The effects of salts on the formation of gluten structure during hydration

Tuhumury, H 2014, The effects of salts on the formation of gluten structure during hydration, Doctor of Philosophy (PhD), Applied Sciences, RMIT University.


Document type: Thesis
Collection: Theses

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Title The effects of salts on the formation of gluten structure during hydration
Author(s) Tuhumury, H
Year 2014
Abstract The search for ways to reduce dietary salt intakes has intensified as evidence accumulates concerning the adverse effects this component has on health. However, in dough-based products, salt has important technological functions. This current research has been based on the need to establish a knowledge and understanding of the influence of salts on the gluten network at the molecular level during hydration. Rheological, microstructural and chemical properties of gluten as a function of salt have been investigated. In addition, the effects of various salts belonging to the Hofmeister series on gluten and wheat flour properties have been compared. A variety of techniques was applied to evaluate the effects on the structural and rheological properties of gluten as well as doughs. NaCl was found to increase the non-covalent interactions of the gluten and the β-sheet structure which results in a fibrous network structure. Water molecules appear to be drawn away from the gluten by the salt so that a more closely aligned structure is formed.

Gluten samples were prepared in the presence and absence of NaCl during mixing and washing. The effect of subsequent heating were a gradual decrease in G’ and G’’ values up to a certain temperature and the onset of sharp increases in those values during heating depends on the extent of hydrogen bond formation as a function of NaCl. The delay in the sharp increase to the G’ to higher temperatures during heating is the result of the formation of the gluten network rather than the presence of residual starch.

Different cation salts of the Hofmeister series were evaluated and the impacts of these on gluten structure and dough rheology at large deformation were relatively small. K+ gave similar microstructural and rheological properties of both dough and gluten samples to those observed for NaCl. Different anion salts influenced gluten network formation by causing changes in gluten protein composition, as well as the relative amount of the unextractable polymeric protein fraction by interacting directly with specific amino acid residues. These result in remarkable differences in dough mixing profiles, microstructural features of the dough, the small deformation properties of the gluten, as well as the strain hardening behaviour of dough and gluten samples. The effect of the Hofmeister anion salts on gluten network formation are more pronounced than for the cation salts.

This study, for the first time, provides a strong basic understanding on how NaCl influences gluten network formation. The present study demonstrates the important role of anions in determining the structure and functionality of the gluten, as well as wheat flour dough. Therefore, the chloride ions of NaCl cannot be readily replaced by other anions of sodium salts. On the other hand, the NaCl could be substituted by chloride salts of other cations, particularly KCl. These findings have significant implications for the formulation of strategies to reduce the sodium intakes and facilitate the production of wheat-based foods without causing undesirable effects on dough functionality.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Applied Sciences
Subjects Food Chemistry and Molecular Gastronomy (excl. Wine)
Analytical Chemistry not elsewhere classified
Keyword(s) Gluten
Dough development
Salts
Hopfmeister salts
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Created: Wed, 13 Jan 2016, 08:08:00 EST by Keely Chapman
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