Amino Acids, Proteins and Enzymes

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Wheat Protein

Wheat proteins contain albumins, globulins, gliadins and glutenins, these four basic proteins depending on their varied solubility in different slovents.

As far as the practical utilization and commercial benefit for industries, two of these proteins are of maximum value in terms of food processing and food quality, and they are gliadins and glutenins. Why? Please look at the following chart:



During the production of wheat starch, dough is firstly formed by mix water and flour together, and then under the stream of water, the starch and solublies are washed away and gluten is left. Gluten generally contains 75-80% protein which are mostly composed of two proteins, gliadins and glutenins.

Can you guess why the gluten giladins and glutenins? 

Originally, wheat gluten is as humble as a byproduct of the production of wheat starch. However, with the develpoment of necessity for nutritional food or healthy food, wheat gluten has been becoming an important role in the food industry while wheat starch actually acts as a byproduct. For example, the bakers need gluten so much for the newer fomulators like low calorie or high fiber bread on the basis of the enhancement of water holding capacity.

Why gluten can enhance the water capacity? 


 
 
 
 

Wheat gluten has some properties specific to baking quality due to its special amino acid composition and structure. The figure shown left can tell us the structures of glutenins and gliadins contributing to the development of gluten.

There is one important difference between gliadins and glutenins, that is, gliadins have intra-molecular disulfide linkage while glutenins have both inter- and intra-molecular disulfide linkages. That is why the gliadins are compact and in the globular shape and the glutenins are linear and have relatively higher molecular weight 50,000-millions compare with the molecular weight of gliadins 20,000-50,000. To some degree, refer to the left figure, you can imagine how tacky, sticky and rubbery the gluten is.


 
 

The subunits of gliadins and glutenins are found as this chart.

Some researches show that the high molecular weight glutenin subunits are the exact part contributing to the development of gluten and that the a-gliadins are the real part resulting in the coeliac disease.

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301 Home : Course Modules / Amino Acids, Proteins and Enzymes / Question 4 : Wheat Protein