What is Mixing?
Dough mixing is an important process in bread making, which directly affects the product quality. It both homogenizes and hydrates the ingredients in dough.
Most bread uses hard wheat flour, which has dense particles that slow water penetration.1 During mixing, the particles rub against each other, exposing the next layer for hydration.
All the mixing machines available today are designed to incorporate both the mixing and the kneading processes. Kneading is the development of the dough gluten structure after the homogenized distribution of the ingredients.2
Bread dough requires a method by which the ingredients are homogeneously mixed and hydrated, resulting in a well-developed gluten network. The mixing required could be viewed as the energy necessary to develop the dough. Most bakers use the standard ‘stretch to a window pane’ test to determine proper development. This requires an extensible dough that would stretch to a thin film, without breaking. Final temperature of dough is recommended not to exceed 80oF (27oC) when it exits the mixer.3
In bread dough, both the dough gluten network development and dough temperature are established after mixing. Times are varied depending on the speed of mixer, mixer design, dough size, dough temperature, water absorption of the flour, etc. Dough mixing need to meet the following requirements:
- Disperse the recipe ingredients uniformly.
- Enable full hydration of these ingredients (especially flour protein).
- Provide the necessary energy for gluten development.
- Incorporate air bubbles within the dough to provide gas nuclei for the carbon dioxide generated from yeast fermentation.
- Incorporate oxygen for oxidation and yeast activity.
- Provide a well developed dough in a suitable form for subsequent processing.
Characteristics determined by the mixing stage4
If the dough is under or over mixed, the handling properties of the dough will be influenced, which results in lower volume bread.
If the temperature isn’t right, the fermentation rate will be faster or slower and that will influence the volume of the bread and the color of the crust.
If the length of time is not proper, the bread texture and crumb will also be influenced.
- Pick up: dough is sticky, cold and lumpy
- Initial development: dough is getting warmer, smoother and drier
- Clean up: dough is at maximum stiffness and comes together as one mass. The color will also change from yellowish to more white
- Final development: dough is at its correct temperature and handling quality. A gluten film can be easily obtained by extending a piece of dough
- Letdown: dough is too warm and sticky. It lacks elasticity and has too much flow
- Breakdown: dough is beginning to liquefy
Types of mixing machines
There are the following common machines used in bakery industry:
- Spiral mixer: in which a spiral-shaped mixing tool rotates on a vertical axis.
- High speed and twin spiral mixer: where a high level of work can be inputed to the dough in a short time.
- Horizontal mixer: where the beaters are driven horizontally within the bowl and fixed to one or two shafts.
- Low speed: where mixing is carried out over an extended period of time and the commonly used slow mixing system includes twin reciprocating arm mixer and oblique axis fork mixer.
- Continuous mixing: where the ingredients are incorporated at one end of the extruder, and the dough leaves the mixer at the other end in a continuous flow.
- Hoseney, R. Carl. “Yeast Leavened Products.” Principles of Cereal Science and Technology.
- St. Paul, MN: American Association of Cereal Chemists, 1994. P238.
- Cauvain, Stanley P., and David Marsh. “Mixing and Dough Processing.” Technology of Breadmaking. New York: Springer, 2007. P93.
- Pyler, E. J. “The Dough Mixing Process.” In The Baking Science and Technology 3rd Edition, Vol II. 1988 P 615
- “Bakery Technology – Mixing.” www.classofoods.com/page2_1.html. Accessed 02 May 2017.