Spatial variation of starch retrogradation in Arabic flat bread during storage

Abstract

Research Highlights(i) Evaporative cooling keeps the inside of the bread within a few degrees of 100°C.(ii) A slight rise in internal temperature accompanies inflation.(iii) Different parts of the bread exhibit different rates of retrogradation during subsequent storage.(iv) This variation may be due to different local heating rates experienced by the different parts of the bread during baking. 2 AbstractSamples from different radial positions of flat Arabic bread were analysed by differential scanning calorimetry (DSC) immediately after baking and after up to 3 days storage. This showed that whilst almost complete gelatinisation initially occurs, higher levels of subsequent retrogradation (typically 1.5 to 3 times) occurred in an area intermediate between the centre and outside of the pita bread (viewed from above). This coincided with the region with the highest moisture content (30% w.b.) immediately after processing, and which is likely to have heated at the slowest rate. A parallel study using DSC which subjected dough samples to a temperature profile similar to that found in baking also found that relatively low heating rates of 20 °C min . In each case moisture contents during storage were comparable between samples, thus suggesting that the local heating rate experienced during baking is a key parameter that can explain differences in subsequent retrogradation in different regions of the pita bread.

Effect of inulin on rheological, textural, and structural properties of brown wheat flour dough and in vitro digestibility of developed Arabic bread

“…The difference in the initial moisture contents of doughs reflected in the finished products since the baking temperature and time combination were maintained constant. The moisture contents observed in this study are in agreement with earlier results for white flour Arabic bread (23 to 30%) (Al‐Hajji, Nassehi, & Stapley, 2016), however, lower than the inulin fortified regular breads (38 to 43%) (Rubel et al., 2015). The crust color of BWF/Inulin bread was measured from both the surfaces, and the average values are presented.…”

Impact of Emulsifiers Addition on the Retrogradation of Rice Gels during Low-Temperature Storage

“…Hydrophobic groups on GMS were plugged into the alpha-helix structure of gelatinized amylose and combined with starch forming strong stable amyloselipid complexes, thereby decreasing and preventing rapid retrogradation of amylose during the first 5 days of storage [4,14]. Al-Hajji et al [14] reported that, during prolonged storage time (one to seven weeks), retrogradation mainly occurs in amylopectin. In our research the amylose content of rice was 10.43% and amylopectin was 89.57%.…”

Spatial Variation of In Vitro Starch and Protein Digestibility in White Wheat Bread

“…On a 100 g wheat flour basis, the recipe included water (60.0%, w/w), yeast (2.0%, w/w), sugar (3.0%, w/w), and salt (1.5%, w/w). Similar recipes are commonly used in studies of bread to characterize specific effects, like spatial variations of starch retrogradation, starch retrogradation, and hydration depletion effects of in vitro starch digestibility . In particular, the recipe described above was based on a recipe used in Ref.…”

“…Compared with previous reports of in vitro digestibility, which focused on the crust and crumb of bread, our study provides a more detailed description of the: i) in vitro starch and protein (which has not been explored) digestibility spatial variation, and ii) also of some associated physicochemical properties occurring that can shed more in depth information of the underlying phenomena taking place.…”

“…Björck et al reported significant differences of starch digestibility between crumb and crust samples. Al‐Hajji et al reported that even when complete starch gelatinization was achieved during the baking process, bread samples exhibited spatial (radial) retrogradation variations, the highest rate occurring in an intermediate region between crust and crumb. Recently, Martinez et al studied effects of hydration depletion in the in vitro starch digestibility of white bread, finding that bread crust contained significantly higher slowly digestible starch than the crumb.…”