Some of the Minor Constituents of Wheat Starch and its Hydrolysates ‐ Part 1.‐

Abstract

Abstract The application of sedimentation analysis to the calculation of specific surface area of various wheat starch fractions in conjunction with determination of lipid content indicated that much of the lipid is contained in the outer layer of the starch granule. In order to rupture the lipid‐rich layer of the starch, it was necessary to heat the starch for long periods in 0.1 M sodium hydroxide at a temperature of 42°C. Nitrogen contents were reduced from 0.044% to less than 0.014% and reduction of the lipid content in a similar ratio was also achieved. In ordinary refined starch fractions, ratios of the nitrogen content to lipid content were reasonably constant, similar to those obtained on the lipid separated from acid hydrolysates of 42 D. E. which suggests a close association between lipid and nitrogen. Crude starches, which had a greater proportion of their nitrogen in the form of gluten and pentosan proteins gave higher nitrogen to lipid ratios than the refined starch. An approximately linear relationship between the percentage of nitrogen in the separated lipid and the D. E. of the hydrolysate was found to hold in the range 30–70 D. E. If it could be assumed that the same relationship held below 30 D. E., extrapolation to zero D. E., indicated a nitrogen content of 3.1% in the lipid of the starch. This takes into account practically all of the nitrogen of a refined wheat starch. In order to limit the amount of lipid present in wheat starch hydrolysates and thereby reduce the number of problems encountered in processing wheat starch into refined syrups, the fine granules should be removed efficiently. This would reduce the extent of foaming when hydrolysates are partially neutralised, and improve the efficiency of the filtering operation.