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Improving pasting and textural properties of waxy wheat flour and starch by chemical and physical modifications
Y. SHI (1), S. Garimella Purna (1), L. Guan (1) (1) Kansas State University, Manhattan, KS, U.S.A..

Waxy wheat is a potentially valuable specialty wheat. Starch in waxy wheat endosperm comprises essentially amylopectin. In normal wheat, starch contains approximately one-fourth of its weight as amylose. The physical properties of starches when heated with water depend in large measure on their amylose content.  Amylose promotes the gelling and film-forming properties of a starch, and creates highly associated starch. The highly associated starch in food digests slowly and incompletely when consumed by humans. Amylopectin, on the other hand, increases the thickening power of starch and promotes clarity of starch pastes and gels. Starch pastes control the consistencies of soups, gravies, sauces, and fillings, while starch gels control the textures of puddings, spoonable salad dressings and confections. Waxy wheat starch gelatinizes and begins to swell at a temperature about 10ºC below that of waxy corn starch. The lower cooking temperature increases waxy wheat starch’s marketing potential in microwaved foods and as a starch thickener that saves energy during food processing. However, when cooked in water, waxy wheat starch gives a cohesive texture, which is not desirable in many food applications. In this study, waxy wheat starch was chemically cross-linked to eliminate the undesirable cohesive texture. Cross-linked waxy wheat starch gave a somewhat higher thickening power compared to cross-linked waxy corn starch.  Furthermore, the same modification on both waxy corn and wheat starches gave a modified waxy wheat starch with better freeze-thaw stability than waxy corn starch. Freezer-stability of starch-based thickeners is required for frozen foods. In comparison, thermal processes were used to develop non-cohesive texture from waxy wheat flour.