Isoamylase debranched fractions and granule size in starches from kidney bean germplasm: Distribution and relationship with functional properties

Fine structure, granule size distribution, thermal and rheological properties of starch separated from twenty kidney bean lines were determined. Apparent amylose content (MC), intermediate fraction (mixture of relatively short amylose and long side chains of amylopectin), long-side chains of amylopectin (AP) and short side chains of amylopectin (AP) of starches were measured after debranching with isoamylase and fractionating using gel permeation chromatography. Starches from different lines showed unimodal, bimodal and trimodal distribution profiles for the granules size, majority of starches showed bimodal profile. The granule size ranged between 0.4 and 103 mu m, however, granules of 10 to 30 mu m were present in the highest proportion. Paste viscosities (Peak-, breakdown- and final-viscosity) had negative relation with MC and positive with short side chains of AP. Starches with high proportion of granules of size between 1 to <= 10 mu m and > 10 to 30 mu m size, respectively had lower and higher paste viscosities. Starches with higher proportion of long side chains of AP had higher gelatinization temperature (To, Tp, Tc) and enthalpy. Starches with higher proportion of granules of size > 10 to 30 mu m had lower AAC and higher To, Tp and Tc. Gel hardness, To, Tp and Tc were lower for starches with higher proportion of granules of size > 1 to <= 10 mu m. Viscoelasticity of cooked starch varies with MC, short side chains of AP and granules size distribution. (c) 2011 Elsevier Ltd. All rights reserved.