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ARS Home » Plains Area » Lincoln, Nebraska » Wheat, Sorghum and Forage Research » Research » Publications at this Location » Publication #320673
Title: Functionality of chemically modified waxy, partial waxy and wild-type starches from common wheat

Author
item Graybosch, Robert
item HANSEN, LAVERNE - Retired ARS Employee

Submitted to: Starch/Starke
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2015
Publication Date: 5/1/2016
Citation: Graybosch, R.A., Hansen, L.E. 2016. Functionality of chemically modified waxy, partial waxy and wild-type starches from common wheat. Starch/Starke. 68:496-504 doi:10.1002/star.201500241.

Interpretive Summary: Value-added crops contain special quality or end-use characteristics that enhance their value in the marketplace. Successful development of value-added crops can add needed income to America’s family farmers and provide new food products for consumers. One such possible value-added crop is waxy wheat, or wheat that lacks amylose in its starch. Amylose is a large polymer, composed of glucose molecules in long chains. When amylose is absent, starch is composed only of amylopectin. Amylopectin differs from amylose in that it has branched chains, and provides different cooking, processing and starch stability properties. This paper reports a number of experiments in which ARS scientists chemically modified waxy starch, reduced-amylose starches, and blends produced by mixing waxy and normal wheat starches. Modified waxy wheat starches gave markedly different properties after chemical modification. Especially notable was long stability after cooking. This property would make waxy wheat useful in the preparation of foods in which cooked starch is required. Reduced amylose starches, and blends, produced modified starches with properties intermediate to those of waxy and normal. Waxy wheats, therefore, afford the end-user the opportunity to produce a variety of starches, with a variety of properties, for a variety of food products.

Technical Abstract: Waxy wheat (Triticum aestivum L.) starch contains little or no amylose. Partial waxy wheats have amylose concentrations intermediate between those of waxy and wild-type (normal) starches. A factorial design was used to compare waxy, wild-type, partial waxy, and blends (10 and 17% amylose) of waxy and wild-type starches in native states, and after cross-linking with phosphorus oxychloride, substitution with propylene oxide, and a sequential modification procedure using both approaches. In analyses via the Rapid Visco Analyser (RVA), native waxy wheat starch reached peak viscosity at a significantly lower temperature, and displayed significantly higher viscosity (>3000 cP), than starches of all other genotypes and blends. Hydroxypropylation of waxy wheat starch increased peak viscosity to >3500 cP. In contrast, native and hydroxypropylated wild-type starches demonstrated peak viscosities of 1000 and 1500 cP, respectively. Cross-linked waxy starches demonstrated stable viscosities, with no breakdown or setback. With both native and modified starches, partial waxy pasting curves displayed viscosities intermediate between those of waxy and wild-type, though the same effect was obtained via use of the 17% blend. The 10% native starch blend displayed pasting properties intermediate between those of the partial waxy/17% blend group, and the waxy sample. The results suggest that appropriate selection of amylose contents, ideally formed by blending of waxy and wild-type starches, and chemical modification method, can result in wheat starches with predictable functional properties for a variety of food and industrial uses.