Role of cell wall integrity of wheat durum in modulating the starch digestibility during the bread processing

In this study, we investigated the effect of increasing particle size, and therefore of a higher fraction of intact cells, in decreasing the starch digestibility of durum wheat flour, as well as of dough and bread obtained therefrom. Flours of small (<200µm), medium (>1000 µm <1800 µm), and large (>1800 µm) particle size were selected. Confocal laser scanning microscopy showed that the integrity of the cells wall was retained during the whole of bread processing for the medium and large particle sizes, whereas the cell walls were mostly damaged in the small particle size. The in vitro starch digestibility (Englyst’s method) of flour was significantly affected by its particle size, the starch digestibility of small particle flour being two times higher than the large one. In the dough, no differences in starch digestibility were found between the three particle sizes. In bread, instead, a modest decrease of starch digestibility for the bread produced with large particle flour was observed, mainly due to the denser structure of the crumb. In conclusion, a higher particle size (and thus a higher fraction of intact cells) could limit starch digestibility in flour but not in bread.