Question

Describe the chemical reactions and chemical interactions that occur among gluten proteins during gluten development. Include in your answer the functional roles of the major classes of gluten proteins.

Answer 1

Gluten is insoluble protein and it is formed when water and wheat flour are mixed. Protein is large molecules composed of amino acids. Two naturally occurring proteins in flour are called glutenin and gliadin. When water is added to the flour both proteins emerge and becomes flexible. The process of wetting the proteins is called hydration. Both proteins begin to emerge with each other through the formation of chemical bonds. These newly chemically bonds are called cross-links. In the formation of gluten a number of different types of chemical bond forms between two proteins like disulfide bonds being stronger than others like ionic and hydrogen bonds.

Continuous mixing causes more cross-links to form between the proteins until a large network of chemically linked proteins are formed. When the dough is mixed or kneaded the hydrated flexible proteins are stretched and aligned in a direction to form more cross-links between the proteins. Kneading also incorporates air, which helps to form strong disulfide bonds. As kneading continues the protein network combines to form sheets of proteins.

Protein alone is not as elastic as gluten. These chemically formed cross-links between glutenin and gliadin form flexible and elastic gluten.

The major functional role of gluten protein in gluten development is as follows:

1) Variety of wheat: Soft wheat contains less glutenin, smaller proteins forms weaker gluten. Hard wheat contains more glutenin, larger proteins forms strong and elastic gluten.

2) Amount of water: Hydration is essential for gluten development. If less water is used it causes less development of gluten and at the same time more water dilutes the protein which restricts the interaction resulting in less gluten development.

3) Water hardness: Hard water containing Calcium and Magnesium strengthen gluten.

4) Water pH: Ideal pH of gluten development is 5-6. Above or below 5-6 pH reduces gluten strength.

5) Leavening: Expanding air bubbles strength gluten and its elasticity producing higher volume.

6) Enzymes: Enzymes present naturally in flour breaks down gluten in smaller pieces to produce more extensible dough with more volume. This process is known as autolyse.

7) Salt: Salt slows down the enzymes activity and rate of fermentation. Salt strengthens gluten producing bread with higher volume.

8) Fat, oils, emulsifiers and sugars tenderize the dough. Fat and emulsifiers coat protein reducing hydration and gluten development. Shortening shortens gluten strands producing more tender baked goods. Sugar competes for water reducing protein hydration and gluten development.