51A-4

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

JUSTIFICATION: Conventional surimi processing for white fish utilizes <25% because refined myofibrillar proteins are washed away while removing unnecessary foreign materials. A recent patent (Hultin and Kelleher) that employs an acid-aided process demonstrated excellent gel forming ability for cod and mackerel with extremely higher yield. However, the role of sarcoplasmic proteins including enzymes, which are not removed in acid-aided processing, must be determined to apply this new method to Pacific whiting.

OBJECTIVES: To investigate effects of proteases during acid-aided surimi processing and to determine physico-chemical properties of surimi.

METHODS: Fillet was homogenized at 1:9 (w/v) ratio using 1 mM citric acid and adjusting pH to 2.5 using 1 N HCl. Acid homogenate was centrifuged at 10,000 x g for 20 min and the middle layer was saved. The pH was adjusted to 5.5 using 1 N NaOH. After dewatering by centrifugation at 3,000 x g for 20 min, sediment was collected. For conventional surimi, ground flesh was washed with 20 mM EDTA. Effect of pH and ionic strength on protein solubility during acid-aided surimi processing was assayed. Other biochemical properties measured inlcude: total protease, cathepsins (L, B, and H), Ca and Mg-ATPase, SH group, and hydrophobicity.

RESULTS: Muscle homogenates showed the highest solubility at pH ~2.3. Surimi from acid-aided processing showed higher proteolytic activities than that from conventional processing. However, during frozen storage at -20°C after 50 days, no difference was found between acid-aided and conventional surimi for cathespin L and B activities. Hydrophobicity also showed little difference between acid-aided and conventional surimi. Acid-aided surimi did not show significant difference between total and free SH group. Acid-aided surimi showed lower gel point compared to conventional surimi. Acceptable quality of surimi gels was produced using acid-aided method.

SIGNIFICANCE: Acid-aided surimi processing for Pacific whiting demonstrated great potential with its high yield and acceptable quality.