Nutrition & Food Science Theses and Dissertations

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    (2023) Huang, Xinyang; Meng, Jianghong; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In this study, we first utilized high-throughput next-generation sequencing (NGS) and bioinformatic analyses to characterize potential public health threats posed by non-top-7 Shiga toxin-producing Escherichia coli (STEC). NGS allowed us to detect virulence (n = 46) and antimicrobial resistance (AMR) (n = 27) factors within the genomes of the STEC strains, to make genome-wide comparisons with published human clinical isolates, and to characterize three novel O-antigen gene clusters. We found that the distribution of 33 virulence genes and 15 AMR determinants exhibited significant differences among serotypes (P < 0.05), and that 47 strains were genetically related to human clinical strains inferred from a pan-genome phylogenetic tree. We secondly developed a web tool, PhyloPlus, that allowed users to generate customized bacterial and archaeal phylogenies, which can be incorporated into their own microbial community studies. We also utilized two public datasets (human microbiome, n = 60; fermented food metagenomes, n = 62) to illustrate how application of phylogeny improved our analyses. We showed that the integration of phylogenies introduced alternative phylogeny-based diversity metrics and allowed more conservative null model constructions, thereby reducing potential inflation of type I errors. Finally, we employed deep metagenomic shotgun sequencing, and our developed web tool, to investigate on a collection of 404 surface water samples collected from four regions in Latin America. We reported the high detection rates of pathogenic and contaminant bacteria in these samples, including Salmonella (29.21%), Listeria (6.19%), and E. coli (35.64%), necessitating the monitoring and proper treatment on these surface waters. We also described the regional differences in terms of sample taxonomic composition and the resistome, and further presented key factors that drove the separation patterns for each sampling region. We utilized recent metagenomic assembly and binning algorithms to report the construction of 1,461 de-replicated metagenome-assembled genomes (MAGs) that were of at least medium quality. The incorporation of the MAGs into the taxonomic classifier Kraken2’s database led to a 12.85% increase in classifiable sequence reads. Additionally, we conducted network analysis on AMR genes and the genus-level taxonomy, based on assembled contigs, to provide information to better understand the dynamics of the transferring of AMR genes.
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    (2023) ALHAMMAD, GHADAH ABDULRAHMAN; Lei, David K. Y.; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Aquaponic (AP) food production systems integrate aquaculture and hydroponics in soilless controlled environments while conserving space and natural resources (soil, water, air). Increasing global demand for high-quality quality nutritious, safe food continues to increase exponentially. Information specific to AP is needed to validate operational and handling practices for AP food safety. The first study is to assess the persistence of E. coli TVS 354 in bench-scale aquaponic systems (180 days after primary plant harvest). Methods: follow-up on the previous study and evaluate growth and persistence of E. coli TVS 354 at 180 days after primary plant harvest. Samples were collected from 10 independent aquaponic systems and bacterial growth was evaluated including aerobic plate count (APC), coliform bacteria (CB), heterotrophic plate count (HPC), and cultural enrichment for E. coli TVS 354 levels. Results: E. coli TVS 354 was not detected in samples from hydrotons (25 g), filters, fish feces, core and roots. The aerobic bacteria count of fish and plant tank samples ranged between 2.5 to 3 log CFU/mL for all treatments, while aerobic bacteria count on the core of the lettuce plant was significantly lower, ranging from 1.44 to 2.08 log CFU/mL. The second study is to evaluate the survival of Listeria innocua 2066 in effluent from fish tanks and plant tanks of aquaponic research units. Methods: four different treatments: fish tank water, fish tank water-replenished, plant tank water, and plant tank water-replenished. Each bottle was inoculated with Listeria innocua 2066, and bacterial growth and water chemistry conditions were evaluated over 7 days to identify physiochemical parameters associated with Listeria innocua 2066 survival and growth. Results: In 24 hours a significant reduction (p<0.05) in Listeria inccoua 2066 populations was observed for all treatments with a total reduction 3.9-3.7 log CFU/mL. Listeria innocua 2066 counts were lowest on day 7 for treatment groups, ranging from 1.1 log CFU/mL to 1.0 log CFU/mL. Treatments that were replenished daily from the aquaponic systems had higher counts of Listeria innocua 2066 compared to treatments that were non-replenished. The lowest APC on day 0, immediately after inoculation, ranged from 4.16 log CFU/mL to 4.32 log CFU/mL. A significant increase (P<0.05) in APC count was observed for all treatments in 24 hours while there is no significant difference in APC values between the treatments (p=0.35). The final and third study is to evaluate survival of inoculated Listeria innocua 2066 and nonpathogenic Escherichia coli and changes in AP physicochemical parameters. Methods: A four-week bench-scale AP experiment (n=12) with four goldfish (Carassius auratus)/aerated 37L tank, a 3-step biofilter, and four lettuce plants (Lactuca sativa var. Truchas)/37L hydroponic tank was conducted. Treatments were high and low-dose (6-log and 2-log CFU/mL, respectively) of Listeria innocua 2066-Er or E. coli-Rifr TVS 354, and uninoculated controls. Listeria innocua-2066-Er and E. coli-Rifr populations, mesophilic counts (APC), and physicochemical parameters (pH, temperature, dissolved oxygen, turbidity, ammonia, nitrite, and nitrate) were analyzed in plant tank water, and biofilters until plant harvest. Listeria innocua 2066-Er and E.coli-Rifr enumeration and APC (Petrifilm®) from lettuce shoots, roots and rockwool were determined at harvest. Results: Listeria innocua 2066 and E. coli TVS 354 populations declined significantly within 24 hours post-inoculation and were undetectable at day 14 and day 12 respectively (P <0.05). This decline was observed for both high and low-dose treatments. Listeria innocua 2066 and E. coli TVS 354 were detected in biofilters until week 4. At harvest, Listeria innocua 2066 and E. coli TVS 354 were recovered from lettuce roots, and rockwool, but not from plant leaves, and 100mL plant tank water grab samples. Lower leaves preharvest had a significantly higher APC (5.1- 6.4 log CFU/mL) relative to harvested lettuce upper leaves (2.8 - 4.2 log CFU/mL). Plant tank water pH had a significant effect (P<0.05) on Listeria innocua 2066 and E. coli TVS 354 survival. Significance: These results provide insights into the survival dynamics and sites of E. coli TVS 354 and Listeria innocua 2066 in AP and associated physicochemical conditions. These findings contribute to our understanding of potential food safety risks and associated risk factors such as inputs, physicochemical factors, and other environmental conditions in aquaponics systems.
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    (2023) Tarwa, Kevin; Wang, Qin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Nanoparticle delivery systems composed of food polymers are a sustainable and eco-friendly approach to protect functional ingredients and promote healthier food options. In this research, a hordein-pectin nanoparticle complex (HP-NPC) was fabricated using an anti-solvent precipitation and electrostatic deposition (pH 4) method for the encapsulation of hydrophobic bioactive compounds to enhance their functionalities. First, hordein was extracted from whole barley grains to obtain a dried powder to synthesize hordein nanoparticles (HNP). Then pectin with a degree of esterification (DE) around 71% was applied as a coating material. The average particle size of the freshly prepared nanoparticle complex was relatively small (~246 ± 11 nm), and Fourier transform infrared spectroscopy (FTIR) indicated that cationic hordein interacted with anionic pectin mainly though newly formed hydrogen bonds and electrostatic interaction as indicated by their opposite surface charges. Scanning electron microscopy (SEM) revealed that the morphology of the nanoparticle complex was spherical with a smooth surface. The pectin coating was shown to have a protective effect against pH (3.0-9.0), heat (80 °C for 0-120 mins), and salt (0-100 µM) which are all factors known to degrade proteins. Second, lutein, a hydrophobic bioactive xanthophyll was encapsulated into HP-NPC to develop a lutein-hordein/pectin nanoparticle complex (L-HP-NPC). Since lutein has low water solubility and low bioavailability in the gastrointestinal tract (GIT), the effect of the encapsulation system on the functional properties of lutein was investigated. The loading capacity (LC%) and encapsulation efficiency (EE%) was around 15.5 and 82%, respectively. In vitro digestion resulted in a higher bioaccessibility of lutein for encapsulated HP-NPC (~22.3%), which is defined as the percentage of lutein accessible for absorption in the simulated intestinal fluid (SIF) compared to lutein encapsulated into HNP (~9%). The ability of pectin to produce gels in acidic media was shown to have a significant effect against gastric enzymes that can degrade both hordein and lutein. Also, lyophilization (an important step in food processing) had no significant effect on the stability of L-HP-NPC. This encapsulation system could potentially be used as a functional ingredient in the food industry to develop healthy and nutritious foods for consumers. Third, carvacrol, a phenolic monoterpene known for its antimicrobial properties was encapsulated into HP-NPC to develop a carvacrol-hordein/pectin nanoparticle complex (CA-HP-NPC). Special focus was on the solubility of encapsulate carvacrol due to its known low solubility in aqueous solutions. The antimicrobial effectiveness of the encapsulated nanoparticle complex was tested against non-pathogenic gram-positive L. innocua and gram-negative E. coli K12. CA-HP-NPC was still able to maintain a relatively small particle size (~207 ± 8 nm) after being dispersed into water post-lyophilization. Carvacrol was shown to be effective against the two bacteria, however, CA-HP-NPC did not show antimicrobial effectiveness. Although carvacrol was successfully encapsulated into the nanoparticle complex, further studies on their release properties need to be investigated to further understand their functional properties for food applications.
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    (2023) Subedi, Ujjwol; Obanda, Diana; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The properties of kale as a functional food are well known. Fermentation is a process that has been shown to improve the health impacts of foods. In this study, we sought to determine how fermentation further improves or augments the functional food properties of kale. We tested six different fermentation methods which included traditional practices and inoculation with different bacterial species and compared outcomes to the unfermented control. After 16 days of fermentation, we quantified (i) selected bioactive components and (ii) anti-nutritional factors. We then determined (i) the antioxidant capacity of the whole vegetable, (ii) the microbiota composition of the vegetable, and (iii) the anti-inflammation capacity of the ethanolic extract of the vegetable. Fermentation significantly increased (i) the quantities of total polyphenols from 8.54 to 10.71 mg GAE/g (ii) sulforaphane from 960.8 ± 41.76 to 1777 ± 45.95 μg/g, and (iii) antioxidant capacity from 61.99 to 67.37 % respectively, and antinutritional factors oxalate and tannin content significantly reduced by 49 % and 29.83 % respectively. Fermented kale extract exhibited potent anti-inflammatory effects in macrophages by reducing the iNOS expression by 84.3% and TNF-α, IL-1β, and IL-6 mRNA levels by 62, 68, and 85.5 %, respectively. Fermenting kale changed the surface microbiota by reducing the population of the inflammation-inducing Proteobacteria while increasing health-promoting Firmicutes; including Lactobacillus. All fermentation methods had a beneficial impact compared to the unfermented control, but the mixed culture of L. lactis and L. acidophilus was the most effective. In summary, fermenting enhanced the health benefits of kale by increasing the concentration of total polyphenol, sulforaphane content, antioxidant capacity, anti-inflammation capacity, and reducing the quantity of anti-nutritional factors. Furthermore, it promoted the prebiotic and/or probiotic vehicle properties of the vegetable by changing the proportion of beneficial bacteria and those associated with inflammation.
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    (2023) Kwon, Hee Jin; Meng, Jianghong; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Listeria monocytogenes, a Gram-positive bacterium, is a foodborne pathogen that causes listeriosis in humans. L. monocytogenes can persist in various environmental conditions, including food-relevant conditions such as high salinity, refrigerated temperatures, and low moisture contents. Contaminated food products, including dairy products, deli meats, fresh produce, and soft cheeses, are the primary transmission vehicles for L. monocytogenes. The complex and dynamic population structure of L. monocytogenes complicates control efforts, particularly due to certain strains that may possess increased resistance to stress conditions and/or enhanced virulence. The advent of whole genome sequencing has facilitated comprehensive genomic analyses of L. monocytogenes, enabling a comprehensive understanding of its adaptation and survival characteristics over time and across various geographic locations. Understanding the population and genetic diversity of L. monocytogenes is crucial for the development of effective control measures, as it helps infer the spread and transmission pathways of L. monocytogenes through the integration of spatial-temporal factors. Furthermore, these analyses provide insights into the evolutionary relationships among L. monocytogenes strains. This dissertation aimed to investigate the population diversity of L. monocytogenes in various food sources and food processing facilities, utilizing the whole genome sequencing technology. The findings contribute valuable insights into the genetic diversity and population structure of L. monocytogenes, thereby aiding the understanding of the risk associated with L. monocytogenes contamination and the development of effective control measures to ensure food safety.
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    (2023) Tsai, Shawn; Tikekar, Rohan V.; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This dissertation explores the growth and inactivation of Salmonella enterica subsp. enterica Serovar Typhimurium in oil-in-water emulsion systems, with a particular focus on the effects of emulsifier type, oil fraction, temperature, molecular weight, and surface charge. First, investigation was conducted on the effects of emulsifier type (Tween 20, Tween 80, Triton X-100) and oil content (20%, 40%, 60%) on growth and thermal inactivation of S. Typhimurium in emulsions. The results indicated that while emulsifiers did not affect the bacterial growth rate or lag phase, the presence of high oil content (60%) prolonged the lag phase in emulsions. In addition, Tween 80 and Triton X-100 emulsifier solutions exhibited protective effects against thermal inactivation. Next chapter was focused on evaluating the impact of temperature on growth (7, 22, 37°C) and inactivation (55, 58, 60°C) kinetics of S. Typhimurium in emulsion systems with same emulsifier and oil fraction as previous chapter. The results indicated that temperature had a significant impact on bacterial kinetics, with increasing temperatures leading to faster growth and inactivation rates. Next, the effect of emulsifier molecular weight and surface charge on the growth and thermal inactivation of S. Typhimurium in emulsions was examined. To control the molecular weight with similar structure, whey protein was selected for experimentation. By adjusting the pH, it was possible to change the surface charge in whey protein. Results indicated that whey protein hydrolysate (WPH) with a lower molecular weight did not exhibit a lag phase in Salmonella growth. However, whey protein isolate (WPI) with higher molecular weight demonstrated no difference in the lag phase when compared to bacterial growth in TSB. Similar effects were observed with a positively charged emulsifier (WPI+). The findings suggest that the molecular weight of emulsifiers has a more significant impact on bacterial growth than their surface charge. Regarding the evaluation of inactivation, emulsifier solutions exhibited no significant difference compared to TSB, while emulsions stabilized by WPH and WPI+ showed some protective effects on S. Typhimurium. This observation can be attributed to the ability of positively charged emulsifiers to interact with the bacterial membrane, providing protective effects during thermal treatment. Lastly, to gain a comprehensive understanding of the mechanism concerned with the impact of emulsifier and oil inclusion on bacterial growth and inactivation behavior, S. Typhimurium was cultured in different emulsion-related environments and evaluated for nine stress-related genes (rpoE, rpoH, otsB, proV, fadA, fabA, dnaK, ibpA, ompC) after 20 hours of incubation at 37°C and after thermal treatment at 55°C for 45 min. It was found that ibpA was upregulated in all emulsifier environments, regardless of the presence of oil, indicating that IbpA was synthesized in emulsifier environments. Moreover, increased expression of fabA was also observed in Triton X-100 stabilized 60% emulsion, indicating poor heat resistance due to increased membrane fluidity. In the combination of gene expression data, our results showed that emulsifier solutions without oil exhibited a greater number of regulatory mechanisms compared to those containing oil, indicating that the presence of oil did not provide as much protection after thermal treatment. Based on these findings, the stress-related mechanism was constructed by the expression of those selected genes. Overall, this dissertation provides valuable insights into the factors influencing bacterial growth and inactivation in oil-in-water emulsion systems, as well as bacterial stress response in these systems. These findings provide important insights into the growth and inactivation behavior of S. Typhimurium in oil-in-water emulsion systems and the stress response mechanisms involved. Understanding these factors is crucial for developing effective control measures to ensure food safety and prevent foodborne illness outbreaks caused by this pathogen. This information can be used to optimize the formulation and processing of emulsion-based food products to minimize the risk of bacterial contamination and ensure their safety for consumption.
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    (2023) Tamia, Gillian; Lee, Seong-Ho; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Cancer is a major public health problem and the second-leading cause of death in the world. Colorectal cancer (CRC) is the third most diagnosed cancer in the U.S. CRC is highly associated with daily diet and eating patterns. A plant-based diet rich in phytochemicals has been known to be protective against the initiation and progression of CRC occurrence. The hop plant, a key ingredient in beer, contains a diverse form of bioactive compounds that possess biological benefits in tumorigenesis. Xanthohumol (XN), the most abundant prenylated flavonoid, has been used over the years to treat a broad range of chronic diseases such as diabetes, obesity, and cancer. Several derivatives of XN, including isoxanthohumol (IXN), 8-prenylnaringenin (8-PN), and tetrahydroxanthohumol (TXN), possess similar and greater biological benefits compared to XN. While XN's anti-cancer properties are well known, the effects of these derivatives have not been evaluated in human CRC models. Our study aimed to test the cancer-suppressive activities of these derivatives and elucidate anti-cancer mechanisms using human adenocarcinoma CRC cells. The results indicate that four hop compounds (XN, IXN, 8-PN, and TXN) significantly suppressed the proliferation of different types of human CRC cell lines. We selected TXN and XN for further studies due to their more significant and promising anti-proliferative activity compared with other forms. Flow cytometry analysis indicated that TXN and XN led to significant induction of S-phase and G2/M-phase arrest. An apoptotic assay showed a huge induction of early and late apoptosis in cells treated with TXN and XN at doses of 12 µM and 18 µM. Western blot data indicate that TXN and XN induce the cleavage of PARP and increase the expression of CHOP, IRE1α, and ATF4, indicating activation of caspase-dependent apoptosis and ER stress. In addition, a dose-dependent increase in intracellular ROS was observed in cells treated with 12 and 18 µM of TXN and XN, affecting mitochondrial dysfunction. Taken together, our current study proposes an anti-cancer mechanism by TXN and XN through their action on the induction of ROS release and mitochondrial dysfunction, ER stress, and apoptosis in human CRC cells.
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    (2023) Muruvanda, Tim; Meng, Jianghong; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The longstanding problem with culture-dependent methods has been a reliance on pre-enrichment/enrichment steps which often comprise within them background microbial flora capable of outcompeting the target organism. Here, the genomic factors associated with Pseudomonas virulence and antagonism were studied in strains from selective media where it was shown to outcompete Salmonella, the target organism. 34 Pseudomonas strains of various species were sequenced and annotated. Results identified quorum sensing (QS) as the main factor of driving virulence and antagonism through the recruitment the type VI secretion system (T6SS). Additionally, two potential effectors corresponding to DUF 4225 and 4280 were found along with P.fluorescens strains containing the Pseudomonas virulence factor (PVF). These results may be valuable in the development of new strategies to better circumvent the effects of Pseudomonas in cultures.
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    Age, Nutrition, and Bone Metabolism: Analyses of Effects Using a Short-Term In Vivo Bone Model
    (1987) Sinha, Rashmi; Soares, Jos; Nutritional Sciences Program; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    The preventative effects of dietary calcium, zinc, and vitamin D metabolites on the net loss of bone were assessed using rats of different ages. Biochemical changes were monitored in femurs, humeri, mandibles, scapulas, and tibias. In addition femora were sectioned into epiphyses-metaphyses and diaphyses to evaluate nutritional influences on the trabecular and cortical type bone. since measurable bone degradation due to aging and nutritional status requires long period of time, a short-term in vivo system was developed to simultaneously examine bone formation and resorption. The system consisted of subcutaneous implantation of demineralized (DB) and mineralized (MB) bone powders. There was evidence of bone formation and resorption in the DB and MB implants respectively, as assessed by marker enzyme (formation-alkaline phosphatase; resorption-acid phosphatase) activities, mineral concentrations, radioisotope incorporation, and histological studies. The results indicated that several different bone samples are required to adequately predict changes occurring in the skeletal system. The epiphysesmetaphyses of long bone is a useful sample site examining changes occurring in trabecular bone while the diaphysis can assess cortical bone status. There was decreased bone formation and resorption as assessed by alkaline and acid phosphatase activity in the MB and DB implants in the 24 month-old rats as compared to 2 month-old rats. Dietary calcium and zinc levels did not affect the overall status of the bones and implants in the aged rats. Conversely, in 2 month-old rats dietary calcium at 1.0% stimulated bone formation in the DB implant, whereas 0.2% calcium increased bone resorption in the MB implants. Furthermore, 75 ng dietary 1,25-dihydroxycholecalciferol (l,25(OH) 2 D) per day increased resorption in MB implant and inhibited mineralization of DB implants in the young rats. Dietary zinc at 300 ppm reduced bone calcification in 2 month-old. The results of these studies indicated that neither high levels of dietary calcium, nor zinc, act as prophylaxes to counteract bone loss due to aging. The dietary use of l,25(OH) 2 D in old animals needs to be investigated further, since results in young animals are contradictory with reports in older rats.
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    (2022) Montemayor, Abraham Moses; Tikekar, Rohan V; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Ultraviolet (UV) radiation has been used in the food industry during processing, and with increased demands for safer and higher quality foods, UV-A and UV-B are being explored as antimicrobial treatments. This project consisted of three studies: the first study investigated the production of reactive oxidative species (ROS) by the action of UV radiation on fructose. The second study focused on evaluating the impact of UV-A irradiated chitosan-gallic acid (CH-GA) antimicrobial film on the quality of strawberries. The third study evaluated the effects of using UV-C individually or in combination with UV-A and UV-B to improve the fruit color and safety, respectively, of Honeycrisp apples. It is known that fructose can generate ROS under thermal treatments and UV-C (254 nm) exposure. However, it is unknown whether UV-A or UV-B exposure can generate similar effects. For the first study, fluorescein, a fluorescent dye, was used as an indicator due to its known loss of fluorescence when exposed to ROS. Varying concentrations of fructose solutions combined with fluorescein were exposed to up to 1 J/cm2 of UV-A or UV-B radiation. Ascorbic acid (AA), a known ROS scavenger, was added to the fructose-fluorescein solutions prior to UV exposure to verify ROS generation. The fluorescence was measured at 485 nm (excitation) and 510 nm (emission), respectively. A storage study was done to determine whether ROS continued to generate following UV exposure. Fructose-fluorescein solutions were exposed to 0.1 J/cm2 of UV-B radiation and stored at 4°C or 37°C. The UV-B exposure of fructose-fluorescein showed a dose-dependent fluorescence decay, whereas UV-A did not elicit this response. Fluorescein degradation followed first-order kinetics, as indicated by the rate constants. The rate constants in the presence of 10-, 50-, and 100- mM fructose were 0.7±0.01 J/cm2, 4.3±0.6 J/cm2, and 0.3±0.03 J/cm2, respectively. However, in the presence of AA, fluorescein degradation deviated from first-order kinetics. The storage study indicated no significant difference between the UV-B exposed and control solutions, indicating ROS generation ceased after UV-B exposure. The results of the studies using control solutions were extrapolated to coconut water, a commonly consumed beverage. UV-B exposure did have a degradation effect on AA, but the ROS generated did not affect the AA. The ROS was produced only when fructose was exposed to UV-B. ROS can have adverse effects on the organoleptic properties of foods containing fructose, and the addition of AA can help quench ROS in a concentration-dependent manner. The second study evaluated quality parameters such as color, texture, pH, total soluble solids, and titratable acidity of strawberries coated with an edible chitosan-gallic acid (CH-GA) coating. The strawberries were dipped in the CH-GA solution and allowed to dry. The coated strawberries were exposed to UV-A with appropriate, unexposed controls also being used for comparison. Previous studies have indicated that the coating can exhibit moderate antimicrobial activity when irradiated with UV-A at 360nm. A 180-minute exposure reduced Escherichia coli (E. coli) O157:H7 on CH-GA coated strawberries by ~2-3-log CFU/mL. However, when the quality parameters were evaluated, it was found that the UV irradiated strawberries may have been initially affected with respect to color and texture, but the loss in quality slowed down over a 14-day refrigerated storage period. It was also seen that no significant differences were observed in color and firmness between the control and experimental groups on day 14. The third study (appendix 1) aims to evaluate UV-C radiation's efficacy on the inactivation of Listeria monocytogenes (L. monocytogenes) on apple surfaces. This study was performed within the broader aim of evaluating the effects of UV-A, UV-B, and UV-C and their combinations on the quality and safety of Honeycrisp apples. UV-C radiation can serve as an antimicrobial agent, while UV-A and UV-B radiations can affect the quality parameters such as color through the hormetic effect. Therefore, our goal was to identify optimum UV-A, UV-B, and UV-C radiation doses that can be applied to Honeycrisp apples to improve their coloration and microbial safety as the marketability of apples often depends on the redness of the fruit. The UV-C dose of 7.5 kJ/m2 resulted in a 1.2±0.06 log CFU/sample inactivation of L. monocytogenes on the apple surface. Interestingly, the additional UV-C dose exposure did not result in additional inactivation. This observed lack of dose-dependence could be the result of a) UV-C penetration interference from previously inactivated microbial cells resulting in a shadowing effect, b) the formation of a biofilm during ambient air drying and 4°C incubation that provided some protection during treatment, or c) higher resistance of L. monocytogenes sub-population against UV-C inactivation. This data will allow for future exploration of a synergistic treatment that can improve the color and appearance of Honeycrisp apples and improve their safety at the same time. UV radiation has shown promising antimicrobial activity and, through the studies carried out in this project, demonstrated potential beneficial or deleterious effects on food quality. The results from the first study showed the significance of understanding the interaction of food ingredients with UV radiation. The strawberry and apple studies show that UV radiation, when used at the correct dosage, can increase, or maintain the visual appearance of the fruits, making them more marketable. When used at the correct wavelength and for the appropriate duration, UV radiation can mitigate the prevalence of foodborne pathogens and contribute to food products' quality and shelf life.
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    (2022) Mendez, Izabelle; Sahyoun, Nadine; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The Expanded Food Security Screener (FSS-Exp) is a screening tool for determining food insecurity risk based on individuals’ physical, economic, and social access to food. The FSS-Exp is the only tool that provides a simple and quick method for identifying which home-delivered meal (HDM) applicants are most vulnerable. However, further testing is required to determine the tool’s validity when compared with health and food-related measures associated with food security. Therefore, this study aimed to validate the FSS-Exp and HDM prioritization tool using concurrent and construct validity methods. To evaluate the concurrent validity, we examined the correlations between the FSS-Exp and other health and food-related tools such as SF-36, MOS-SSS, SWFL, SNAQ, and DST, which were associated with economic food insecurity and physical limitation To determine construct validity using the known-groups approach, we compared those health and food-related scores among participants grouped by different access barriers to food (priority levels). The results showed that the FSS-Exp correlated moderately (r=0.20 to 0.33) with other “gold standard” measures: SF-36, MOS-SSS, and SWFL. Furthermore, our results showed that individuals categorized as priority level A and B had significantly lower mean scores than priority level E for the SF-36 (HRQL) summary measures (p<0.05), SWFL (p<0.05), and the tangible social support ( p<0.01). Thus, the FSS-Exp was shown to be a valid measure in identifying and prioritizing older adults with physical and/or economic access to food, which is especially important for HDM programs with limited resources experiencing increased demand for services. For HDM programs which exist to serve vulnerable older adults, using the validated FSS-Exp tool can help identify those who are most vulnerable and in need of immediate service.
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    Enhancement of thermal processing with food-grade antimicrobial compounds in low-moisture food matrix to improve food safety
    (2022) Ding, Qiao; Tikekar, Rohan V; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Heat resistant foodborne pathogens have been a concern in low-moisture foods and ingredients (LMFs). Increased thermal resistance of pathogens such as Escherichia coli O157:H7 and Salmonella Typhimurium at low water activity (aw) reduces the efficiency of thermal treatment in LMFs. Alternative methods are therefore needed to augment thermal processing and reduce food safety risk. This study investigated the enhancement of thermal treatment efficiency against pathogenic bacteria in LMF matrices at different aw by inclusion of food-grade antimicrobial compounds. Based on their similar target sites in cells, it is hypothesized that antimicrobial compounds may work synergistically with heat treatment in LMF matrices. The treatment effect may be dependent on both aw and matrix compositions. Physiological and transcriptional changes may take place within cells adapted to different environments and contribute to the varied bacterial resistance. A combination of Butylparaben (BP), a known antimicrobial and thermal treatment was tested to enhance inactivation rates of S. Typhimurium and E. coli O157:H7 in meat and bone meal (MBM) equilibrated to water activity (aw) of 0.4 and 0.7. Presence of BP significantly accelerated thermal inactivation of E. coli O157:H7 in MBM at both 0.4 and 0.7 aw. However, inactivation rate of S. Typhimurium was not affected by the combined treatment at either 0.4 or 0.7 aw. BP accelerated the inactivation of the thermal-resistant subpopulation in E. coli O157:H7 but not S. Typhimurium. Therefore, further studies were conducted to identify alternative antimicrobial compounds to enhance thermal treatment against S. Typhimurium in LMF matrices and investigate the resistance mechanisms. Trans-cinnamaldehyde (CA) and eugenol (EG) were selected from a screening study to assist thermal treatment against S. Typhimurium adapted to different aw in whey protein (WP), corn starch (CS) or peanut oil (PO). Although addition of CA or EG significantly accelerated thermal inactivation of S. Typhimurium in water and LMF components at 0.9 aw, similar effect was not observed in bacteria adapted to lower (0.4) aw in any of those matrices. The matrix effect on bacterial thermal resistance was observed at 0.9 aw and were ranked as WP > PO > CS. The combined heat treatments reduced bacterial metabolic activity, which was partially dependent on the food components as well. S. Typhimurium had lower membrane fluidity because of membrane fatty acid composition change when adapted to a lower aw, which contributed to resistance against the combined heat treatments. Based on the aw- and matrix- dependent bacterial resistance and physiological changes observed in the two previous studies, transcriptional analysis was conducted to further understand the molecular mechanism behind the bacterial resistance. Expression of nine stress-related genes in S. Typhimurium adapted to different aw in LMF components were analyzed with or without the CA-assisted heat treatment. The upregulation of rpoH and dnaK in S. Typhimurium was induced by the stress during bacterial adaptation to the low aw environments as well as the combined heat treatment, which contributed to the bacterial resistance to both desiccation and the combined treatment. Although its link to the desiccation response in bacteria is not fully understood, the downregulation of ompC during the combined treatment also partially contributed to the treatment resistance. The upregulation of rpoE, otsB, proV and fadA in S. Typhimurium was induced by the desiccation stress during incubation at the low aw environment but was not a major contributor to the resistance during the combined treatment. The observed upregulation of fabA and downregulation of ibpA could not be directly linked to either bacterial resistance to desiccation or the combined heat treatment. Differential expressions were also observed among different aw levels or in different matrices at the same aw. The inconsistencies between the expression profiles of dnaK and ompC and bacterial resistance during the combined treatment suggested the presence of additional stress-response pathways.In conclusion, the results have demonstrated the potential of using food-grade antimicrobial compounds to complement thermal treatment in LMF during processes that start with a relatively high aw (such as dehydration). However, their effectiveness may subside at low aw environments. Future works should focus on optimizing the parameters of the CA/ EG-assisted heat treatment for higher efficiency, studying the molecular mechanism behind the bacterial resistance at global scale, and exploring alternative non-thermal processing technologies to enhance thermal treatment efficiency in LMFs without raising thermal treatment intensity.
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    Determinants of Food Insecurity in the League of Arab States
    (2022) Sheikomar, Olfat Bakur; Sahyoun, Nadine R; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Background Food insecurity (FI) is widespread in the League of Arab States (LAS) due to factors including gender inequality, conflict, and political turmoil. However, limited data are available on its prevalence and determinants in that region. This dissertation aims to 1) validate the Food Insecurity Experience Scale (FIES), developed by the UN Food and Agriculture Organization, and assess the prevalence of FI in that region; 2) examine the association between FI, physical health, and mental well-being by sex and whether social support modifies this association in women; 3) examine the relationship between Palestinian live-in grandparents (GP) and the health and well-being of their grandchildren.Methods Rasch modeling was applied to the Gallup World Poll data to validate FIES in 19 countries of the region. Descriptive and logistic regression analyses were applied to data from 62,261 respondents aged 19 and over to examine determinants of FI. Logistic regression was also used to analyze the data of 2707 households and 8,034 children ages 0-17 from two surveys of Palestinian refugees. Results FIES met the Rasch assumptions indicating good internal validity. The prevalence of severe FI was 15.7% and women were at highest risk compared to men (17.6% vs. 14.1%, respectively, p<0.0001). Older age, living in rural areas, and high dependency ratio were associated with severe FI in women. High negative experience and low income were associated with severe FI, but good physical health and high positive experience with lower prevalence of severe FI. Having a live-in GP in the household was associated with grandchildren’s lower odds of experiencing an acute disease and higher odds of attending school. Conclusion FIES is a valid tool; however, cognitive testing of some items and omission of correlated ones may improve the scale. FI is highly prevalent and should be monitored to develop multi-sectoral intervention strategies. Mixed method studies are needed to better understand the relationship between grandparents and their grandchildren.
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    (2022) ma, peihua; Wang, Qin Q. W.; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Metal-organic frameworks (MOFs), a type of cutting-edge designable porous scaffolding materials attracted attention in reticular chemistry, which satisfied fundamental demands for delivery research in the past years. In this research, UiO-66 MOF family with different modifications was applied in the food delivery system and freshness monitoring.First, zirconium (IV) chloride and benzene-1,4-dicarboxylic acid were used to make the Zr-based MOF UiO-66. Then, using a post-synthesis loading process, curcumin was encapsulated in it. The system attained a high loading capacity of 3.45 percent w/w, according to both spectroscopic and thermogravimetric measurements. X-ray diffraction (XRD), physisorption analyzer, scanning electron microscopy (SEM), and energy-dispersive X-ray spectrometer (EDS) were used to characterize the crystal structure, porosity, and morphology of the curcumin delivery system, respectively. Curcumin was shown to be released in a controlled manner in simulated intestinal fluids using an in vitro digestion test. After 180 minutes of digestion, almost 60% of the curcumin was released. Second, two types of curcumin-loaded UiO-66 (representative high biocompatibility and water-stable metal-organic framework) deliver systems, curcumin-loaded UiO-66 Pickering emulsion and curcumin loaded UiO-66 high internal-phase Pickering emulsions (HIPPE) were prepared, named curcmin@UiO-66 PE and curcumin@UiO-66 HIPPE, respectively. The loading capacity for the two delivery systems was reached 7.33, and 26.18% w/w respectively. All systems were characterized using X-ray diffraction (XRD), physisorption analyzer, scanning electron microscopy (SEM), and energy-dispersive X-ray spectrometer (EDS), for crystallography, morphology, physicochemical properties, with computer assistant optimization with DFT and GCMC simulation for maximum loading capacity. The result showed that these systems both exhibited extremely high surface area and porosity, as well as strong chemical and thermal stability, which demonstrated their great potential for application as a food delivery system. On this basis, the emulsion system was further optimized using the response surface method. These novel MOF nanoparticle stabilized delivery systems could be practically utilized for other bioactive components and antimicrobial agents, which would find applications in functional food, food safety, and biomedical areas in the future. Third, incorporating or positioning multi-functional MOFs into the smart package is one of the next steps toward reticular chemistry for commercial application. Here, a cheap and versatile method to incorporate MOFs into smart food packages via generic patterning was developed. Meanwhile, deep convolutional neural networks (DCNN) were combined to form a system for monitoring food freshness that provided scent fingerprint recognition. The ice-template-based UiO-66-Br/chitosan sensor array and MOF-MMM-based UiO-66-OH/PVA sensor array comprising 6 different dyes absorbed at MOF matrix formed scent fingerprints that were identifiable by DCNN. Several state-of-art DCNN models were trained for shrimp freshness monitoring by using 31584 labeled images and 13537 images for testing. The highest accuracy achieved was up to 99.94% by the Wide-Slice Residual Network 50 (WISeR50). MOF-MMM-based sensor array showed a similar result where chicken freshness estimation achieved up to 98.95%. These platforms are intuitive, fast, accurate, and non-destructive, enabling consumers to monitor food freshness.
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    (2021) ZHANG, ZHI; Yu, Liangli; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This thesis research was designed to evaluate the effects of maturity stages, cooking methods, and growing conditions on the phytochemical profile and antioxidant ability of Brassica vegetables. First, kale was used as a model vegetable species to evaluate the influence of maturity stages including microgreen, baby green, and mature vegetables. In the second study, mature kale was used to examine the effects of cooking methods on availability of the selected bioactive factors and the antioxidant properties. In addition, the effects of growing conditions on the health beneficial factors were evaluated using kale, broccoli, and red cabbage microgreens. The two growing conditions were chamber and windowsill, reflecting a commercial and a home growing condition. All of the testing vegetable samples were extracted with 70% methanol and evaluated for their phytochemical compositions, total phenolic contents, ABTS• scavenging capacities, and total dietary fiber. Five, twenty-three, twenty-six, and twenty-three polyphenols were tentatively identified in the kale microgreen, baby kale, mature kale harvested at 56th day, and mature kale harvested at 87th day using a HPLC-MS/MS method, with trisinapoyl-diglucoside, quercetin-3-sinapoly-diglucoside-7diglucoside, feruloyl-glucoside, and disinapoyl-diglucoside being the primary components in each, respectively. The aliphatic glucosinolates including sinigrin and glucoraphanin were predominant in the kale, broccoli, and red cabbage microgreens grown under both chamber and windowsill conditions. In addition, microwaved mature kale had a greater level of phytochemicals than that boiled. It was noted that the baby kale extract possessed the greatest ABTS• scavenging capacity. The results of this thesis may be used to improve vegetable consumption.
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    Development of machine learning and advanced data analytical techniques to incorporate genomic data in predictive modeling for Salmonella enterica
    (2021) Karanth, Shraddha; Pradhan, Abani K; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The past few decades have seen a renaissance in the field of food safety, with the increasing usage of genomic data (e.g., whole genome sequencing (WGS)) in determining the cause of microbial foodborne illness, particularly for multi-serovar agents such as Salmonella enterica. However, utilizing such data in a preventative framework, specifically in the field of quantitative microbial risk assessment (QMRA) remains in its infancy, because incorporating such large-scale datasets in statistical models is hindered by the sheer number of variables/features introduced. Thus, the goal of this research is to introduce machine learning (ML)-based approaches to potentially incorporate WGS data in various stages of a risk assessment for Salmonella enterica. Specifically, we developed a machine learning-based workflow to obtain an association between gene presence/absence data from microbial whole genome sequences and severity of Salmonella-related health outcomes in host systems. A key contribution of this dissertation is assessing the applicability of Elastic Net model, a recursive feature selection technique, which resolves a well-known issue concerning WGS-based data analysis: variables/features outnumber the count of observations. Building on this finding, we developed a gene weighted Poisson regression method to incorporate genes into a dose-response framework for Salmonella enterica, thereby incorporating genetic variability directly into a risk assessment framework. Finally, we combined machine learning with count-based models to determine how significant genes interact with meteorological factors in impacting the severity of salmonellosis outbreaks. This dissertation uncovers some interesting findings. First, although commonly used classifiers (such as random forest) performed well in predicting disease severity, logistic regression, in conjunction with Elastic Net, performed significantly better. This finding is important, as the result of a logistic regression is generally more interpretable than that of other classifiers, easing its incorporation into predictive microbial modeling. Next, machine learning-supported count-based models, such as Poisson regression also proved to be a good fit for gene-informed dose-response modeling and determination of outbreak severity when combined with extrinsic factors such as atmospheric temperature and precipitation. Overall, this dissertation identified areas within a QMRA framework that could benefit from incorporating genetic information, and introduced ML models to incorporate such information.
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    Role of Transient Receptor Potential Vanilloid 4 (TRPV4) Calcium-permeable Channels in Fibro-inflammatory Diseases
    (2021) Goswami, Rishov; Rahaman, Shaik O.; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Tissue fibrosis and foreign body response (FBR) have emerged as two major public health problems globally over the last few decades. While fibrosis is an outcome of a dysregulated wound healing process, FBR, a chronic inflammatory disease, develops when the body responds and reacts to the implantation of biological materials. Interestingly, recent studies have associated these non-specific inflammatory diseases with altering stiffness although the exact underlying mechanisms by which mechanical cues can regulate the diseases remain poorly understood. The objective of this thesis work is to determine how the changing of tissue stiffness and implant rigidity mediates disease progression of fibrosis and FBR respectively. Here we identify a novel role of a polymodal mechanosensitive calcium channel, Transient Receptor Potential Vanilloid 4 (TRPV4), as a potential cell membrane receptor/channel in the pathophysiology of FBR and skin fibrosis associated with Scleroderma, a multisystem idiopathic fibro-inflammatory connective tissue disorder. Our results showed that TRPV4 is over expressed in fibrotic skin tissue and colocalize with alpha-smooth muscle actin (a-SMA), a common myofibroblast marker. Using mouse model, we demonstrated that TRPV4 knockout mice are protected from bleomycin-induced skin fibrosis development. Additionally, in a separate mouse model, we showed that genetic ablation of the TRPV4 channel protects mice from implantation-induced macrophage foreign body giant cell (FBGC) formation, macrophage accumulation, and FBR development to biomaterials. The results of our studies also determined an essential role of TRPV4 for macrophage fusion and the mechanism by which TRPV4 and matrix stiffness leads to cytoskeletal remodeling through a feed-forward functional interaction generating cellular force to modulate FBGC formation. We also identified a mechanosensing domain of TRPV4 which is crucial for FBGC generation. Altogether, the results presented in this thesis suggest TRPV4 as a potential regulator of stiffness-dependent fibrosis and inflammation development, and multinucleated FBGC formation. The results of this thesis work proposes that interaction between TRPV4 and substrate stiffness leads to cytoskeletal remodeling and cellular force generation to modulate FBGC formation under FBR. Overall, the work presented in this thesis provides a better understanding about the role of mechanosensitive calcium channel TRPV4 in the regulation of fibro-inflammatory diseases and highlights the possibilities of therapeutically targeting of this channel for disease management.
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    Seasonal Variation in Goat's Milk Composition and Its Effect on Cheese Quality
    (2021) Wimsatt, Stratton Thomas; Tikekar, Rohan V; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The composition of goat cheese was evaluated over a 12-month period to evaluate the influence of seasonal variation in goats’ milk composition on variation in yield and composition of cheeses. Milk analysis included total fat, nonfat solids, and total protein. Yield was significantly correlated with milk composition. Cheese analysis included moisture content, water activity, crude lipid content, and ash content. Goat’s milk was found to have significant variation in all parameters between seasons, with peak content in winter months. Significant differences were found in the compositions of cheeses, although not all followed the seasonal trends observed in milk. Correlations between milk and cheese compositions were evaluated but not found to be significant. Finally, an in-house environmental monitoring plan for Listeria spp. was evaluated using Hygiena® swabs. The in-house method was accurate in 78% of samples with no instances of false negatives.
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    Food Insecurity, Service Awareness, Social Factors, and Quality of Life in Community-Dwelling Older Adults
    (2021) Vaudin, Anna Margaret; Sahyoun, Nadine R; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Older adults are at risk for food insecurity due to financial constraints, physical difficulties, social isolation, and the resulting limitations on food access. Social isolation has two components – objective, such as social contacts, and subjective, such as loneliness – and each may have a unique relationship with food insecurity. Unmet needs exist for services that aim to improve food access in older adults, and research is limited on how those who do use the services find out about them. Additionally, these services aim to improve quality of life (QOL), and yet this impact cannot be quantified because current tools do not capture the ways food affect QOL beyond nutritional status. This dissertation uses qualitative methods to understand (1) how food and eating impact QOL in community-dwelling older adults, (2) how individuals become aware of the services they use to address barriers to food and eating, and (3) the interaction between food security, loneliness, and QOL. In-depth interviews were conducted with 25 urban- and suburban-dwelling older adults. Interview scripts were transcribed and themes identified in the data using grounded theory methods. The first study showed that health and vitality, independence, mental and emotional well-being, socialization and support, and activities, both inside and outside the home, affected participants’ QOL. Food and eating affected QOL through access and choice, health and vitality, enjoyment of food, and food preparation. The second study showed that participants primarily found out about the resources they use through encounters in their daily lives, rather than service outreach. The final study showed that, compared with those who were food secure, those who were food insecure were more likely to report a negative effect of loneliness on their QOL, primarily experienced as depressive symptoms. This dissertation shows that food and eating affect older adults through not only the physiological effects of good nutrition, but also through social, psychological, and sensory effects on QOL. Additionally, the results point to the importance of social factors for both service awareness and mental health in those who face barriers to food and eating. Future studies and new tools are needed to quantify these impacts.
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    Identification and functional analysis of a biflavone as a novel inhibitor of TRPV4-dependent atherogenic process in macrophages
    (2021) Alharbi, Mazen Obaid; Rahaman, Shaik O.; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Cardiovascular disease is the major cause of death throughout the world. Atherosclerosis, a chronic inflammatory disease of large arteries, is the major contributor to the growing burden of cardiovascular disease-related mortality and morbidity throughout the world. During early atherogenesis, as a result of inflammation and endothelial dysfunction, monocytes transmigrate into the aortic intimal areas, and differentiate into lipid-laden macrophage foam cells, a critical process in atherosclerosis. Numerous natural compounds such as flavonoids and polyphenols are known to have anti-inflammatory and anti-atherogenic properties. Transient receptor potential vanilloid 4 (TRPV4), a non-selective Ca2+-permeant ion channel and a mechanosensor, is widely expressed in diverse cell types including macrophages. Accumulating reports from our laboratory and others on TRPV4 recognized this plasma membrane receptor/channel as an essential modulator of various physiological functions in cardiac, pulmonary, urinary, skeletal, digestive system, and central and peripheral nervous systems. Thus, it is expected that aberrant regulation of TRPV4 activity may lead to multiple pathological conditions such as cardiovascular disease, pulmonary disease, inflammation, neurological disorders, inflammatory bowel disease and wound healing. Previous studies by our group and others have reported that TRPV4 can be activated by numerous mechanical and biochemical stimuli including shear stress, osmolarity, temperature, and growth factors, as well as by alterations in matrix stiffness in vitro and in vivo. Recently, we reported that oxidized low-density lipoprotein-mediated and matrix stiffness-induced macrophage foam cell formation, a critical pathological process in atherosclerosis, is regulated in a TRPV4-dependent manner. Given that TRPV4 is a mechanosensitive channels and mechanical factors like hypertension, disrupted laminar flow of blood, and matrix stiffening are recognized pro-atherogenic factors, makes TRPV4 an important target for therapeutic intervention of atherosclerosis. The objectives of this proposal is to: i) identify natural inhibitor (s) of TRPV4 utilizing a fluorometric imaging plate reader-supported Ca2+ influx assay, ii) functionally characterize the identified compound, and iii) determine the mechanisms by which the identified compound blocks pro-atherogenic/inflammatory TRPV4 activity in macrophages. We expect that the results of this study may strengthen the rationale for the use of natural compounds for developing therapeutic and/or chemopreventive molecules.