College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item DEVELOPMENT OF ΒETA-LACTOGLOBULIN BASED PARTICLES AS COLLOIDAL STABILIZERS AND EVALUATION OF THEIR PERFORMANCE ON INTERFACES(2020) ZHANG, JINGLIN; Wang, Qin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Beta-lactoglobulin (Blg) is a major whey protein in bovine milk. The desirable functional properties of Blg make it a versatile material, which has been processed into various types of colloidal systems such as nanoparticles, microgels and emulsions. This dissertation first developed several stable colloidal systems using native Blg molecules or denatured Blg aggregates as stabilizers. The study then elucidated the stabilization mechanism by characterizing Blg microgels adsorption on the interface. Firstly, novel selenium nanoparticles were developed using Blg as a stabilizer. The synthesized Blg-selenium nanoparticles were stable at pH 2.5-3.5 and 6.5-8.5 at 4ºC for 30 days as a result of electrostatic repulsions. Furthermore, the cell toxicity of selenium nanoparticles was significantly lower than that of sodium selenite on both cancerous and non-cancerous cells, implying their potential uses as anti-cancer medicines. The second part of this study was to stabilize a novel water-in-water (W/W) emulsion system using self-assembled Blg microgels. The microstructure and stability of the W/W emulsion were investigated under different environmental conditions. Microgels accumulating at the liquid-liquid interface led to a stable emulsion at pH 3 to 5. When pH was increased above the pI of the microgels, the emulsion was destabilized because the microgels tended to stay in the continuous phase (i.e., dextran) rather than the interface. In addition to electrostatic interactions, interfacial tension and hydrophobic attraction between microgels and two polymer phases were investigated to better understand the driving force for particles’ accumulation at the interface. Lastly, we proposed a new method to study the interfacial properties of Blg microgel. Quartz crystal microbalance with dissipation (QCM-D) was employed to investigate adsorption behavior of Blg microgels on a hydrophobic solid surface, which was hypothesized to mimic the oil-water interface. Coupling with atomic force microscopy (AFM), QCM-D showed the ability to characterize the microgels adsorption efficiency and viscoelasticity of adsorbed layer on the solid surface. The application of QCM-D and AFM enabled us to generate insights into the fundamental behavior of soft particles at a solid-liquid interface.Item POTENTIAL LOW TOXICITY CROSSLINKER FOR PROTEIN-BASED NANOPARTICLES(2015) XU, RUOYANG; Wang, Qin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Crosslinking is an essential procedure for maintaining the integrity of protein-based nanoparticles, but the application of toxic crosslinkers is usually undesirable. In this study, a tyrosinase-aided crosslinking procedure was developed and compared to a conventional crosslinker (i.e. glutaraldehyde). Nanoparticles were firstly synthesized from sodium caseinate (SC) in both aqueous and alcoholic solvent systems. The particles were crosslinked by tyrosinase (alone or with added natural phenols) or glutaraldehyde and then examined for their integrity under simulated environmental stress, including pH variation and solvent evaporation. Under aqueous condition, SC nanoparticles were not crosslinked sufficiently by tyrosinase or phenols alone, despite the abundance of tyrosine residues in SC. Conversely, satisfying crosslinking was achieved by tyrosinase combined with two natural phenols (catechol or chlorogenic acid, both at 2.5 mol/mol protein), as evidenced by stable particle size and count rate under environmental stress. A higher dose of 7.5 mol/mol protein was required for glutaraldehyde to achieve a comparable efficacy. Upon introduction of alcohol, the efficacies for both glutaraldehyde and tyrosinase-phenol mixtures decreased, but glutaraldehyde required lower dose and exhibited more significant crosslinking for achieving same crosslinking efficiency. However, a considerable number of nanoparticles were detected by scanning electron microscopy with both crosslinkers. Overall, tyrosinase-aided oxidation is a competitive, low-toxicity approach for crosslinking protein nanoparticles.Item FOOD PROTEIN-BASED NANOPARTICLES AS BIOAVAILABILITY ENHANCING ENCAPSULANTS(2015) Teng, Zi; Wang, Qin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Proteins are attractive bioavailability enhancers for poorly absorbed nutraceuticals or drugs, owing to their natural abundance, amphiphilic nature, and desirable biocompatibility. This study systematically investigated the preparation, characterization, and application of protein-based nanoparticles as effective nutraceutical/drug carriers. Soy protein, one of the most widely utilized proteins, was firstly employed for preparing nanoparticles. The particle formation involved partial unfolding of protein molecules, limited aggregation in the presence of the antisolvent, crosslinking via chemical bonds, and refolding of the constituent monomers. Satisfactory encapsulation efficiency (EE) and time-dependent release of curcumin, a chemopreventive compound, were observed. The nanoparticles were further subjected to conjugation with folic acid, a cancer cell-targeting ligand. A pronounced increase in the accumulation in tumor cells such as Caco-2 was achieved upon folic acid conjugation, which demonstrated the potential of this technique for the targeted delivery of anti-cancer drugs. To overcome the rapid digestion of soy protein nanoparticles in the gastrointestinal tract, carboxymethyl chitosan was employed as a second coating layer by a simple ionic gelation method. The formed particles exhibited satisfactory EE for vitamin D3 and controlled releasing profile in vitro. Beta lactoglobulin (BLG) as another protein of interest is a major component of whey protein, serving as a natural carrier for lipophilic nutrients. Our study suggested that the interaction between BLG and curcumin could be promoted by tuning the antisolvent content. A loading capacity (LC) and EE of up to 11% and 98% respectively could be achieved under the optimal conditions. Moreover, nanoparticles prepared with cationic beta-lactoglobulin (CBLG) were able to transport most of the encapsulated drug intact through the gastrointestinal (GI) tract owing to its desirable particle integrity. Other advantages of CBLG-based systems included superior mucoadhesion, permeation across the small intestine epithelia, and cellular uptake. Finally, as CBLG molecules/nanoparticles absorbed the negatively charged serum proteins in the cell culturing medium, their surface properties, cytotoxicity, and cellular uptake were significantly altered. This series of studies not only demonstrated the efficiency and versatility of protein-based nanoparticles as bioavailability enhancers but also shed some light on the mechanisms for the encapsulation, transport, and delivery of nutraceuticals or drugs.Item COMBINED EFFECTS OF SUNLIGHT AND TITANIUM DIOXIDE NANOPARTICLES ON DIETARY ANTIOXIDANTS AND FOOD COLORS(2014) Li, Meng; Lo, Yangming M; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The breakthroughs in material science have enabled industrialized fabrication and production of nanomaterials. To date, nanoscale materials have been shown to exhibit improved functionalities, providing numerous novel applications. Titanium dioxide (TiO2) nanomaterials have been widely utilized in the food industry due to their unique properties under light. Upon light irradiation, TiO2 nanoparticles (NPs) generate highly active reactive oxygen species (ROS) therefore can be potentially used as light tunable antibacterial packaging materials. Moreover, it has also been reported that a considerable amounts of TiO2 NPs is found as an ingredient in food, cosmetics, personal care, and pharmaceutical products. With improved photoactivity, nano TiO2 generates higher amounts of ROS upon light irradiation that can result in oxidative damage. The present study investigates the combined effect of sunlight irradiation and TiO2 nanoparticles (NPs) on sensitive antioxidants and food colors. Upon simulated sunlight irradiation, TiO2 NPs weakened the radical scavenging ability of antioxidants by photocatalytic decomposition or surface adsorption. The decomposition of a widely used food azo dye FD&C Yellow No. 5 (tartrazine) by sunlight activated TiO2 NPs was also investigated. The mechanism is pH dependent, involving the depletion of two main ROS species, hydroxyl radical and singlet oxygen. Compared with the photocatalyst TiO2 sample P25, food-grade TiO2 NPs also showed strong ROS promoting ability and resulted in the degradation of selected synthetic dyes, including tartrazine, allura red and sunset yellow, as well as the semi-synthetic food color chlorophyllin sodium copper salt. Thus, TiO2 NPs should be used with caution when added to or used in contact with food ingredients that depend solely on the existing antioxidants and colors in the system. The ability of TiO2 to generate ROS was found to be phase-dependent. The rutile phase TiO2 generated the least amount of ROS when compared to anatase phase and did not lead to noticeable color degradation in the studied light irradiation period. Thus, when possible, rutile phase TiO2 should be used in food as it provides a more stable system compared to anatase and mixed phases. The results in this study provide clear insights on setting up proper protocols for evaluating and administrating nanosized TiO2 in food uses.Item Development of Encapsulation Systems from Zein and Metal-Organic Frameworks (MOFs) for Improved Functional Properties of Essential Oils(2013) Wu, Yunpeng; Wang, Qin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Essential oils (EOs), which are derived from plants, have antifungal, insecticidal and antimicrobial activities, but they are slightly soluble in water and impart to the water their odor and taste, which limit their applications in food area. Zein, a prolamin from corn, is able to form nanoparticles by liquid-liquid dispersion process. These nanoparticles are well dispersed in water and stable, which can be further applied to encapsulate functional materials that are insoluble in water. We have developed zein nanoparticles to encapsulate thymol and carvacrol in order to improve their solubility. The DLS (dynamic light scattering) and SEM (scanning electron microscopy) proved that zein nanoparticles encapsulated with EO were formed. The particles size was between 200~300nm before lyophilizing. 65-75% EOs have been encapsulated in the nano-sized particles. DPPH assay results proved good antioxidant property of the product. For the Ferric-ion spectrophotometric assay, hydroxyl free radicals had been cleared by 60~90% in overall. In the antimicrobial experiment, the nanoparticles encapsulating EOs reduced 0.8-1.8 log units of E. coli after 48h incubation. Furthermore, we have applied Metal-Organic Frameworks (MOFs) to encapsulate thymol. Metal-Organic Frameworks (MOFs) or porous coordination polymers (PCPs) is a new class of hybrid materials, which are formed by the self-assembly of metal-connecting points and polydentate bridging ligands. MOFs in this study was synthetized by Zinc nitrate hexahydrate and 2-aminoterephthalic acid in N, N-dimethylformamide (DMF). Thymol was then loaded inside the MOFs at the loading rate of 3.95%. The structure of porous crystal MOFs was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Inhibition to E. coli O157:H7 was measured both in TSB medium and on TSA agar. An E. coli O157:H7 reduction of 4.4 log CFU/mL have been achieved at a thymol to broth ratio of 0.04g/100g. An inhibition area of 223.73 mm2 was observed after 12h incubation. With the two methods (zein nano-particles and MOFs), EOs can be encapsulated and well dispersed in water solution. The enhanced antioxidant activity and antimicrobial ability of the encapsulated EOs promise their further applications in food industries.