Acetylated and hydroxypropylated distarch phosphates from waxy barley: Paste properties and freeze-thaw stability

Waxy barley is a potential source for production of waxy starch and dietary fiber. Starch was isolated from a waxy barley (Wanupana) and purified using 0.15% sodium hydroxide solution; the yield of waxy barley starch was 40% of kernel weight with 0.2% protein content (N x 6.25). Waxy barley starch was cross-linked with phosphorus oxychloride in an aqueous medium of alkaline pH in the presence of 2% sodium sulfate (based on starch). Waxy maize starch was also modified for comparison. The optimum reaction conditions to make cross-linked waxy barley starch with high paste viscosity and stability to shear were determined by response surface analysis. The optimum cross-linking conditions (at 25;Acetylated distarch phosphate and hydroxypropylated distarch phosphate derivatives were prepared from waxy barley. Acetylation (DS 0.1) increased the paste viscosity, swelling power, solubility, paste clarity, and freeze-thaw stability of the cross-linked waxy barley starch. The gelatinization temperature of the waxy starch was lowered by substitution. Hydroxypropylation (MS 0.10-0.13) was equally effective as acetylation in increasing paste viscosity, swelling power, and solubility. However, acetylation gave better clarity but poorer freeze-thaw stability.;Hydroxypropylated distarch phosphate made from waxy barley starch exhibited extraordinary freeze-thaw stability, as compared to modified waxy maize, wheat, and tapioca starches, while maintaining the thickening power, clarity, and hot paste stability expected of a modified waxy starch.;Microloaves baked from reconstituted flours in which highly cross-linked waxy barley starch was interchanged with wheat starch were comparable with control loaves containing normal wheat starch.