|Jackson, D. S. - UNIVERSITY OF NEBRASKA|
|Wehling, R. L. - UNIVERSITY OF NEBRASKA|
Submitted to: American Association of Cereal Chemists Meetings
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2007
Publication Date: October 1, 2007
Citation: Hansen, L.E., Jackson, D., Graybosch, R.A., Wilson, J., Wehling, R. 2007. Characterization of chemically modified waxy, partially waxy, and wild type tetraploid wheat starch. American Association of Cereal Chemists Meetings. Technical Abstract: Durum wheats (Triticum turgidum L. var. durum) contain two Granule Bound Starch Synthase (GBSS) genes (wx-A1and wx-B1) controlling amylose synthesis; the other major starch polymer in durum wheat is amylopectin. Starches with little or no amylose are “waxy.” A GBSS null (non-producing) gene results in a starch granule with reduced amylose content, or a “partial waxy” character. Sets of wild type, partial waxy (wx-A1 null or wx-B1 null), and waxy (wx-A1 and wx-B1 double null) durum wheat lines were developed in several genetic backgrounds. Seed from the individual genotypes, wild type to full waxy, were composited across genetic backgrounds with the intent of removing confounding genetic background effects. The starches from each genotype from two crop years were isolated using dough ball washing followed by flow table separation. Protein (0.1% to 0.4% dwb), lipid (0.0% to 0.3% dwb), and amylose (0% to 30% dwb dependent upon genotype) contents in the isolated starches were determined. These isolated starches had mostly large granules with a size distribution profile similar to commercially prepared waxy or wild type starches. Hydroxypropylation using propylene oxide was performed three times on each sample, resulting in an average molar substitution of 0.040 (± 0.010). Rapid-Visco Analyses (RVA) were performed and profile changes, defined as the average of the mathematical difference of substituted minus native results in cp of the pasting curves for waxy (peak viscosity, 176; breakdown, 329; final viscosity, -206; setback, -53.5; and pasting time, -0.8) and wild type (peak viscosity, 510; breakdown, 677; final viscosity, 646; setback, 813; and pasting time, -2.2) were observed. Substituted fully waxy starches had increased peak viscosities, breakdowns, reduced final viscosities, setbacks, and pasting times. Regular (full wild type) substituted starches had increased peak viscosities, breakdowns, final viscosities, setbacks, and decreased pasting times. These modified forms of starches are used as thickeners in foods and frozen preparations such as pie fillings, sauces, gravies, and salad dressings. RVA results for the partial waxy genotypes and a phosphorus di-ester cross-linking reaction will also be presented.