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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.)

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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.)

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.)

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No description available.