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Mak, Sze Pui Cheryl (2009) Impact of sodium chloride on wheat doughs. PhD thesis, University of Nottingham.

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Abstract

The impact of salt (sodium chloride) on the wheat dough was studied, with a particular focus on the state and distribution of water and sodium in the dough system. In this study, dough samples were prepared using the same processing techniques as in commercial bakery (i.e. Chorleywood Bread Process) and were investigated simultaneously using molecular spectroscopy 1[subscript]H and 23[subscript]Na NMR), deformation stress measurement (Kieffer test, Texture Profile Analysis and Chen-Hoseney test) and calorimetry (DSC). A progressive study of experimentation was carried out in which dough samples between zero and 5% added salt (on flour base) to exaggerate the effects of salt. Furthermore, test baking was also used to study the mechinability of doughs. All of the techniques studied enabled the construction of a complete picture of the sequential events occurring when salt is reduced.

Test baking confirmed that machine moulding of bread dough became more difficult at lower salt contents. This was more apparent when dough temperature was elevated, or when the delay time between mixing and moulding was increased. Laboratory measurements were not able to distinguish the increase of stickiness occurring in the low salt (1.4%) doughs and modifying the method also failed to establish variations in stickiness, although changes in the hardness of the dough at the different salt levels were detectable.

Measurements of the dough fluid phases were compared using three techniques: isolation of aqueous phase through ultracentrifugation, freezable water as measured by differential scanning calorimetry (DSC) and proton mobility using low field nuclear magnetic resonance (1[subscript]H NMR). Salt increased the amount of dough liquor expressed on ultracentrifugation, however, the amount of freezable water and the molecular mobility of water (T2) did not show significant changes. The findings suggest that the gluten-starch matrix is sensitive to salt in way that it affects the "drainage" properties and the capillarity of the dough matrix, but not the intrinsic levels of fluid in the dough.

The distribution of salt on the dough was also investigated using 23[subscript]NaNMR. A large proportion of the salt added was not detectable with this technique and could be thought of as immobile. Increasing the concentration of sodium in the dough gave the same proportion of "bound" sodium. It would seem to be the starch component in the flour that dominated the sodium binding in the dough samples. Salt may exert its effects through polymer-polymer interactions rather than polymer–water interactions and its exact influence on cereal products performance still needs to be established before the reduction of salt is a viable option for commercial bakers.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Hill, S.E.
Subjects:	T Technology > TX Home economics
Faculties/Schools:	UK Campuses > Faculty of Science > School of Biosciences
Item ID:	13925
Depositing User:	EP, Services
Date Deposited:	16 Jan 2014 14:29
Last Modified:	19 Dec 2017 16:35
URI:	https://eprints.nottingham.ac.uk/id/eprint/13925

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