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Composition, quality and physicochemical properties of catfish surimi compared to catfish protein isolates from acid and alkali-aided processing |
N. DEMIR and H. G. Kristinsson. Dept. of Food Science & Human Nutrition, Univ. of Florida, 359 FSHN Bldg., Newell Dr., PO Box 110370, Gainesville, FL 32611-0370 Proteins can be successfully recovered from fish muscle with a novel acid or alkali-aided process. This process has been shown to compare well with surimi processing for many species. Its success with catfish remains to be investigated. The objective was to compare the composition, quality and physicochemical properties of catfish surimi vs. catfish protein isolates (PI) produced with acid and alkali-aided processing. Acid and alkali PI’s were prepared from ground catfish muscle by solubilizing the muscle proteins at low (2.5) and high (11) pH followed by centrifugation and collecting the proteins with isoelectric precipitation. A variation of the acid and alkali process was used where one centrifugation step was omitted. Surimi was prepared using a conventional method. Recovery of proteins and reduction of lipids were measured for the final material. Color and oxidation (TBARS) changes during storage (4°C) were analyzed. The ability of surimi and PI’s to form gels was studied in a rheometer using oscillatory testing and also using gel penetration tests. Compared to surimi, the acid and alkali process gave significantly higher protein recoveries (62.3% vs. 71.5% and 70.3%, respectively) and more lipid reduction (58.3% vs. 85.4% and 88.6%, respectively). Omitting one centrifugation in the acid and alkali process gave higher protein recoveries but lower lipid reductions. Alkali produced PI’s exhibited best color characteristics of the samples, with higher L* and lower b* values and also exhibited the best oxidative stability. Alkali PI’s and surimi had similar gel forming abilities which were superior to the acid PI’s. Omitting one centrifugation step led to PI’s with lower oxidative stability but better gelation properties. The results show that the alkali process is more successful then surimi in producing protein ingredients of good quality and functionality from catfish. The reason why acid processing yields lower quality protein ingredients needs further study.
Session 40, Aquatic Food Products: Surimi and proteins
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