83A-9 |
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J. G. MONTEJANO, V. E. Hernández, and O. G. Morales. Dept. of Agriculture & Food Technology, Instituto Tecnologico de Estudios Superiores de Monterrey, Epigmenio González No. 500, Col. San Pablo, Santiago de Querétaro, Querétaro, 76130, Mexico Surimi is usually handled as a frozen block which may be troublesome in developing countries. Freeze-drying will facilitate its handling, storage and use. Freeze-drying, however, decreases the strength and deformability of rehydrated gels, main quality criteria for evaluating a surimi. Our objective was to select the best combination of parameters and their levels that maximize the rheological quality of gels prepared from freeze-dried croaker surimi. Surimi was prepared by a series of three washing-dewatering steps and subjected to freeze-drying. The parameters were: (A) rehydation at moisture:protein levels of 4:1, 5:1 & 6:1; (B) 1, 3 & 5% modified potato starch; (C) 1, 2 & 4 % whey protein concentrate (WPC) and, (D) heating schedule: 90°C/15min, 25°C/120min+90°C/15min & 40°C/15min+90°C/15min. Gels were prepared by mixing the ingredients with a constant 2.5% NaCl and applying the appropriate heating schedule. A factorial design with fractional replication reduced the actual experimental combinations from 81 to 27. Shear stress and strain at failure were measured in the gels by a torsion test. A factorial ANOVA with confounded interactions was used. Once the statistical analysis predicted the best combination(s), a confirmatory experiment was conducted to corroborate the prediction(s). All the parameters showed a significant contribution to shear stress, with the highest due to the starch (26%) and the lowest to the WPC (8%). For strain the rehydration level had the highest contribution (22%) while the modified starch had the lowest (4%). The combination that maximized the rheological parameters was: rehydration level 5:1, 5% starch, 2% WPC and 25°C/120min+90°C/15min. Other 5 combinations presented values that were near the maximum. Experiments corroborated the predictions. It is possible to revert the decrease in rheological quality of surimi due to freeze-drying by selecting appropriate combinations of additives, rehydration levels and heating schedules. These combinations can also be used to achieve desired structural characteristics in different foods prepared from freeze-dried surimi.
Session 83A, Aquatic Food Products: Byproducts, mince and surimi
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