Crystallization of amylose—fatty acid complexes prepared with different amylose chain lengths

Highly crystalline samples were prepared by complexation of five amylose fractions (number average degrees of polymerization (DP) 20, 30, 40, 80 and 900) with three fatty acids. Crystallization was performed in water-DMSO mixture at 90 °C. The yields of crystallization increased with increasing amylose chain lengths. Moreover, DP20 amylose never precipitated whatever fatty acid was used. All complexes presented similar diffraction diagrams characteristic of the Vh amylose complex structure with narrow peaks. Broader diffraction bands for the DP30-C16 complex indicated smaller crystal domains in the latter case. The melting temperatures of these different complexes increased with amylose chain length; this result suggests a crystallite size dependence on amylose chain length.