Publication no. C-1997-1029-07R |  VIEW ARTICLE

Extraction of Wheat Starch with Aqueous Sodium Hydroxide (1).

Naoko Matsunaga (2,3) and Paul A. Seib (2,4). (1) Contribution 97-332-J, Kansas Agricultural Experiment Station, Manhattan, KS. (2) Graduate research assistant and professor, respectively. Department of Grain Science and Industry, Shellenberger Hall, Kansas State University, Manhattan, KS 66506. (3) Present address: Kyoritsu Women's University, College of Home Economics, 2-2-1 Chiyoda-Ku, Tokyo 101, Japan. (4) Corresponding author. Fax: 913/532-7010. Cereal Chem. 74(6):851-857. Accepted August 19, 1997. Copyright by the 1997 American Association of Cereal Chemists, Inc.

Wheat starch was extracted with aqueous sodium hydroxide at 30-38% starch solids, pH 11.5-12.3, and 25-42°C for 0.17-24 hr. Stirring wheat starch at pH 12.3 and 25°C for 3 and 24 hr, then washing with water, neutralizing, and washing again, removed 70 and 90% phosphorus (P), respectively. Adding 16% sodium sulfate (dry starch basis) into the alkaline medium removed approximately 80% of P at pH 12.0 and 25°C in 3 hr and >95% of P at pH 11.7 and 42°C in 3 hr. Sulfate ion was absorbed strongly by wheat starch in aqueous sodium hydroxide at pH 12.0, and sodium sulfate also increased the starch's uptake of hydroxide ion. Low-P wheat starch (>90% of P removed) retained the fatty acids in the untreated starch, but a fatty acid-amylose complex was not detectable by differential scanning colorimetry. The enthalpy of gelatinization of the low-P wheat starch almost matched that of prime starch, as did its X-ray diffraction pattern. Those data are consistent with saponification of the lysophospholipid in the amorphous phase of the starch to form fatty acid salts and glycerol-choline or glycerol-ethanolamine phosphodiesters that slowly diffused out of the granules. The low-P wheat starch was judged to have less "cereal" odor than the prime starch, and its pasting temperature at 9.3% starch solids was lowered by approximately 10°C.