51A-39

J. A. RAMíREZ, Depto. de Ciencia y Tecnología de Alimentos, Universidad Autónoma de Tamaulipas, Apdo. Postal 1015, Reynosa, Tamaulipas, 88740, Mexico, I. A. Santos-Sánchez, Depto de Ciencia y Tecnología de Alimentos, Universidad Autónoma de Tamaulipas, O. G. Morales, Instituto de Ecología y Alimentos, Universidad Autónoma de Tamaulipas, Cd. Victoria, Tamaulipas, M. T. MORRISSEY, Seafood Laboratory/Dept of Food Sci & Technology, Oregon State University, Room 253, 2001 Marine Dr, Astoria, OR 97103, and M. VáZQUEZ, Depto. Química Analítica, Bromatología y Nutrición, Universidad de Santiago de Compostela, Área de Tecnología de los Alimentos, Escuela Politécnica Superior, Lugo, 27002, Spain.

JUSTIFICATION:Fish protein below 40°C forms an elastic gel after adding NaCl. This aggregation phenomenon of myofibrillar proteins is termed setting. Optimal setting conditions for setting depend on fish species and habitat. Setting is associated with activity of an endogenous transglutaminase (TGase). Therefore the use of microbial Tgase to improve the setting can be an interesting alternative.

OBJECTIVES:The objective of this work was the optimization of setting using microbial TGase in silver carp (Hypophtalmichtys molitrix), a warm water fish.

METHODS: Surimi sols were obtained with 2.5% sodium chloride. A second-order, incomplete, factorial design of experiments was used to develop empirical models providing a quantitative interpretation of the relationship between the operational conditions of the setting process. Concentration of microbial TGase (0, 5 or 10 g/kg), temperature (25, 35 or 45°C) and time (1, 3 or 5 h) were optimized to improve the mechanical properties of surimi produced from silver carp. Surimi gels were analyzed employing the torsion test to determine shear stress and shear strain at the failure.

RESULTS: The shear stress varied over a wide range (24 - 149 kPa). Enzyme concentration had the most influence on shear stress. Shear strain showed a behavior different. The experimental results varied within the narrow range 0.8542-1.6343, the most favorable conditions being defined by intermediate values of enzyme concentration and the lowest values of temperature and time. The the variable time did not affect shear strain.

SIGNIFICANCE: Optimal predicted mechanical properties were obtained by employing the following setting conditions: a concentration of microbial TGase of 8.8 g/kg of surimi, at 39.6°C for 1 hr. Under these conditions, a surimi from silver carp with a shear stress at the failure of 146 kPa and a shear strain at the failure of 1.68 was obtained.