Objective: To extract gluten from wheat flour
Background: Gluten is a protein formed when two other proteins called gliadin and glutenin combine to form a network when water is added and the dough is mixed. The ability of gluten to stretch without easily breaking makes it an excellent flour for bakery goods. These products rely on the strength of gluten to stretch and hold their shape without collapsing during yeast fermentation and increasing gas pressure during baking. Some people are allergic to gluten and so should avoid all products that contain wheat and other grains that have gluten-forming proteins (barley, rye and triticale). In this lab you will get to develop and isolate gluten from wheat flour.
- All purpose or baking flour
- Kneading bowl
- Measuring cup
- Measure and transfer 4.5 cups of all purpose or baking flour in a kneading bowl
- Add 1.5 cups of water gradually and knead to form a dough. (Note: This amount of water is estimated for all-purpose flour. You may need a little more water for baking flour. If the dough feels too dry you may need to add a little more water. If it is too sticky you may need to add a little more flour to absorb the excess water)
- Knead rigorously by hand for 10-15 minutes to develop the gluten in the dough (feel free to use a bread dough mixer if you have one). Signs of good dough development is when the surface of the dough appears smooth and it is able to stretch without easily breaking
- Now that the dough is fully developed, it is time to remove the starch, leaving the gluten behind. You can do this by washing the dough using cold running water until the water is clear. See illustrations below.
Fig 1. Dough after early kneading (Notice rough surface)
Fig 2. Dough at end stage of kneading (Notice much smoother surface)
Fig 3. Mixing bowl with dough being filled with cold running water for starch washing
Fig 4. Early stage of dough washing (Notice the white color of water due to starch removal)
Fig 5. End stage of dough washing, revealing gluten (Notice that water beneath is much clearer, indicating that almost all the starch has been washed out)