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J. C. Rankin, J. G. Rall, C. R. Russell, and F. R. Senti. Copyright 1960 by the American Association of Cereal Chemists, Inc. Corn starch with an amylose content of 50% was hydroxyethylated in the dry state with ethylene oxide and an alkali catalyst to give products containing from 1 to 27% by weight of combined ethylene oxide in quantitative yields. Aqueous slurries of hydroxyethylated high-amylose starch (etherified to an extent of 5% or more) when cooked to temperatures between 73 and 90 C. gave pastes which were fluid in character and had improved dispersion stability on cooling and aging over that of the unmodified starch. In the cooking-cooling cycle the viscosity curves exhibited by these products are considerably lower than those of similarly substituted waxy and normal corn starches. Pastes of modified 50%-amylose starch are less translucent than those of like derivatives of the other two starches. Pasting characteristics of hydroxyethylated high-amylose starch are correlated with such variables of preparation as degree of substitution, alkali catalyst concentration, and pH of product. Microscopic examination and film-forming properties of their pastes are discussed. Improved pasting properties obtained by hydroxyethylation of high-amylose starch indicate promise for this derivative of the new starch in industrial applications. |
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