Orientador: Pedro de Oliva Neto / Banca: Valéria Marta Gomes de Lima / Banca: Ivanise Guilherme Branco / Resumo: Xanthomonas campestris é uma bactéria fitopatogênica que causa a podridão negra no sistema vascular das plantas da família das cruciferaceaes. Produz um exopolissacarídeo denominado goma xantana, que possui propriedades reológicas únicas sendo utilizada amplamente como agente de suspensão, espessante, emulsionante e estabilizante. É aplicados em indústrias petrolíferas, alimentícias, farmacêuticas, mineração, têxtil, termoquímicas, tintas, cosméticos e produtos agropecuários. O Brasil é um grande produtor mundial de cana de açúcar e álcool etílico. Produtos estes utilizados para a produção de xantana; o primeiro como substrato da fermentação e o segundo para a separação da goma. Apesar de todo esse potencial, o Brasil importa grande quantidade de goma xantana que poderá ser produzida com grande competitividade internacional. Portanto, este trabalho objetivou a utilização da técnica de irradiação ultravioleta, em uma linhagem específica de Xanthomonas campestris, para a obtenção de mutantes estáveis que possam melhorar o rendimento e/ou qualidade de goma obtida. A quantificação foi realizada através da determinação da biomassa, viscosidade, cálculos do rendimento da biomassa e goma. A irradiação UV por 600 segundos causou uma redução de 92,2% na população irradiada e as linhagens sobreviventes foram isoladas e analisadas nos testes de produção e viscosidade da goma xantana. As linhagens I6, I7, I9 e I10 apresentaram um aumento de 102% na produção de goma comparando com a linhagem não irradiada. Em relação à viscosidade do caldo, as linhagens irradiadas obtiveram um aumento de 48% comparadas com as não irradiadas de 20 e 30 rpm. A viscosidade da solução de goma xantana 1%, também foram superiores quando comparadas com a não irradiada. O aumento de...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Xanthomonas campestris is fitopatogenic bacterium that causes the black rotten in the vascular system of the plants of the family of the cruciferaceaes. It produces an exopolysaccharides that forms the xanthan gum, which is used in ample variety as agent of suspension, thicker, emulsifier and stabilizing, and singular rheological properties. It is applied in petroliferous, nourishing, pharmaceutical industries, of mining, textile, thermo chemistries, inks, cosmetics and farming products. Brazil is the worldwide producing greater of sugar cane of sugar and ethyl alcohol. Products theses used for the xanthan production; the first one as substratum of the fermentation, and the second as for the separation of the gum. Despite all this potential, the Brazil imports lot of xanthan gum that could be produced with great international competitiveness. This aimming work the used of the ultraviolet technique of irradiation in a specific strain of Xanthomonas campestris to obtain the mutants that can improve the income and/or quality of produced gum, through the determination of the biomass, viscosity, calculations of the income of the biomass and gum. The UV irradiation during 60 seconds caused a reduce of the 92.2% in the irradiated strains and the survived strains were isolated and analysed in the tests of production and viscosity of xanthan gum. The strains I6, I7, I9 e I10 showed increased in the xanthan production of 102% comparing with the non-irradiated strain. In relation the viscosity of the broth the irradiated strains the increase of 48% in shear rate of 20 and 30 rpm compared with the no irrdiated. The viscosity of the xanthan solution 1% irradiated were higher also whwn compared with no irradiated in both shear rate (20 and 30 rpm. The increase of viscosity was of 17% to rotational speed of 20 rpm and 16% to 30 rpm. The ...(Complete abstract click electronic access below) / Mestre

Compte tenu que la capacité de panification de l'amidon aigre, amidon de manioc modifié par fermentation et irradiation UV, n'a pas encore été complètement élucidée, l'influence du génotype et les traitements post-récolte sur le pouvoir de panification de l'amidon aigre a été l'objectif de ce travail. 13 génotypes de manioc de Colombie, cultivés à 1000 m. et 1700 m.p.n.m (3 de plaine et 10 d'altitude, respectivement) modifiés par fermentation (0 ou30 jours) et séchage (four ou soleil) ont été étudiés. Les analyses de la taille des granules, la viscosité d'empesage RVA et la viscosité intrinsèque révèlent que les traitements post-récolte ont été les facteurs prépondérants en vue de l'amélioration de la capacité de panification tandis que le facteur génotype a présenté une influence moins importante. Parmi les traitements post-récolte, la fermentation a présenté un effet plus prononcé sur la structure des granules d'amidon, que le séchage au soleil. Cependant, la combinaison de ces deux traitements a été nécessaire pour obtenir une forte capacité de panification. L'effet d'altitude de culture a été mis en évidence lors de la fermentation par des sensibilités différentes trouvées entre les granules de plaine et d'altitude (exocorrosion et endocorrosion, respectivement). Les génotypes d'altitude, donc, ont montré une bonne capacité de panification. Néanmoins, d'autres facteurs entrent en jeu, la teneur en amylose mesurée par DSC a influencé négativement l'expansion de la pâte, probablement en raison de la formation de complexes amylose-lipide. Par conséquent, la combinaison de génotypes de manioc (la teneur en amylose principalement) et les traitements post-récolte sont un élément clé de la capacité de panification de l'amidon aigre. Ces contributions peuvent aider à l'établissement de standards de qualité de l'amidon aigre vis à vis de leur potentielle utilisation dans la fabrication des produits sans-gluten. / The breadmaking ability of sour cassava starch, cassava starch modified by fermentation and UV irradiation, have not been yet fully elucidated. The influence of genotype and postharvest treatments on expansion ability of sour cassava was the objective of this work. Thirteen cassava genotypes have been studied. All genotypes proceeded from Colombia. Two altitudes of origin (1000 m. and 1700 m.a.s.l. refered to respectively as lowland and highland), fermentation treatments (0 or 30 days) and drying treatments (oven or sun) were considered. Analyses of the granule size, RVA pasting behavior and intrinsic viscosity were analysed as indicators of breadmaking ability. Results showed that post-harvest treatments were prevailing factors in improving breadmaking ability while the genotype factors had a smaller influence. Among post-harvest treatments, fermentation had a greater influence than sun-drying on these indicators, in particular on starch granular structure. The combination of both treatments was needed to obtain a high capacity bread. Furthermore, the altitude of origin of cassava genotypes was observed to affect the fermentation process: different sensitivities to fermentation were found between granules of lowland and highland (exocorrosion and endocorrosion, respectively). Highland genotypes showed a better breadmaking ability. Other influencing factor related to genotype was the amylose content measured by DSC: it negatively influenced the expansion of the dough, probably due to the formation of amylose-lipid complex. As a conclusion, the combination of cassava genotypes (mainly amylose content) and post-harvest treatment is key for expansion ability of sour starch. This knowledge is a first, essential step to provide quality standards for sour starch, targeted particularly for use in gluten-free products.

Des polyacides lactiques hydroxy téléchélique de masses molaires variées ont été synthétisés par polymérisation par ouverture de cycle du LLA en présence de 1,4 -butane diol. Des polyhydroxybutyrate hydroxy téléchéliques ont été préparés transesterification du PHB et du 1,4-butanediol catalysée par l'acide p-toluène sulfonique .Ces oligomères ont été utilisés pour préparer des polyesters amides fonctionnalisés acrylates ou mercaptans. Dans une approche parallèle, du PCL multi acrylate a été préparé avec succès par copolymérisation par ouverture de cycle de méthacrylate de glycidyle avec du caprolactone. Des copolymères (GMA -co- CL) ayant des masses molaire et de la fonctionnalité variables, ont été préparés en modifiant les paramètres de la réaction tels que le catalyseur, la nature du co-amorceur et le rapport des stœchiométriques des différents réactifs. Les polymères multi acrylates ont été copolymérisés principalement avec l'HEMA sous irradiation UV pour obtenir des réseaux PLA, PHB et PCL segmentés. Les mécanismes de dégradation de ces réseaux ont été étudiés en examinant particulièrement les décompositions des liaisons uréthanes et esters. Des dépolymérisations du PHEMA ont été détectées avec TGA -FTIR à plus haute température (450°C). Pour les réseaux à base de PCL, les propriétés thermo -mécaniques ont été étudiées. Le résultat montre que les phases riches en PCL ont une bonne compatibilité avec le poly HEMA. Les modules caoutchoutiques et l’étendue des températures des zones d’amortissement peuvent être contrôlées en fonction des paramètres réactionnels. Les Polymères multifonctionnels Thiols du PCL, PHA et PLA ont été utilisés pour faire croître des chaines méthacrylates et construire des polymères de type étoile / Hydroxyl telechelic polylactic acids of various molecular weights were synthesized by ring opening polymerization in the presence of LLA and 1,4-butanediol. Telechelic hydroxy polyhydroxybutyrate were prepared transesterification of PHB and 1,4- butanediol catalyzed by p- toluene sulfonic acid. These oligomers were used to prepare polyesteramides functionalised acrylates or mercaptans. In a parallel approach, the PCL multi acrylate was successfully prepared by ring-opening copolymerization of glycidyl methacrylate with caprolactone. Copolymers (GMA-co-CL) with variable molar masses and functionality were prepared by changing the reaction parameters such as catalyst, the nature of the co-initiator and the ratio of different stoichiometric reagents. Multi-acrylated polymers were copolymerized with HEMA under UV irradiation to obtain PLA, PHB and PCL segmented networks. Degradation mechanisms of these networks have been studied by examining particular decomposition of urethane bonds and esters. Depolymerization of the PHEMA was detected with TGA -FTIR at higher temperature (450°C). For PCL based networks, the thermo- mechanical properties were studied. The result shows that the PCL-rich phases have good compatibility with poly HEMA. The rubber and the working temperature range of the damping zones modules can be controlled as a function of reaction parameters. Multi mercapto functionalized polymers with PCL, PLA and PHA segments were used to grow methacrylate polymer chains and build star type

O presente trabalho apresenta a síntese e a caracterização de derivados de quitosana, bem como o preparo e caracterização de filmes de nanocompósitos à base de quitosana comercial (ou seus derivados), argila (MMT) e nanopartículas de prata (NPs-Ag), obtidas via Fotoquímica. Para tanto, foram preparados, a partir da quitosana comercial (QC), os derivados: quitosana desacetilada (Q30des), quitosana purificada (QP), quitosanas parcialmente despolimerizas (QD30, QD21 e QD5), quitosanas hidrofílicas (QD21-40DEAE e QD5-49DEAE) e quitosanas anfifílicas (QD21-40DEAE-6DD, QD21-40DEAE-18DD, QD5-49DEAE-6DD e QD5-49DEAE-17DD). O grau médio de desacetilação das QC, QP e Q30des e de substituição por grupos DEAE e dodecila foram determinados por Espectroscopia de Ressonância Magnética Nuclear de Hidrogênio (RMN de 1H). Ademais, os biopolímeros foram caracterizados por Espectroscopia no Infravermelho (FTIR-ATR), Viscosimetria, Análise Termogravimétrica e Microscopia Eletrônica de Varredura (MEV). Em seguida, foi estudada a síntese de nanopartículas de prata, sob radiação UV, em filmes de nanocompósitos de quitosana comercial ou seus derivados e argila. Em um primeiro momento, estudou-se a formação das NPs-Ag em filmes de QC com diferentes formulações e posteriormente em filmes de derivados de quitosana contendo 10% de MMT (m/m). A técnica de Difração de Raios-X (DRX) foi utilizada para a determinação do espaçamento interlamelar da argila montmorilonita pura e nos compósitos preparados. A síntese das NPs-Ag foi acompanhada por Espectrofotometria de Absorção Molecular no UV-vis, e monitorada após um ano de sua formação, sendo suas características morfológicas, bem como a dispersão da argila nos nanocompósitos examinados por Microscopia Eletrônica de Transmissão (MET). Por fim, a atividade antimicrobiana dos filmes de nanocompósitos foi avaliada pelo método de Disco de Difusão contra as bactérias Escherichia coli e Bacillus subtilis. / The present work presents the synthesis and characterization of chitosan derivatives, as well as the preparation and characterization of nanocomposite films based on commercial chitosan (or its derivatives), clay (MMT) and silver nanoparticles (NPs-Ag) obtained by photochemical method. Therefore, were prepared from commercial chitosan (QC): deacetylated chitosan (Q30des); purified chitosan (QP); partially depolymerized chitosans (QD30, QD21 and QD5); hydrophilic chitosans (QD21-40DEAE and QD5-QD5) and amphiphilic chitosans (QD21-40DEAE-6DD, QD21-40DEAE-18DD, QD5-49DEAE-6DD and QD5-49DEAE-17DD). The deacetylation degrees of QC, QP and Q30des were determined by Nuclear Magnetic Resonance Spectroscopy (1H-NMR). This technique also used to determine the degrees of substitution by DEAE and dodecyl groups. In addition, the biopolymers were characterized by Infrared Spectroscopy (FTIR-ATR), Viscosimetry, Thermogravimetry and Scanning Electron Microscopy. Moreover, the NPs-Ag synthesis under UV radiation was studied on nanocomposite films of commercial chitosan or its derivatives and clay. At first, the Ag-NPs formation was studied on QC films with different formulations and secondarily, on films of chitosan derivatives containing 10 wt % of MMT. The X-Ray Diffraction (XRD) was used to determine the interlamellar spacing of pure montmorillonite clay and in the nanocomposites prepared. The synthesis of the NP-Ag was accompanied by UV-vis Spectroscopy. Its morphological characteristics, as well as the clay dispersion in the nanocomposites were examined by Electron Transmission Electron Microscopy (TEM). Finally, the antimicrobial activities of materials were investigated by the disk diffusion method against the bacteria Escherichia coli e Bacillus subtilis.

O presente trabalho apresenta a síntese e a caracterização de derivados de quitosana, bem como o preparo e caracterização de filmes de nanocompósitos à base de quitosana comercial (ou seus derivados), argila (MMT) e nanopartículas de prata (NPs-Ag), obtidas via Fotoquímica. Para tanto, foram preparados, a partir da quitosana comercial (QC), os derivados: quitosana desacetilada (Q30des), quitosana purificada (QP), quitosanas parcialmente despolimerizas (QD30, QD21 e QD5), quitosanas hidrofílicas (QD21-40DEAE e QD5-49DEAE) e quitosanas anfifílicas (QD21-40DEAE-6DD, QD21-40DEAE-18DD, QD5-49DEAE-6DD e QD5-49DEAE-17DD). O grau médio de desacetilação das QC, QP e Q30des e de substituição por grupos DEAE e dodecila foram determinados por Espectroscopia de Ressonância Magnética Nuclear de Hidrogênio (RMN de 1H). Ademais, os biopolímeros foram caracterizados por Espectroscopia no Infravermelho (FTIR-ATR), Viscosimetria, Análise Termogravimétrica e Microscopia Eletrônica de Varredura (MEV). Em seguida, foi estudada a síntese de nanopartículas de prata, sob radiação UV, em filmes de nanocompósitos de quitosana comercial ou seus derivados e argila. Em um primeiro momento, estudou-se a formação das NPs-Ag em filmes de QC com diferentes formulações e posteriormente em filmes de derivados de quitosana contendo 10% de MMT (m/m). A técnica de Difração de Raios-X (DRX) foi utilizada para a determinação do espaçamento interlamelar da argila montmorilonita pura e nos compósitos preparados. A síntese das NPs-Ag foi acompanhada por Espectrofotometria de Absorção Molecular no UV-vis, e monitorada após um ano de sua formação, sendo suas características morfológicas, bem como a dispersão da argila nos nanocompósitos examinados por Microscopia Eletrônica de Transmissão (MET). Por fim, a atividade antimicrobiana dos filmes de nanocompósitos foi avaliada pelo método de Disco de Difusão contra as bactérias Escherichia coli e Bacillus subtilis. / The present work presents the synthesis and characterization of chitosan derivatives, as well as the preparation and characterization of nanocomposite films based on commercial chitosan (or its derivatives), clay (MMT) and silver nanoparticles (NPs-Ag) obtained by photochemical method. Therefore, were prepared from commercial chitosan (QC): deacetylated chitosan (Q30des); purified chitosan (QP); partially depolymerized chitosans (QD30, QD21 and QD5); hydrophilic chitosans (QD21-40DEAE and QD5-QD5) and amphiphilic chitosans (QD21-40DEAE-6DD, QD21-40DEAE-18DD, QD5-49DEAE-6DD and QD5-49DEAE-17DD). The deacetylation degrees of QC, QP and Q30des were determined by Nuclear Magnetic Resonance Spectroscopy (1H-NMR). This technique also used to determine the degrees of substitution by DEAE and dodecyl groups. In addition, the biopolymers were characterized by Infrared Spectroscopy (FTIR-ATR), Viscosimetry, Thermogravimetry and Scanning Electron Microscopy. Moreover, the NPs-Ag synthesis under UV radiation was studied on nanocomposite films of commercial chitosan or its derivatives and clay. At first, the Ag-NPs formation was studied on QC films with different formulations and secondarily, on films of chitosan derivatives containing 10 wt % of MMT. The X-Ray Diffraction (XRD) was used to determine the interlamellar spacing of pure montmorillonite clay and in the nanocomposites prepared. The synthesis of the NP-Ag was accompanied by UV-vis Spectroscopy. Its morphological characteristics, as well as the clay dispersion in the nanocomposites were examined by Electron Transmission Electron Microscopy (TEM). Finally, the antimicrobial activities of materials were investigated by the disk diffusion method against the bacteria Escherichia coli e Bacillus subtilis.

In this dissertation, the electrical characteristics of generally used hydrogenated amorphous silicon (a-Si:H) TFTs in LCD and newly risen amorphous indium-gallium-zinc oxide (a-IGZO) TFTs were studied. For modern mobile display and large-size flat panel display application, the traditional thin-film transistor-liquid crystal display (TFT-LCD) technology confronts with a lot of challenges and problems. In general, flexible displays must exhibit some bending ability; however, bending applies mechanical strain to electronic circuits and affects device characteristics. Therefore, the electrical characteristics of a-Si:H TFTs fabricated on stainless steel foil substrates with uniaxial bending were investigated at different temperatures. Experimental results showed that the on-state current and threshold voltage degraded under outward bending. This is because outward bending will induce the increase of band tail states, affecting the transport mechanism at different temperatures. In addition, for practical operation, the electrical characteristics of a-Si:H TFTs under flat and bending situations after AC/DC stress at different temperatures were studied. It was found that high temperature and mechanical bending played important roles under AC stress. The dependence between the accumulated sum of bias rising and falling time and the threshold voltage shifts under AC stress was also observed. Because a-Si:H is a photosensitive material, the high intensity backlight illumination will degrade the performance of a-Si:H TFTs. Thus, the photo-leakage current of a-Si:H TFTs under illumination was investigated at different temperatures. Experimental results showed that a-Si:H TFTs exhibited a pool performance at lower temperatures. The indirect recombination rate and the parasitic resistance (Rp) are responsible for the different photo-leakage-current trends of a-Si:H TFTs under varied temperature operations. To investigate the photo-leakage current, the a-Si:H TFTs were exposed to ultraviolet (UV) light irradiation. It was found that the photo current of a-Si:H TFTs was reduced after UV light irradiation. The detail mechanisms on reducing/increasing photo-leakage current by UV light irradiation were discussed. Recently, the oxide-based semiconductor TFT, especially a-IGZO TFT, is considered as one of promising candidates for active matrix flat-panel display. However, the a-IGZO TFT exists significant electrical instability issue and manufacturing problems. As a consequence, we investigated the effect of hydrogen incorporation on a-IGZO TFTs to reduce interface states between active layer and insulator. Experimental results showed that the electrical characteristics of hydrogen-incorporated a-IGZO TFTs were improved. The threshold voltage shift (£GVth) in hysteresis loop is suppressed from 4 V to 2 V due to the hydrogen-induced passivation of the interface trap states. Finally, we reported the effect of ambient environment on a-IGZO TFT instability. As a-IGZO TFTs were stored in atmosphere environment for 40 days, the transfer characteristics accompanying strange hump were observed during bias-stress. The hump phenomenon is attributed to the absorption of H2O molecule. Additionally, the sufficient electric field is also necessary to cause this anomalous transfer characteristic.

Flavobacterium psychrophilum, the causative agent of bacterial cold water disease (BCWD), is tolerant of recommended ultraviolet (UV) doses used in recirculation aquaculture systems (RAS). Membrane filtration (MF) is used to remove pathogens from wastewater in many industries, but has not been thoroughly tested in RAS. In this study, bacterial removal efficiencies were assessed between MF and UV treatments over 30 days in an RAS. Bacterial removal efficiencies were not significantly different (p > 0.05) between MF and UV treatments, which removed 98.5 ± 0.4 % and 99.6 ± 0.1 % of total bacteria and 93.2 ± 5.2 % and 92.5 ± 4.1 % of heterotrophic bacteria, respectively. Under laboratory conditions, a MF system was challenged with concentrated doses of F. psychrophilum and achieved 5.8 ± 0.2 log reductions of the pathogen. Therefore, MF represents a potential alternative to UV irradiation and could be used to reduce the prevalence of F. psychrophilum in RAS, potentially reducing the incidence of BCWD and its impact on the aquaculture industry. / Environment Canada and Ontario Ministry of Agriculture, Food and Rural Affairs.

L’environnement géostationnaire autour de la Terre présente des conditions complexes influençant les performances ainsi que la durée de vie des satellites. En vol et au cours du temps, les polydiméthylsiloxanes se dégradent ce qui se manifeste par une perte de souplesse, de transparence, ou encore une dégradation de l'état de la surface. Dans ce contexte, le but de cette thèse consiste à étudier l’évolution de la stabilité des polydiméthylsiloxanes en environnement géostationnaire simulé et d’autre part à proposer des solutions qui permettent de limiter la dégradation des propriétés d’intérêts technologiques, optiques en particulier. La stabilisation des polydiméthylsiloxanes soumises aux irradiations UV par l’incorporation de différentes structures d’additifs (Hindered Amine Light Stabilizers, absorbeurs UV, nanocristaux de cellulose) a été étudiée. Une autre approche pour augmenter la stabilité des polydiméthylsiloxanes aux rayonnements UV a été envisagée avec le remplacement du système catalytique actuellement utilisé (catalyseur de Karstedt) par l’emploi de dérivés organométalliques à base de Rhodium ou de Platine. Des solutions concernant la stabilisation de ces polydiméthylsiloxanes aux irradiations H+, comme l’ajout d’additifs tels que le polystyrène, les silsesquioxanes ont également été proposées. / The geostationary environment around Earth is complex which strongly influences the satellites performances and lifetime. In flight and over time, polydimethylsiloxanes exhibit degradations like a loss of flexibility and transparency, or a deterioration of the surface state. In this context, the aim of this work was to study the evolution of polydimethylsiloxanes stability in geostationary environment to find solutions to limit the degradation of interest technological properties, in particular the optical one. The stabilization of silicone resins under UV irradiation has been performed by the incorporation of different additives such as Hindered Amine Light Stabilizers, UV Absorbers and cellulose nanocrystals into the PDMS matrix. Generally, polydimethylsiloxanes networks are obtained by hydrosilylation with highly active Karstedt catalyst. Various organometallics derivatives based on Rhodium and Platinum were studied as alternative catalysts for the cross-linking of polydimethylsiloxane in order to improve the UV stability. Finally, different solutions concerning the stabilization of polydimethylsiloxane to proton irradiation, such as the addition of various additives like polystyrene or silsesquioxanes have been investigated.

>Magister Scientiae - MSc / This study explores the use of UV-assisted reduction method to synthesise the catalysts, aiming at reducing synthesis time. The Pd and Au catalyst loading is kept at 5 wt% in order to reduce the cost associated with high loading (20 wt%) of platinum group metals. The synthesised catalysts have SnO2 incorporated in them for two purposes, one being to activate the chemical reaction by absorbing UV-light and the second one is to serve as a promoter for binary and ternary catalysts. All the synthesised electrocatalysts in this study were denoted as Au/10wt%SnO2-C, Au/15wt%SnO2-C, Au/20wt%SnO2-C, Au/40wt%SnO2-C, Au/60wt%SnO2-C, Pd/10wt%SnO2-C, Pd/15wt%SnO2-C, Pd/20wt%SnO2-C, Pd/40wt%SnO2-C, Pd/60wt%SnO2-C and PdAu/10wt%SnO2-C respectively. The UV-assisted reduction method was proved to be effective with the obtained results from TEM, SEM, XRD and electrochemical studies. TEM micrographs revealed nanoparticles of Pd, Au and SnO2 which were proved by the measured d-spacing values corresponding to the element’s structures. The measured average particle size ranged from 3.05 to 14.97 nm for the electrocatalysts. The XRD profiles confirmed the face centred cubic of Pd, Au and tetragonal structures of SnO2. These electrocatalysts showed varied activity towards the oxidation of alcohols namely, methanol, ethanol, ethylene glycol and glycerol in alkaline electrolyte The cyclic voltammetry results showed improved performance towards the oxidation of glycerol on Au-based electrocatalysts, highest current density of 22.08 mA cm-2 than on Pd-based electrocatalysts. Pd-based electrocatalysts were more active towards the oxidation of ethanol than Au-based electrocatalysts with the highest current density of 19.96 mA cm-2. The co-reduced PdAu on 10wt%SnO2-C electrocatalysts showed the lowest current density of 6.88 mA cm-2 for ethanol oxidation when compared to Pd/10wt%SnO2-C and Au/10wt%SnO2-C. Linear sweep voltammograms showed more negative onset potentials on Pd-based electrocatalysts than Au-based electrocatalysts. The more negative onset potential obtained on Pd-based electrocatalysts was observed for ethanol oxidation. These results correspond to the trend observed in literature for ethanol oxidation being more favoured on Pd-based electrocatalysts whereas the polyalcohol oxidation is more favoured on Au-based electrocatalysts. The best performing and most stable electrocatalyst among the Au-based electrocatalysts is Au/10wt%SnO2-C and Pd/10wt%SnO2-C for the Pd-based electrocatalysts.

Consumer demand for fresher and minimally processed foods has brought about a movement to find effective, non-thermal processing technologies for the treatment of milk. The influence of temperature on bacterial reduction in UV irradiated milk was tested. Commercially processed skim, reduced fat (2%), and whole milk samples were inoculated with a naladixic acid resistant E. coli O157:H7 surrogate (ATCC 25922), maintained at or brought to 4oC and 20oC, respectively, and then exposed to a UV light dose between 5.3-6.3 mJ/cm2 for approximately 1.5 sec using the CiderSure 3500 apparatus (FPE Inc., Macedon, NY). Bacterial concentrations before and after UV exposure were enumerated and the results indicated that processing temperature was not significantly related to bacterial reduction (p > 0.05). The results did indicate that skim milk samples had a greater bacterial reduction, regardless of processing temperature compared to reduced fat milk and whole milk samples (p < 0.05). Solids such as milk fat, protein, lactose and minerals, in the milk have a greater effect over bacterial reductions than processing temperatures. Traditional goat cheeses are produced using unpasteurized milk, which increases the food safety concerns for these types of products. Fresh goat's milk was inoculated to 107 cfu/ml with Listeria monocytogenes (L-2289) and exposed to UV light using the CiderSure 3500 apparatus. Inoculated milk was exposed to an ultraviolet dose range between 0 and 20 mJ/cm2 to determine the optimal UV dose. A greater than 5-log reduction was achieved (p < 0.0001) when the milk was processed 12 times for a cumulative exposure time of roughly 18 sec and a cumulative UV dose of 15.8 +/- 1.6 mJ/cm2. The results of this study indicate that UV irradiation could be used for the reduction of L. monocytogenes in goat's milk. Organoleptic consequences of goat's milk treated with UV technology were assessed. Olfactory studies were conducted and a highly significant difference was determined between the odor of fresh goat's milk and UV processed milk (p < 0.05). The extent of lipid oxidation and hydrolytic rancidity was measured by thiobarbituric acid reactive substances (TBARS) and acid degree values (ADVs). Results indicated that as the UV dose increased, there was a significant increase in TBARS values and ADVs of the milk samples (p < 0.05). Milk samples were processed using the UV processor under the same conditions as previously described without exposure to the UV source to determine if the agitation from pumping was causing off-flavors by way of hydrolytic rancidity. The ADVs from these samples increased at the same rate as the UV irradiated samples; however, sensory studies indicated that the increase of free fatty acids (FFA) was not enough to cause detectable off-odors in the milk. Solid phase microextraction and gas chromatography (SPME-GC) was utilized to quantify the production of volatile compounds that were formed due to UV processing. The formation of pentanal, hexanal and heptanal was identified after as little as 1.3 mJ/cm2 UV dose. Peak areas were measured and analyzed after 7.8 mJ/cm2 and 15.6 mJ/cm2 and were determined to increase significantly as UV dose increased (p < 0.05). The chemical analyses supported the findings from the olfactory studies. The outcome of this research showed that UV irradiation at the wavelength 254 nm, was detrimental to certain chemical properties of fluid milk. The properties that were perceived as negative in fluid milk may be considered an attribute in certain types of cheese and future studies in the cheese production sector should be considered. Other applications for this technology could be for use in developing countries where milk is not typically processed because of the high costs of thermal pasteurization. On-farm applications for the treatment of replacement milk should also be considered. / Ph. D.