To provide an adequate initial microbial level for spices containing antimicrobial compounds for use in stability testing of foodborne...
Show moreTo provide an adequate initial microbial level for spices containing antimicrobial compounds for use in stability testing of foodborne pathogens, a dry-transfer inoculation was designed and compared with a traditional aqueous inoculation protocol. A five serovar cocktail of Salmonella spp. was prepared at different concentrations (~11 log CFU/mL, ~8 log CFU/mL and ~4 log CFU/mL). It was inoculated onto 1g silica beads and four types of dried ground spices (clove, oregano, ginger, and black pepper). Both spices and beads were dried for 24h at ambient conditions (~22°C). Silica beads were then used as a carrier to inoculate the same four types of spices. The results suggest that dry-transfer of Salmonella via inoculated silica beads provided a greater starting inoculum than aqueous transfer alone and are a viable alternative to aqueous inoculation when spices contain antimicrobial components. This dry-transfer inoculated ground clove with 8.4 log CFU/g and 3.9 log CFU/g initial populations was then used to determine the survival of Salmonella on spices containing antimicrobial components. Salmonella spp. survival on silica beads with 9.2 log CFU/g and 5.9 log CFU/g initial populations and subsequent transfer to ground clove was also examined. Samples were enumerated at selected time point up to 210 d. Results of this study indicate that Salmonella transfer and recovery from beads and in ground clove was not affect by storage and that Salmonella may persist for an extended period of time. The calculation of recovery was, however, affected by detection limits in clove. To improve detection limits an oil extraction was used and compared to the BAM method (detection limit 3.7 log CFU/g). After oil extraction the clove samples were soaked for 1 h (or 24 h for low inoculum concentration) in TSB at 37ᵒC and subsequently enumerated on tryptic soy agar with 0.6% yeast extract and xylose lysine deoxycholate agars. The result demonstrates that the oil extraction detection method holds promise as an alternative method to detect Salmonella in dry spices containing antimicrobial components and can provide a lower detection limit (1.7 log CFU/g).
M.S. in Food Process Engineering, May 2016
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Title: INACTIVATION OF MURINE NOROVIRUS AND MS2 COLIPHAGE DURING FREEZE-DRY DEHYDRATION OF CONTAMINATED STRAWBERRIES
Creator: Wang, Xueyan
Date: 2013, 2013-07
Description: Human norovirus (HuNoV) is the major causative agent of foodborne acute gastroenteritis in the US and worldwide. A 2012 norovirus outbreak...
Show moreHuman norovirus (HuNoV) is the major causative agent of foodborne acute gastroenteritis in the US and worldwide. A 2012 norovirus outbreak that was associated with frozen strawberries has led to more than 11,000 illnesses in Germany. Freezedrying, a common process used to preserve berries, has been questioned for its effectiveness of norovirus inactivation. In our study, the survival of MS2 coliphage and murine norovirus-1 (MNV-1), surrogates of HuNoV, on inoculated strawberries were evaluated during a 24hr freeze-dry dehydration process with and without radiant heat. Fresh strawberries were 7 mm-thickness sliced, virus-inoculated, 1hr frozen, and 24hr freeze-dried. Freeze-drying of inoculated berries with the temperature ranging from 0 to 40°C was studied with continuous recording of the temperatures once every 20 min. Infectious MNV-1 was quantified using a Raw 264.7 cell culture plaque assay. The quantification of MS2 was conducted using a double agar plaque assay. The average recovery of MS2 coliphage from berry slices by an elution protocol developed in the study was 97% ± 27% based on the inoculum as 100%. Only 57% ± 11% of MNV was recovered from berry slices using the identical elution protocol. Approximately half of the recoverable population (either MS2 or MNV-1) became undetectable after 24hr cold storage, the final average recovery being 46% and 29% for MS2 and MNV-1 respectively. Radiant heat was found to accelerate the reduction of MS2 up to 2.56 logs reduction per sample in the process. The overall reduction of MS2 was about 3 logs as maximum after 24hr freeze-drying. Regression analysis illustrated a significant correlation between MS2 log reduction and radiant heat applied. The x regression formula suggested that an increase of one degree Celsius in radiant heat during the 24hr freeze-drying would increase the log reduction of MS2 on berries by 0.044 log. The reductions of MNV on berries after the 24hr freeze-drying ranged from 0.85 to 1.82 logs. Via ANOVA analysis, MNV reduction on berries with radiant heat ≥20°C was significantly greater than heating at 10°C or without heat (~0°C), p<0.05. The overall maximum reduction of MNV on berries after the 24hr-process, therefore, was >2 logs. Although radiant heat inactivated MNV during the freeze-drying process, the inactivation of MNV by heat was less efficient than that of MS2. These data may be helpful in designing processes to control viral contaminants during freeze-drying of virus-contaminated berries.
M.S. in Food Safety and Technology, July 2013
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Title: MINIMIZING SALMONELLA CONTAMINATION IN SPROUTS BY CONTROLLING THE IRRIGATION CONDITIONS DURING GERMINATION
Creator: Xie, Jing
Date: 2014, 2014-07
Description: The objective of this study was to examine whether the proliferation of Salmonella can be minimized during sprouting by controlling the...
Show moreThe objective of this study was to examine whether the proliferation of Salmonella can be minimized during sprouting by controlling the irrigation conditions using seeds that have been either treated or not treated with 20,000 ppm of calcium hypochlorite, Ca(OCl)2. 200 g of alfalfa seeds spiked with 2 g (or 1 %) of inoculated seeds (containting~1 log cfu/g of Salmonella) were allowed to germinate in a glass jar or in an automatic sprouter (EasyGreen) for 5 days at room temperature. The sprouts germinated in the automatic sprouters were irrigated with either sterile tap water or chlorinated water (containing 100 ppm of calcium hypochlorite) at various frequencies (once every 1, 2 or 4 h); the sprouts germinated in glass jar were rinsed every 24 h with sterile tap water. The same growth studies were performed on seeds treated with 20,000 ppm Ca(OCl)2 for 15 min prior to sprouting. Sprout samples were taken daily and analyzed for the level of Salmonella using the three-tube most probable number method as described in the FDA BAM. Seed treatment with 20,000 ppm Ca(OCl)2 reduced Salmonella level in seeds to a level that was below the detection limit (< -2.5 log MPN/g). The pathogen was not detected during five days of germination in automatic sprouters or jars. Using untreated seeds, the level of Salmonella changed from an increase of ~ 7 log MPN/g in sprouts grown in jars and irrigated once every 24 h to an increase of ~ 4 log MPN/g during sprouting in the automated sprouters and irrigated once every 1 h. Irrigation with chlorinated water although inhibited Salmonella re-growth but affected the quality of sprouts. Overall, seed treatment combined with frequent irrigation with tap water or chlorinated water can control the level of Salmonella to an undetectable level during sprouting.
M.S. in Food Safety and Technology, July 2014
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Title: COMPARISON OF THE EFFICACY OF THREE SANITIZERS WITH 20,000 PPM CALCIUM HYPOCHLORITE FOR INACTIVATION OF SALMONELLA ON ARTIFICIALLY CONTAMINATED ALFALFA SEEDS
Creator: Li, Qing
Date: 2015, 2015-12
Description: This study evaluated the efficacy of three alternative sanitizers, acidified sodium chlorite (ASC, also known as Sanova), stabilized oxychloro...
Show moreThis study evaluated the efficacy of three alternative sanitizers, acidified sodium chlorite (ASC, also known as Sanova), stabilized oxychloro-based sanitizer (SOC, also known as Germin-8-or), and Tsunami 100 in comparison with 20,000 ppm Ca(OCl)2 for treatment of alfalfa seeds artificially inoculated with Salmonella. Small-scale experiments were conducted to determine the best treatment conditions for each sanitizer and how the initial Salmonella contamination level on seeds or Salmonella type may have on the efficacy of the sanitizers. Large-scale studies were performed to evaluate the commercial applicability of these sanitizers. As a comparison, seeds were also treated with 20,000 ppm Ca(OCl)2 for 15 min. To determine the optimal treatment condition, ten g of seeds containing 103 CFU/g (seed lot 1) or 105 CFU/g (seed lot 2) of S. Typhimurium expressing green fluorescent protein was treated with different concentrations of ASC, SOC, and Tsunami 100 for different period of treatment time. Results showed that the efficacy of ASC and SOC increased with increasing concentrations (up to 1500 ppm) and treatment time (up to 3 h); however, the germination rates for seeds treated with > 1200 ppm of either sanitizer was < 80%. When seeds from lot 1 were treated with 800 ppm of ASC or SOC for 3 h, the level of Salmonella reduced, respectively, by 2.6 log units or >2.5 log units to an undetectable level, compared with the 1.1 log unit decrease observed in seeds treated with Ca(OCl)2. When seeds from seed lot 2 (5 log units) were treated with 800 ppm of ASC or SOC for 3 h, the level of Salmonella were reduced by 3.8 log units or >4.3 log units to an undetectable level, respectively, compared with the 2 log units decrease observed in seeds treated with Ca(OCl)2. Treatment with 80 ppm of Tsunami 100 from 10 min to 24 h kept the germination rate higher than 85% but only reduced the Salmonella count by 0 to 1.8 log units. Between two seed lots, results of ASC showed that sanitizer could reduce more pathogen when the seeds contained higher initial Salmonella level. Ten g of seeds containing 105 CFU/g of four-strain cocktail of Salmonella was treated with ASC and SOC by optimal treatment condition. SOC and ASC eliminated Salmonella number by 2.8 and 1.6 log units respectively, less effective compare with the treatment of seed lot 1. For large-scale runs, 1 kg of seeds spiked with 1 % (w/w) of inoculated seeds containing 105 CFU/g of S. Typhimurium was treated with SOC and ASC under optimal treatment conditions. Salmonella level in seeds treated with 800 ppm SOC or ASC for 3 h decreased by 3.9 or 3.6 log units, compared with a 3.3 log reduction in seeds treated with 20,000 ppm Ca(OCl)2. The stabilized oxychloro-based sanitizer may provide an alternative seed treatment method for sprout growers.
M.S. in Food Safety and Technology, December 2015
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Title: POSTPRANDIAL PLASMA POLYPHENOL PROFILE AND BIOAVAILABILITY OF ANTHOCYANINS IN INSULIN RESISTANT HUMANS AFTER CONSUMING MULTIPLE DOSES OF STRAWBERRIES BEVERAGE WITH A MEAL
Creator: Wei, Hequn
Date: 2014, 2014-05
Description: Strawberries represent a rich source of polyphenolic compounds that are purported to be important for human health. However, data on their...
Show moreStrawberries represent a rich source of polyphenolic compounds that are purported to be important for human health. However, data on their bioavailability are limited. Therefore, the objective of the present study was to assess the absorption and metabolism of strawberry polyphenols in the postprandial phase using LC-MS/MS. Plasma was collected from humans (n=17) every 30-60 min over 6 h after ingestion of a 650 kcal standard meal accompanied with a beverage containing 0, 10, 20 or 40 g freeze dried strawberry powder. Pelargonidin-O-glucuronide (PG) was the most abundant strawberry metabolite in plasma. Maximum concentrations (Cmax) of PG were achieved at 188 ± 44 min and the levels were significantly different among beverages containing 0, 10, 20, 40 g strawberry powder: 0, 66.0±4.15, 113.64±10.11 and 202.1±15.18 nmol/L, respectively (P<0.05). Area under the concentration curve (AUC) over 6 h also increased with increasing doses (P<0.05); Cmax and AUC of PG was reduced as a percent of pelargonidin-3-O-glucoside (P3G) delivered in the 4 strawberry beverages (P<0.05). The 3 major anthocyanin polyphenols (PG, Pelagonidin-3-Glucoside (P3G) and Cyanidin-3-O-glucoside (CG)) found in plasma increased significantly after consumption of all strawberry-containing beverages compared to placebo (p<0,05). Bioavailability of PG from P3G among beverages containing 10, 20, 40 g strawberry powder were 1.76%, 1.40%, 1.30%, respectively. While higher concentrations of key strawberry compounds and metabolites were achieved with consumption of more strawberry powder, adjusting for dose suggested possible saturation of absorptive capacity of pelargonidin-based anthocyanins. These data provide the basis for understanding the relationship between dose, kinetic profile and efficacy outcomes for making recommendations to deliver optimal health benefits of strawberries; and moreover, serve as a model of the type of data required for understanding the relationship between dietary phytochemical intake and their biological effects.
M.S. in Food Processing Engineering, May 2014
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Title: IN VITRO CELLULAR ASSAY FOR ASSESSING THE IMPACT OF PROCESSING ON THE ALLERGENIC POTENTIAL OF EGG ALLERGENS
Creator: Wei, Kunni
Date: 2013-04-24, 2013-05
Description: An understanding of the impact of processing on food allergenicity is critical for allergen risk assessment. In vitro cell-based assays have...
Show moreAn understanding of the impact of processing on food allergenicity is critical for allergen risk assessment. In vitro cell-based assays have been developed to assess the allergenicity of food proteins by measuring the capacity of these proteins to induce degranulation in effector cells. This study evaluated the use of sensitized rat basophilic leukemia (RBL) cells for assessing the allergenic potential of ovalbumin (OVA), ovomucoid (OVM) and NIST whole egg standard reference material (NIST egg) by measuring the proteins’ ability to induce the release of β-hexosaminidase and histamine. RBL-2H3 cells at a concentration of ~105 cells/mL were seeded in six-well plates and incubated for 24 hours. After washing with PBS and resuspension in Eagle’s minimal essential medium, cells were sensitized by incubation for 24 h with various dilutions of anti-OVA, anti-OVM or anti-egg antisera derived from Brown Norway or Wistar rats. The sensitized cells were then challenged with different concentrations of unheated or boiled (for 10 min) OVA, OVM or NIST egg. After 45 min, cell degranulation was determined by measuring the increase in β-hexosaminidase and histamine in culture supernatant. The release of β-hexosaminidase was observed after the cells were challenged with OVA, OVM or NIST egg. Assay optimization studies using sensitized cells challenged with OVA indicated that the greatest degree of release occurred when RBL-2H3 cells were sensitized with 1:10 dilution of anti-sera and challenged with 0.01mg/mL of OVA. Histamine release was not detected under any serum or OVA concentration. Boiling caused a decrease in the recovery of OVA and NIST egg (70.34±3.61% and 73.69±7.66% respectively), but did not affect the recovery of OVM (96.28±2.95%). Under the optimal assay conditions, boiled OVA and boiled NIST egg x triggered the release of more β-hexosaminidase than the unheated forms of these proteins in most cases. However, boiling did not significantly affect the ability of OVM to induce the release of β-hexosaminidase. Due to the large variation in % release of β-hexosaminidase obtained from different trials, the RBL mediator release assay may not be an accurate method to evaluate the impact of thermal processing on the allergenic potential of egg allergens.
M.S. in Food Safety and Technology, May 2013
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Title: CELL SHRINKAGE STRATEGY FOR SALMONELLA DURING DESICCATION
Creator: Megalis, Christina
Date: 2013, 2013-07
Description: Salmonella is a growi ng concern in low-moisture foods. The objective of this project is to further unlock the mechanism for Salmonella...
Show moreSalmonella is a growi ng concern in low-moisture foods. The objective of this project is to further unlock the mechanism for Salmonella desiccation survival. Salmonella Tennessee and Typhimurium LT2 were used in this study, each demonstrating a strong and weak resistance to desiccation , respectively. Exponential phase cells were desiccated (RH= II %) for 5 days on steri le paper discs and were reduce d by 4 and 7-logs CFU/mL, respectively. This study examined the role of rod/cocci conversion in Salmonella stress res istance using an SEM. The typical rod-shape of Salmonella was altered upon a 5-day desiccation treatment (aw=O. l l), produ cing a cocci shape and significantly more so in the case of S. Tennessee. S. Tennessee fresh and desiccated cell lengths were 1.32 ± 0.12 and 1.14 ± 0.07 urn, respectively, compared to S. LT2 fresh and desiccated that were 1.55 ± 0. 19 and 1.42 ± 0.14 urn, respectively. Scatter plot analysis showed that the convers ion from rod shape to cocci occurred at greate r extent in S. Tennessee than S. Typhimurium LT2 responding to the 5-day desiccation treatment Cytoskeletal genes involved in cell elongation (rodA, rodZ, mrdB, mreB, mrdA, mrcA, and mrcB) were anal yzed for expression using qRT-PCR. The gene expression profile for the two strain s significantly differed with S. Tennessee virtually having no change in expression after 24-hour desiccation while S. LT2 exp ression ranged from 38 to 91-fold up-regulated . This thesis provided additiona l understanding of Salmonella desiccation resistant strategy; however, to fully understand the expression change of those genes, study of gene expression at different time point is needed in future.
M.S. in Food Safety and Technology, July 2013
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