Gluten Rises to the Challenge

In 1729, an Italian scientist described a rubbery substance that emerged after rinsing wheat flour dough. This early extraction became the foundation for isolating one of the most fundamental components of the modern baking industry. Today, the baking industry uses gluten to strengthen doughs, increase gas retention and control dough expansion, and improve water absorption and retention. Plus, the ingredient is finding other applications.

Two proteins in one 

Gluten is composed of two insoluble proteins: glutenin and gliadin, which interact when water is added to wheat flour. Although similar in composition, these proteins offer different structural characteristics that create the viscoelastic behavior of gluten. Glutenin is a large molecule—100,000 to 3,000,000 daltons—made up of subunits that are connected by disulfide bonds. The polymeric structure is flexible yet resistant to extension. In its pure form, glutenin exhibits a tough, rubbery texture when fully hydrated. Gliadin is monomeric, ranging in molecular weight from 30,000 to 40,000 daltons. This single-chain molecule becomes extremely thick and sticky when hydrated, and offers little resistance to extension.

In dough systems, glutenin provides strength and elasticity, while gliadin provides lubrication to the gluten matrix and allows the gluten to expand uniformly. Excess glutenin yields a tough dough, while excess gliadin results in softer, more extensible dough.

Manufacture of gluten is straightforward, but far from simple. After milling, specially selected wheat is blended with water to create a dough from which the gluten and non-gluten proteins are separated by washing. The remaining gluten mass must be dried to approximately 6% to 8% moisture, without heating the protein beyond 140°F (about 60°C), or else denaturation of the protein can occur. Denatured gluten loses some of its “vitality,” the potential to increase loaf volume.

Glutenin is practically insoluble in water under typical pHs. Gliadin’s solubility increases outside the pH range of 6.0 to 9.0. With this isoelectric behavior in mind, gluten can be dispersed into dilute acetic acid or ammonium hydroxide solutions at 12% to 14% solids for spray drying. Drying flashes off the acid or base, leaving a gluten with typical vitality. The energy requirement is great, however, as 6 lbs. of water must be evaporated for every 1 lb. of dried gluten produced.

The Barr-Rosin Ring Dryer is one of the most common systems for drying gluten. Blending gluten at approximately 70% moisture with gluten at approximately 8% moisture forms small “pellets,” which are introduced into a countercurrent of hot air. Dry gluten is transferred to a separator for collection, while still-moist material is recycled through the drying chamber. This innovative system takes advantage of evaporative cooling to maintain a particle temperature below 140°F, despite air temperatures up to 340°F.

Dry gluten is milled to specific particle sizes for specific applications. Particle size will affect the time required for full hydration. Larger particles require more time for hydration than finely ground material. The ability to increase loaf volume doesn’t depend on initial particle size, assuming the gluten has enough time for full hydration.

4 and 20 uses

The baking industry is the most common application area for gluten, accounting for over 60% of sales. Vital wheat gluten is approved by FDA as GRAS for use as a dough strengthener, formulation aid, nutrient supplement, processing aid, stabilizer and thickener, surface finishing agent and texturizing agent.

In bread formulations, gluten addition can help compensate for low-protein flours and support heavy particulate ingredients like cracked grains, nuts and raisins. Addition rates vary, depending on the function being served by the gluten. Levels in the 1% to 2% range will provide strength to a pizza crust. Adding 4% to 5% assists in “carrying” weight. Levels upward of 6% may be used in “high protein” products. Gluten’s viscoelasticity is a function of the interaction between glutenin and gliadin, and can enhance the strength of doughs, increase tolerance to mixing and improve general handling properties. Gluten added to pre-sliced hot dog and hamburger buns at approximately 2% (flour basis) will strengthen the hinge and improve crust character of buns held in a steamer.

Viscoelasticity also gives rise to gluten’s film-forming property. As carbon dioxide or water vapor develop within a hydrated gluten mass, the pressure can cause the mass to expand. Gas retention provides controlled expansion and subsequent increases in volume and uniformity. Mark Baczynski, director, protein development, Manildra Group USA, Shawnee Mission, KS, cautions against using too much gluten. “When gluten is used at high levels, its viscoelastic attributes start to become its own worst enemy,” he says. “At very high levels of gluten, bread doughs become impossible to mix and process. Water absorption is so high that it takes much longer to bake, which also leads to other sensory issues such as crust thickness and color.”

Beyond the bakery 

As a pre-dust, gluten improves adhesion of batter crusts and breadings, resulting in reduced cooking loss and improved finished appearance. In cereal products, gluten can bind vitamin or mineral enrichment components to grains, and also improve the strength of flakes.

Thermosetting properties of hydrated gluten complement film-forming and adhesive properties, making gluten an option for meat, poultry and seafood applications. Wheat gluten can bind chunks or trimmings to create restructured items. In poultry rolls, gluten’s binding ability can reduce cooking losses during processing and preparation, and improve slicing characteristics.

Gluten can also be used as an extender in ground meat patties, as well as a binder for sausage products. Hydrated gluten may be extruded, texturized or spun into fibers to produce a variety of meat, poultry and seafood analogs. Steve Ham, MGP Ingredients, Atchison, KS, says, “Textured wheat proteins are available in a wide array of sizes, shapes and colors that can partially or completely replace meat at a cost savings while enhancing sensory properties due to their neutral taste and unique textures.

Fibrous pieces that are great for applications such as chicken nuggets or shredded barbecue products effectively mimic chicken breast meat, beef and pork, with the convenience to the manufacturer of being pre-shredded.”

Changing identity 

Product developers continue to explore the use of gliadin and glutenin separately, or in ratios designed to increase specific benefits each component brings to the gluten complex. Increasing gliadin enhances film-forming properties that can improve a pizza crust by relaxing the dough and reducing total mixing time. Noodles with added gliadin exhibit enhanced texture and reduced stickiness and cooking loss.

Modified forms of gluten allow processors to enjoy the beneficial properties of gluten in systems that might not allow for gluten addition. Partial hydrolysis of gluten, for example, yields a protein with dramatically increased solubility. Ham suggests, “When added to bread formulas at a level of 0.5% to 1.5%, a partially hydrolyzed wheat protein reduces both mixing time and resistance to extension, which increases dough extensibility. In addition, it is a good source of peptide-bonded glutamine for nutritional bars and drinks.”

R.J. Foster has over a decade of experience in research & development and technical service in the food industry. A freelance writer specializing in technical communications, he can be reached at

[email protected].