Cereal Chem 42:175 - 186.  |  VIEW ARTICLE

An Anomalous Low-Molecular-Weight Branched Component in Dent Corn Starch.

S. R. Erlander, J. P. McGuire, and R. J. Dimler. Copyright 1965 by the American Association of Cereal Chemists, Inc. 

Ultracentrifugal schlieren patterns at both acidic and alkaline pH values with or without ethanol show that the peak corresponding to amylose comprises 33 or 34% of the total pattern for normal dent corn starch. The slower peak is absent in waxy corn starch samples, and only a single skew peak is present in samples of high-amylose (70%) corn starch. The percentage of amylose obtained by iodine-iodide absorption spectra was 26 or 27% for normal dent corn starch. The discrepancy between absorption and ultracentrifugal analyses reveals that the greater percentage of amylose obtained from schlieren patterns is due to an anomalous component that has 4.0% branching, a beta-amylolysis limit of 56%, and a weight-average molecular weight of 1.4 million. Other studies such as hydrolysis of amylopectin with proteolytic enzymes or with acid suggest that the anomalous component of normal dent corn starch is amylopectin not aggregated or complexed with protein. Data presented also suggest that the apparent absence of aggregates in high-amylose amylopectin and the absence of low-molecular-weight components in waxy starch are due to an affinity of enzymes or proteins for short-branch lengths. Data also show that the ultracentrifuge cannot be used to obtain the percentage of amylose in starch.