A Comparative Study of the Effect of Acetylation on Starches of Phaseolus vulgaris Biotypes

Abstract

AbstractEnzyme hydrolysis, X‐ray diffraction, differential scanning calorimetry and Visco/Amylo/Graphy were used to examine the strength of associative bonding forces between starch chains of native legumes. Addition of acetic anhydride resulted in unequal degrees of substitution. Scanning electron microscopy revealed no differences between the external morphology of native and acetylated starches. Similarities in the X‐ray diffraction patterns of native and acetylated starches indicated that acetyl groups mainly entered the amorphous regions. On acetylation, decreases in starch hydrolysis, gelatinization temperatures, enthalpies of gelatinization, extent of viscosity increase during the holding period at 95°C and syneresis, and increases in 95°C viscosity, set‐back and amylose exudation were observed. It appeared the extent of distribution of the acetyl groups between the amylose and the amorphous regions of the amylopectin fraction varied among legume biotypes, and differences existed between legume starches with regard to the ratio of the concentration of the acetyl group at the 2—O position relative to that at 6—O.