Polysaccharides of lotus root

Abstract

The lotus (Nelumbo nucifera Gaertn.) is a crop of local importance in south-east Asia, both for the starchy roots and for the nut-like seeds. The monosaccharide composition of whole lotus root and extracted polysaccharide fractions were analysed by anion exchange high performance liquid chromatography (HPLC). The major polysaccharide was starch but the lotus root also contained appreciable quantities of other non-starch polysaccharides. Lotus root flour was fractionated by sequential extraction with cold water, hot water, and 3% NaOH. Analysis of the fractions suggested the probable presence of a water-soluble arabino-galactan, mannan, and fructan. Lotus root is a useful raw material for starch production in China although commercial starch tested was found to contain arabinogalactan. In a model cooking for lotus root, the polysaccharides were extracted and those remaining in the tissue were quantified. The texture of lotus roots was analysed and the fibrous cellulosic nature of the root limited softening after cooking. Lotus seeds were also tested and found to have a predominantly starchy endosperm with the presence of pectic type polysaccharides being indicated.