Afhandling (Ph. D.) - Copenhagen. / Summary in Danish and English.

Thesis (doctoral)--Freie Universität Berlin, 1980.

Thesis (M.Sc. in Biochem.) -- Mahidol University, 1970.

Proefschrift - Utrecht.

Master of Science / Department of Grain Science and Industry / Greg Aldrich / Since 2010, there have been seven recalls related to thiamine deficiency in cat food products (FDA, 2017; FSA, 2017). Cats have a high requirement of thiamine (5.6 mg/kg), and deficiencies can lead to death within a month if not treated (AAFCO, 2017). A few studies have been published regarding the impact of retort processing on thiamine loss in canned pet food but no work has been reported on heat penetration in other containers (pouches and trays). Therefore, our objectives were to determine the effect of container size and type on thiamine retention during processing of cat food. Our hypothesis was that thiamine retention would be impacted by container size and type. To address this, a 2x3 factorial arrangement of treatments in which two container sizes (small: 89-104 mL vs medium: 163-207 mL) and three container types (can, pouch, and tray) were evaluated for B-vitamin losses and thermal process lethality of a wet pet food. A model wet cat loaf type formula was produced for all six experimental treatments and each was processed in duplicate over six-days. All ingredients including the vitamin premix (10x level) were thoroughly mixed, heated to 43ºC, and containers were manually filled. The filled and sealed containers were cooked in a retort (cans: SJ Reid Retort, Bellingham, WA; trays and pouches: FMC retort, Madera, CA) with thermocouples attached to the center of representative containers (n=14) in each batch. Software (Calsoft Systems, v. 5.0.5) was used to record the internal temperatures. The retort time was targeted to meet an F₀=8 at 121ºC and 21 PSI. Treatment sample were analyzed for included pH, moisture, crude protein, crude fat, ash, and B-vitamins. Results were analyzed using the GLM procedure in SAS (v. 9.4; Cary, NC) with means and interactions separated using Fisher LSD method by significant F and an α of 5%. The proximate composition and pH were similar (P > 0.10) among treatments. There was an interaction (P < 0.05) between container size and type for time to reach the F₀=8; wherein, the medium can and tray had the longest time (45.5 and 46.3 min, respectively); the small can and tray, and medium pouch were intermediate (35.4, 36.0, and 32.0 min, respectively); and the small pouch had the shortest time (36.0 min). There was no difference for either main effect of container type or size on heating lethality values (each main effect average F₀=10.3) and total lethality ranged from 12.7-16.7 min. Thiamine retention was lowest (70%) among the B-vitamins, and there was minimal loss throughout the process. The excess heating beyond F₀=8 may account for the dramatic impact on the retention of heat labile nutrients like thiamine. This may be more difficult to control in the newer packaging systems like pouches and trays.

Thesis (Ph. D.)--University of Wisconsin, 1944. / Typescript. Includes bibliographical references.

Cancer is one of the leading causes of death. There have been many investigations into therapeutic ways to prevent and reverse cancerous growth. We report a new approach in this thesis, which is to investigate the functions of Vitamin B1 (thiamine) in cancerous cells and their regulation. A number of thiamine analogs were synthesized to carry out the structure-activity relationship (SAR) studies with two transporters THTR1 and THTR2. Initial results show that the modifications of thiazole reduced the uptake of thiamine.

Thesis (M.Sc. (Biochemistry))--Mahidol University, 1976.

Thiamine is an important nutrient found in significant amounts in wheat flours. This vitamin is heat labile thus destruction occurs during bread baking. Using a kinetic approach, the effect of heat and pH on thiamine degradation in a model system were studied. In order to compare the stability of thiamine from natural (whole wheat) and synthetic (enriched white) sources, thermal destruction of thiamine in the two breads was investigated. Destruction rates of thiamine hydrochloride in phosphate buffer at pH 6.0 and temperatures between 80 and 120°C were measured. The breakdown reaction could be described by first order kinetics. An energy of activation of 34.2. kcal/mole was obtained. Destruction rates of thiamine hydrochloride in phosphate buffer at 120°C were measured for pH values between 4.0 and 7.0. The reaction rate increased as the system was made more alkaline, with greater destruction at pH 6.0 and above. Thiamine losses in an enriched white flour system baked at a nominal temperature of 246°C (475°F) for 60, 75 and 90 min were found to be 2.4, 27.9 and 29.2%, respectively. Two experiments were carried out with 450 g (1 lb) enriched white loaves baked at 221°C (430°F). Baking times were 30 min for the first experiment, and 15, 37 and 60 min for the second experiment. No appreciable thiamine destruction were found in either experiment. The main investigation was with a semi-model system of 12g bread loaves made from enriched white and whole wheat flours. Four different nominal oven temperatures of 177, 221, 246 and 288°C (350, 425, 475 and 550°F) were used with four different baking times for each run. The pH of the dough and baked bread were determined. Oven, crust and loaf center temperatures were monitored. The mass average temperature data of the bread during baking showed a changing rate of temperature rise, and because of this, it was not possible to obtain kinetic data. However, a linear relationship was obtained when the logarithm of the percent thiamine retention was plotted against time. This experiment showed a lower thiamine stability with higher oven temperature. Thiamine was less stable in whole wheat bread than in enriched white bread. This might be explained by higher pH and ash content in whole wheat bread. Thiamine losses during normal baking of whole wheat and enriched white bread were found to be in the range of 28.3 to 47.8%. / Land and Food Systems, Faculty of / Graduate

La thiamine (vitamine B1) est essentielle pour toutes les formes de vie. Le diphosphate de thiamine (ThDP) est un coenzyme indispensable au métabolisme oxydatif des cellules. Dans la plupart des tissus, on trouve également le triphosphate de thiamine (ThTP), dont le rôle biologique est encore mal connu. Néanmoins, le fait quil ait été observé dans tous les organismes étudiés, depuis les bactéries jusquaux mammifères, suggère un rôle assez général comme, par exemple, une réponse à certains types de stress cellulaire (privation dacides aminés chez E. coli, flétrissement des feuilles chez A. thaliana). Lobjectif de notre travail a été de déterminer le mécanisme de synthèse du ThTP. Avant détudier son mécanisme de synthèse, nous avons étudié sa distribution dans des biopsies tissulaires et fluides corporels humains. Une telle étude systématique était intéressante car un déficit en ThTP (ou une perturbation de son métabolisme) pourrait être impliqué dans certaines pathologies, par exemple neurodégénératives ou cardiaques. Nos résultats montrent que les niveaux de diphosphate de thiamine dans les tissus humains sont relativement faibles, alors que le triphosphate de thiamine est relativement abondant. Nous avons ensuite étudié le mécanisme de synthèse du ThTP dans le cerveau de rat. Les données recueillies au cours de ces études nous ont permis de dresser plusieurs conclusions. Dans le cerveau, la synthèse du triphosphate de thiamine a lieu dans les mitochondries avec le ThDP et le phosphate inorganique (Pi) comme précurseurs. La réaction est stimulée par les substrats de la chaîne respiratoire comme le pyruvate et le succinate, et est inhibée par des agents bloquant la chaîne respiratoire, ce qui suggère que le flux délectrons à travers la chaîne respiratoire est la source dénergie pour cette réaction endergonique ThDP + Pi ↔ ThTP. La synthèse du ThTP est inhibée lorsque la Δp est dissipée par des protonophores ou par la valinomycine en présence de K+ à lextérieur. La lyse des mitochondries induit également une abolition de la formation du ThTP. La dissipation de la Δp aboutit à une hydrolyse rapide du ThTP synthétisé, suggérant que la réaction ThDP + Pi ↔ ThTP + H2O est catalysée par une ThTP synthase réversible capable de transporter des protons. Les mitochondries peuvent libérer du triphosphate de thiamine. Ce mécanisme de libération nécessite la présence de Pi et pourrait impliqué un ou plusieurs composants du pore de transition de perméabilité mitochondriale. Ainsi, la synthèse et la libération du ThTP sont soumises à des régulations spécifiques. Nos résultats montrent, pour le première fois, la production dun composé hautement énergétique, autre que lATP, par un mécanisme de couplage chimiosmotique.