Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 126-137). Also available on the Internet.

Thesis (Ph. D.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 3, 2007) Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed Aug. 29, 2007). Includes bibliographical references.

Use of electronic cigarettes (e-cigarettes) is rapidly growing around the world. E-cigarettes are commonly used as an alternative nicotine delivery system, and have been advocated as generating lower levels of harmful chemicals compared to conventional cigarettes. Cigarette smoke-like aerosols are generated when e-cigarettes heat e-liquids. The main components of e-cigarette liquids are propylene glycol (PG) and glycerol (GL) in a varying ratio, plus nicotine and flavor chemicals. Both PG and GL are considered safe to ingest in foods and beverages, but the toxicity of these chemicals in aerosols is unknown. Current studies of e-cigarettes have mainly focused on dehydration and oxidation products of PG and GL. In this study, the other degradation products that can be generated during the vaping process are discussed. In addition, the gas/particle partitioning of chemicals in vaping aerosols is determined. This work finds that the formation of benzene in electronic cigarettes depends on the wattage, types of coils, and devices. To simulate commerical e-cigarette liquids, mixtures containing equal parts of PG and GL by volume were made with the following added components: benzoic acid (BA), benzoic acid with nicotine (Nic), benzaldehyde (BZ), band enzaldehyde with nicotine. PG only, GL only, and PG and GL mixtures were also made for comparison. The data presented here demonstrate that more benzene is generated as the wattage of a device increases. The results also seem to support the importance of ventilation in the generation of benzene. More benzene is generated from the mixtures containing benzoic acid when using the EVOD device with a smaller vent. However, benzaldehyde yields more benzene when using the Subtank Nano device with a larger vent. Findings also indicate that more benzene is produced from GL rather than PG. This thesis also addresses the chemical formation pathways of degradation compounds found in the aerosols formed from isotopically labeled e-cigarette liquids. Mixtures of both 13C-labeled and unlabeled PG as well as GL were made. The mixtures were vaped and gas-phase samples were collected to determine which chemicals were in the gas-phase portion of the aerosols. With the use of GC/MS methods, these isotopic labeling experiments provided evidence that the majority of the benzene, acetaldehyde, 2,3-butanedione, toluene, xylene, acrolein, and furan found in e-cigarette aerosols originates from GL in the PG plus GL mixtures. It was also shown that the majority of propanal is derived from PG: while hydroxyacetone can be formed from both PG and GL. Possible mechanisms for the formation of acetaldehyde, benzene, 2,3-butanedione, toluene, and xylene formation are proposed. Last, this study investigated the gas/particle partitioning of nicotine and flavor-related chemicals in e-cigarette fluids. The gas/particle partitioning behavior of chemicals in e-cigarettes fluids is highly dependent on the chemical volatility. A total of 37 compounds were examined. The target compounds were divided into 3 groups based on their vapor pressures: high, medium, and low. Headspace gas samples were collected and analyzed to determine the concentration of a compound in equilibrium with the liquid phase. The gas and liquid concentrations were used to calculate the gas/particle partitioning constant (Kp) for each compound. In an e-cigarette aerosol, volatile compounds have smaller Kp values and tend to be found in greater proportion in the gas-phase, whereas the less volatile compounds are likely to stay in the particle phase. General agreement with theory was found for compounds with known activity coefficients in PG and GL, indicating that theory can be used to predict Kp values for other compounds.

Radish anthocyanin extract has potential as a natural colorant because of its pigment stability and attractive red hue. Presence of undesirable aroma compounds could limit its applications in foods. The pungent principle of radish, 4-methylthio-3-butenyl isothiocyanate (MTBI), is produced enzymatically upon cell injury from its glucosinolate precursor, 4-methylthio-3-butenyl glucosinolate (MTBG), and undergoes subsequent degradation to produce a number of volatiles. To evaluate the potential of flavor formation, juices were prepared from winter and spring radish cultivars. Whole radishes, peels and flesh, as well as radish extracts, were analyzed for glucosinolates and isothiocyanates. Aroma intensities of radish juice extracts were evaluated using sensory analysis. MTBI was monitored by HPLC (detection level 160 ppb). MTBG was extracted from freeze-dried radish tissue with boiling methanol, purified by anion exchange and enzymatically desulfated. DesulfoMTBG was quantified by HPLC, using desulfosinigrin as internal standard. Identification was performed by fast atom bombardment and electrospray mass spectroscopy. MTBI formation was higher in winter than in spring cultivars (1.5-2.8 and 0.8-1.3 mg/100g fresh weight, respectively), and higher in flesh than in peels. MTBG ranged from 30-65 mg (spring cultivars) to 260-320 mg/100g fresh weight (winter cultivars) with greater concentration in peels than in flesh. Isothiocyanates and glucosinolates were not detected in radish juices. Overall aroma intensities of radish juice concentrates, diluted to 150, 300, 600 and 1200 mg anthocyanin/L in water, were rated using a 16-point scale. Radish concentrates from cultivars Fuego (pigmented peels) and Red Meat Takii (whole red flesh) were compared to commercial red cabbage and radish colorants. Aroma intensities followed first order relationships with anthocyanin concentrations. The commercial colorants were rated slight to moderate, while radish extracts (Fuego and Takii) were rated moderate to large. The aroma intensity of red flesh radish extract was more potent than those prepared from radish peels. Further work includes development of purification techniques which would provide an odorless aqueous extract. / Graduation date: 1997

Possible mechanisms for the formation of isovaleraldehyde from l-leucine and isobutyraldehyde from l-valine in bananas are described. These aldehydes are key intermediates for the development of the branched-chain alcohols and esters, which are prominent components of banana flavor volatiles. When amino acids were incubated with dopamine and banana enzyme extract, these aldehydes were formed. Greater amounts of aldehydes were produced when hydrogen peroxide was included in the reaction mixture. It is proposed that the reaction mechanism involves oxidation of dopamine to o-quinones catalyzed by polyphenoloxidase and peroxidase, followed by the nonenzymic reaction of the quinone with the amino acid to form the corresponding aldehyde. At levels of leucine, polyphenoloxidase (PPO) and dopamine tested, aldehyde production increased with leucine concentration (up to 75 mM) and tended to peak at relatively low levels of PPO (0.1 units/ml) and dopamine (0.5 mM). / Master of Science

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on January 4, 2008 Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 151-159). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references. Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references. Also available on the Internet.