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  • 1
    Electronic Resource
    Electronic Resource
    Thermal isoelectric precipitation of α-lactalbumin from a whey protein concentrate: Influence of protein-calcium complexation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 121-130 
    Details
    ISSN: 0006-3592
    Keywords: α-lactalbumin ; whey ; isoelectric precipitation ; calcium complexation ; modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The selective precipitation of α-lactalbumin (α-LA) at a pH around its isoelectric point (4.2) under heat treatment is the basis for a fractionation process of whey proteins. As precipitation is a phenomenon dependent on the protein hydrophobicity, and as the release of the tightly bound calcium occurring at pH around 4 modifies the α-LA hydrophobicity, the specific role of calcium on isoelectric precipitation is investigated. A study of the extent of α-LA precipitation in a whey protein concentrate under various operating conditions of pH, temperature, protein concentration, and calcium content is presented. We propose a mechanism for this phenomenon as a combination of a complexation equilibrium and of an irreversible precipitation, to account for the influence of temperature, α-LA concentration total ionic content, and calcium concentration, and also to estimate the complexation equilibrium constant. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470202
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  • 2
    Electronic Resource
    Electronic Resource
    Whey protein fractionation: Isoelectric precipitation of α-lactalbumin under gentle heat treatment (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 391-397 
    Details
    ISSN: 0006-3592
    Keywords: whey ; fractionation ; α-lactalbumin ; citrate ; co-precipitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The selective precipitation of α-lactalbumin (α-LA) at a pH around its isoelectric point (4.2) under heat treatment is the basis for a fractionation process of whey proteins. In these conditions, β-lactoglobulin remains soluble, whereas bovine serum albumin and immunoglobulins co-precipitate. Knowledge of the mechanism governing the α-LA precipitation influences the choice of operating conditions and enables optimization of the fractionation process. α-LA is a calcium metallo-protein and its isoelectric precipitation is governed by the protein-calcium complexation equilibrium. Citrate, a sequestrant of calcium, decreases the free calcium concentration and displaces the precipitation phenomenon to a lower temperature range. A study of the effect of citrate on the precipitation phenomena of whey proteins is presented. Whatever the citrate content, precipitation curves for bovine serum albumin (BSA) and α-LA intersect at a temperature around 45°C. For a temperature of heat treatment lower than 40°C, a selective enrichment in α-LA of the precipitated phase is observed. As addition of citrate leads to high α-LA precipitated fractions at a temperature around 35°C, the precipitation step may be performed at this temperature. It results in a reduced heat denaturation of whey proteins and in a higher α-LA purity in the precipitated fraction. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 391-397, 1997.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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