Cereal Chem 65:138-143   |  VIEW ARTICLE

Relationship Between Amylose Content and Extrusion-Expansion Properties of Corn Starches.

R. Chinnaswamy and M. A. Hanna. Copyright 1988 by the American Association of Cereal Chemists, Inc. 

Corn starches with 0-70% amylose contents (db) were extrusion cooked at different temperatures and moisture contents. The product quality measures of expansion ratio, shear strength, and bulk density were studied in relation to starch amylose contents. The expansion ratio of starch increased from 8 to 16.4 as amylose content increased from 0 to 50% (db), and then decreased. Low- and high-amylose starches mixed to obtain various amylose levels and pure amylose/amylopectin mixes showed expansion property patterns similar to native corn starches but with lower expansion ratios (9.9-11.4). Different native corn starches had different optimum temperatures for expansion, i.e., 130 C for 0% amylose, 140 C for 25% amylose, 150 C for 50% amylose, and 160 C for 70% amylose starch. Overall, the highest expansion (16.4) was obtained with 50% amylose starch at 150 C. All starches had a uniform moisture content optimum of 13-14% (db) for maximum expansion. The bulk density of the extrudates decreased with increased amylose contents of starches. In contrast, shear strength estrudates increased with amylose content of starch but decreased with expansion ratio.