Investigating structure-function relationships of dough stickiness within low sodium bread dough formulations
Avramenko, Nicole A 1988-
The overarching goal of this research was to gain a greater understanding of the underlying structure-function relationships leading to the sticky dough phenomenon when sodium chloride is reduced in bread dough formulations. The primary objectives of this research were to: a) examine the effect of flour composition (focusing on gluten content/quality) on the dough handling properties of four flours ranging from good to poor dough handling; b) examine the effect of NaCl level on the dough handling properties, morphology (focusing on the gluten network formation), stickiness and water mobility with the same four flours; and c) examine the effect of various salts from the lyotropic series on the dough handling properties, morphology, stickiness and water mobility of a known strong/non-sticky dough producing flour and a weak/sticky dough producing flour to achieve similar properties to that of NaCl. Within Chapter 3, the chemical compositions of flours milled from four different Canada Western Red Spring (CWRS) wheat cultivars (i.e., Pembina, Roblin, McKenzie and Harvest) were investigated and then related to the rheological properties, stickiness, morphology and water mobility of each dough with 2% NaCl. All cultivars showed similar proximate composition, with the exception of the protein content, and were all of high quality with minimal enzymatic activity/degradation. Major differences were noted for flour cultivars with respects to gluten quality and damaged starch level. Pembina and Roblin, which are both known strong dough producing flours, showed a significantly higher gluten index and gluten performance index than both McKenzie and Harvest, which are both known to be intermediate and weak dough producing flours, respectively. However, dough prepared with Pembina was found to have the greatest resistance to extension relative to the other flour cultivars. Pembina was found to have greater amounts of low molecular weight glutenin subunits (insoluble) than Roblin which could account for Pembina’s greater resistance to extension than Roblin. McKenzie and Harvest flours had higher levels of gliadin than Pembina and Roblin, in part accounting for the weaker doughs. McKenzie and Harvest both had significantly higher damaged starch (~7.1%) (i.e., harder kernels) than Pembina and Roblin (~5.7%) which would impact the hydration of gluten proteins and therefore would ultimately impact the formation of the gluten network. Within Chapter 4, the dough rheological properties, stickiness, morphology and water mobility for the four CWRS wheat cultivars were examined as a function of NaCl (0-4%). More specifically the dough rheology was investigated with respect to the oscillatory shear, creep recovery and extensibility. The loss tangent of doughs prepared with Roblin, McKenzie and Harvest flours had similar values and greater than that of dough prepared with Pembina flour. This trend was similar to the strength trend seen in Chapter 3 with the examination of resistance to extension. Rheological data indicated that with increasing NaCl levels doughs prepared with the four cultivars increased in strength. The magnitude of changes in dough strength with different NaCl levels tended to be cultivar specific. For dough stickiness Pembina and Roblin showed the least stickiness when compared to McKenzie and Harvest at the 0 and 2% NaCl levels, with the addition of 2% NaCl decreasing stickiness for all cultivars. However at the 4% NaCl level a greater cultivar effect was observed with regard to stickiness. Water association measurements (i.e., distribution of water as free, associated with starch or associated with gluten) found that with the addition of NaCl there was a decrease in free water among the doughs prepared with the different cultivars and an increase in the water associated with the starch-fraction. Overall, Pembina and Roblin formed stronger gluten networks with lower stickiness than McKenzie and Harvest and NaCl sensitivity was found to be cultivar dependent. Pembina was chosen as a strong/non-sticky dough producing flour and Harvest was chosen as a weak/sticky dough producing flour to move forward to Chapter 5 to investigate the effect of salts from the lyotropic series. Within Chapter 5, the impact of salts from the lyotropic series (NH4Cl, KCl, NaCl, MgCl2, CaCl2, and MgSO4) at the 1 and 2% salt levels on the dough rheology, morphology, stickiness and water mobility of doughs prepared using a CWRS flour producing a strong/non-sticky dough (Pembina) and a flour producing a weak/sticky dough (Harvest), were investigated. Overall, Pembina developed stronger gluten networks than Harvest as determined by a lower loss tangent and reduced amount of deformation during creep recovery. However, the effect of salt-type was dependent on the cultivar. For instance, in the case of Pembina only dough prepared with NH4Cl was found to experience significantly reduced deformation during creep recovery compared to NaCl, whereas all other salt-types were similar. However for Harvest, KCl, CaCl2 and MgCl2 were found to have a weakening effect on the gluten network with respect to the higher deformation experienced when compared to NaCl; whereas NH4Cl and MgSO4 resulted in lower deformation compared to NaCl. Overall Pembina had lower dough stickiness in all cases when compared to Harvest. Dough stickiness saw the greatest decrease for both flour cultivars with the use of NH4Cl. Enhanced dough morphology was noticed for Pembina and Harvest in the presence of NH4Cl. Findings from the rheology and stickiness measurements indicate NH4Cl could serve as a replacement for NaCl in low sodium dough formulations, however future studies are necessary to determine the impact on final loaf quality, consumer acceptability and potential health implications.
DegreeDoctor of Philosophy (Ph.D.)
DepartmentFood and Bioproduct Sciences
SupervisorNickerson, Michael T
CommitteeScanlon, Martin G; Hucl, Pierre; Newling, Ben; Tanaka, Takuji
Copyright DateSeptember 2017