The Interplay Between the Main Flour Constituents in the Rheological Behaviour of Wheat Flour Dough

Abstract

There is still considerable debate in the literature about the respective roles of starch and gluten in both the linear and non-linear rheology of wheat flour dough. Hence, to elucidate the individual contributions of gluten and starch to the overall dough behaviour, the rheological properties of dough and mixtures of different gluten-starch ratios were studied systematically in shear and extension, by means of an adequate rheological toolbox consisting of linear small amplitude oscillatory shear tests and non-linear tests such as creep-recovery in shear and uniaxial extension.The starch component plays a pivotal role in linear dough rheology. With increasing starch content, the linearity limit observed in oscillatory shear tests decreases as a power-law function. Starch also clearly affects the extensional viscosity at small strains. Consequently, in the linear region differences between different gluten systems may become obscured by the presence of starch. As breadmaking qualities are known to be intrinsically linked to the gluten network, it is imperative to probe the non-linear behaviour of dough in order to expose differences in flour quality. The quality differences between a strong and a weak flour type were revealed most clearly compliance in non-linear creep-recovery tests.Notwithstanding its earlier successful application to pure gluten gels, the accuracy of the critical gel model in predicting the linear rheological properties of dough was found to be limited, due to dough having a small linearity limit and a finite longest relaxation time.

The Impact of Water Content and Mixing Time on the Linear and Non-Linear Rheology of Wheat Flour Dough

“…Two stress levels were applied (σ = 5 Pa and σ = 500 Pa) to access both the linear and the non-linear region [43]. The shear stress σ was applied for 30 min, after which the dough sample was allowed to recover for an additional 60 min.…”

“…in which η + e (ε max ) represents the actual value of the transient extensional viscosity at the maximum strain (2.7), and η + e0 (ε max ) is the value of the linear viscosity extrapolated to the maximum strain [43]. The extensional viscosity curves shown in this study are the average of 10-15 measurements on at least 3 separately prepared batches.…”

“…The dough was allowed to relax for 30 min before loading in the ARES-G2 rheometer. Additional information about the rheological setups and methodology can be found in Meerts et al [43].…”

“…However, for weak flour doughs the long-term relaxation effects are more likely to become apparent in oscillatory tests. After all, for a weak dough system, the transition point from solid-like to liquid-like behaviour will be situated at a higher frequency [43]. The water content-frequency superposition is no longer obtained in case the transition point shifts into or approaches the frequency region that can be probed adequately with oscillatory tests.…”

“…Besides linear oscillatory tests, our rheological toolbox comprises extensional tests and creep-recovery tests, which enables us to study dough behaviour in both the linear and non-linear regimes, thereby relying on fundamental techniques rather than empirical ones. Instead of the more commonly used Kieffer extensibility rig, the Extensional Viscosity Fixture was used here for extensional tests as this setup allows to obtain a truly uniaxial extensional flow field [43]. Our aim is to understand how under-and overmixing affect the interplay between the two major flour constituents (gluten and starch).…”