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Nutrition

Gluten

Although the gluten content of flour is talked about, in reality gluten does not exist as such in flour. Instead there are two major protein components present in flour, which when combined with water form Gluten.

To obtain gluten, flour is mixed with water and the starch is washed out. This process is completed commercially and a great deal of care is needed to maintain the baking quality of gluten.

First step: The flour and water are mixed together. The resulting dough is left to rest to allow the protein components time to absorb the water.

Second step: The dough is then conveyed into long horizontal water filled tank containing screw-type conveyors, which knead the dough until all the starch is suspended in the wash water.

Third Step: All that remains between the screws is the gluten mass which is then forced through fine openings, chopped into small pieces and dried in a hot turbulent air stream ready for bagging.

There are different strengths of commercial gluten – stronger glutens are usually a grayish green colour while weaker glutens are yellow. Commercial gluten is available as either a dried powder or in a wet form

The approximate composition of dry gluten is:

Protein 70-75%
Starch 11-16%
Moisture 8%
Fat 5-8%
Fibre 1%

Grains containing gluten are used as ingredients for a wide range of prepared and commercial foods. Wheat flour alone is found in thousands of products due to its ability to give products structure and assist with the thickening and coating of products.

In addition to the gluten found in grains, gluten can also be added as a separate ingredient in its own right. This product is made from washing the starch out of a flour slurry.

This additional Gluten is used in the bread industry to supplement the gluten proteins already naturally present in flour and subsequent dough. To the baker gluten adds valuable properties:

Crumbed product gluten

  • increased dough strength
  • better gas retention and elasticity, which gives products good structure and uniform shape to bread
  • better water absorption and retention, improving yield, product softness and extending shelf life of bread
  • enhanced flavour

An example of additional gluten being added to the ingredients of a bakery product is in the manufacture of hamburger buns. The addition of gluten to the dough provides the elasticity needed so that the buns retain a uniform shape when filled.

Gluten can also be a useful ingredient in products other than bakery products, as the following examples highlight:

  • Batter: Ensuring a durable adhesion of batter crusts to foods is a quality problem, especially in frozen foods. Using a dusting of gluten powder before applying the batter vastly improves the adhesion in both hot and cold temperatures and the results are comparable to (more expensive) egg. The gluten also assists with food moisture as the product is better sealed and the surface crust that results is crispier and more appealing.
  • Pasta: Pasta manufacturers prefer to use semolina made from Durum wheat as it produces better quality pasta. However the addition of gluten to semolina made from other wheat varieties can improve their suitability for pasta doughs.
  • Meat products: Gluten is widely used in processed meats, as a binding and enriching ingredient. It is used in beef, pork and chicken sausage products and as a common ingredient of pizza toppings.

When compared to flour, commercial gluten is an expensive product at about six times the price, so it should be used at only the required level to meet product quality requirements. Some useful points to remember when using gluten as an ingredient at home or in a bakery setting are:

To make a useful improvement in the dough structure, approximately 4% of extra gluten is added (based on cereal weight).

If adding dried gluten to a bread formula then more water is required. This is approximately 1.5 times the weight of gluten added.

There are many components of wheat used in bakery products or other food items which are may not actually be called wheat in the ingredient list. These ingredients include:

  • Bran: Protective outer coating of the wheat grain, which is separated from flour after grinding and commonly found in breakfast cereals and wholemeal breads.
  • Wheatgerm: Part of the wheat grain and a rich source of B Vitamins, Oil and Vitamin E. It is used in many health food products as well as baked products.

pasta gluten

There are also different names for wheat. These may relate to a particular species of wheat or the name may indicate the way in which the grain has been milled. Here are some examples:

  • Durum Wheat: Species of wheat which has the hardest wheat grains. It is preferred for pasta making.
  • Spelt: Closely related to modern day wheat, which was popular staple in medieval times and is now making return as a ‘health food’ in breakfast cereals.
  • Semolina: Refers to a particular grain being milled to a larger or coarser particle size than commonly used flour. Semolina is used in the manufacture of pasta. Although the term semolina can be applied to any grain it is commonly associated with wheat.
  • Couscous: Is a dish made up of spherical granules made by rolling and shaping moistened semolina wheat, which is then coated with finely ground wheat flour.

Rye

  • Rye is a dark coloured, fibrous flour with a low gluten content and strong flavour.
  • It is the only non wheat flour with enough gluten protein for bread making. Although it is usually mixed with strong wheat flour to produce a lighter loaf of bread.
  • Breads made with Rye flour have a distinctive sour tang.
  • Used to make traditional bread like pumpernickel.

Barley

  • A cereal grain derived from the annual grass Hordeum vulgare.
  • Barley contains all eight essential amino acids. These are amino acids that the body must receive from the diet as the body can not produce them.
  • Barley-meal, a wholemeal barley flour which is lighter than wheatmeal but darker in colour, is used in porridge and gruel.

Triticale

  • A hybrid or combination of wheat (Triticum) and rye (Secale) to achieve the best attributes of both of these cereals.
  • It has grayish brown oval shaped kernels that are larger than wheat but plumper than Rye.
  • Triticale’s nutty flavour is similar to that of wheat.

Barley gluten

Unfortunately there is not a straight forward answer to this question.

Oats gluten

Oats are the seed of the cereal plant Avena sativa or A. byzantina.  Although they do not contain gluten they do contain the protein avenin which is similar to gluten. Most people who react to gluten do not react to this protein but some people do.

However due to high possibility of cross contamination during planting, harvesting and processing many brands of oats do have detectable amount of gluten in them. Therefore to be safe and avoid any issues, oats are usually grouped with the grains containing gluten; however in reality oats may have a place in a gluten free diet. Oats are commonly included in breakfast foods and health products, as well as in some baked products.

Gluten is a protein. Bread flour does not contain large amounts of protein (approx. between 10.5 – 13%) but it is very important for the bread making process. When flour is mixed with water, the gluten swells to form a continuous network of fine strands. This network forms the structure of bread dough and makes it elastic and extensible.


Kneading/High Speed mixing in bakeries

  • The addition of water to flour causes hydration of the Gliadin and Glutenin proteins and leads to the formation of gluten.
  • This stage “works” the dough, stretching the gluten complexes.
  • Stress induced by mixing breaks bonds between protein chains, allowing the chains to move and become realigned. The new bonds that are formed allow relaxation of the dough.
  • Gluten strengthening (or oxidising) agents, such as, ascorbic acid stimulate the formation of these new bonds, strengthening the dough structure.

Proofing (Rising)

  • At this stage starch breakdown and fermentation occur.
  • As bread dough ferments and proves, the yeast produces carbon dioxide gas that causes the gluten network to expand.
  • This leaves an open cellular structure with the gasses trapped in pockets.

The quality of gluten in dough is very important:

  • If gluten is too weak it can’t stretch in thin films around the air bubbles produced during fermentation.
  • The gas bubbles would then swell and burst, causing the loaf to lack volume.
  • If gluten is too strong then it won’t stretch so the gas bubbles can’t expand causing a very dense loaf.

A model which can be used to explain the mixing and proofing stages is the action of bubble gum. Firstly the gum is hydrated in the mouth by saliva then mixed and softened by chewing until it forms an elastic mass. This is then able to expand and support an air bubble.


Baking

  • As bread bakes, the gluten protein coagulates.
  • This sets the gluten so that it is no longer elastic and determines the bread size and shape. This change does not reverse when bread is cooled.
  • The end result after removal from the oven and cooling, should be a firm but open and light textured loaf of bread.

Cakes and biscuits are also commonly made from wheat flour, although it is usually low protein flours (7.5-9% protein). Gluten is present in these products; however unlike for bread, the development of gluten is usually discouraged as it can result in an undesirable and tough texture in these products.

There is no need to develop the gluten network during cake mixing as this would make a cake tough. The mixing step in cake making focuses more on combining the ingredients and incorporating air into a uniform batter to give a light desirable cake texture.

Biscuit mixing tends to be a single step, all-in system, or mixed in two steps where fat and sugar are creamed first. Gluten development is generally regarded as undesirable as it can lead to problems such as excessive shrinkage or distortion and checking, which causes biscuits to break or crack after baking.

The gluten proteins are very important in bread making and are given special consideration by the miller and baker. It is realised that without gluten, light, porous wheat bread, as we are accustomed to, would be impossible.

The gluten of a loaf is the structure or frame work that holds the loaf together and retains the gas in the dough. It is the elastic nature of gluten which allows dough to rise and to expand in the oven.

When water is mixed with flour the gluten is formed as a rather homogeneous mass, and it is during the mixing process and rising of the dough that the fibres and sheets of gluten which form the supporting tissue of the loaf are developed.

Flours without gluten do not provide the same elastic matrix for the structure and textures we associate with bread and baked goods.

So gluten free bread can be described as more dense and lacking in the open light texture that we associate with wheat bread. In addition to this Gluten free bread has a crumbly texture which stales quickly. Gluten free breads are available on the market made from grains, such as, rice or corn. Improvements are constantly being made to the texture of these breads as new ingredients and manufacturing techniques are developed, although product development of these products is difficult because without gluten, there is no framework to trap gases given off by raising agents.

Extra gluten is usually added to bread recipes due to either a large number of ingredients in the recipe which don’t contain gluten or because of the addition of ingredients which contain coarser particles.

If bread contains a high amount of ingredients that don’t contain gluten, then the overall amount of gluten in the recipe is diluted. This will ultimately affect the structure of the end bread product. Ingredients such as bran or germ can have this affect as can non flour ingredients such as fats or liquids. Adding extra gluten ensures that the gluten network is strong enough to hold up these extra components. This is a common practice in the manufacture of Variety breads due to the large amount of non gluten containing ingredients.

The addition to bread of large coarse particles such as bran or seeds can weaken the dough structure physically, as these larger particles can upset the gluten structure. Again extra gluten can prevent any structural problems with the bread occurring. Also bread requiring extra volume such as Vienna loaves may require extra gluten, especially if the flour is weak.

Types of bread that may need extra gluten are: wholemeal bread, high fibre bread, corn bread, hearth breads and mixed grain bread.