Cereal Chem 67:202-208   |  VIEW ARTICLE

Acetylated and Hydroxypropylated Distarch Phosphates from Waxy Barley: Paste Properties and Freeze-Thaw Stability.

Y. Wu and P. A. Seib. Copyright 1990 by the American Association of Cereal Chemists, Inc. 

Waxy barley starch was cross-linked with phosphorus oxychloride (POCl3) at 25 C in alkali containing sodium sulfate. In a modeling study of the cross-linking reaction, the level of POCl3, pH, temperature, and reaction time were varied while the responses of shear stability of the hot paste and its consistency at 50 C were measured in an amylograph. The cross-linking conditions giving highest paste consistency together with highest shear stability were pH 11.1-11.5, POCl3 0.005-0.007%, and reaction time 20-60 min. At the same pH and reaction time, the optimum level of POCl3 to cross-link waxy maize starch was 0.010-0.015% POCl3. The thickening power, hot paste stability, and clarity of optimally cross-linked waxy barley starch matched those of cross-linked waxy maize starch. Hydroxypropylation (molar substitution 0.10-0.13) of cross-linked waxy barley starch improved freeze-thaw stability more than acetylation (degrees of substitution 0.10), but the opposite was true for paste clarity. Hydroxypropylated distarch phosphate from waxy barley exhibited much better freeze-thaw stability than commercial samples of similarly modified waxy maize and tapioca starches. In fractionation-reconstitution experiments on flour in breadmaking, cross-linked waxy barley starch of low consistency was substituted for wheat starch, and the compositie low-amylose flour gave bread with loaf volume and grain equivalent to those obtained with normal amylose flour.