Effects of thermal and electron beam (e-beam) processing on microbial inactivation and physichochemical properties of surimi and surimi seafood were investigated. Thermal-death-time (TDT) concept was used to model Staphylococcus aureus inactivation by heat and e-beam. Gurney-Lurie charts were used to estimate temperature during thermal processing of surimi seafood. Dose mapping technique was used to estimate dose absorbed by surmi seafood during e-beam processing. The dose absorbed increased up to 2 cm and then it gradually decreased, reaching a minimum at 5 cm depth of surimi seafood. It was determined that one and two-sided e-beam can efficiently penetrate 3.3 and 8.2 cm of surimi seafood, respectively. The D-value for thermally inactivated S. aureus was 0.65, 1.53, 6.52, 49.83, and 971.54 s, at 95, 85, 75, 65, and 55°C, respectively. The D-value for S. aureus inactivated with e-beam was 0.34 kGy. The z-value for thermally inactivated S. aureus between 55-95°C was not linear. Thermal processing degraded texture and color of surimi seafood. E-beam enhanced firmness and decreased the b* value of surimi seafood. Myosin heavy chain (MHC) degraded proportionally to the e-beam dose. Actin was not affected by e-beam except treatment at 25 kGy. Hydrophobic interactions and disulfide bonds were formed in raw Alaska pollock surimi when treated with e-beam. / Graduation date: 2002

Graduation date: 1998

Optimization of comminuting and heating conditions for surimi gel preparation obtained from three fish species: Alaska pollock (AP) (Theragra chalcogramma), Pacific whiting (PW) (Merluccius productus), and threadfin bream (TB) (Nemipterus spp.) was the focus of this study. Three parameters during comminution were separately evaluated: chopping time, chopping temperature, and salting time. Results from fracture gel analysis suggested a strong relation between the fish's environmental habitat and optimal final chopping temperature. Extending chopping time to 15 min under strictly controlled temperature at 0 ��C was preferable for cold water fish AP surimi. Even though high chopping temperature (20 ��C) for a shorter time (12 min) surprisingly resulted in strong gel texture similar to that of 0 ��C for 15 min, high chopping temperature should not be employed for AP surimi. AP could set as a gel at this temperature within a shorter time in a holding tank which could subsequently cause a problem when extruded on the cooking belt. Temperate water fish Pacific whiting, demonstrated its maximum gel strength when chopped at 15-20 ��C. The optimum comminution condition for warm water fish threadfin bream surimi was to chop the surimi until the paste temperature reached between 25-30 ��C. Prolongation of chopping once the surimi hit its threshold (optimum) temperature diminished the quality of the resulting protein gel. Cooling system connected to the chopping bowl is strongly recommended as it will allow the comminution process to be extended as long as possible until the surimi paste reaches its target temperature. Raman spectroscopy disclosed the different level of protein unfolding based on secondary structure of ��-helix and ��-sheet during various comminuting conditions. Unfolding of protein was facilitated by increased chopping temperature to a greater degree than extended chopping time. Extending chopping could denature the light meromyosin structure as it could not form a semi gel-like structure at temperatures between 32-40 ��C. Protein solubility of surimi paste in salt solution always decreased with prolonged chopping time. The decrease rate accelerated with increased chopping temperature. The formation of disulfide interchange gradually took place during chopping as observed from Raman spectroscopy. Also the surface hydrophobicity increased with extended chopping time. However, gel strength behaved differently according to the various chopping conditions indicating the lack of its relationship between salt soluble protein, disulfide formation, and surface hydrophobicity to gel strength. During extending chopping time, not only more mechanical force is applied to unfold protein structure, but proteins also have longer time to be extracted more by salt. Addition of salt at a different time during chopping process was therefore conducted using threadfin bream surimi due to its higher thermostability. Extending chopping time without salt followed by salt addition at the last step resulted in lower gel texture compared to the conventional chopping protocol where salt is always added at the early stage of comminution. Mechanical chopping could unfold protein structure; however, proteins, rather than staying solubilized, would precipitate and form a randomized structure under the chopping condition without salt. The heating condition greatly affected the gelation and rheological properties of AP surimi. The highest elastic modulus was obtained with the slowest heating rate at 1 ��C/min. Increased heating rate did not only shorten the time for proteins to unfold and form a well-organized network, it also interfered with the protein network through the vibration of water molecules as phase angle increased. This suggested that AP surimi gained more viscous properties and failed to form an elastic gel. Adjusting moisture content along with applying various frequencies did not alter the pattern of G' formation when paste was heated at different heating rates. AP surimi favored the slow heating. / Graduation date: 2013

Production of surimi represents a potential utilization of a number of low-valued fish species, one of which, Pacific whiting, represents the largest biomass off the West Coast of the United States. However, a protease enzyme softens the fish flesh in Pacific whiting and limits the expansion of surimi production. Many studies have demonstrated the importance of time and temperature in minimizing the texture softening. An optimal design of the surimi seafood process is possible only when an accurate prediction of the time-varying temperature distribution throughout the surimi product can be obtained. This provides a measure of the heating rate and the extent of thermal processing. Such a prediction necessitates a study of the surface heat transfer coefficient which is one of the most important parameters for the heat transfer analysis. Associated with automated-machinery processing of surimi seafoods, a full understanding of the heat transfer coefficient (h) is especially important because high-quality surimi products using Pacific whiting only can be obtained through rapid and controlled heating. This study was intended to determine transient surface heat transfer coefficients in a steam heating environment, simulating the widely-used steam heating of thin-sheet surimi paste in the seafood industry. In determining the heat transfer coefficient, many different methods have been used including the inverse calculation method, the lumped mass method and the heat flux method. This study employed all three to measure and model the heat transfer coefficient (h) under similar steam conditions. A comparative evaluation was made to define the best method and model for the h determination. The inverse calculation method produced an h model which, when applied to a heat transfer analysis, provided the best agreement between predicted and experimental temperature profiles at three locations in surimi paste during a 1000-sec cooking period. The lumped mass method overestimated the heat transfer coefficients to food; the heat flux method gave inconsistent measurements. It is a classic inverse problem to estimate surface heat transfer coefficients from temperature measurements inside a product, a procedure which involves solution of the inverse heat conduction problem and parameter optimization. A whole domain function specification procedure was developed for the inverse calculation method. This procedure simulates heat transfer coefficients as specified functions by estimating all the unknown parameters in the functions over the total time interval. A nonlinear regression computer program was written for the inverse calculation of surface heat transfer coefficients, incorporating the implict Crank-Nicolson scheme for the finite-difference formulation of the one-dimensional heat conduction problem and the downhill simplex method for parameter optimization. This inverse calculation method provided relatively accurate models of the surface heat transfer coefficient. / Graduation date: 1997

Optimization programming techniques were applied to develop the least cost formulations for Pacific whiting surimi-based seafood (PWSBS). To develop the quality constraint functions, texture and color of whiting surimi gels were determined by torsion test and colorimeter, respectively. Whiting surimi gels were produced by heating at 90��C for 15 min. with 2% NaCl, five final moisture contents (74, 76, 78, 80, 82%), and various combinations of beef plasma protein (0-2%), potato starch (0-8%), and two whey protein concentrates (0-8%). Due to the non-linear constraint functions describing texture and color, a non-linear programming search technique was required to solve the least cost model for PWSBS. Results for target quality constraints are reported in this study and show that whey protein concentrate increases the texture properties and can remain economically competitive with other ingredients which similarly influence functionality in PWSBS. Water holding capacity indicated by thermal transition was also studied as a measure of gel quality. The water evaporization process was quantified using differential scanning calorimetry (DSC) for surimi gels with added potato starch or whey protein concentrate. Pacific whiting surimi gels were produced by heating in a sealed DSC pan from 30 to 90��C at a rate of 5��C/min.; gelled samples were then re-heated from 30 to 180��C at 2��C/min. in an open pan using an equivalent water mass as a reference. The DSC thermogram showed one exothermic peak followed by one endothermic peak, the former indicating a relative energy flow from the protein gels due to the delayed water evaporation. DSC parameters derived in this study showed good correlation with the texture properties of protein gels. The addition of whey protein concentrate and the increase of heating rate increased the water holding capacity of whiting surimi gels. / Graduation date: 1996

Feasibility of ohmic heating to overcome gel-weakening in Pacific whiting surimi was investigated. An ohmic heating apparatus was developed using two rhodium-coated stainless steel electrodes inside a polyvinyl chloride (PVC) tube, a variable transformer, and voltage and current transducers. Rapid heating associated with the ohmic process quickly inactivated endogenous proteinase(s), resulting in significantly high shear stress and shear strain of surimi gels (78% moisture content, 2% NaCl). Degradation of myosin heavy chain (MHC) and actin examined by SDS-PAGE were significantly reduced and continuous gel structure were shown by scanning electron microscopy. Whiting surimi heated in a 90°C water bath for 15 min exhibited poor gel quality and disordered microstructure due to proteolysis of MHC. Electrical conductivity, a critical parameter influencing rate of heat generation during ohmic heating, was elucidated. Electrical conductivities of whiting surimi pastes with four moisture contents (75, 78, 81, and 84% wet basis) and added NaCl (1, 2, 3, and 4%) were measured from 10 to 90°C using ohmic heating at voltage gradient of 3.3, 6.7, and 13.3 V/cm. Electrical conductivity significantly increased with temperature and salt content and slightly increased with moisture content. The effect of the voltage gradient was evident at combinations of high moisture (81, 84%) and NaCl content (3, 4%), due to electrochemical reactions at the electrodes. The empirical model of electrical conductivity as a function of temperature and compositional characteristics predicted values with an error range of 0-15.6%. Finally, kinetic models of textural degradation of whiting surimi were developed using two different approaches: isothermal and nonisothermal procedure over a range of temperature (40-85°C) and time (0.5-35 min). The effect of thermal lag was accounted for using the models derived from the Arrhenius equation. Textural degradation obtained from both methods followed first order kinetic. Degradation of MHC derived from nonisothermal procedure was best described by apparent reaction order of 1.4. Degradation rate of gel texture and MHC increased with temperature and reached the highest rate at 55 and 57°C, respectively. Then they decreased to minimum rate at 70 and 75°C, respectively. The kinetic model for the loss of MHC satisfactorily estimated MHC content of the controls with an averaged error of 10.8%. Relationship between degradation of MHC and gel texture are discussed. / Graduation date: 1996

Graduation date: 1998

Thesis (M.S.)--Oregon State University, 1999. / Typescript (photocopy). Includes mounted photographs. Includes bibliographical references (leaves 77-86). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 70-82). Also available on the World Wide Web.

Anserine and carnosine are water-soluble dipeptides that have antioxidant properties and are found in the skeletal muscle of mammals and fishes. These dipeptides are removed through the washing process in surimi production. The objective of this research was to determine the concentration of anserine and carnosine in surimi wash water (SWW) at all stages of surimi processing, and undertake preliminary methods to remove and concentrate the two dipeptides and study the effect of surimi wash water extract on color. Wash water samples were collected from a local surimi plant. The samples were treated by the following methods: centrifugaion, heat-treatment at 60, 80 and 100°C and filtration using different ultrafiltration (UF) membranes. The concentrations of the protein and the two dipeptides were analyzed using Lowry and high performance liquid chromatography with a fluorescent detector, respectively. Iron content was determined in SWW samples using atomic absorption spectrometry and colorimetry. Effect of SWW extract and other antioxidants on the color of fresh-farmed salmon were studied using color parameters-hue angle, chroma and lightness. Results showed that there was a trend: content of protein and dipeptides (anserine and carnosine) in SWW (raw) was higher in the first two stages of surimi processing. In the second set of experiment, where different heat treatments were used, it was found that the proteins and dipeptides showed similar trends. Additionally, 80°C followed by 100°C treatment were effective in removal of proteins and recovery of dipeptides. Among UF treatments, 1K molecular weight cut-off membrane was the most effective in recovery of dipeptides. Iron was less than 1 ppm in all SWW samples. Color measurement of fresh farmed salmon patties revealed that treatments of SWW extract (1%) in addition to other food antioxidants such as butylated hydroxy toluene and camosine (1%), mamtained salmon color until day 5. Therefore, SWW extract at lower concentrations may have an economical and potential use as a food antioxidant. / Graduation date: 2000