17E-20 |
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B. INGADOTTIR and H. G. Kristinsson. Dept. of Food Science & Human Nutrition, Univ. of Florida, 130-B Aquatic Foods Pilot Plant, PO Box 110370, Gainesville, FL 32611-0370 Functional proteins can be successfully recovered with acid and alkali-aided solubilization followed by isoelectric precipitation. For maximum recovery, high solubilization of proteins at low or high pH as well as low viscosity is required to facilitate separation of soluble proteins from undesirable components with centrifugation. The objective was to investigate changes in protein solubility and viscosity of tilapia light muscle homogenate in the pH range utilized in the acid and alkali-aided processes. Tilapia light muscle homogenates were prepared by using three different homogenization times 60, 90 or 120 sec. The homogenates were adjusted to pH 1.5-12 in 0.5 pH intervals and protein solubility determined with the Biuret method after centrifugation. For more detailed analysis at high and low pH, homogenates were adjusted to pH 10.8-11.4 and 2.3-2.9 in 0.2 pH intervals. The viscosity and time dependent flow properties of the homogenates were analyzed at various low and high pHs at 5°C using a single gap, cylinder geometry and an advanced research rheometer. The tilapia proteins exhibited high solubility below pH 4 and above pH 10.5, with minimum solubility at pH 5-5.5. Different homogenization times at low and high pH resulted in very similar solubilities, or approximately 90%. The viscosities of the homogenates were low (~50-80 mPa) at pH 2.3-2.5 and 10.8-11.4, sufficient to facilitate the separation of membranes from proteins, while they were significantly higher at pH 2.7-2.9 (200-300 mPa). The tilapia homogenates exhibited shear thinning when run with an oscillatory frequency sweep. Using time sweep, the homogenates treated with low pH exhibited an increase in viscosity when pH was raised, whereas treatment with high pH showed a decrease in viscosity The results identified the range of pHs suitable for the recovery of muscle proteins from tilapia. Future research is aimed at studying the functionality of the recovered proteins.
Session 17E, Food Chemistry: Proteins
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