MEASUREMENT OF AMYLOSE AMYLOPECTIN RATIO BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY/

Amylose content has been measured by iso-amylase digestion of starch f ollowed by quantitation of the amounts of the higher molecular weight chains (from amylose) and the lower molecular weight chains (from amyl opectin). The separatrion and quantitation has been performed by size- exclusion high performance liquid chromatography an hydrophilic column s. Three columns were tested and an Ultrahydrogel 250 was found to pro vide the optimum separation. Starches of up to 30-35 per cent amylose may be analysed in this way without the need for first removing the li pids. With starch of higher amylose content, precipitation of the amyl ose in the sample may occur while it is awaiting HPLC analysis. This p recipitation can be prevented in starches of up to 40 per cent amylose by the use of dimethyl sulfoxide in the reaction mixture. Samples wit h amylose content higher than this always show some precipitation and the amylose contents obtained are similar for all starches with amylos e in the range from 40 to 80 per cent, measured by iodine determinatio n. The method gives results which are more repeatable than those obtai ned by spectrophotometric determination of iodine binding, and which a ppear to be unaffected by the lipid content of the starch.