On the lamellar width distributions of starch

Advances in the structural understanding of the lamellar organization of starch obtained through small-angle X-ray scattering (SAXS) technique are presented. An accurate starch sample preparation followed by appropriate background subtraction and Lorentz correction were able to evidence the second harmonic SAXS peak. Interface distribution functions (IDF) were generated from SAXS data to obtain dimensions and distributions of starch lamellae without any constraints or predefined assumptions. Dimensions and distributions of crystalline and amorphous lamellae were consistent with the molecular architecture of amylopectin. IDF fit results clearly indicate that amorphous and crystalline lamellae present different degrees of paracrystallinity, i.e. peak width/peak position ratios. The results of lamellar domain boundary are interpreted as a consequence of enzymatic trimming required to generate order in the amorphous lamellae for subsequent synthesis of the crystalline lattice. Amylose content seems to affect amorphous and crystalline lamellar distributions while the allomorph-type content is only reflected within the distribution of crystalline lamellae.