The effect of pasteurizing dose levels of irradiation on the lipid and protein fractions of raw bovine muscle was studied by chemical amalysis and taste panel evaluation. The following storage conditions were evaluated: (a) Long term anaerobic storage at 39°F (b) Short term aerobic storage at 39°F (c) Frozen storage at -10°F (d) Cooking and short term aerobic storage at 39°F. Free fatty acid content increased with time of storage at 39°F. Irradiation with 1 Mrad of γ irradiation depressed free fatty acid development. During frozen storage the unirradiated sample was significantly higher in free fatty acids than the irradiated samples (0.1 Mrad and 0.5 Mrad). The quantity of phospholipid was reduced by both aerobic and anaerobic storage but no significant difference was evident between irradiated and unirradiated samples. The formation of free amino acids during storage was retarded by irradiation. A significant difference in flavour between control samples and those which received 0.5 Mrad of irradiation was found consistently by taste panel evaluation. The flavour difference resulted from characteristic irradiation odour. Rancid flavours were not detected by the panel. Thiobarbituric reactive substances (TBRS) increased during short term aerobic storage, however a significant difference did not exist between irradiated and unirradiated samples. During long term anaerobic storage the TBRS of irradiated samples increased faster than that of unirradiated samples, but the difference was relatively small. During frozen storage TBRS increased in direct proportion to the level of irradiation. Aerobic storage of cooked meat at 39°F resulted in a rapid increase of TBRS but the level was not affected by irradiation. / Land and Food Systems, Faculty of / Graduate

Oxygen is known to sensitize X-irradiated cells to lethal radiation damage. At low ambient oxygen tensions, however, the molecular mechanisms of the sensitization process and the metabolic requirements of the cell may be forced to compete for the cellular oxygen supply. The effect of cell respiration on the availability of intracellular oxygen during irradiation was consequently investigated by comparing the radiosensitivities of respiring and non-respiring cells. Cultured mammalian cells were irradiated in single cell suspensions and thin film monolayers at respiration inhibiting (4°C) and at normal cell culturing (37°C) temperatures. Due to oxygen equilibration and radiolytic depletion problems, the results of the suspension culture experiments were inconclusive. By subsequently analyzing the diffusive mass transfer of oxygen in the suspension medium, the stirrer flask was determined to be an inappropriate culture vessel in which to irradiate cells at constant low oxygen concentrations. A thin film cell culture system in which the oxygen concentrations to which the cells were exposed during irradiation could be more accurately controlled was then developed. A comparison of the oxygen enhanced radiosensitivities of the respiring and non-respiring cells in thin film monolayers suggested that the metabolic depletion of oxygen at low oxygen tensions has a significant effect on the local and intracellular oxygen distribution. These effects are representative of those that would be produced if respiration induced oxygen gradients existed inside and immediately around respiring cells. The magnitude of the differential radiosensitivities was found to be dependent on cell shape and to have values that agreed very well with theoretical predictions based on the existence of such gradients. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1933 W525

LD2668 .T4 1947 P38 / Master of Science

Call number: LD2668 .T4 1958 L33 / Master of Science

LD2668 .T4 1966 B67 / Master of Science

Pasteurization radiation offers a new means of extending the refrigerated storage life of foods. This procedure avoids many of the undesirable changes which result when sterilization radiation is used and still eliminates most of the spoilage organisms. Shrimp was treated with 5 ppm chlortetracycline and subjected to pasteurization levels of gamma radiation and stored at 38°F. The levels of irradiation used were 0.5 and 0.75 megarad. These levels were based on the flavor threshold of irradiation intensity. The quality of the stored irradiated shrimp was determined by subjective evaluation, chemical analyses and microbiological examinations. The storage life of the shrimp irradiated at 0.5 megarad was extended to 5 weeks, compared with 1 week for the unirradiated samples held at the same temperature. Throughout the ten week storage period, the samples which received doses of 0.5 megarad and CTC and those which received 0.75 megarad with and without CTC remained in good condition. / Graduation date: 1963

The performance of multilayer thin film optical filters depends largely on the microstructure of the component layers. This microstructure varies with the deposition parameters inside the coating chamber. By controlling these parameters, optical filters can be produced to exacting specifications. In 1947, R. M. Rice established the technique of bombarding the substrate with electrons of several kilovolts as the fils were being deposited. This process improved the durability of zinc sulfide films dramatically. This study was performed to quantitatively analyze the effects of bombardment on film microstructure and subsequent effects on optical and mechanical properties. I installed an electron source filament inside the coating chamber and electrically isolated the substrate holder, which was connected to a positive high voltage supply. An accelerating loop placed just above the filament enhanced its efficiency. The source was calibrated by measuring the current through the substrate holder. Single layer films of five different materials were deposited, each at its own set of electron bombardment parameters. The microstructure was analyzed with an X-ray diffractometer and a transmission electron microscope. Optical properties were measured with guided waves, induced absorption, and spectrophotometric analysis. Film durability was analyzed with scotch tape, eraser, and controlled humidity tests. Antimony trioxide films showed a shift in lattice orientation, but this did not affect columnar structure or macroscopic quantities. Potassium hexafluorozirconate films showed elimination of both crystal structure and columnar growth, resulting in slightly reduced durability and some absorption. Silicon monoxide films suffered no change in structure or properties. Zinc sulfide films demonstrated the change in crystal structure, which was quantified and shown to improve moisture resistance. Optical properties were unaffected. Magnesium fluoride films showed a slight increase in crystallinity with only subtle changes in durability and optical properties. Generally, electron bombardment reduced or rearranged crystal structure. The effects on macroscopic properties varied with each material, with no clear trend evident.