51A-9

P. LIAN and C. M. Lee. Dept. of Food Science & Nutrition, University of Rhode Island, Kingston, RI 02881

Fish mince is an important raw material in producing formulated seafood such as fish cakes and nuggets. Lean fish mince from gadoid species, however, develops textural hardening and poor dispersibility during frozen storage, which makes mixing difficult with added ingredients. To restore dispersibility and improve texture, it is necessary to study the textural deterioration mechanism and develop a proper cryoprotective system.

Our objectives were (1) to screen cryoprotective ingredients for preventing muscle fiber interaction and improving the dispersibility of fish mince; (2) to determine the extent of changes in free amino acids, protein extractability, free sulfhydryl content, textural properties, and microstructure of fish mince as affected by ingredients.

Red hake and Alaska pollock mince were respectively mixed with various levels of ingredients [0-4% sorbitol, 0-0.3% sodium tripolyphosphate (STPP), 0-4% soy protein concentration (SPC), 0-0.4% alginate, 0-0.4% iota-carrageenan] and stored at -20°C for 17 weeks. Changes in physicochemical properties and microstructure were investigated using the Instron testing machine, SDS-PAGE, HPLC, protein extractability, sulfhydryl content, cooking loss, quantitative descriptive analysis, and stereo and scanning electron microscopies.

The addition of 0.4% alginate, 4% sorbitol, and 0.3%STPP significantly improved the dispersibility by preventing congelation and myofibrillar protein denaturation in both frozen fish mince. This was indicated by significantly (p<0.05) lower penetration and shear forces and higher levels of salt- and SDS-soluble proteins and free sulfhydryl contents as compared to control or samples with other ingredients. Sorbitol-STPP with or without SPC and iota-carrageenan did not improve dispersibility. The formation of more free hydrophobic amino acids, especially leucine, was accompanied by less textural hardening. The differences in susceptibility between pollock and red hake may be attributed to calcium content.

The results show that fish mince from gadoid species can be cryostabilized with 0.4% alginate-4% sorbitol-0.3% STPP, thus making it suitable for formulated seafood products.