89B-18 |
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Y. J. CHOI, Div. of Marine Bioscience, Gyeongsang National Univ., 445 Inpyeong Dong, Tong Yeong, 650-160, South Korea and J. W. Park, Dept. of Food Science & Technology, Oregon State Univ., OSU Seafood Lab., 2001 Marine Dr., Rm. 253, Astoria, OR 97103. The quality of surimi is determined by color, along with other factors (moisture content, visual contaminants, gel strength. To be graded as a high grade, the whiteness must be high. Fish protein isolates obtained by alkaline and acidic processes contain more myoglobin and hemoglobin compared with conventional surimi. Therefore, to keep the color quality high, additional steps are likely needed in the alkaline and acidic processes. Our objectives were to determine the pH and thermal properties of myoglobin, and to investigate optimum processing steps for improving whiteness of fish protein isolates. Croaker and mackerel muscle were subjected to various methods of fish protein isolation using pH shift. Air-floatation was used as a means to improve whiteness. Myoglobin content and color of heat-induced gels were measured using a spectrophotometer and colorimeter, respectively. Breaking force and deformation values of gels prepared using 2% salt were measured using a penetration test. Myoglobin content in croaker and mackerel was 1.44±0.01 and 2.00±0.03 mg/g-muscle, respectively. The ratio of met-myoglobin was 79.3% for croaker and 88.1% for mackerel. Precipitation of myoglobin was observed at pH 5-6 for croaker and pH 6-7 for mackerel. Fish protein isolates showed a higher yield when air-float was applied after adjusting to pH 11 than before adjusting to pH 11. The yield increased as air-float time extended. When minced muscle was air-floated for 20 min, before adjusting to pH 11, lightness increased and yellowness decreased. Air-float for 10-20 min before adjusting to pH 11 was an optimum condition to improve whiteness of recovered proteins. However, gel properties such as breaking force and deformation were reduced by air-float. The air-float step in alkaline processing of fish muscle showed potential for improving the whiteness of fish protein isolates.
Session 89B, Aquatic Food Products: Surimi, gels and by-products
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |