Spatial variation of starch retrogradation in Arabic flat bread during storage

Samples 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−1 produced slightly higher amounts of retrogradation (typically 5-25%) than higher heating rates of 200 °C min−1. 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.