Acetylation of banana (Musa paradisiaca L.) and corn (Zea mays L.) starches using a microwave heating procedure and iodine as catalyst: II. Rheological and structural studies.

Abstract The effect of iodine concentration on the acetylation of starches with low and moderate degree of substitution (DS  shear-thinning ) was shown in the pastes of native and modified starches. Storage modulus (G’) and loss modulus (G”) showed low dependence on frequency (G’ α ω 0.1 ; G” α ω 0.2 ) on frequency sweep test, which is characteristic of a viscoelastic gel. Debranched native banana and corn starches presented trimodal chain-length distribution. The pattern was maintained in the acetylated starches, but with different level of short and long chains. The structural differences in native and acetylated samples explain the rheological characteristics in both starches.