Colorimetric assay for the determination of molecular weight distribution and branching characteristics of starch hydrolysates.

Here, we present a gold nanoparticle-based colorimetric assay for the determination of molecular weight distribution and branching characteristics of enzymatically hydrolyzed starch. The steric stabilization effect of starch hydrolysate on the colloidal stability of AuNPs was found to be proportional to the ratio of high molecular weight amylopectins, which was clearly reflected by the intensity of the characteristic surface plasmonic resonance (SPR) absorbance peak of the AuNPs. The fractional change of high molecular weight amylopectin over the course of enzymatic hydrolysis reaction could be measured based on the intensity of SPR peak, in which the results correlated well with those obtained by conventional gel permeation chromatography. With the proper calibration of a specific set of enzyme and starch type, this method would provide a fairly simple and fast means of analyzing the molecular weight distribution of starch hydrolysate on site as well as the amylose content in native starch.