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.
