Gel formation in acidified aqueous suspensions of cereal flours

Abstract

The amounts of gel formed when wheat flours are suspended in IM acetic acid or in phenol-acetic acid-water (1 : 1 : 1, w/v/v) are highly correlated with the total nitrogen contents and the Zeleny sedimentation values of the flours. It is concluded that the Zeleny sedimentation test depends on the formation of this gel. Gel formation in acidified aqueous suspensions is markedly affected by the ionic strength and pH of the suspending medium, but not by non-polar molecules or reagents that react specifically with sulphydryl groups or disulphide bonds. The gel is readily dispersed by ultrasonic treatment and gel formation is prevented completely by the amounts of sodium chloride added to dough during breadmaking.

Relationship of the Extrusion Temperature and the Solubility and Disulfide Bond Distribution of Wheat Proteins

“…Since the solubility of heated proteins depended on their molecular weights (Pomeranz, 1991), the decrease in wheat protein solubility after extrusion in the extracting buffer indicated the increase in its molecular weight, which might be the result of the aggregation of proteins during extrusion processing. Sonication carried out at a low energy level could disrupt the weak noncovalent bonding forces to reduce the molecular weight of aggregated proteins, which made proteins resolubilize (Jennings, 1978). Most of the insoluble proteins in the extrudates extruded at a die temperature of up to 120 °C could be resolubilized by using sonication, indicating that noncovalent bonding forces contributed to wheat protein aggregations extrusion processing.…”

The composition of a gel formed when wheat flour is suspended in phenol‐acetic acid‐water (1:1:1, w/v/v)

“…The chemical analysis of the gel has not shown any one flour component to be responsible for the formation of a gel in solvent PAW, or in IM acetic acid, the amount of which is highly correlated with the total nitrogen content.2 Instead, the gel consists of a heterogeneous mixture of components, of which the lipids are not necessary for gel formation since their removal had no effect on the amount of gel formed. 2 The interactions studied by Udy7 and by Jennings2 were similar in many respects, although there were significant differences in the responses to reducing and oxidising agents and in the ability of the gel to reform after it was dispersed by mechanical techniques. Udy7 concluded gluten proteins and polysaccharides of high molecular weight were interacting, but did not determine the nature of the polysaccharides.…”

“…2 The interactions studied by Udy7 and by Jennings2 were similar in many respects, although there were significant differences in the responses to reducing and oxidising agents and in the ability of the gel to reform after it was dispersed by mechanical techniques. Udy7 concluded gluten proteins and polysaccharides of high molecular weight were interacting, but did not determine the nature of the polysaccharides.…”

Effect of Extrusion Temperature on the Solubility and Molecular Weight of Lentil Bean Flour Proteins Containing Low Cysteine Residues

“…The decrease in lentil protein solubility after extrusion in the extracting buffer indicated the increase in its molecular weight, which might be the result of the association of proteins during extrusion processing. Sonication carried out at a low level of power could disrupt the weak noncovalent bonding to reduce the molecular weight of associated proteins, resulting in the resolubilization of proteins (Jennings, 1978). Most of the insoluble proteins in the lentil flour extrudates could be resolubilized by using sonication, indicating that the lentil proteins interacted mainly through noncovalent bonds during the extrusion process.…”