The combined effect of various gas packaging atmospheres (air, vacuum and gas packaging), films of different oxygen transmission rate (OTR) and storage temperature (4 and 12°C) were investigated on the shelf-life and safety of flesh rainbow trout fillets. / Preliminary studies were done to determine the optimum packaging atmospheres to maintain the bright pink color of trout packaged in a high gas barrier film. Both vacuum and gas packaging (85% CO2:15%N2) resulted in the longest shelf-life (~28 days) in terms of color at 4°C. Based on these optimum gas atmospheres for color, shelf-life studies were performed at both refrigerated and temperature abuse conditions (12°C). / Challenges studies were also done with Listeria monocytogenes and Clostridium botulinum type E, two psychrotrophic pathogens of concern in modified atmosphere packaged (MAP) fish. / Subsequent studies were done to determine the effect of various levels of headspace oxygen (0--100%, balance CO2) or film OTR on the time to toxicity in trout stored at 12°C. (Abstract shortened by UMI.)

No description available.

No description available.

The spoilage pattern of carp (Cyprinus carpio) fillets was investigated. The studies were aimed at evaluating the potential use of pressure-shift freezing to reduce quality deterioration during frozen storage. The effects of pressure treatment at low temperature on fish carp fillets were evaluated and conditions were chosen to reduce any adverse effect on the quality of fish fillet. Pressure-shift freezing treatment was applied to carp fillets and biochemical properties were evaluated and correlated with objective measurement of texture, drip loss and the size of ice crystals formed. Changes in these properties were monitored during frozen storage for a period of 75 days. / Results indicated that proteolityc changes due to endogenous enzymes in fish muscle play an important role in quality deterioration of carp fillets during ice storage. No changes were observed in Ca2+-ATPase, Mg2+-ATPase or Mg2+-EGTA-ATPase activity of actomyosin from carp fillets during iced storage (p > 0.05). In contrast, Mg2+-Ca2+-ATPase and Ca2+ sensitivity of actomyosin decreased during ice storage of fish fillets. No changes were found in the SH content of actomyosin throughout the ice storage of carp fillets (p > 0.05). The surface hydrophobicity of actomyosin and auto-degradation products increased during the storage period (p < 0.05). / Response surface methodology (RSM) was used to study the effect of high-pressure treatment on some physico-chemical properties (actomyosin extractability, Ca2+-ATPase activity, surface hydrophobicity, TBA value, liquid loss and firmness) of intact fish fillets. Balancing the benefits of low temperature pressurization with the denaturing effects of pressure on fish proteins, it is evident that there is a region in which the responses of the factors (protein extractability, Ca2+-ATPase activity and protein hydrophobicity) to the processing variables (time and pressure) seemed to be adequate to keep protein denaturation to a minimum. This region lies between 140--175 MPa and 16--18 min. However, it was observed that high-pressure treatment induced changes in colour on fish fillets. The L*, a* and b* values increased as pressure and time treatment increased. / The application of pressure-shift freezing or air-blast freezing resulted in decrease in myofibrillar and sarcoplasmic protein extractability, and reduced actomyosin Ca2+-ATPase activity during frozen storage. However, actomyosin Ca2+-ATPase activity in pressure-shift frozen samples remained relatively higher than that of air-blast frozen samples. On the other hand, levels of thiobarbituric acid and free fatty acids were relatively lower in samples frozen by PSF. The freezing procedure did not seem to have a significant effect (p > 0.05) on the texture of carp fillets. The ice crystals found in PSF fish samples were mainly intracellular, smaller and more regular shaped than those found in the ABF samples, which were mainly extracellular. Differential scanning calorimetry showed that PSF treatment appeared to be more effective in preventing protein denaturation in post-rigor fish fillets than in the pre-rigor fish fillets.

This study is aimed at evaluating the safety and quality of pressure treated fish. In order to assess safety of refrigerated fish, the sensitivity of key pathogens like Escherichia coli O157:H7 and Listeria monocytogenes Scott A, which thrive under refrigerated storage conditions, needs to be assessed. / In the first part of the study, the pressure destruction kinetics of E. coli and L. monocytogenes in fish were evaluated at 250 to 400 MPa with a holding time ranging from 0-60 min. A slurry was prepared by blending 20 g filleted fish and 80 ml sterile peptone water (0.1%) in a stomacher. To the slurry, stock cultures of E. coli O157:H7 and L. monocytogenes were added separately and final counts of 107 and 106 CFU/ml were achieved, respectively. Due to the higher overall pressure resistance at 400 MPa, E. coli was selected as the target microorganism in this study for pressure destruction. / The second part of the study focused on storage studies. The first phase of the storage study was a repeat of previous set of experiments with fish slurry inoculated with only E. coli O157:H7 which was more resistant to pressure destruction (challenge study). / The second phase of storage studies evaluated the quality changes associated with pressure treated fish. (Abstract shortened by UMI.)

When a porous honeycomb core is glued to plane facings to make a sandwich construction, glue fillets (concave menisci) are formed around the core cell edges. It is known that glue fillets play an important role in strengthening the bond of the construction, but only few studies on the real function of the fillet have been reported. This thesis investigates the relationships between fillet size and bonding strength in sandwich construction followed by a stress analysis of the fillets. Sandwich panels with various fillet sizes were produced by means of a glue applicator of original design using a modified phenol-resorcinol resin glue, kraft paper honeycomb cores and Douglas fir plywood facings. Tensile strength tests normal to the sandwich specimens of 1 by 1 inch, and flexure tests on the sandwich beams of 3.75 by 12 inches were performed. Fillet rupture sizes and actual fillet dimensions were measured. A highly significant correlation was found between fillet size and bonding strength. Larger fillets provided greater bonding strength. When a sandwich was subjected to tensile load, a vertical shear failure took place at the center of the fillet concave meniscus regardless of fillet size. By assuming the uniformity of fillet shape, the following equation: [symbol omitted]= my + d , was found to express the relationship between the vertical shear stress [symbol omitted] at the fracture point B and the fillet height y at B, where m and d were constants. Too large fillets had tendency to form voids or bubbles within them resulting in lowering strength values. The appearance of fracture in the glueline in flexure test specimens was similar to that in the tensile test. Most of the sandwich specimens with smaller fillets failed in the glueline, while those with larger fillets mostly failed in core shear. This observation also indicated the superiority of larger fillets in bonding of honeycomb-to-plywood. The cause of glueline failure in the flexure test was deemed to result from a complex system of shear, compression and tensile stresses. However, a mathematical expression describing that system of stresses was not found. / Forestry, Faculty of / Graduate

No description available.

Increasing the combustion temperatures in a gas turbine engine to achieve higher efficiency and power output also results in high heat loads to turbine components downstream of the combustor. The challenge of adequately cooling the nozzle guide vane directly downstream of the combustor is compounded by a complex vortical secondary flow at the junction of the endwall and the airfoil. This flow tends to increase local heat transfer rates and sweep coolant away from component surfaces, as well as decrease the turbine aerodynamic efficiency. Past research has shown that a large fillet at the endwall-airfoil junction can reduce or eliminate the secondary flow. Also, leakage flow from the interface gap between the combustor and the turbine can provide some cooling to the endwall. This study examines the individual and combined effects of a large fillet and realistic combustor-turbine interface gap leakage flow for a nozzle guide vane. The first study focuses on the effect of leakage flow from the interface gap on the endwall upstream of the vane. The second study addresses the influence of large fillets at the endwall-airfoil junction, with and without upstream leakage flow. Both studies were performed in a large low-speed wind tunnel with the same vane geometry. Endwall shear stress measurements were obtained for various endwall-airfoil junction geometries without upstream leakage flow. Endwall heat transfer and cooling effectiveness were measured for various leakage flow rates and leakage gap widths, with a variety of endwall-airfoil junction geometries. Results from these studies indicate that the secondary flow has a large influence on the coverage area of the leakage coolant. Increased leakage flow rates resulted in better cooling effectiveness and coverage, but also higher heat transfer rates. The two fillet geometries tested affected coolant coverage by displacing coolant around the base of the fillet, which could result in undesirably high gradients in endwall temperature. The addition of a large fillet to the endwall-airfoil junction, however, reduced heat transfer, even when upstream leakage flow was present. / Master of Science

Orientador: Elisa Helena Giglio Ponsano / Co-orientador: Giovani Sampaio Gonçalves / Co-orientador: Eduardo Giani Abimorad / Banca: Rachel Cristina Prehi Alves / Banca: Roberson Sakabe / Banca: Silvia Helena Venturoli Perri / Banca: Manoel Garcia Neto / Resumo: A tilápia, além de possuir vantagens produtivas, origina produtos com grande aceitação pelo mercado. Em sua nutrição, podem ser utilizados aditivos com fins zootécnicos, pigmentantes ou antioxidantes. Este estudo avaliou o efeito da suplementação da dieta para tilápias com biomassa de Rubrivivax gelatinosus sobre o desempenho zootécnico e parâmetros hematológicos e histológicos dos animais, e sobre as características de qualidade dos filés. O experimento contou com seis tratamentos, compostos de um grupo controle, um grupo com pigmentante comercial e quatro grupos com a biomassa nas concentrações de 175, 350, 700 e 1400 mg/kg. Peixes pesando 21,42 ± 5,65g foram criados por 74 dias em sistema com recirculação de água e abatidos nos dias 0, 18, 43, 58 e 74. Não foram encontradas diferenças para os resultados das análises de desempenho, histológicas e hematológicas. Os filés dos grupos alimentados com os aditivos apresentaram menor umidade que o controle (p < 0,05) e os filés dos grupos alimentados com biomassa apresentaram maiores teores protéicos (p < 0,05). Não houve diferenças entre os tratamentos para os valores de pH, lipídeos e cinzas. Quanto à cor dos filés, todos os tratamentos com aditivos aumentaram a intensidade de vermelho (p < 0,05). Em todos os tratamentos, a rancidez dos filés foi crescente durante o armazenamento, embora em menores valores nos filés dos grupos tratados com as maiores concentrações de biomassa (p < 0,05). A biomassa de R. gelatinosus não promoveu alterações no desempenho nem nos parâmetros hematológicos e histológicos, e mostrou-se capaz de melhorar os aspectos de qualidade e conservação dos filés. Dessa forma, confirma-se a viabilidade do uso desse aditivo na alimentação de tilápias para incrementar a preservação da carne congelada / Abstract: More than having productivity advantages, tilapia fish yields products with great market acceptance. For its nutrition, additives aiming at increasing zootechnical, pigmenting or antioxidant features may be used. This study evaluated the effect of the supplementation of tilapia diets with Rubrivivax gelatinosus biomass on the performance and hematological and histological parameters of the animals, and on the quality of the fillets. The experiment comprised six treatments, made of a control group, a group containing commercial pigment and four groups with biomass concentrations of 175, 350, 700 and 1400 mg/kg. Fishes weighing 21.42 ± 5.65 g were reared for 74 days in a system with water recirculation and slaughtered at days 0, 18, 43 and 74. No difference was detected for performance, histological and hematological analyzes among treatments. Fillets of the groups fed additives had lower moisture than the control (p < 0.05) while the fillets of the groups fed the biomass had the highest protein percentages (p < 0.05). No differences were detected among treatments for pH, lipids and ash values. Regarding to the color of the fillets, all treatments with additives increased redness at the measured sites (p < 0.05). For all treatments, rancidity in the fillets increased during storage, although the groups treated with the highest biomass concentrations had the lowest values (p < 0.05). R. gelatinosus biomass did not change performance or hematological and histological parameters, and proved to be capable of improving fillets quality features and conservation. Thus, it was shown the viability of the use of this additive in tilapia feed to increase the preservation of frozen meat / Doutor

The application of high pressure (HP) processing on trout and shrimps was investigated in order to study its effect on their quality attributes. Five levels of pressure, holding time and temperature were selected using a central composite rotatable design (CCRD), the central point being. 200 MPa, 30 min and 10°C. This design was used in order to permit the measurement and modeling of changes in various quality parameters as a result of changes in the process variables. The color parameters (L*, a*, and b* values), physical attributes (drip-loss, protein leaching and water holding capacity) and texture parameters (firmness and springiness) in each case were evaluated, and modeled as second order polynomial equations. / Artificial Neural Network modeling was employed to investigate its ability in predicting the quality changes in both pressure-treated trout fillets and shrimp samples, and its performance was with statistical models. / High pressure (HP) kinetics of the microbial destruction in both trout and shrimp was also studied. (Abstract shortened by UMI.)