Amylose and amylopectin branch chain reactivity in a model derivatization system

Abstract

The impact of starch granule structure on amylose (AM) and amylopectin (AP) chain reactivities was investigated over a 24h period in a model reaction system utilizing a fluorescent probe [DTAF, 5-(4,6-dichlorotriazinyl)aminofluorescein] as a reagent. For various reaction time intervals (0.5, 4, 12, or 24h), molecular reactivities of debranched starch derivatives were assessed via size-exclusion chromatography equipped with refractive index and fluorescence detection. For all starch chain fractions, the initial rate of derivatization (0–0.5h) was rapid, but decreased thereafter. Starch chain reactivities followed the general order: AP long chains≫AM, AP medium chains>AP short chains, though both AM and AP long chain reactivities were somewhat impacted by the high relative reactivity of starch chains eluting in the AM/AP long chain boundary region. Varied starch chain reactivities were attributed to their relative locale within the granule, corroborating the impact of granule architecture on molecular-level reaction patterns of starch chains.