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Chapter 14: Proteins that Complement the Roles of Gliadin & Glutenin


B.L. Jones, RR1, Box 6, Kooskia, Idaho 83539, USA; C.F. Morris, USDA ARS Western Wheat Quality Lab., Pullman, WA 99164-6394 USA; F. Békés, CSIRO Plant Industry, Canberra, ACT 2600, Australia; C.W. Wrigley, Food Science Australia and Wheat CRC, North Ryde (Sydney), NSW 1670, Australia

Gliadin and Glutenin: The Unique Balance of Wheat Quality
Pages 413-446
DOI: https://doi.org/10.1094/9781891127519.019
ISBN: 978-1-891127-51-9





Abstract

The complete story of how proteins relate to flour quality cannot be told only in terms of the gliadin and glutenin proteins. Even water-washed gluten contains more than these two classes of protein. Furthermore, specific proteins besides (and in cooperation with) gliadin and glutenin have been shown to play significant roles in determining the functional properties of flour. Despite its restricted title, this book would not have been complete without acknowledging these complementary proteins and devoting a chapter to them. If the term “prolamins” is used to designate the gliadins and glutenins, then the “other” proteins can best be described as the “non-prolamin” proteins of flour.

The contribution of the non-prolamin proteins to flour quality, and especially to its breadmaking properties, makes them potentially important players for improving flour quality. There is thus a need for gaining a better understanding of these proteins and of the genes controlling their synthesis. The gluten proteins are undoubtedly the major contributors defining the rheological properties of doughs, and are most responsible for the breadmaking properties of a flour. About 70% of the variation in the baking properties of a dough can be explained by the “quality” and quantity of glutenin and gliadin. The remaining 30% of the quality variation and the actual ‘quality’ – for example, the size distribution of polymeric glutenin – are related to other components of the flour.

These protein components can contribute to baking quality in various ways:

  1. They may form a part of the gluten matrix, and even be covalently bound into the polymeric glutenin fraction, as are the beta-amylases
  2. They may alter some important baking-quality attribute (such as grain hardness) and thereby alter the medium in which the gliadin and glutenin proteins operate
  3. Lipid-binding proteins may interact with and control the functional availabilities of lipids, and thereby govern the contribution of this important non-protein fraction to baking quality
  4. "Chaperone”-type proteins may help control the deposition of the prolamin proteins in wheat grains, thereby altering the structural and functional properties of the gluten proteins
  5. Endoproteinases can readily hydrolyze the prolamin proteins, thereby reducing their molecular sizes and modifying how they function to determine dough properties
  6. The activities of these proteolytic enzymes will in turn be modified in the presence of endogenous enzyme inhibitors.

This chapter describes some of the non-prolamin protein components of flours that are reportedly either directly or indirectly related to their breadmaking quality.