Mechanism underlying the weakening effect of β-glucan on the gluten system

The high β-glucan content in barley disrupts the gluten network in dough. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), and solid-state nuclear magnetic resonance (NMR) techniques were used to clarify how β-glucan affected the quality of the gluten network structure with β-glucan contents of 0-2%. The results suggest that the physical hindrance of the β-glucan gel destroyed the formation of the gluten network structure. When 1.0-2.0% β-glucan was added, the percentage of α-helical structures increased significantly. When the added amount of β-glucan reached 2.0%, the sulfhydryl group (SH) content increased from 8.06 to 10.27 µmol/g, and the disulfide bond (SS) content decreased from 240.09 to 217.38 µmol/g. The interaction between β-glucan and gluten mainly resulted from the interaction of electron-withdrawing groups, such as carbonyl groups (CO) and double bond carbons (CC), and carbon atoms on the side chains of β-glucan, which play an important role in the central structure of glutenin.

Control of wheat starch rheological properties and gel structure through modulating granule structure change by reconstituted gluten fractions

Reconstituted gluten fractions (RGF) varying in glutenin/gliadin (glu/gli) ratios was applied to change the property of wheat starch. The addition of RGF, irrespective of glu/gli ratio, significantly decreased the gelatinization enthalpy, viscosity, storage modulus (G'), and gel strength of starch. Starch particle size and leached amylose decreased by 4.5% and 22.2%, respectively, as the ratio of glu/gli changed from 1:0 to 0:1, indicating that the increase in gliadin ratio could inhibit swelling and rupturing of starch granules to a larger extent. Confocal laser scanning micrographs showed that gliadin could surround starch granules more effectively, thereby stabilizing the granule structure better than glutenin. With the increasing of gliadin ratio, the storage modulus (G') and loss modulus (G″) of the starch paste declined, accompanied by more loose gel structure and weaker gel strength. By varying the ratios of glu/gli in RGF, the change of wheat starch granule structure could be modulated, and therefore the rheological properties and gel structure could be regulated.

Biochemical and functional properties of wheat gliadins: a review

Gliadins account for 40-50% of the total storage proteins of wheat and are classified into four subcategories, α-, β-, γ-, and ω-gliadins. They have also been classified as ω5-, ω1, 2-, α/β-, and γ-gliadins on the basis of their primary structure and molecular weight. Cysteine residues of gliadins mainly form intramolecular disulfide bonds, although α-gliadins with odd numbers of cysteine residues have also been reported. Gliadins are generally regarded to possess globular protein structure, though recent studies report that the α/β-gliadins have compact globular structures and γ- and ω-gliadins have extended rod-like structures. Newer techniques such as Mass Spectrometry with the development of matrix-assisted laser desorption/ionization (MALDI) in combination with time-of-flight mass spectrometry (TOFMS) have been employed to determine the molecular weight of purified ω- gliadins and to carry out the direct analysis of bread and durum wheat gliadins. Few gliadin alleles and components, such as Gli-B1b, Gli-B2c and Gli-A2b in bread wheat cultivars, γ-45 in pasta, γ-gliadins in cookies, lower gliadin content for chapatti and alteration in Gli 2 loci in tortillas have been reported to improve the product quality, respectively. Further studies are needed in order to elucidate the precise role of gliadin subgroups in dough strength and product quality.