Location: Wheat, Sorghum and Forage ResearchTitle: Dough Rheology and Wet Milling of Hard Waxy Wheat Flours) Author
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2009
Publication Date: 7/13/2009
Publication URL: http://hdl.handle.net/10113/36046
Citation: Guan, L. P. A. Seib, R. A. Graybosch, S. Bean and Yong-Cheng Shi. 2009. Dough rheology and wet milling of hard waxy wheat flours. J. Agric. Food Chem., Publication Date (Web): July 13, 2009 (web version) DOI: 10.1021/jf900438v Interpretive Summary: Wheat starch typically is composed of two complex molecules, amylose and amylopectin. Each is in turned formed by the linkage of small sugar molecules known as glucose. In amylose, the glucose molecules are linked in long straight chains; in amylopectin, both straight chains and branched chains exist. Typical wheat starch is a mixture of approximately 25% amylose: 75 % amylopectin. We have developed a new type of wheat which produces starch composed only of amylopectin. These wheats, known as “waxy” types, produce starch with dramatically different cooking properties. These include shorter cooking times, better water retention, and the ability to disperse in cold solutions. Companies that produce wheat starch for food and industrial applications often extract the gluten protein as a co-product. Gluten is used in a variety of food applications, both for humans and domestic beasts. Unfortunately, gluten extraction in waxy wheats is less efficient. This paper presents the results of a study designed to correct this defect. By mixing a weak dough with 2% NaCl (table salt) solution or by adding hemicellulase (an enzyme that dissolves cell wall components), stickiness of the dough subsided during the washing step and thereby improved recovery of the gluten and starch fractions.
Technical Abstract: To realize the full potential of waxy wheat (Triticum aestivum L.), wet milling of waxy wheat flour to produce gluten and waxy wheat starch was investigated. Flours of six advanced lines of waxy hard wheats, one normal hard wheat (‘Karl 92’), and one partial waxy wheat (‘Trego’) were fractionated by the dough-washing (Martin) process, and yield and recovery of starch and gluten were compared. A model of a mixture of wheat gluten and starch was designed to understand whether differences between waxy and normal wheat starch affect flour dough rheology. When waxy and normal wheat starches were each blended with a wheat gluten to give a mixture containing 14.5% protein, they gave very different mixograms even though the protein in the blends was the same. Waxy wheat starch absorbed more water than normal wheat starch, which retards hydration of the gluten and its development. Higher water content had to be used for some waxy wheat flours to develop optimum dough. Compared with wet milling control doughs from Karl or Trego wheat varieties, washing any of the waxy wheat doughs under a stream of water caused dough to become slack, spread out more on the sieve and break apart into several pieces. However, slack dough pieces did not “blind” the screen, and when approximately two-thirds of the starch had been washed away, the small dough pieces coalesced into elastic dough that behaved like the controls. By mixing a weak dough with 2% NaCl solution or by adding hemicellulase, stickiness of the dough subsided during the washing step and thereby improved recovery of the gluten and starch fractions.