Solid-State 13C CP/MAS NMR studies on aging of starch in white bread.

The effects of storage methods and glycerol on the aging of breadcrumbs were studied using solid-state 13C CP/MAS NMR. After baking, a shift in C1 peaks from triplet (A-type) to singlet (V-type) was observed. Addition of glycerol reduced the carbon peak intensities of fresh and aged breads, which correlated well with the DSC amylopectin “melting” enthalpy (r 2 = 0.91). Upon storage of bread with crust in hermetically sealed containers (when moisture migrated from the crumbs to the crust), the 13C CP/MAS NMR peak intensity increased more rapidly during aging than when the bread was stored without crust. Although addition of glycerol retarded the starch retrogradation, as observed by 13C CP/MAS NMR and DSC, it accelerated the firming rate. Therefore, bread firming in this case was controlled not only by starch retrogradation but also by other events (such as local dehydration of the matrix or gluten network stiffening). Keywords: White bread; 13C CP/MAS NMR; starch retrogradation; staling; firming