|Graybosch, Robert - Bob|
Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2002
Publication Date: 2/11/2003
Citation: Wook, K., Johnson, J.W., Graybosch, R.A., Gaines, C.S. 2003. Physicochemical properties and end-use quality of wheat starch as a function of waxy protein alleles. Journal of Cereal Science. Interpretive Summary: Waxy wheats produce flours that have a modified form of starch. This starch is composed only of amylopectin, branched chains of glucose. Typical wheat starch contains approximately 75% amylopectin, and 25% amylose. Amylose consists of straight chain glucose polymers. Typical (wild-type) wheats have 3 functional genes encoding forms of the enzyme granule-bound starch synthase (GBSS). Partial waxy wheats have one of two such genes inactive, and produce starch with amylose contents that range from 15-25%. Waxy wheats have no active genes for GBSS. In this study, wheat lines with various numbers of active GBSS were produced in a common, soft wheat background. The effects of active gene number and amylose contents were studied. Both physicochemical effects on starch properties and effects on traditional soft wheat quality attributes were investigated. Waxy wheat starch was found to differ markedly from both partial waxy and wild-type wheat starch, both in physical properties and in effects on soft wheat quality. The effect on soft wheat quality was generally negative, but the markedly different aspects of waxy wheat starch suggest it could serve as a novel substrate for the production of chemically modified starches with unique properties.
Technical Abstract: The effect of amylose concentration on starch pasting properties, and milling and baking quality was studied in eight granule-bound starch synthase (GBSS: waxy protein) genotypes in a soft wheat (Triticum aestivum L.) background. Double null lines showed lower amylose concentration than single null lines and wild-type lines. In single null genotypes, the wx-B1 null also induced lower amylose concentration compared to the wx-D1 null and the wx-A1 null. Milling and baking quality traits were clearly different between waxy (zero amylose) and the other genotypes. Waxy lines showed the lowest flour yield of 69.5%. The typical A-type patterns of X-ray diffractograms were observed for all starches. No intensity peak at 2q = 23o was observed for waxy starch. Waxy starch showed higher crystallinity than non-waxy starch. Analysis by rapid viscoanalyser (RVA) showed distinctive differences among the eight genotypes. The peak viscosities of waxy starches were higher than those of all other genotypes. Breakdown and setback also differed