Thesis (MSc (Production Animal Studies, Veterinary Science))--University of Pretoria, 2008. / Includes bibliographical references. Also available in print format.

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This thesis investigates the nature and distribution of ground ice occurrences on the central Fosheim Peninsula, Ellesmere Island, and assesses the potential for thermokarst in light of possible climatic warming. / Field observations conducted in 1990 and 1991 involved geomorphological and cryostratigraphic examinations of twenty-eight ground ice sections exposed in retrogressive thaw slumps and ground probing radar surveys of two of the thaw slumps. Samples were taken of ground ice and sediments exposed in thaw slump headwalls for laboratory analysis. / Samples were analyzed for moisture content, grain size distribution, and Atterberg limits. Gravimetric ice contents were calculated and an average ice content profile was constructed for the study area. / Ground ice was found to be an important component of permafrost on the Fosheim Peninsula and was widely observed in Holocene marine sediments. The ice occurred in two stratigraphic settings at depths of one to five meters in silt and clay, and at ten meters or deeper beneath massive clay. Ice contents were generally found to increase rapidly with depth down to three meters, below which ice content was stabilized. / Ground probing radar was found to be a useful tool for permafrost research, given its ability to discriminate between ice and soil, as well as between frozen and unfrozen water.

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Myofibrillar proteins, the main components that impart functional properties to muscle foods, can undergo denaturation and aggregation during frozen storage. The overall objective of this research was to study the changes in protein structure that are associated with the preparation and frozen storage of surimi. In addition, the relative cryoprotective effects of whey protein concentrate, whey protein isolate, soy protein isolate, flaxseed meal and flaxseed protein were assessed in surimi during storage. / Raw surimi was prepared by repeatedly washing Alaska pollock flesh with chilled water. The product was either slowly frozen or underwent rapid freezing using liquid air; in either case it was then subjected to frozen storage at -20°C for 24 months. Protein structural changes were monitored using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), native-PAGE, Fourier transform infrared/attenuated total reflectance (FTIR/ATR) spectroscopy, and differential scanning calorimetry (DSC). / FTIR/ATR spectroscopy showed that during preparation of surimi the alpha-helix content increased with increased number of washing cycles. DSC results revealed a shift in the thermal transition of actin to a higher temperature during surimi preparation. All electrophoresis, FTIR/ATR spectroscopy and DSC results revealed a loss of myofibrillar proteins from surimi after three washing cycles, suggesting that three washing cycles were adequate to prepare surimi. / Native-PAGE showed no major changes in surimi after 24 months storage at -20°C. SDS-PAGE showed relatively minor changes in protein subunit structure with some loss of the myosin light chains (MLC); myosin heavy chain (MHC), actin and tropomyosin were found to be relatively stable. FTIR/ATR spectroscopy indicated a significant decrease in alpha-helix relative to beta-sheet structure in surimi after 2 years of storage at -20°C. The loss of alpha-helical content was more significant in slowly frozen surimi compared to rapid-frozen surimi samples. DSC results revealed a shift in the thermal transition of actin to lower temperatures during frozen storage of surimi. / Changes in the ratio of alpha-helix to beta-sheet structures suggested that flaxseed protein was the most effective cryoprotectant, followed by whey protein isolate and soy protein isolate, for maintaining protein structure stability during frozen storage. Whey protein concentrate and flaxseed meal showed the least cryoprotective ability. After 15 days storage at 4°C, the SDS-PAGE results showed that flaxseed protein was the only cryoprotectant that prevented the degradation of myosin heavy chain, actin and myosin light chains.

Graduation date: 1948