Premium
The structural evolution of water and gluten in refined and whole grain breads: A study of soft and hard wheat breads from postmixing to final product
Author(s) -
Bock Jayne E.
Publication year - 2019
Publication title -
cereal chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.558
H-Index - 100
eISSN - 1943-3638
pISSN - 0009-0352
DOI - 10.1002/cche.10152
Subject(s) - bran , food science , glutenin , gluten , chemistry , whole grains , whole wheat , wheat gluten , raw material , biochemistry , organic chemistry , protein subunit , gene
Background and objectives Recent work investigating gluten secondary structure in dough systems has provided tantalizing insights as to how small perturbations in gluten structure may impact bread quality. Specifically, shifts in gluten structure from β‐turns to β‐sheets in doughs with bran may be partially responsible for quality defects in whole grain bread. This study aimed to further that knowledge by monitoring gluten secondary structure in soft and hard wheat refined and whole grain bread at different stages during processing. Commercial hard red spring (HW) and soft red winter wheat (SW) flours were used to make breads with whole grain doughs created by substituting bran for 15% of the refined flour. ATR‐FTIR spectra were collected from samples and analyzed for gluten secondary structural content. Findings Freshly mixed doughs demonstrated the greatest β‐sheet content (53%–57%) compared to any other dough stage. Refined HW doughs demonstrated continual relaxation of β‐sheets to β‐turns through dough processing (−13% to panning), whereas relaxed SW doughs (−6% to 10%) partially reverted to sheets during punching and panning (1%–3%). The data also confirmed earlier findings that the presence of bran triggers the formation of additional β‐sheets (+4% to 5%) in both HW and SW doughs. Doughs with bran exhibited less structural relaxation (−3% to 6% β‐sheets) during processing. Interestingly, HW doughs exhibited only 1%–2% more β‐turns and only 1%–4% fewer β‐sheets than SW doughs. Analysis of the bread during baking revealed that SW generates a larger sheets:turns ratio compared to HW in refined bread, 21.3 versus 3.6, respectively, that grows to 129 versus 5.3 on addition of bran. Conclusions Gluten structural relaxation takes place during proofing in optimally hydrated doughs and largely follows water relaxation trends. The ratio of sheets:turns increases rapidly as water is lost during baking. The extent of this build‐up in the ratio is dependent on the wheat source for the flour (hard vs. soft wheat), presence/absence of bran, and the water loss (i.e., denaturation). Significance and novelty These results show that the ability of gluten to resist significant loss of bulk water during baking is related to better bread making performance. Additionally, the ability of gluten to resist substantial secondary structural alteration during baking, specifically formation of excessive β‐sheets, may be a key factor in high‐quality bread.