Protein solubility of Pacific whiting muscle with isoelectric point at pH 5.5 was significantly affected by pH. The highest breaking force was measured from fish proteins treated at pH 11, while high deformation values were obtained at pH 2 and 11. Texture of gels made using the conventional method were quite inferior to gels made using fish proteins treated at pH 2 or 11, while color of conventional gels was significantly better than the other treatments. SDS-PAGE revealed that fish proteins were highly denatured during acid or alkali treatment. High cathepsin B-like activity was detected from acid-aided fish proteins. Strong cathepsin L-like activity was found in fish proteins treated at pH 10.5, which corresponded with the lower breaking force and deformation obtained from those samples. Disulfide bonds contributed to high texture value in fish proteins treated at pH 11. Physicochemical characteristics of sarcoplasmic proteins (SP) from rockfish and their interaction with Alaska pollock surimi (myofibrillar proteins) were investigated. Solubility of SP was significantly suppressed at acidic pH (2-4) plus high salt concentration (0.5 M NaCl). This was also supported by SDS-PAGE results (extensively degraded SP). DSC results revealed SP gave three endothermic transitions. The least amount ofproteins was lost when treated at pH 2 or 3 followed by precipitation at pH 5.5. SP did not enhance the gelation properties of myofibrillar proteins, but positively contributed to gelation with myofibrillar proteins when compared to sucrose. Myofibrillar proteins were primary components contributing to heat-induced gelation. Salt effect on acid- or alkali-treated surimi gel was investigated. Good gels were obtained without salt using acid- and alkali-treated fish proteins. Their texture properties decreased as NaCl content increased, unlike conventional surimi gels. Consequently, NaCl did not solubilize myofibrillar proteins once the fish proteins were treated by acid or alkali. Solubility was apparently not a key factor for the texture properties of acid- or alkali-treated surimi. Transglutaminase-mediated setting reaction was partially inactivated during acid or alkaline treatment. Acid-treated surimi gel gave the best color properties. / Graduation date: 2003

The effect of salt (0, 0.9, 1.7, 2.5%) and pH (range 4 to 10) on surimi gels made from Pacific Whiting (Merluccius productus) was investigated. Gel-forming ability was measured by the torsion test. In general, surimi gels increased in gel strength with increased pH. Breaking shear stress increased to a greater degree than breaking shear strain above pH 7.0. The increase in gel strength was greater at higher pHs for gels made without salt than those made with salt. At neutral pH, the salted surimi showed greater gel forming abilities than the unsalted whiting surimi. Poor gels were formed at low pH (pH 4 to 6) for both the salted and no-salt surimi. These results demonstrated that pH and salt concentration had an interactive effect on the gel-forming ability of the Pacific whiting surimi and that improved gel strength at low salt levels might be obtained by increasing the pH. / Graduation date: 1993

In surimi manufacturing, less than 25% of the total weight of the fish is utilized. This research focused on meat recovery from fish frames, the residual portion of the fish after filleting headed and gutted fish. A new technology, the water jet deboning (WJD) system, was tested. The WJD system uses oscillating high pressure water jet nozzles to recover edible flesh from the frames without breaking the kidney located under the backbone. To evaluate the function of added salt on dewatering and process recovery, the WJD was operated without NaCl (WJD1) and with 0.2% NaCl added to the discharge slurry (WJD2). In conventional mechanical deboning process (MD), which was the other deboning system applied in the study, no salt was used. The recovered frame meat was further processed to surimi and then stored at -18��C. Meat recovery and surimi processing yields were compared between the three meat recovery processes. Functional properties of gels (texture and color) were evaluated after 1 and 6 mo frozen storage and compared to commercially manufactured surimi, which served as a control. As a result of manual trimming, the maximally recoverable meat from the frames was 42.8% of frame weight. MD showed the highest mince yield (mince prior to cryoprotectant addition), 24% of frame weight, while the two WJD methods resulted in only 5% yield. Color and shear strain for gels from WJD1, MD surimi and mixtures of those and control (10-20% frame mince surimi/80-90% control), were comparable to control. Gels from WJD2 showed significantly lower lightness (L*) but did not differ otherwise. Shear stress values of all frame meat surimi gels and the gels from mixtures of those and the control were significantly lower than the control. This low shear stress is probably due to a difference in processing equipment and processing conditions between the lab scale and the commercial scale. Due to the promising processing yield for the MD system an additional study was performed where effects of kidney and kidney blood contamination in the frame mince were investigated. Pacific whiting frames were mechanically deboned with/without kidney and the frame mince further processed into surimi. Functional properties of gels (texture and color) were evaluated after 1 and 6 mo frozen storage and compared to commercially manufactured surimi, which served as a control. At 1, 2, 4, and 6 mo, salt extractable proteins (SEP) concentration, dimethylamine (DMA) formation and pH were measured to monitor protein denaturation. Removing the kidney and washing the frames prior to MD resulted in higher gel strength after 1 and 6 mo frozen storage. / Graduation date: 2000

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.

The major portion of Pacific whiting (PW) is commercialized in the form of frozen surimi. Alternative products for PW were investigated focusing on fresh surimi and texturized meat from PW mince. Fresh surimi is made without additives and kept refrigerated instead of frozen. Texturized meat is a meat-like product made from PW mince through freeze-texturization. Fresh surimi was stored at 5°C and analyzed for its total aerobic plate count (APC), shear stress, shear strain, and color during 7 days storage. Frozen surimi from PW was prepared with 0, 3, 6, and 9% cryoprotectants and was compared with fresh surimi for its gel forming ability. Fresh surimi had a shelf life of 5 days and the gel forming ability remained unchanged throughout storage time. Shear strain of fresh surimi was not different from frozen surimi with 9% cryoprotectants but shear stress was almost 3 times higher than the frozen one. Texturized meat from PW mince was prepared from unwashed or 1-washed mince kept frozen for 6-8 mo with or without the addition of 6% cryoprotectants. The minces were comminuted into a protein slurry, formed into patties, and frozen at -7, -18, and -50°C. The evaluations of ice formation (by microscopic study), hardness, cook loss, color, and water holding capacity were carried out during 20 days storage. The results showed that texturized meat with parallel layers was made from 1-washed PW mince. Unwashed PW mince created a sponge-like texture and had rapid quality deterioration, thus it is not recommended for this product. Cryoprotectants did not significantly affect the texture formation of the product and are not required to store mince as raw material for the texturized meat. The optimum freeze-texturized temperature for this product was -18°C or lower because it minimized quality changes during storage depending on the desirable texture. The lower the temperature (higher freezing rate), the finer the layers created. / Graduation date: 1996

The results of SDS-PAGE and densitometry indicated that a significant amount of myofibrillar proteins was lost during surimi processing. Microfiltration (MF) was utilized to recover insoluble particulate. The MF-recovered proteins showed highly functional properties in gel hardness, cohesiveness, color, and water retention ability. The soluble proteins concentrated by ultrafiltration (UF) possessed dark colors and strong odors. However, the use of UF demonstrated the possibility of recycling water in leaching systems. To reduce the loss of myofibrillar proteins during processing, the factors causing solubilization of myofibrillar proteins were investigated. Myosin and actin were highly soluble when their ionic strengths were substantially reduced. Salt concentrations of 0.25%, 0.5%, and 1.0% NaCl reduced the solubility of myosin and actin but did not remove sarcoplasmic proteins effectively. At 2.0% NaCl, severe loss of myosin, actin, α-tropomyosin, β-tropomyosin, and troponin-T was observed. At low water/meat ratio (2:1) with increased washing cycles and washing time, more sarcoplasmic proteins per unit of water were removed without a noticeable loss of myosin or actin. Myosin heavy chain (MHC) content, water retention ability, and whiteness of the washed mince were comparable to that at high water/meat ratio (4:1). Prolonged storage and elevated temperatures caused a severe proteolysis of myofibrillar proteins. The degraded proteins had higher solubility than their native myofibrillar proteins. MHC and actin degradation both showed a good correlation to protein solubility. The relationship between conformational changes and solubility of myofibrillar proteins was investigated using myosin as a model system. The results showed that adding salt or shifting pH from the isoelectric point of myosin caused an increased surface hydrophobicity and a decreased helix structure. A slightly increased sulfhydryl content was also observed. These conformational changes resulted in an increased solubility. At high salt concentration (>1.0 M), myosin regained its helix structure with a concomitant loss of solubility. The salting out effect was probably due to the dominant hydrophobic interaction among nonpolar amino acids residues. / Graduation date: 1996 / Best scan available. Original is a black and white photocopy.

Graduation date: 2000

No description available.

Graduation date: 1997

The rheological, color, micro-structural, and electrical properties of surimi seafood gels were investigated. Various starches and protein additives at different ratios were evaluated with Alaska pollock surimi under ohmic heating at different heating rates to determine their functional properties and further to compare these properties with those of conventionally cooked gels. Native starches at low concentration were able to enhance rheological properties due to their gelatinization during heating. Pregelatinized starch decreased texture properties; however, it could suppress the undesirable appearance of the final product because its granules could absorb the surrounding water during chopping and perform a higher degree of retrogradation when cooling. A mixture of native and pregelatinized starches showed a positive trend at high concentration. The more starch added, the lower the L* and b* values of the gels. Protein additives improved textural properties, but negatively affected gel colors. Lower moisture content of the final products showed higher strength in texture, but lower lightness values. Gels cooked under ohmic heating with a slow heating rate mostly exhibited better texture properties than conventionally cooked gels. Electrical conductivities increased when temperature increased, resulting in a linear relationship. Electrical conductivity also significantly increased with moisture content, and slightly increased with applied frequency and voltage. There were some changes in the magnitude of electrical conductivity of surimi-starch paste when temperature increased, most obviously seen at a high concentration of native starch with slow ohmic heating. This indicated that starch gelatinization affected the electrical conductivity of surimi-starch paste while heating. / Graduation date: 2003