Effect of bran on bread staling: Physico-chemical characterization and molecular mobility

High fibre breads were produced with the addition of durum wheat bran fractions (regular bran and a fraction extracted from the most internal bran layer) and their physico-chemical properties and water status were characterised during storage. Bran enriched breads exhibited similar properties during storage, they were harder, less springy and less cohesive than the control. Water status was strongly affected by bran addition, independently of bran composition: water activity, moisture and frozen water content (measured by Differential Scanning Calorimetry) were generally higher in the bran samples than in the control bread during storage. Amylopectin retrogradation was significantly larger in the presence of bran fractions. 1H NMR mobility (T2 number of populations and relaxation times) was different in the high fibre breads as compared to the control sample. The changes in protons mobility observed upon storage indicated an influence of bran on water/gluten/starch molecular domains and their dynamics, that may have affected the development of the gluten network resulting in different textural properties.