Some Chemical and Nutritional Properties of Feather Protein Isolates Containing Varying Half-Cystine Levels

  • John P. Cherry
  • Kay H. McWatters
  • Josephine Miller
  • A. Lorne Shewfelt
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 86)


Feather (keratinous) protein isolates containing 2.8 and 7.2% half-cystine were prepared. Solubility of the former increased to 100% between pH 6 and 12, whereas, that of the latter reached only 2.5% at pH 12. Tests showed that mixtures of sodium dodecyl sulfate and 2-mercaptoethanol were needed to completely solubilize the high half-cystine protein, and that sodium dodecyl sulfate alone or in combination with urea and/or 2-mercaptoethanol increased solubilization of the low half-cystine product. The rates of these reactions are further increased by heat. Dry heat denatured the low half-cystine isolate more readily than the high half-cystine product; moist heat denatured both at a similar rate. Gel electrophoretic properties were unique for each keratinous product. Only the low half-cystine isolate had desirable functional properties in that it formed thick, viscous mayonnaise-like emulsions and desirable foams. Functional properties of this isolate were improved dramatically by adjusting the pH from 5.0 to 8.2 or by a two-step change from pH 5.0 to 4.0 to 8.2. Apparent nitrogen digestibility of the two keratinous isolates was greater than 90% as measured by rat growth and by pepsin-HC1 digestion.


Zinc Manganese Steam Boron Glycine 
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Copyright information

© Springer Science+Business Media New York 1977

Authors and Affiliations

  • John P. Cherry
    • 1
  • Kay H. McWatters
    • 1
  • Josephine Miller
    • 1
  • A. Lorne Shewfelt
    • 1
  1. 1.Department of Food ScienceUniversity of Georgia College of Agriculture Experiment StationsExperimentUSA

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