Isolation and Molecular Composition of Starch from Roots of Medicago sativa L.

Abstract

AbstractThe concentration and molecular composition of starch from alfalfa (Medicago sativa L.) taproots were determined using dimethyl sulfoxide (DMSO) extraction and gel permeation chromatography. Three 24‐h extractions with 90% (v/v) DMSO were required to solubilize an average of 97% of the starch from freeze‐dried root tissues. Amylopectin comprised approximately 80% of starch isolated from alfalfa roots. The relative proportions of amylose and amylopectin were similar among three diverse alfalfa germplasms and one cultivar even through starch concentrations ranged from 20 to 410 g kg−1 dry weight. Elution profiles of debranched starches from alfalfa taproots contained two pools of low molecular weight chains with degrees of polymerization similar to debranched starches from maize (Zea mays L.), and potato (Solanum tuberosum L.). The molecular composition of starches from these alfalfa germplasms was similar to that commonly observed for most starches from cereals and tubers.