Preliminary study of the influence of dextran on the precipitation of legumin from aqueous salt solutions |
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| Authors: | GALINA E. PAVLOVSKAYA D. JULIAN McCLEMENTS MALCOLM J.W. POVEY |
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| Affiliation: | Department of Food Science, University of Leeds, Leeds, UK, Institute of Food Stuff Substances, USSR Academy of Sciences, Moscow, Russia and Department of Food Science and Technology, University of California, Davis, CA, USA |
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| Abstract: | Ultrasound has been used to study the behaviour of dextran, legumin (11s globulin of the broad bean Vicia faba ) and their mixtures in aqueous salt solutions under different physico-chemical and thermodynamic conditions. The attenuation coefficient of the solutions was measured as a function of pH (3–10) and ionic strength (0, 0.025, 0.05 M NaCl). The attenuation in the dextran solutions was independent of pH and ionic strength, whereas that in the solutions containing legumin had a maximum value near to the isoelectric point of the legumin (∼φ 5). The magnitude of this maximum depended on the ionic strength of the solution. The cause of the observed attenuation was scattering of ultrasound by precipitated protein. The addition of dextran to solutions where the biopolymers are thermodynamically compatible decreases the attenuation, whereas its addition to solutions where the biopolymers are incompatible increases it. This is because protein precipitation is greater in incompatible systems. |
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| Keywords: | Scattering ultrasound thermodynamic incompatibility precipitation measurement |
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