Structural and stoichiometric studies of complexes between aroma compounds and amylose. Polymorphic transitions and quantification in amorphous and crystalline areas

Amylose V complexes were prepared as semi-crystalline powders from aqueous solution with three different molecules: decanoic acid, hexanoic acid, and 1,5-decanolactone. Structure and stoichiometry of the resulting amylose complexes were investigated. As evidenced by Wide Angle X-ray Scattering (WAXS), the aroma compounds lead to three different types of V amylose structure similar to Vh, Vbutanol and Visopropanol, respectively. Extraction of aroma when included between helices, induced some polymorphic transitions towards a structure with smaller unit cells (i.e., from Visopropanol to Vbutanol and from Vbutanol to Vh). The location of the ligand within and/or between helices was deduced. Its content in amorphous and crystalline areas was also investigated using FT-IR spectroscopy, WAXS, and mild acid hydrolysis.