Rheology and water mobility of low sodium bread doughs prepared with crosslinking enzymes and organic acids
Date
2019-03-10
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Journal Title
Journal ISSN
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ORCID
Type
Thesis
Degree Level
Doctoral
Abstract
New regulations from the Government of Canada regarding sodium limits in foods have generated technical challenges for products such as bread, which requires sodium chloride (NaCl) as one of its four essential ingredients. NaCl has importance in proper gluten network development, where reduced NaCl can cause high dough stickiness and handling issues. The overall goal of this study was to examine the use of enzymes to help alleviate stickiness within a low NaCl environment, and to deepen our understanding of the role water and some yeast metabolites play in dough handling.
This work examined the effectiveness of two crosslinking enzymes, glucose oxidase (GO) and transglutaminase (TG) at improving dough handling characteristics and reducing stickiness in low sodium doughs prepared with two cultivars Pembina and Harvest. The cultivars were chosen due to their opposing characteristics: Pembina was previously shown to have strong dough handling and low stickiness in reduced-salt systems, whereas Harvest was the opposite. Overall, it was found that both GO and TG were effective at improving parameters (dough rheology, stickiness), however, GO was more effective than TG at lower concentrations. Cultivar-type was significant in the case of every investigated parameter, whereas enzymes produced more significant changes to these characteristics when dough was produced with the weaker flour (Harvest) and at low salt levels.
Slightly more complex model doughs were also assessed, containing a variety of organic acids which can be produced by yeast. The inclusion of these acids (excluding ascorbic acid) had negative effects on dough rheology and increased dough stickiness but did not have large effects on percentage of glutenin macropolymers, and minimally increased the freezable water content. Ascorbic acid trends were different than other acids, which was expected due to its use as an oxidizing agent for increasing dough strength, however, it did not produce improvements when used in tandem with GO. The inclusion of GO improved dough rheology and reduced dough stickiness as expected, and when it was included with these acids (excluding ascorbic acid) samples showed behavior in between the observed results of GO without acid, and control samples without either acid or GO.
The molecular mobility and diffusion properties of water in model dough systems by low-field 1H nuclear magnetic resonance spectroscopy were also investigated. It was determined that acid inclusion did not affect the overall structure of the doughs, and was only slightly affected by cultivar-type. Molecular motion on the MHz timescale, which relates to water molecule tumbling and motion on the polymer surfaces, was significantly lower in doughs containing acid or for those prepared with Pembina flour. Motion on the kHz timescale (relating to protein side chain motion) was significantly altered by Pembina doughs and acid inclusion, however, it was not determined if this motion became faster or slower. Diffusion characteristics were not altered by formulation changes. Overall, the inclusion of acids reduced motion significantly on the MHz timescale and altered it significantly on the kHz timescale but did not appear to affect the overall structure significantly, suggesting that these acids are mostly active at the surfaces of the polymers such as protein side chains.
Description
Keywords
Low sodium, bread dough, dough handling, stickiness, rheology, organic acids, NMR
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Food and Bioproduct Sciences
Program
Food Science