Improved calorimetric determination of amylose in starches or flours

The quantitative determination of amylose by means of its color reaction with iodine has been practiced for many years. Several procedures have been described. but there are many reports in the literature about the inconsistency. inaccuracy. and lack of reproducibility of these procedures’X. The frequently employed methods of McCready and Hassid’. Wu ef ~1.~. Wolf et ~1.~. or Williams et nI.h used neutral or alkaline solutions to develop the colored amylose-iodine complex. Juliano’ used acetic acid for neutralization. and a large excess of iodine to develop the color. Recently. Morrison and LaigncleP attempted to minimize the poor reproducibility of the previous methods by solubilizing lipid-fret, purified starches in urea-MclSO. WC have found. however. that these methods are sensitive to the pH. the tcmpcrature. and the concentration of amylose and of iodine. We now report, for the calorimetric quantitation of amylose. an improved method which is reproducible and results in a stable color of the amylosc-iodine complex.