The staling of bread: an X-ray diffraction study

Bread crumb X-ray patterns were analysed by different methods, the objective being to provide more in-depth knowledge of the relationships among starch crystallinity, amylopectin retrogradation and bread firming. Both crumb-firming and amylopectin retrogradation increased with storage time. However, total mass crystallinity grade and relative crystallinity increased only in the first 24 h. The determination of starch crystallinity requires the separation of the crystalline and amorphous intensities, which is sometimes arbitrary, so it would be useful to improve this methodology. Different methods used to determine total crystallinity grade only show the differences existing between fresh and stored bread. B-type crystal structure—corresponding to the amylopectin retrogradation—increased during bread storage, showing a high correlation with bread-firming and storage time. This fact emphasized the above results and suggested that amylopectin retrogradation is an important component to the elucidation of bread staling.