Crystallinity and structuring role of water in native and recrystallized starches by C-13 CP-MAS NMR spectroscopy 1: Spectral decomposition

Amorphous, native, and recrystallized starches were studied by C-13 CP-MAS NMR spectroscopy with respect to their behavior with hydration. The study o f space groups, associated to crystalline polymorphs (B2 and P6(1) for A an d B forms, respectively), provided decomposition rules for the spectral par t due to crystalline phases. Moreover, the subtraction of a standard amorph ous spectrum apparently showed the existence of three phases in native star ches (amorphous, partially-ordered and crystalline) and only two in spherul itic crystals (partially-ordered and crystalline). The proportion of each p hase was estimated at two different hydration levels. The amount of crystal line phase was compared to the degree of crystallinity as evaluated by wide angle X-ray scattering. The NMR spectral changes with hydration could be i nterpreted in terms of two complementary roles of water molecules, i.e. str ucturing and plasticizing. (C) 1999 Elsevier Science Ltd. All rights reserv ed.