Multi-structural characterization of sorghum flour addition on bread staling dynamics: texture, thermal properties and molecular mobility

Abstract

The effect of sorghum flour inclusion (0 %, 10 %, 20 %, and 30 %) on the quality and staling of composite wheat-sorghum bread was investigated, to explore its potential as a sustainable alternative in breadmaking. Fresh bread samples were characterized for color, specific volume, and stored up to 8 days at 25°C. Staling was evaluated at different structural levels, from the macroscopic to the mesoscopic, and molecular levels (water activity and moisture content, texture, thermal properties by DSC, and ¹H molecular mobility and dynamics by ¹H NMR Relaxometry). Sorghum addition resulted in darker bread and reduced specific volume compared to standard wheat bread. Sorghum-containing breads exhibited higher frozen water content, reflecting weaker water-biopolymer interactions at the mesoscopic level. Texture analysis revealed increased hardness and decreased cohesiveness with higher sorghum levels, while 10 % sorghum enhanced springiness. Molecular mobility assessments indicated that sorghum inclusion increased the rigidity of the starch-gluten-water network, which was associated with hardness. DSC analysis showed increased amylopectin retrogradation during storage, though no clear trend was associated with sorghum content. This multilevel structural approach revealed that sorghum addition generally intensified staling in composite bread, with 10 % inclusion partially mitigating staling-promoting effects. Integrated structural analyses are key to understanding staling dynamics and guiding strategies to enhance sorghum-based bread quality and shelf life.