Master of Science / Department of Chemistry / Christopher T. Culbertson / Chemists have been trying to relate the structure and composition of different cereal proteins to their physical properties to better inform their product use for more than 250 years now. Among these cereals, wheat is considered the most important due to its unique ability to form viscoelastic dough and retain gas during fermentation, the latter being important for bread making. This property is due to the endosperm part of wheat that contains proteins mostly gliadins and glutens. It is known that the composition and relative ratio of these proteins is determined by both the growing environment and genetics. Manipulation of the genetics allows one for control of only about 50% of the end use quality of the wheat and the rest is controlled by environment. Currently, the bread making quality of wheat is determined by baking test loaves of bread. This process is time consuming and wasteful. The main goal of this project was to create fingerprints of gliadin proteins for different wheat cultivars as a function of environmental conditions. This would then allow wheat kernels to be analyzed and assessed right after harvest to determine their appropriateness for making the various wheat products. Researchers have tried to create a catalogue of information for individual wheat cultivars by ‘fingerprinting’ the gliadins proteins in wheat using various analytical techniques including capillary electrophoresis (CE). CE offers advantages like high separation efficiency, and faster analysis. Further miniaturization of CE on microfluidic devices has enhanced the speed and efficiency of separation. Furthermore, it is possible to integrate multiple chemical analysis processes like sample preparation, separation and detection in a single microfluidics device. Microfluidic uses micron sized separation channels defined in a glass, quartz or polymer. This dissertation is focused on fabricating multilayer microfluidic devices from Poly(dimethylsiloxane) (PDMS) and using these devices to electrophoretically separate wheat gliadin proteins followed by detection using UV absorption in less than 5 min. PDMS is cheap, easy to fabricate and is optically transparent above ~230nm. Initial results of the UV absorbance detector developed for this device are presented.

Master of Science / Department of Food Science / Weiqun Wang / We previously selected a purple-fleshed sweetpotato p40 clone that has been shown to protect against colorectal cancer in a murine model. This study is to identify anthocyanins by using HPLC/MS-MS and assess the stability during various coking conditions. P40 possesses a high content of anthocyanins up to 13 mg/g dry matter. Total 12 acylated anthocyanins with caffeic, ferulic, and p-hydrobenzoic acid have been identified on either cyanidin or peonidin bases. The top three major anthocyanins are cyanidin 3-caffeoyl-p-hydroxybenzoyl sophoroside-5-glucoside, peonidin 3-caffeoyl sophoroside-5-glucoside, and cyanidin 3-(6'' -caffeoyl-6''-feruloylsophoroside)-5-glucoside, which account for an half of the total anthocyanin contents. Seven non-, mono-, or di-acylated cyanidin species and five mono- or di-acylated peonidin species contribute for 69% and 31% of total anthocyanins, respectively. Over 80% of total anthocyanins measured by acid hydrolysis were cyanidin derivatives. Therefore, as a cyanidin-predominated variety, p40 is unique when compared with other reported purple-fleshed sweetpotatoes that usually contain more peonidin than cyanidin. While baking does not impact overall contents of anthocyanins, steaming, high pressure cooking, microwaving, and frying significantly reduce 20% of total anthocyanin contents. Mono-acylated anthocyanins show a higher resistance against heat than di- and non-acylated. Among of which, cyaniding 3-p-hydroxybenzoylsophoroside-5-glucoside exhibits the best thermal stability. Better understanding of dietary anthocyanins and their stabilities may lead to the development of a functional anthocyanin-enriched sweetpotato product for health benefits.

Master of Science / Department of Grain Science and Industry / D.L. Wetzel / Chemical imaging enables displaying the distribution of different substances within a field of view based on their fundamental vibrational frequencies. Mid-IR bands are generally strong and feature direct correlation to chemical structure, while near IR spectra consist of overtones and combinations of mid-IR bands. Recently, mid-IR microspectroscopy has enabled determination of the relative substitution of hydroxyl groups with the modifying agent for individual waxy maize starch granules by using synchrotron source. The brightness and non-divergence of the synchrotron source and confocal masking enabled obtaining individual spectra with 5 [mu]m[superscript]2 masking and 1 [mu]m raster scanned steps. Each 1 [mu]m step results from the coaddition of hundreds of scans and lengthy data collection is required to produce data. The recent breakthrough at the Synchrotron Research Center uses a multi-beam synchrotron source combined with a focal plane array microspectrometer. This major improvement in localized detection of the modifying agent within single waxy maize starch granules is the increased efficiency of focal plane array detection and an effective spatial resolution of 0.54 [mu]m. Mixtures of granular solids represent an analytical challenge due to the range of heterogeneity and homogeneity within samples. Near IR imaging provides deeper sample penetration allowing for solid mixture analysis. However, the broad, overlapping bands present in the near IR necessitates statistical data treatment. This requires imaging specimens representative of the individual components to create spectral libraries for classification of each component. Partial least squares analysis then allows characterization and subsequent pixel analysis provides quantitative results. The primary break system for wheat milling was studied as it is key in releasing endosperm to be further ground into fine flour in subsequent processes. The mass balance of endosperm throughout individual unit processes was determined by obtaining flow rates of incoming and outgoing millstreams and calculating endosperm content through pixel identification. The feed milling industry requires the use of a tracer to determine adequate mixing and mix uniformity to limit the time and energy in processing. Near IR imaging allows individual components of a formula feed to serve as a self-tracer, eliminating the need of an inorganic tracer.

Doctor of Philosophy / Department of Chemistry / Jun Li / Developing new and rapid methods for pathogen detection with enhanced sensitivity and temporal resolution is critical for protecting general public health and implementing the food and water safety standards. In this research vertically aligned carbon nanofiber nanoelectrode arrays (VACNF NEAs) have been explored as a sample manipulation tool and coupled with fluorescence, surface enhanced Raman scattering (SERS) and impedance techniques for pathogen detection and identification. The key objective for employing a nanoelectrode array is that the nano-Dielectrophoresis (nano-DEP) at the tip of a carbon nanofiber (CNF) acts as a potential trap to capture pathogens. A microfluidic device was fabricated where nanofibers (~ 100 nm in diameter) were placed at the bottom of a fluidic channel to serve as a ‘point array’ while an indium tin oxide coated glass slide acted as a macroscale counter electrode. The electric field gradient was highly enhanced at the tips of the CNFs when an AC voltage was applied. The first study focused on the capture of the viral particles (Bacteriophage T4r) by employing a frequency of 10.0 kHz, a flow velocity of 0.73 mm/sec, and a voltage of 10.0 Vpp. A Lithenburg type of phenomenon was observed, that were drastically different from the isolated spots of bacteria captured on VACNF tips in previous study. At the lowest employed virus concentration (1 × 10[superscript]4 pfu/mL), a capture efficiency of 60% was observed with a fluorescence microscope. The motivation of the second study was to incorporate the SERS detection for specific pathogen identification. Gold-coated iron-oxide nanoovals labeled with Raman Tags (QSY 21), and antibodies that specifically bound with E.coli cells were utilized. The optimum capture was observed at a frequency of 100.0 kHz, a flow velocity of 0.40 mm/sec, and a voltage of 10.0 Vpp. The detection limit was ~210 CFU/mL for a portable Raman system with a capture time of 50 seconds. In the final study, a real-time impedance method was employed to detect Vaccinia virus (human virus) in the nano-DEP device at 1.0 kHz and 8.0 Vpp giving a detection limit of 2.51 × 10[superscript]3 pfu/mL.