Life Sciences Commons^™

Switchgrass Extractives Have Potential As A Value-Added Antimicrobial Against Plant Pathogens And Foodborne Pathogens, Alexander Ian Bruce

Masters Theses

Panicum virgatum (switchgrass), a perennial grass native to North America, is a leading biomass feedstock candidate for the manufacture of cellulosic ethanol. Switchgrass is considered a viable option for biofuel production due to its cheap production cost and ability to grow on marginal land. Biofuel derived from switchgrass has been shown to be very energy efficient, producing 540% more renewable energy versus nonrenewable energy expended. Switchgrass-derived biofuel is also estimated to have greenhouse gas emissions that are 94% lower than emissions from gasoline (Schmer et al 2008). Biofuels are created through biochemical processes that utilize various enzymes and microorganisms for …

Encapsulation Of Probiotic Microorganisms In Food-Grade Hydrogel Microbeads For Improving Long-Term Storage And Oral Delivery, Timothy W. Yeung

Masters Theses

Probiotics die over time during processing, storage and digestion, resulting in reduced health benefits to the consumer. Microencapsulation of microorganisms is an effective way to improve probiotic viability by restricting cell exposure to extreme conditions through the gastrointestinal tract until release in the colon. In this work, appearance and survival of encapsulated probiotic species from two genera was explored. Lactococcus lactis and Bifidobacterium longum were suspended in calcium alginate microbeads by spraying droplets of alginate-probiotic mixture into calcium chloride solution. This produced uniformly shaped transparent microbeads with high encapsulation yield. Encapsulating Lactococcus lactis extended viability during dry room temperature storage. …

Investigate The Interactions Between Silver Nanoparticles And Spinach Leaf By Surface Enhanced Raman Spectroscopic Mapping, Zhiyun Zhang

Masters Theses

Owing to their increasing application and potential toxicity, engineered nanoparticles (ENPs) have been considered as a potential agricultural contaminant that may pose unknown risk to human beings. However, many techniques require invasive and complicated sample preparation procedures to detect and characterize engineered nanomaterials in complex matrices. In the first part of this thesis, we present a non-destructive and label-free approach based on surface enhanced Raman spectroscopic (SERS) mapping technique to qualitatively detect and characterize gold nanoparticles (AuNPs), on and in spinach leaves in situ. We were able to detect the clearly enhanced signals from AuNPs at 15 to 125 nm …

Utilizing Nutritive Sweeteners To Control Lipid Oxidation In Low Moisture Baked Goods, Samantha Vieira

Masters Theses

In this study, we determined the effect of nutritive sweeteners at 0 to 0.50 moles/kg on lipid oxidation in a model cookie system. Confocal microscopy using Bodipy 493 as a fat soluble dye showed that the fat formed a continuous phase surrounding the starch granules regardless of sugar type. The impact of glucose concentration on lipid oxidation was monitored by lipid hydroperoxides and headspace hexanal during storage at 55°C. Low concentrations of glucose (0.09) were strong inhibitors. At equal molar concentrations, reducing sugars (glucose and fructose) inhibited lipid oxidation, greater than a two months increase in lag phase compared to …

Distribution Of Enterotoxigenic Clostridium Perfringens Spores In U.S. Retail Spices, Chi-An Lee

Masters Theses

246 samples of bulk and packaged spices from retail stores in the western, southeastern, southern, midwestern, and northeastern areas of the U.S. were examined for the presence of Clostridium -perfringens. Isolates were checked for the presence of the lecithinase gene (cpa) and enterotoxin genes (cpe) by PCR. Enterotoxin formation during sporulation was investigated using the Oxoid Toxin Detection Kit. Forty-three confirmed isolates (from 17% of total samples) were cpa-positive. Of those, 27 were cpe-positive. Together, levels of C. perfringens spores ranged from 3.6-2400/gm. The amount of enterotoxin in cell extracts ranged from …

Identification Of Potential Bacterial Surrogates For Validation Of Thermal Inactivation Processes Of Hepatitis A Virus, Marcel Schmidt

Masters Theses

Thermal treatment is a method for inactivating pathogens in a wide range of food products. Recent studies have shown that hepatitis A virus (HAV) has a D_72°C [D72 degree celcius] of 0.9 min in buffer which is greater than vegetative bacterial pathogens. Common surrogates, such as Listeria innocua, are not resistant enough to be used as surrogates for HAV, thus, new surrogates need to be identified. The purpose of this study was to compare the thermal inactivation kinetics (D- and z-values) of Staphylococcus carnosus in different foods and different incubation temperatures to identify a potential surrogate for HAV. …

Combinations Of Multiple Natural Antimicrobials With Different Mechanisms As An Approach To Control Listeria Monocytogenes, Savannah Grace Hawkins

Masters Theses

To improve food safety and shelflife requires the use of preservation processes, such as physical (heat, refrigeration) or chemical (antimicrobial addition) processes. Regulatory approved synthetic food antimicrobials (preservatives) have some uses but are very limited in their spectrum of activity. Thus, alternatives are needed to conventional chemical antimicrobials. One method is to use naturally occurring antimicrobials, especially those found in spices and herbs, essential oils (EO) and essential oil components (EOC). EOs have been shown to have antimicrobial activity but the activity is highly variable. Finding a combination of EOs, EOCs, or other natural antimicrobials that act synergistically would allow …

Curcumin And Its Oxidative Degradation Products: Their Comparative Effects On Inflammation, Julia Zhu

Masters Theses

The anti-inflammatory agent curcumin degrades rapidly, leading to speculations that curcumin’s reported effects stem from its degradation products. Curcumin can degrade via hydrolysis, and more recently it was discovered that curcumin can degrade via oxidation at physiological pH. Additionally, bicyclopentadione is the major degradation product from this oxidation reaction. Evidence from the literature suggests that curcumin degrades primarily through oxidation. However, the biology of the oxidation products is not well characterized, and there is debate on whether oxidation intermediates or curcumin itself is more biologically active. To further elucidate the biology of the oxidation products, their effects on inflammation were …

Enzymatic Digestion Improved Bacteria Separation From Leafy Green Vegetables, Danhui Wang

Masters Theses

An effective and rapid method for the separation of bacteria from food matrix remains a bottleneck for rapid bacteria detection for food safety. Bacteria can strongly attach to the food surface or internalize within the matrix which makes their isolation extremely difficult. Traditional methods of separating bacteria from foods routinely involve stomaching, blending and shaking, however these methods may not be efficient at removing all the bacteria from complex matrices. Here, we investigate the benefits of using enzyme digestion followed by immunomagnetic separation to isolate Salmonella from spinach and lettuce. Enzymatic digestion using pectinase and cellulase was able to break …

Influence Of Hierarchical Interfacial Assembly On Lipase Stability And Performance In Deep Eutectic Solvent, Stephanie M. Andler

Masters Theses

Hierarchical systems that integrate nano- and macroscale structural elements can offer enhanced stability over traditional immobilization methods. Microparticles were synthesized using interfacial assembly of lipase with (CLMP-N) and without (CLMP) nanoparticles into a crosslinked polymeric core, to determine the impact of the highly ordered system on lipase stability in extreme environments. Kinetic analysis revealed the macrostructure significantly increases the turnover rate (k_cat) following immobilization. The macrostructure also stabilized lipase at neutral and basic pH values, while the nanoparticles influenced stability under acidic pH conditions. A greener solvent, choline chloride and urea, was applied to produce sugar ester …

Chemical Stability Of Curcumin: Structure And Activity Relationship (Sar) Study, Zheyuan Du

Masters Theses

Over the past decades, numerous studies have shown that curcumin has potent biological activities. As a potential chemopreventing agent, curcumin was demonstrated to exert anti-cancer effects in both in vitro and in vivo studies. However, low bioavailability of curcumin limited human clinical trials and its application to be formulated as therapeutics. In this thesis, we will summarize the anti-cancer effects of curcumin in animal studies and clinical trials. In addition, an SAR study will be introduced to elucidate the mechanism of curcumin degradation at physiological pH. We synthesized various curcumin analogues and compared their stability in phosphate buffer using HPLC …

Odor-Induced Taste Modifications In Teas, Rachel Elizabeth Isaacs

Masters Theses

Although odorants and tastants are perceived by two different sensory modalities, the perceived taste qualities of a solution may be modified with the addition of an odorant. While many studies have investigated odor-induced taste modifications in model solutions, there is a lack of conducted research examining odor-induced taste modifications in complex food systems. The research objective was to determine the effect of added vapor-phase stimuli on the perceived sweetness of a model solution and complex food system.

Eight vapor-phase stimuli (i.e. blueberry, caramel, ginger, honey, lemon, orange, peach, and strawberry) were selected for investigation. The study was conducted in two …

The Food Industry’S Perception Of Economically Motivated Adulteration And Related Risk Factors, Lindsay Colleen Murphy

Masters Theses

The United States of America has numerous safeguards in place to protect our food supply, including federal regulations and the food and beverage industry’s dedication to food safety. One of the issues that the food and beverage industry continuously battles is the prevalence of intentional adulteration. The Food Safety Modernization Act (FSMA) specifically addresses intentional adulteration and its sub-category of economically motivated adulteration (EMA) by requiring all facilities that supply food to the US to assess the vulnerabilities within their operation in order to prevent events that could cause public harm. The purposes of this study are threefold: (1) to …

High Intensity Ultrasound Assisted Extraction Of Oak Compounds For Accelerated Aging Of Wines And Whiskies, Lindsay Elizabeth Rogerson

Masters Theses

Aging of wines and whiskies in oak barrels is a timely and expensive process which could be reduced by acceleration. The purpose of this study is to identify if the use of high intensity ultrasound (HIUS) assisted extraction as an alternative, accelerated aging method could be utilized in the production of an oak extract to be used in wine and whiskies. HIUS will also be compared to reflux and room-temperature control extraction treatments as other accelerated aging methods. Secondary objectives of this study were to compare the heat treatment of charred and toasted staves donated by an anonymous donor, their …

Echerichia Coli Biofilm Formation In Musca Domestica Crops, Lufan Wang

Masters Theses

The house fly, Musca domestica can transmit human pathogens including Escherichia coli O157:H7 through regurgitation of ingested bacteria from the crop which is a foregut organ of house fly and stores the excess ingested nutrients. Interactions between the ingested bacteria and the crop have a direct influence on bacteria persistence, survival and ultimately fly vector competence. In this research, in situ crop vessel assay was developed to investigate bacterial growth within fly crops up to 48 hours post-ingestion. Flies were fasted for 12 h prior to feeding E. coli O₁₅₇:H₇ pEGFP and then fed bacteria with red …

Influence Of Inoculum Preparation Upon Sensitivity Of Common Food Borne Pathogens To Emulsion Based Antimicrobials, Dillon Sd Murray

Masters Theses

Antimicrobial optimization procedures use the most resistant bacterial culture that could be present in the food to determine the levels of treatment needed to ensure safety. These procedures usually only focus on one method of preparing these inoculums for testing despite prior research showing that the preparation of the culture can influence how the culture reacts to a treatment. In this work, planktonic cells grown in a liquid media and sessile cells grown on a similar solid media were subjected to identical emulsion based antimicrobial systems. The cultures were monitored over time and their numbers periodically enumerated. Weibullian destruction models …

Fish Oil Nanoemulsions: Optimization Of Physical And Chemical Stability For Food System Applications, Rebecca M. Walker

Masters Theses

Emulsion-based delivery systems offer many potential benefits for incorporating omega-3 oils into foods and beverages. Nanoemulsions are emulsion-based delivery systems that are gaining popularity because of their ease of preparation, small particle size, relatively high stability, high bioavailability, and production of optically transparent emulsions. Fish oil (FO) nanoemulsions are potentially more susceptible to lipid oxidation because of their high degree of lipid unsaturation, high surface area of exposed lipids, and greater light penetration. In the first study, spontaneous emulsification, a low-energy method, was used to fabricate FO nanoemulsions. The influence of surfactant-to-oil-ratio (SOR) on particle size, turbidity, and physical stability …