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Neutron scattering at extremes of pressure is a powerful tool for studying the response of structural and magnetic properties of materials on microscopic level to applied stresses. However, experimental neutron studies require a relatively large sample volume, which makes it necessary to use rather large presses. One of the most commonly used high-pressure devices in neutron diffraction experiments is the Paris-Edinburgh (P-E) press. This compact hydraulic press has been successfully used at various neutron facilities across the world for over 20 years. However, there are some limitations imposed by the design of the press and this project addressed two of them. The first objective of this research was to solve the problem of the spatial restriction on the scattered beam imposed by the tie-rods of the P-E press which results in the limited access to the reciprocal space of a single-crystalline sample. In order to overcome this challenge a rotating device has been designed and built to work with the existing P-E press mainframe. The purpose of the device is to rotate the anvils at a high load in a controlled fashion so that neutron diffraction data can be collected from the sample at particular angles. A number of technical challenges had to be overcome in the design process. One of the problems was caused by the significant friction in the commercially available thrust roller bearings at loads above 25 tonnes. To resolve this issue a set of custom-designed hydraulic bearings has been developed. In these bearings a thin layer of oil separates the two parts that can rotate with respect to each other.

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Native and pressure-treated (600 MPa) soy protein isolates (SPI) were subjected to in vitro digestion to study the effect of pressure processing on the digestibility of SPI and the antioxidant activity of the hydrolysates and isolated low molecular weight (<1 kDa) peptides. The digestibility of SPI increased significantly (P < 0.05) with pressurization following 10 min of pepsin digestion. The total peptide content in the pepsin-pancreatin hydrolysates was unaffected by pressurization; however, the peptide profiles were altered. Peptides from hydrolysates of pressurized SPI showed higher antioxidant activity than peptides from native SPI hydrolysates as measured by the FRAP assay. In contrast, peptides from native SPI hydrolysates exerted higher antioxidant activity than peptides of hydrolysates of pressurized SPI as assessed by the DPPH assay. These results indicate that peptides from hydrolysates of native and pressurized SPI produce differential in vitro antioxidant activities that might impact their in vivo antioxidative effects.

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.