Strain Hardening of Dough as a Requirement for Gas Retention

Abstract

Mechanisms that can be responsible for the ability of wheat flour doughs to retain gas are discussed. It is concluded that the relevant types of physical instabilities are Ostwald ripening (disproportionation) and coalescence of gas cells. The extent of Ostwald ripening is probably primarily controlled by surface rheological properties; it certainly affects crumb structure, but it cannot explain the differences in gas retention among doughs from various cereals or various wheat cultivars. It is argued that surface forces only provide a stabilizing mechanism for dough films between gas cells, i.e., against coalescence, for films that are much thinner than the diameter of a starch granule. It is concluded that variation in the potential for gas retention among wheat flour doughs is largely due to variation in bulk rheological properties. We propose a new rheological criterion for the extensibility of dough films between gas cells (and thereby for gas retention) that is based on the strain hardening of the dough in biaxial extension exceeding a specific lower limit. The criterion is translated into measurable parameters. Preliminary experiments on doughs with poor and with satisfactory baking performance illustrate its potential importance.

Effect of Pentosans on Gluten Formation and Properties

“…Previous studies 40 , in which the effect of WEP was studied, showed that addition of free FA led to a loss of gluten yield in the control sample (without WEP addition), but resulted in a higher gluten yield in the presence with WEP. Does free FA also give a higher gluten yield in the presence of WUS?…”

“…In flour and dough, glutenin polymeric proteins are extremely polydisperse 39 , varying both in composition and size as reflected by differences in extractability. Moonen et al found that the SDS insoluble gel protein fraction highly correlated with SDS sedimentation values and loaf volume 40 . This fraction was later named the Glutenin Macro Polymer (GMP) to reflect the importance of glutenins and the highly aggregated nature of this fraction 41 .…”

“…Just as with WEP 40 , addition of WUS or WUS x led to a significant decrease in protein yield and starch yield, therefore, a lower gluten yield (expressed as % dm). Adding WUS or WUS x together with FA improved protein yield and as a result, gluten yield.…”

“…In addition, several authors have shown a clear quantitative correlation between GMP gel quantity, GMP rheological properties, dough properties and bread loaf volume 40,42,[74][75][76][77] . Weegels et al 75 reported that GMP content of dough after 45 min rest was related to R max; whereas the GMP contents of flour was better related to E xt and loaf volume.…”

Surface Layer Properties of Dough Liquor Components: Are They Key Parameters in Gas Retention in Bread Dough?

“…Previous studies have mainly focused on the role of gluten proteins in determining the gas holding ability of dough. 1,2 In this respect, the strain hardening properties of dough/gluten are considered relevant. 1,2 However, some studies indicated that the contribution of a liquid film surrounding the gas cells is also relevant.…”