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Article| Volume 79, ISSUE 5, P782-790, May 1996

Effects of Limited Proteolysis on the Microstructure of Heat-Induced Whey Protein Gels at Varying pH

  • J. Otte
    Correspondence
    Corresponding author.
    Affiliations
    Institute for Dairy and Food Science, The Royal Veterinary and Agricultural University, Rolighedsvej 30, 1958 Fredericksberg C, Denmark
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  • Author Footnotes
    2 Permanent address: Department of Animal Science, South China Agricultural University, Guangzhou 510642, China.
    Z.Y. Ju
    Footnotes
    2 Permanent address: Department of Animal Science, South China Agricultural University, Guangzhou 510642, China.
    Affiliations
    Institute for Dairy and Food Science, The Royal Veterinary and Agricultural University, Rolighedsvej 30, 1958 Fredericksberg C, Denmark
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  • A. Skriver
    Affiliations
    Institute for Dairy and Food Science, The Royal Veterinary and Agricultural University, Rolighedsvej 30, 1958 Fredericksberg C, Denmark
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  • K.B. Qvist
    Affiliations
    Institute for Dairy and Food Science, The Royal Veterinary and Agricultural University, Rolighedsvej 30, 1958 Fredericksberg C, Denmark
    Search for articles by this author
  • Author Footnotes
    2 Permanent address: Department of Animal Science, South China Agricultural University, Guangzhou 510642, China.
Open ArchiveDOI:https://doi.org/10.3168/jds.S0022-0302(96)76426-3
Effects of Limited Proteolysis on the Microstructure of Heat-Induced Whey Protein Gels at Varying pH
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      Abstract

      Whey protein solutions, reconstituted 12% commercial whey protein isolate, were hydrolyzed at pH 7.0 by one of three proteases: trypsin, Neutrase® (from Bacillus subtilis), and a Bacillus licheniformis protease. Heat-induced gels were made from the hydrolysates after pH adjustment, and their microstructure was examined by transmission electron microscopy and compared with the structure of control gels made from unhydrolyzed whey protein solutions.
      The gels formed from the unhydrolyzed whey protein solutions, as expected, were fine-stranded when set at pH 3.0 and 7.0 and particulate when set at pH 5.2. The enzymatic treatments caused alterations in the microstructure of the heat-induced gels. The changes were small at pH 3.0, marked at pH 5.2, and strongest at pH 7.0. Of special interest was the dramatic change in the microstructure of the gels set after treatment with Bacillus licheniformis protease. The Bacillus licheniformis protease gels consisted of small aggregates (∼0.1 μm) arranged in open clusters (pH 5.2) or tightly packed in a regular pattern (pH 7.0), corresponding to a high gel strength.
      Limited hydrolysis is thus a way to change the microstructure and properties of gels at weakly acidic and neutral pH, a range that is suitable for the production of many foods.

      Key words

      Abbreviation key:

      BLP (Bacillus licheniformis protease), WP (whey proteins), WPI (WP isolate), WPS (WPI solution)

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      Article info

      Publication history

      Accepted: December 27, 1995
      Received: July 11, 1995

      Identification

      DOI: https://doi.org/10.3168/jds.S0022-0302(96)76426-3

      Copyright

      © 1996 American Dairy Science Association. Published by Elsevier Inc.

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