Polymeric Assembly of Gluten Proteins in an Aqueous Ethanol Solvent

Abstract

The supramolecular organization of wheat gluten proteins is largely unknown due to the intrinsic complexity of this family of proteins and their insolubility in water. We fractionate gluten in a water/ethanol mixture (50/50 v/v) and obtain a protein extract which is depleted in gliadin, the monomeric part of wheat gluten proteins, and enriched in glutenin, the polymeric part of wheat gluten proteins. We investigate the structure of the proteins in the solvent used for extraction over a wide range of concentration, by combining X-ray scattering and multiangle static and dynamic light scattering. Our data show that, in the ethanol/water mixture, the proteins display features characteristic of flexible polymer chains in a good solvent. In the dilute regime, the proteins form very loose structures of characteristic size 150 nm, with an internal dynamics which is quantitatively similar to that of branched polymer coils. In more concentrated regimes, data highlight a hierarchical structure with one characteristic length scale of the order of a few nm, which displays the scaling with concentration expected for a semidilute polymer in good solvent, and a fractal arrangement at a much larger length scale. This structure is strikingly similar to that of polymeric gels, thus providing some factual knowledge to rationalize the viscoelastic properties of wheat gluten proteins and their assemblies.

Small angle neutron scattering contrast variation reveals heterogeneities of interactions in protein gels

“…Hence, the protein domains involved in intermolecular H-bonds would be likely less available to undergo H/D exchange with the solvent and would contribute to delineate the large scale H-rich domains (600 Å), which are probed by SANS. Interestingly the size of these domains is similar to the size of protein assemblies measured in the dilute regime in a fully hydrogenated solvent 21 . 49 The authors showed that the partition of the proteins between the two phases depends on the molecular weight of the glutenin polymers, as for neutral polymers, whereas the different gliadins display the same interaction parameter.…”

“…Elution of the injected sample (20μl) was performed at 0.7 ml/min and the detection of the different species was recorded at a wavelength of 214 nm. The apparent molecular weight calibration of the column was obtained using a series of protein standards with molecular weight in the range 13 to 2 000 kDa according to 21 .…”

Influence of supramolecular forces on the linear viscoelasticity of gluten

“…Rheological (Kontogiorgos and Dahunsi 2014;Ng and McKinley 2008), microstructural (Jiang et al 2008), and calorimetric modeling (Kontogiorgos and Goff 2006) demonstrate a closer alignment of hydrated gluten networks to polymeric rather than the particulate view. Additionally, recent work using a combination of scattering techniques in water/ethanol at the dilute and concentrated regime show that gluten proteins behave as flexible polymer in a good solvent (Dahesh et al 2014). Utilizing, therefore, the polymeric theoretical framework is possible to divide gluten relaxation into three distinct regimes: a short time relaxation process (t/a T < −1) that corresponds to Rouse-like modes, an intermediate power law relaxation regime (−1 < t/a T < −3.5), and a terminal regime (t/a T > 3.5).…”

Evaluation of Hard Red Spring Wheat Mill Stream Fractions Using Solvent Retention Capacity Test

“…However, ethanol may be used due to the association with extracting gliadins. Gluten proteins are not all soluble in water, but are soluble in ethanol (Dahesh et al 2014). The gluten proteins, specifically gliadins, were the most soluble in water/ethanol solvent (50/50, v/v).…”

“…The gluten proteins, specifically gliadins, were the most soluble in water/ethanol solvent (50/50, v/v). The ethanol solvent is more appropriate to use instead of deionized water or lactic acid when measuring gliadin content in flour (Dahesh et al 2014). The acidic pH allows glutenins to become functional during dough formation, which affects dough strength and loaf volume.…”