Effect of amylose content and gluten on gelatinization and retrogradation of starch blends and starch/gluten blends and on bread staling

The effect of amylose content and gluten on gelatinization and retrogradation properties of starch blends and on staling properties of bread made of flour blends still is unknown. Effects of amylose content on baking and staling properties of bread were investigated by using blends of waxy spring (WS) or waxy durum (WD) wheat flour with non-waxy wheat flour. The effect of amylose content and gluten on gelatinization and retrogradation properties of starch blends was studied by using blends of WD and non-waxy starch, as well as starch blends combined with 30% gluten. Retrogradation enthalpies and bread firmness were higher for waxy than for non-waxy crumbs although waxy crumbs had higher amount of soluble starch than non-waxy crumb. WD crumbs had higher retrogradation enthalpies at the end of storage than WS crumbs with similar amylose content. Waxy flour deteriorated the sensory quality of bread. Gelatinization enthalpy (DeltaH) was higher for starch blends with low than for blends with high amylose content. Retrogradation enthalpy of starch gels (DeltaHBR) increased during storage and it was lower for low amylose blends than for high amylose blends, showing that low amylose content slowed the process of retrogradation. However, DeltaH as well as Delta HBR was not significantly different between each consecutive blend although the amylose contents were different. Gluten did not affect gelatinization enthalpy of starch blends, but it reduced significantly the Delta HBR of low amylose blends vs. high amylose blends. Chromatographic analysis of soluble starch isolated from gels showed different retrogradation patterns of blends even when their DeltaHBR's were similar. Gluten promoted reassociation of branched molecules at the beginning of storage. Overall, gelatinization and retrogradation properties of starch blends, as well as bread staling, were affected by amylose content, but these properties were not a simple sum of contributions of individual components in blends. Properties of analyzed starch or flour blends also could have been governed by specific interactions between two starches or between starch and gluten. Finally, WS and WD flour blends with similar amylose contents differed in all analyzed properties; however, none of them retarded staling of bread.