Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 99-102). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

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In the present study the effects of characteristic freezing times and storage time at -22°C on the quality of the adductor muscle of post-rigor scallops (Pecten maximus)and gilthead seabream fillets (Sparusa urata) were studied in regard to the integrity of muscle structure, myofibrillar protein denaturation and aggregation, lipid degradation, texture and sensory changes. This information would be useful for achieving optimal conditions for freezing these species and assessing their quality during frozen storage for commercial purposes. Scallop muscles and gilthead seabream fillets were frozen individually with characteristic freezing times that can be met in commercial practice of freezing seafoods. After freezing, the samples were thawed and their quality was evaluated. Fresh samples were analyzed as controls. Intermediate characteristic freezing times (i. e. 89 and 49 minutes for scallop muscles and 74 minutes for gilthead seabream fillets) caused more damage to cell structure of both species than the shorter and longer characteristic freezing times tested. Short characteristic freezing times (i. e. 19 minutes for scallop muscles, and 2 and 18 minutes for gilthead seabream fillets) reduced the thawing losses of both species compared to the longer characteristic freezing times (. e. 235 to 1000 minutes for scallop muscles, and 640 minutes for gilthead seabream fillets) tested. Freezing at short characteristic freezing times produced raw fillets similar in texture to the fresh fillets. Therefore, short characteristic freezing times (equal to or less than 19 minutes) are beneficial for freezing both species. Scallop muscles and gilthead seabream fillets were kept frozen for up to 301 and 340 days, respectively. Sampling was carried out at regular intervals on fresh and stored frozen samples. Storage time affected the integrity of infra-cellular organelles, reduced the water holding capacity, caused structural changes to myofibrillar proteins and affected the sensory attributes of both species. Frozen scallop muscles were in acceptable eating condition after a storage period of ten months, with most of the changes in bio-chemical and physical properties being pronounced after three months of storage. Based on the changes in taste scores versus storage time, it was assessed that the practical storage life of frozen gilthead seabream fillets was circa 5 to 6 months Cat+-ATPase activities for scallop muscles and a linear model that combines free fatty acids, peroxide values and protein content in centrifugal tissue fluids for gilthead seabream fillets, may be reliable methods for industry to use for assessing their quality during long term storage at -22°C.

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Pacific whiting (Merluccius productus) is the most abundant groundfish species off the California, Oregon and Washington Coasts. The fish are mainly used as a raw material for the production of surimi. However, it is not economically wise to depend only on one product. There is a need to diversify the industry and develop a portfolio of product forms able to compete on the global marketplace. This study examines the characteristics of Pacific whiting individually quick frozen (IQF) fillets through an evaluation of consumer acceptability and sensory analysis, as well as their correlations to biochemical and physical properties. Additionally, a comparison is made between Pacific whiting IQF fillets and characteristics from seven other fish species. Sensory analysis by a trained panel showed Pacific whiting scoring highest in the flavor category of shellfish, medium in overall flavor intensity and fresh fish flavor, and high in moistness. Two different cooking methods: microwave (rapid) and conventional oven (slow) were studied with the results showing that the rapid method improved a number of texture attributes. Correlations between sensory texture attributes and instrumental texture results of Pacific whiting and the protease activity were found for both cooking methods but much higher in the slow one. All eight species were tested in a consumer test using a nine-point Hedonic scale. There were no significance differences (p>0.05) in flavor, texture, and overall acceptance of Pacific whiting with most of other commercial fish. However, the amount of variation in each group was high. No significant differences were found in firmness of Pacific whiting when compared to Dover sole. Five-point purchase intent scale showed no differences in consumers' willingness-to-buy when compared to species presently available in the marketplace. Pacific whiting IQF fillets, kept in frozen storage for 12 months, showed no differences in the flavor and texture attributes with fillets frozen for one month. The following findings are based on the information gained from the focus group: (1) The most important factor affecting consumers' purchasing decision on fish is flavor, (2) Fish flavor must be fresh, mild, pleasant, and true to species, and (3) Fish texture is varied. Texture is not as important as such factors as flavor, odor, appearance, and thickness of fillets. Pacific whiting was found to be tasty and acceptable to the focus group participants. Qualitative and quantitative data collected from the focus group and the consumer tests, combined with its sensory characteristics' similarity to desirable commercial fish suggest a good potential of Pacific whiting in being utilized as IQF fillets. / Graduation date: 1997