51A-5

O. ESTURK, J. W. Park, and B. Y. Kim. OSU Seafood Lab and Dept of Food Science & Technology, Oregon State University, 2001 Marine Dr. #253, Astoria, OR 97103

JUSTIFICATION: Fracture gel analysis used in surimi industry, which requires 24 hr to complete gel testing, is time consuming. Therefore, results are obtained too late to make proper adjustment during processing. Dynamic rheology measurements, however, do not require troublesome sample preparation or long testing time. It could, therefore, be a useful tool in determining surimi gel quality if a quality index(s) is found based on the relationship between the torsion test and dynamic rheology measurements.

OBJECTIVES: To characterize surimi based on dynamic rheology properties at various moisture, setting, and pH conditions, and to find a relationship between dynamic rheology properties and fracture gel quality

METHODS: Two different grades of Pacific whiting surimi were obtained from local manufacturers. The samples were stored at -30°C throughout the experiment. The surimi was tested at different moisture (75, 78, 81, 84, 87, and 90%), pH (6-9), and setting conditions (24 hr at 5°C and 3 hr at 25°C). Non-fracture properties (G', delta, viscosity) of surimi were measured using Bohlin Rheometer. After cooking at 90°C for 15 min and storing at 5°C for 24 hrs, surimi gels were tested for fracture shear stress and fracture shear strain using a torsion gelometer.

RESULTS: Fracture shear stress values of Pacific whiting surimi were significantly affected by moisture levels, while fracture strain values remained constant. Setting increased fracture shear stress values significantly. However, there was no effect of setting on fracture strain value. Setting at 25°C was more effective than setting at 5°C for shear stress. Temperature sweep, stress sweep and frequency sweep data showed that there is a relationship between fracture properties and dynamic properties (G' and delta). The effects of pH levels and setting conditions were also evaluated using a model relating the two rheological properties.

SIGNIFICANCE: Early determination of the quality of surimi gels can be achieved using dynamic rheology properties.