The abundance and low fat content of Pacific whiting support Its use for the production of surimi. The degradation of muscle proteins by myxosporidian secreted proteinase(s) has been associated with its soft texture. High residual activity is retained through the washing process used in the production of surimi and precludes the formation of a strong heat-set gel by surimi sols. Physical, chemical and SDS-PAGE analysis defined the reinforced oxidation of free sulfhydryl groups on myofibrillar proteins to disulfide bonds by potassium bromate. SDS-PAGE demonstrated myosin degradation during heat-setting and the protection of myosin from protelnase attack by bromate. A level of 0.075% bromate Inactivated 89.87% of the total proteinase activity in sols. It was assumed that cysteine proteinases were Inactivated and residual activity was associated with proteinases with a serine active site. Major iraprovement in gel coheslveness and elasticity was observed at bromate levels [less than or equal to] 0.075% with only a slight improvement at higher levels. Maximum hardness was observed at 0.150% with no (P>0.050) increase at higher levels. Brittleness was improved (P>0.050) by bromate levels [greater than or equal to] 0.100%; no maximum degree of brittleness was observed within the range ([less than or equal to] 0.250%) of concentrations investigated. An optimum folding test grade of AA was achieved by a minimum of 0.150% Potassium bromate improved gelling characteristics of sols of Pacific whiting surimi through proteinase inactivation and reinforced disulfide formation during heat-setting. Improvement in cohesiveness and elasticity was primarily a function of proteinase inactivation. Maximum hardness and brittleness required additional oxidative capacity which was not fully required for an optimum folding test grade. / Graduation date: 1989

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

A heat stable protease was identified as the cause of textural degradation in cooked arrowtooth flounder (Atheresthes stomias) muscle. Maximum proteolytic activity in the fish muscle was observed between 55°C and 60°C and myosin heavy chain appeared to be the primary substrate for the enzyme. Degradation of this myofibrillar protein at 55°C was extremely rapid and myosin heavy chain was completely hydrolyzed to peptide fragments smaller than actin, while actin itself was unaffected. A single strand 32kD proteolytic enzyme was extracted from the muscle and purified 125-fold. The enzyme was stable to freezing for up to 6 months. Activity of the semi-purified enzyme at 55°C was optimal against casein between pH 6.0 and 7.0. Sulfhydryl reagents p-chloromercuriphenylsulfonic acid, iodoacetate, iodoacetamide and cystatin were effective in inhibiting enzyme activity in casein assays. The serine protease inhibitors phenylmethylsulfonylfluoride and trypsin-chymotrypsin inhibitor appeared to activate enzyme activity against casein. Adenosine triphosphate was also an activator. Arrowtooth flounder was then considered as a raw material for surimi, since the surimi process provides for repeated washing of the minced muscle and a final mixing step during which inhibitory substances can be conveniently added. Arrowtooth muscle was monitored at all stages of surimi production. There was no evidence of myosin degradation on sodium dodecyl sulphate polyacrylamide electrophoretic gels at any time during surimi production or during the preparation of samples for testing. However, when the washed mince was incubated at 55°C, 12% residual proteolytic activity was observed. This level was sufficient to degrade the myosin component of surimi gels prepared from the control surimi to which no inhibitors had been added. The food grade substances tested for proteolytic inhibition were bovine blood plasma powder, egg white powder, whey protein concentrate, carrageenan and crude α₂-macroglobulin. Addition of plasma and/or egg white powders to control surimi resulted in a product that was comparable to pollock in functional properties as measured by gel strength, expressible moisture and fold tests. Electrophoretic comparison of surimi made with 1.0% or 2.0% plasma powder or egg white with surimi produced with 0.1% or 0.2% α₂-macroglobulin suggested that the plasma and egg white contributed gel enhancing effects in addition to protease inhibition. Carrageenan was not effective as either a protease inhibitor or gel enhancer. / Graduation date: 1992

Soluble surimi wash water (SWW) proteins could be recovered using chitosan (Chi) complexed with alginate (Chi-Alg) generating co-products for feed formulations. Chi with a degree of deacetylation (DD) of 84% complexed with Alg at a mixing ratio (MR) of 0.2 was used to study Chi-Alg concentration and treatment time protein recovery effects. Insoluble SWW solids were removed by centrifugation and the supernatant was then adjusted to pH 6. Flocculation at 20��C using Chi-Alg at 20, 40, 100 and 150 mg/L SWW was aided by 5 mm agitation and holding for 30 mm, 1h and 24h. Concentration had an effect between low (20 and 40 mg/L) and high (100 and 150 mg/L) levels. Time had an effect between 30 min and 1h but not between 1 and 24 h. Turbidity reduction was affected only by concentration. 100 mg Chi-Alg/L SWW for 1 h achieved 83% protein adsorption and 97% turbidity reduction while lower concentrations yielding higher adsorption required longer times. Fourier Transform Infrared (FTIR) analysis of untreated and Chi-Alg treated SWW solids confirmed protein adsorption. Amide band areas normalized against a common 3005-2880 cm����� region confirmed the high protein recovery by 100 mg Chi-Alg/L SWW. Six Chi samples differing in molecular weight (MW) and degree of deacetylation (DD) were tested to recover soluble SWW solids using 20, 40, and 100 mg Chi-Alg/L SWW (0.2 MR, 1h). High (94%, 93%) and low (75%) DD chitosan had lower protein adsorption (73-75%) when compared to the intermediate (84%) DD chitosan (74-83%). Intermediate DD and high MW Chi seemed to perform better; however, SY-1000 with 94% DD did not follow this trend (79-86% protein adsorption, 85-92% turbidity reduction). Insoluble SWW (P1) and soluble solids (P2) recovered using 150 mg Chi- Alg/L SWW contained 61.4 and 73.1% protein, respectively. Rat diets formulated with 10% protein substitution by P1 and 10% and 15% by P2 had acceptability and protein efficiency ratios (PER) as high as the casein control with no deleterious effects. Rat diets with 100% P2 protein substitution showed higher PER and net protein ratio than the casein control with no deleterious effects. Protein recovered from SWW using Chi-Alg has the potential to be used in commercial feed formulations. / Graduation date: 2004

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

Thesis (Ph. D.)--University of Oregon, 2001. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 143-163). Also available for download via the World Wide Web; free to University of Oregon users.

Cryoprotection in stabilized mince from Pacific whiting (Merluccius productus) was investigated by monitoring changes in physical and chemical properties during 32 weeks of frozen storage. The effects of 4 different cryoprotectants were evaluated by torsion test, color analysis, extractability of salt soluble proteins, and formation of dimethylamine (DMA) and 2-thiobarbituric acid (TBA). The quality of the stabilized mince was significantly higher than the control (mince without cryoprotectants) when compared by shear strain, salt soluble proteins, and DMA. The results show that the functionality of the proteins in the mince can be protected by using cryoprotectants with Polydextrose® being the most effective of the 4 tested. The effect of food-grade protease inhibitors on the gel-forming characteristics of Pacific whiting mince was also investigated. Four levels (1, 2, 3, and 4%) of different protease inhibitors (beef plasma protein, whey protein concentrate, egg white liquid, and egg white powder) were added to the stabilized mince before heating and effects on texture and color were evaluated. Shear strain was significantly increased by increasing the level of inhibitors. Beef plasma protein was most effective and presented significantly higher strain than the other inhibitors tested. Due to higher concentration of proteolytic enzymes in the mince, an increased amount of protease inhibitors is needed compared to surimi to prevent proteolysis during heating. / Graduation date: 1995

Cathepsin B was the most active cysteine proteinase in the Pacific whiting (Merluccius productus) fish fillet, and cathepsin L in surimi when the activities of the most active cysteine proteinases (cathepsin L, B, and H) were compared. Cathepsin L showed maximum activity at 55°C in both fish fillet and surimi, indicating its function in myosin degradation during conventional cooking of fish fillet and surimi. Washing during surimi processing removed cathepsin B and H but not cathepsin L. Autolytic analysis of surimi proteins showed that the myosin was the primary target, while actin and myosin light chain showed limited hydrolysis during 2 hr incubation. When purified Pacific whiting proteinase was incubated with various component of fish muscle, proteinase was capable of hydrolyzing purified myofibrils myosin, and native and heat-denatured collagen. The degradation pattern of myofibrils by the proteinase was the same as the autolytic pattern of surimi. Inhibition by the food-grade proteinase inhibitors varied with the catalytic type of proteinase. Beef plasma protein (BPP) had a higher percentage of papain inhibitors, followed by whey protein concentrate (WPC), potato powder (PP), and egg white (EW). On the other hand, EW had a higher percentage of trypsin inhibitors followed by BPP, PP, and WPC. EW inhibited trypsin activity completely at levels as low as 1%. WPC inhibited the autolytic activity of fresh surimi. Bovine serum albumin (BSA) was not effective as WPC. WPC can be used as an inhibitor for the Pacific whiting surimi, but high concentration is required. A limited number of inhibitory components were found, as the components in food-grade inhibitors were characterized by inhibitory activity staining. Both EW and PP showed more serine proteinase inhibitors than cysteine proteinase inhibitors. PP showed one cysteine inhibitory component while EW did not show any. BSA in both WPC and BPP acts as an nonspecific competitive inhibitor and reduces the enzyme activity. An unidentified high molecular weight protein (HMP) found in WPC, BPP, and BSA functions as an alternative substrate for papain while it functions as true inhibitor for trypsin. / Graduation date: 1995

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 91-109). Also available on the World Wide Web.

This thesis is based on physical properties of fish meat and fish products. Texture of fish meat is considered as one of the most perceived character. Major influence on the textural properties of fish meat has chemical composition of fish meat and fish meat structure. Fish products are changed during production by influence of low temperature during frozen storage and influence of high temperature during cooking. Changes in the textural properties of fish muscle caused during the autolytic process after slaughtering. The aim of the thesis was compared different methods for measurement textural properties of fish and fish products. Surimi sticks and pre-fried fish sticks were tested. Common carp (Cyprinus carpio), Rainbow trout (Oncorhynchus mykiss) and Tench (Tinca tinca) were chosen for testing by penetration test (penetration of the probe into the sample) and Warner-Bratzler shear test (sample cutting by Warner-Bratzler shear).