Effects of amylose chain length and heat treatment on amylose-glycerol monocaprate complex formation.

Aqueous mixtures of amylose with different chain lengths (DP 23-849), which had been enzymatically synthesized or isolated from potato and maize starches, and glycerol monocaprate (GMC, 5:1 weight ratio) were analyzed by using a differential scanning calorimeter (DSC). The mixtures were thermally treated (first DSC scan: 20-140 °C, 5 °C/min and prolonged heat treatment: 100 °C for 24 h) and its effect on the amylose-GMC complex formation was analyzed by DSC and X-ray diffractometer. The amylose, especially short ones, readily associated in the dispersion forming the amylose-amylose crystals but the presence of GMC inhibited the crystal formation. The longer amylose had the greater possibility for the complex formation with GMC, and the prolonged heat treatment facilitated the amylose-GMC complex formation. Both type I and type II complexes were formed during quenching after the initial DSC heating. However, only the type II complexes were formed after the prolonged heat treatment with improved crystallinity and thermostability.