51A-2

G. S. CHOUDHURY, FITC, FITC/SFOS University of Alaska Fairbanks, Kodiak, 900 Trident Way, Kodiak, AK 99615 and A. GAUTAM, FITC/SFOS, Kodiak, AK.

JUSTIFICATION: Studies in our laboratory have shown that addition of fish muscle to rice flour reduced extrudate expansion and increased hardness. Enzymatic modification of proteins in fish muscle may provide an avenue to increase product expansion and reduce hardness. OBJECTIVE: To evaluate the effect of added hydrolyzed fish muscle on macroscopic attributes of rice flour extrudate. METHODS: Hydrolyzed fish muscle was prepared by autolyzing arrowtooth flounder muscle using an endogenous muscle protease and the degree of protein hydrolysis was varied by controlling the hydrolysis time (0, 5, 10 & 15 min). Four blends for each degree of hydrolysis were prepared by mixing rice flour (100%, 95%, 90%, 85%) with hydrolyzed fish powder (0%, 5%, 10%, & 15%), and were extruded using a Clextral co-rotating, twin-screw extruder (BC 21). The length to diameter ratio was 32:1 and a 5 mm diameter circular die was used. The temperature profile in eight barrel sections were set at 0, 30, 30, 30, 70, 100, 150, and 150°C. Feed flow rate, screw speed, and moisture content were kept constant at 12 kg/h, 400 RPM, and 15%, respectively. Macroscopic characteristics evaluated were densities (true and apparent), expansion ratio (radial, axial, overall), porosity and breaking strength. RESULTS: Addition of hydrolyzed fish muscle significantly altered expansion and textural attributes of extrudates. Autolysis changed the properties of arrowtooth flounder muscle so much that the extrudates obtained from blends of autolyzed fish solids and rice flour were more porous and had higher expansion, lower density and lower breaking strength than those produced from rice flour alone. SIGNIFICANCE: The data suggest that the detrimental effects of protein on attributes of expanded products can be overcome or eliminated by enzymatic modification of fish proteins. This may lead to increased use of proteins in expanded products.