Wheat starch and wheat gluten have transformed in recent years into specialty, value-added products.
Wheat starch and its modified versions are available in cook-up or pregelatinized (instant) forms. Two components make up normal wheat starch—the essentially linear amylose fraction, which comprises approximately one-quarter of its weight, with the balance consisting of a highly branched amylopectin fraction. Composition and structural features dictate the performance of wheat starch in foods. Amylose contributes to its gelling tendency, and amylopectin is primarily responsible for its thickening ability.
The value of wheat starch in food applications relates to its unique combination of properties. Although wheat flour inherently contains colored pigments, isolated wheat starch has high purity and is bright white, which is important in flour-based applications, as well as for use as a moisture-control agent in baker’s sugar. Residual protein in wheat starch is primarily from bound starch synthases and branching enzymes, and from friabilin, a biomarker protein for grain hardness. The nitrogen from starch-bound lipids (i.e., lysolecithin) contributes to the apparent protein content when analyzed by the Kjeldahl method or a combustion method using a nitrogen analyzer. Coincidentally, the lipid lysolecithin is trapped inside the amylose helix, making it less prone to oxidation, thereby reducing the sensory perception of cereal flavor.
One domestic producer reports that wheat starch typically contains below 10 ppm gluten, the minimum detection level for gluten content when assayed by the Ridascreen (R-Biopharm) ELISA method. Because the Codex Alimentarius standard for gluten-free is “not exceeding 20 ppm gluten,” wheat starch can be a suitable ingredient in gluten-free foods, although it has to comply with allergen labeling regulations as established in the Federal Allergen Labeling and Consumer Protection Act of 2006.
Native (unmodified) wheat starch exhibits lower viscosity than other commercial starch sources, so it finds some applications where high solids (body) is desired without excessive thickening. Its thickening ability is affected by its heating rate—a faster heating rate generates higher viscosity due to concurrent increases in granular swelling and leaching of solubles. Above 6%, the paste develops into stronger gels compared to corn starch, because of the higher content of linear amylose molecules of wheat starch vs. corn starch.
Application considerations
Major uses of native cook-up or pregelatinized wheat starch are in flour-based foods, such as bakery products, principally because of its compatibility with wheat flour. It helps modulate higher-protein flours and promotes tenderness in baked goods.
Hydroxypropylated and cross-linked wheat starch serves as a batter viscosifier, moisture-retention agent, crumb softener and shelf-life extender in chemically or yeast-leavened bakery products. Bread yield can be increased by incorporating 1.5% to 2.0% of pregelatinized hydroxypropylated wheat starch or pregelatinized hydroxypropylated and cross-linked wheat starch.
