Carbon Dioxide Induced Soybean Protein Precipitation: Protein Fractionation, Particle Aggregation, and Continuous Operation

Authors

  • Russell Thiering,

    Corresponding author
    1. Laboratory for Process Equipment, Delft University of Technology, 2628 CA Delft, The Netherlands
    2. School of Chemical Engineering and Industrial Chemistry, The University of New South Wales, Sydney 2052, Australia
    • Laboratory for Process Equipment, Delft University of Technology, 2628 CA Delft, The Netherlands
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  • Gerard Hofland,

    1. Laboratory for Process Equipment, Delft University of Technology, 2628 CA Delft, The Netherlands
    2. Kluyver Laboratory for Biotechnology, Delft University of Technology, 2628 CA Delft, The Netherlands
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  • Neil Foster,

    1. School of Chemical Engineering and Industrial Chemistry, The University of New South Wales, Sydney 2052, Australia
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  • Geert-Jan Witkamp,

    1. Laboratory for Process Equipment, Delft University of Technology, 2628 CA Delft, The Netherlands
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  • Luuk van de Wielen

    1. Kluyver Laboratory for Biotechnology, Delft University of Technology, 2628 CA Delft, The Netherlands
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Abstract

A novel protein fractionation technique using a volatile electrolyte has been developed. Carbon dioxide was used to isoelectrically precipitate 80% and 95% pure glycinin and β-conglycinin fractions from soybean isolate. The protein fractions precipitated as primary particles 0.2−0.3 μm in diameter, which under optimum conditions may be recovered as aggregates up to 500 μm in diameter. The dependency of protein fractionation efficiency on aggregate settling rates has been demonstrated. The isoelectric points of the two main soybean fractions, glycinin and β-conglycinin, were calculated to be pH 5.2 and 4.95, respectively. Solution pH was accurately controlled by pressure in the isoelectric pH range of the different soybean protein fractions, and a pH “overshoot” was eliminated. Volatile electrolyte technology was also applied to a continuous process in order to eliminate the particle recovery concerns associated with batch precipitation and to demonstrate the potential for scale-up. Glycinin was effectively recovered on-line (94% glycinin recovery) with a purity approaching that of the batch process (95%).

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