EXTRACTION OF WHEAT-STARCH WITH AQUEOUS SODIUM-HYDROXIDE

Wheat starch was extracted with aqueous sodium hydroxide at 30-38% sta rch solids, pH 11.5-12.3, and 25-42 degrees C for 0.17-24 hr. Stirring wheat starch at pH 12.3 and 25 degrees C for 3 and 24 hr, then washin g with water, neutralizing, and washing again, removed 70 and 90% phos phorus (P), respectively. Adding 16% sodium sulfate (dry starch basis) into the alkaline medium removed approximate to 80% of P at pH 12.0 a nd 25 degrees C in 3 hr and >95% of P at pH 11.7 and 42 degrees C in 3 hr. Sulfate ion was absorbed strongly by wheat starch in aqueous sodi um 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) reta ined 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 th at of prime starch, as did its X-ray diffraction pattern. Those data a re consistent with saponification of the lysophospholipid in the amorp hous 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% star ch solids was lowered by approximate to 10 degrees C.