Wheat Starch CapabilitiesWheat Starch Capabilities
September 10, 2008
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 starchthe 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 bakers 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 ratea 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.
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.
Pastes of hydroxypropylated and cross-linked wheat starch have a smooth, nonsticky texture with a melt-in-your-mouth sensation. This property is probably responsible for the absence of flavor masking in foods with modified wheat starch. This is particularly evident when hydroxypropylated and cross-linked wheat starch is formulated as the primary thickening agent in sauces such as marinara, Alfredo, brown onion, and chicken sauce. A pregelatinized hydroxypropylated wheat starch functions as a thick-to-thin additivethe viscous property allows food pieces to be suspended in the initial stages of soup processing, but later thins down to the desired consistency after retorting. Deep-fried, coated foods benefit from the adhesion, crisping and browning properties of oxidized wheat starch.
A healthy dose of fiber
The most-important event in recent years is the development of RS4 resistant wheat starch for use as fiber fortification in foods. Resistant starch is not absorbed in the small intestines of healthy individuals, and is included in the definitions of dietary fiber by the American Association of Cereal Chemists International, Codex Alimentarius and European Food Safety Authority.
Clinical studies using healthy subjects support the attenuation of postprandial glycemic and insulin responses of foods formulated with resistant wheat starch (Al-Tamimi, E.K., Effect of resistant starch type 4 on glycemic and insulin sensitivity in young adults. Ph.D. Dissertation. Kansas State University, Manhattan, KS. 2007).Carbohydrate-rich foods that elicit low glycemic and insulin responses may reduce the risk of type 2 diabetes and other health issues related to glucose regulation.
Consumption of 25 grams of resistant wheat starch per day is well tolerated in humans. In general, resistant wheat starch is allowed in foods at levels that impart the desired technical effect, meet good manufacturing practices, and also comply with FDAs nutrient labeling claims (i.e., good source or excellent source of fiber).
A second resistant wheat starch product on the market has a dual function of fiber enhancement and fat replacement. This particular attribute can enable both a reduced fat claim and good source or excellent source of fiber claim in many food products. Commercial food applications of these two resistant wheat starch products include bread, flour tortillas, English muffins, bagels, pizza crust, muffins, cookies, muffin bars, pretzels, puff pastry, pasta and hand-held crust appetizers.
Ody Maningat is vice president of applications technology and technical services at MGP Ingredients, Inc., Atchison, KS. He has a Ph.D. in Grain Science from Kansas State University, Manhattan, KS. Maningat is a member of AACC, IFT, ACS, and ASQ. Reach him at [email protected].
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