The effect of washing machine separated rockfish flesh on composition, quality and desirability was investigated. Washing machine separated rockfish flesh resulted in a 36.88% loss of solids. The greatest reductions were found in the ash (80.32%) and lipid (65.13%) levels in the washed flesh. Most of the sarcoplasmic proteins were lost during washing and only 77.29% of the protein (N X 6.25) was recovered. Washing the machine separated fish flesh did not appreciably alter the amino acid composition. The content of essential amino acids of the drum-dried treatments was similar to casein and this was reflected by the high protein efficiency ratios compared to the casein reference. The mineral composition of the unwashed machine separated flesh was similar to that of the fillet. Washing the machine separated flesh greatly altered the mineral composition in the flesh. The levels of calcium, magnesium, barium, strontium, boron, and manganese were not appreciably altered by washing. Phosphorus, potassium, and sodium levels were reduced while the iron, copper, zinc and chromium levels were increased in the washed flesh. The rapid formation of trimethylamine (TMA) in the drumdried rockfish fillet and unwashed machine separated flesh treatments may be related to the development of off-odors and off-flavors formed during storage at 30°C. The over-all desirability of bland wafers consisting of 10% drum-dried washed flesh increased slightly during storage but was not appreciably higher than the wafers containing the drum-dried fillet and unwashed fish flesh. Over-all desirability may not be directly linked to the formation of trimethylamine (TMA) since washing drastically reduced the level of trimethylamine oxide (TMAO) in the washed flesh and the subsequent formation of trimethylamine (TMA) during storage at 30°C. The much higher levels of malonaldehyde found in the drumdried washed machine separated rockfish flesh may implicate the oxidation of the lipids as being responsible for the lower over-all desirability of the washed flesh. The rapid formation of malonaldehyde may also indicate that naturally occurring antioxidants are leached from the flesh during the washing process. / Graduation date: 1976

Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 42-45).

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 259-269).

Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The effects of freeze-drying and flake freezing of surimi on biochemical and physical properties as affected by various storage conditions were examined. Using three cooking parameters shear stress and strain values were evaluated to measure gelation properties of surimi gels. Stress values increased up to 3 months and then decreased substantially as storage time was extended. In general, strain values decreased substantially over time, however, freeze-dried surimi kept in the freezer at - 18°C did not change during 9 months of storage. Overall, color decreased during storage and b* values of the freeze-dried surimi kept at room temperature increased significantly. Salt extractable proteins decreased while dimethylamine increased. Electrophoretic patterns, however, did not show any apparent damage to the MHC due to frozen storage and/or proteolysis (with 60°C incubation) until the 9th month of storage. At 9 months, a reduction of the MHC was observed and the lower molecular weight bands were more intense. Freeze-dried samples stored in the freezer maintained the highest quality for the duration of the 9 month study. Low temperature storage is important for retaining good functionality in freeze-dried surimi. The effects of cross-section diameter on shear stress and strain and effects of individual variation in measuring diameter were studied. Gelation properties of surimi using milled and molded gels were compared. The possibility of skin formation using various cook times was also evaluated. Shear stress values were significantly affected by diameter accuracy, whereas the effect was not as significant for shear strain values. Individual variation in measurement was also greatly noted. Molded gels resulted in significantly lower strain values than milled samples, whereas stress values were significantly higher in molded gels than in milled gels. Using a lechitin-based spray appeared to eliminate skin formation on all samples. / Graduation date: 2001

Freezing is one of the important technologies for preservation of foods. In this project, using surimi as a food model, thermophysical properties of frozen foods were evaluated and the freezing process was simulated using a finite element package. To measure temperature-dependent thermal conductivity, a line-source probe system was used. Effects of test conditions and sample history were investigated. Thermal conductivity of Alaska pollock (Theragra chalcogramma) surimi having 0, 4, 6, 8, and 12% cryoprotectant levels was measured in the range of -40 to 30 ° C. Other thermal properties were analyzed using differential scanning calorimetry (DSC) at the same cryoprotectant concentrations and in the same temperature range. Each dynamically corrected DSC thermogram was used to determine initial freezing point, unfreezable water (bound water), apparent specific heat, enthalpy and unfrozen water weight fraction. When water content of the sample is controlled, thermophysical properties of surimi have a relatively weak dependence upon cryoprotectant level in the unfrozen and fully frozen (-40° C) ranges. However, the initial freezing point and the properties just below this point were significantly affected. From measured data, the Schwartzberg thermal property models for frozen foods were investigated. The models agreed well with experimental data. However, possibility for further improvement is demonstrated by using DSC analysis. This research additionally demonstrated the great potential of DSC for measuring and modeling frozen food thermal properties. Using the derived property models, a commercial PC-based finite element package was used to simulate the process of freezing a food block in a plate freezer. The capability of the program to handle temperature-dependent thermal properties and time-dependent boundary conditions enabled a simulation which accounted for measured changes in thermal properties, ambient temperatures and overall heat transfer coefficient. Predicted temperature history agreed well with measured data. Sensitivities of important model parameters, which were varied within their experimental error range, were also investigated using a factorial experimental design method. The result showed that in decreasing order of influencing freezing time prediction, attention should be given to apparent specific heat, block thickness, overall heat transfer coefficient, ambient temperature, thermal conductivity, and density. / Graduation date: 1991

The biochemical and organoleptic changes that took place in raw whole Pacific shrimp and in the cooked meat during eight days of iced storage were investigated. A steady increase of both microbial numbers on the raw shrimp and pH in the raw shrimp and cooked meat was observed. The levels of total and non-protein nitrogen and total carotenoid pigment decreased during the storage period. Tyrosine levels showed a. decrease in the raw shrimp, but a progressive increase in the cooked meat was observed. Although proteolytic and polyphenolase activity in the raw shrimp decreased during storage, the losses in nitrogenous components was probably related to a combination of the autolytic degradation of the shrimp coupled with the washing action of melting ice. Trimethylamine oxide levels were shown to decrease in raw shrimp daring storage due to the washing action of melting ice and its reduction to dimethylamine and formaldehyde and in lower amounts, to trimethylamine. The latter, probably is the result of bacterial activity, while the former is due to the action of enzyme systems in the shrimp. Levels of dimethylamine and formaldehyde increased in a parallel manner during the storage period. Trimethylamine levels also increased, but at a much slower rate. Organoleptic quality as shown by taste panel evaluations progressively declined during the storage period. Dimethylamine and formaldehyde levels appeared to be more sensitive indices of cooked shrimp quality than microbial numbers, pH and trimethylamine levels. / Graduation date: 1973

A method was devised and tested for rapid and quantitative identification of microbial flora in fresh seafoods. The rapid identification of large numbers of isolates was made possible by (1) a simplified identification scheme established by reference culture studies and from the known reactions of microorganisms reported in the literature, (2) the multiple transfer of large numbers of isolates by means of replica-plating, and (3) the use of an electronic computer to analyze data. For the identification of microbial isolates, colonies developing on initial isolation plates were picked by sterile toothpicks and inoculated on a master-plate in prearranged spacing and order. Growth on the master-plate was replicated on a series of solid agar plates containing differential or selective agents. Identifying characteristics consisted of growth responses of the isolates on media containing penicillin, tylosin, vancomycin, streptomycin, chloramphenicol, neomycin and colistin; growth responses on Bacto-SS, Bacto-S-110, Bacto-potato dextrose agar; and culture pigmentation, cell morphology and the Gram-reaction. Information was processed by an IBM 1410 digital computer which sorted and grouped each isolate into one of ten microbial genera or groups, according to a programmed identification key. The identification system was tested by analyzing the microbial flora of dover sole fillets (Microstomas pacificus) and ground beef. This rapid identification method was employed in an investigation designed to determine the nature of the microbial flora shifts in dover sole resulting from irradiation and storage at 6°C. The relationship between the microorganisms which initially survive irradiation, and those making up the final spoilage flora, was determined. A total of 2,723 isolates were examined in this study. The spoilage of unirradiated control samples during storage at 6°C was almost entirely due to the growth of Pseudomonas. This group, which occupied 25 percent of the fresh flora, grew up to nearly 100 percent in two days storage. In contrast, irradiation doses of 0.1, 0.2, 0.3, and 0.4 megarad favored the growth of Achromobacter and yeasts. Micrococcus species, which survived radiation, did not grow at 6°C. At 0.5 megarad, spoilage of fish samples at 6°C was due entirely to yeasts. / Graduation date: 1966

No description available.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.