Effect of l‐Cysteine on the Rheological Properties of Wheat Flour

Abstract

Cereal Chem. 78(3):226-230Extrudate expansion of cereal-based products is largely dependent on the molecular interactions and structural transformations that proteins undergo during extrusion processing. Such changes strongly influence the characteristic rheological properties of the melt. It is possible to modify rheological properties of wheat flour during extrusion processing, in particular shear viscosity, with cysteine. The objective of this work was to further develop an understanding of the molecular interactions and structural transformations of wheat flour from dynamic oscillatory rheological measurements. Temperature and frequency sweeps were conducted in the linear viscoelastic range of the material. Changes in the storage modulus (G′), the loss modulus (G′′) and the loss tangent (tan δ) of 25% moisture wheat flour disks as a function of cysteine concentration (0-0.75%) were monitored. Molecular weight between cross-links (M c ) and the number of cross-links (N c ) per glutenin molecule were determined from frequency sweep data. Increasing cysteine concentration broke crosslinks by decreasing G′ maximum and increasing tan δ values. Molecular weight between cross-links increased and the number of cross-links decreased. G′ values from temperature sweeps showed a similar trend. This information leads to a better understanding of the viscoelastic behavior of wheat flour doughs during extrusion cooking and elucidation of protein-protein reaction mechanisms and other interactions in extruded cereal-based snack foods.

Stress relaxation behaviour of yellow alkaline noodles: Effect of deformation history

“…In pasta, it has been shown that the gluten fraction containing LMW-GS are the primary contributors to mechanical strength in the cooked product (Resmini and Pagani, 1983). It is worth noting that cysteine's mobility was likely not restricted in our low-moisture system as cysteine has been found to be rheologically active in a study that had used wheat doughs with a 25% moisture content (Lambert and Kokini, 2001). It can therefore be argued that cysteine was indeed of value to alter the rheological behaviour of YAN, despite its low-moisture content.…”

“…The sulfhydryl groups (-SH) of cysteine are thought to reduce dough strength by promoting cleavage of intermolecular disulfide bonds and/or by increasing the rate of disulfide-sulfhydryl exchange reactions (McDermott and Pace, 1961). Stress relaxation tests are sensitive to the protein depolymerization effects of cysteine on a wheat flour dough because the changes that could be induced (i.e., changes in molecular weight or conformational structural changes) are intimately related to the rheology of the dough (Dreese et al, 1988;Lambert and Kokini, 2001).…”

Effect of an enzyme preparation on wheat flour and dough color, mixing, and test baking

“…Cysteine cleaves disulfide bonds, resulting in increased protein solubility and decreased gluten elasticity (Li & Lee, 1998). Increasing cysteine content in flour has been shown to adversely affect dough rheology by cross links breakage as evident by decrease in storage modulus (G 0 ) values (Lambert & Kokini, 2001). Removing those reducing agents from the enzyme mix by dialysis resulted in stronger dough with strength that was comparable to the control (Fig.…”

Fractionation and reconstitution of whole wheat flour and its effect on dough and chapatti quality

“…It is reported that wheat flour contains non-protein thiol compounds or free thiols like glutathione (GSH) and cysteine and they have been considered to play an important role in redox reactions in flour. Content of free thiols like GSH and cysteine was reported to influence the rheological and bread properties of flour [50][51][52][53].…”