Cereal Chem. 70:145-152   |  VIEW ARTICLE

Location of Phosphate Esters in a Wheat Starch Phosphate by [31]P-Nuclear Magnetic Resonance Spectroscopy.

S. Lim and P. A. Seib. Copyright 1993 by the American Association of Cereal Chemists, Inc. 

Phosphate esters of D-glucose, methyl alpha-D-glucopyranoside, and maltose, as well as the alpha,gamma- limit phosphodextrins from native potato starch (degree of substitution [DS] 0.0033) and phosphorylated amylose (DS 0.016) served as model compounds in [31]P-nuclear magnetic resonance experiments to locate the phosphate groups on a phosphorylated wheat starch (DS 0.012). The alpha,gamma-limit phosphodextrins were isolated by ion-exchange chromatography after exhaustive digestion of amylose or starch phosphates with Bacillus amyloliquifaciens alpha-amylase followed by Aspergillus niger glucoamylase. The endogenous orthophosphate groups on potato starch were confirmed to be the 6- and 3- esters. The wheat starch phosphate, prepared by heating starch with sodium tripolyphosphate under semidry conditions at an initial pH of 6, contained mainly 6-monophosphate esters along with lower levels of 3- and probably 2-monophosphates. The wheat starch phosphate contained orthophosphate groups at the nonreducing ends of starch molecules, whereas endogenous phosphate esters in potato starch occur on inner anhydroglucose units.