What is dough mixing?
Dough mixing is the mechanical blending of dry and liquid ingredients of a formula to form a dough or batter. After scaling, i.e., the weighing out of ingredients, mixing is the next step in a bakery manufacturing process. The goal is to:
- Incorporate air
- Hydrate dry ingredients
- Homogenize the dough by evenly distributing all the ingredients
- Knead the dough, encouraging the interchange of disulfide bonds and the formation of hydrogen, hydrophobic bonds, salt linkages and Van Der Waals forces
- Develop the gluten by aligning the network and transforming the dough into a cohesive mass
The mixing stage can be viewed as a simple equation in which all reactants are necessary to gradually transform flour, water, air, energy, and any other ingredients into a homogeneous and aerated dough:2
Flour + Water + Air + Energy → Dough
Mixing is a crucial step in all dough systems used for the manufacture of yeast-leavened baked goods. It is critical to obtain the right rheological properties and consistency of the dough for the production process to run smoothly, as well as achieve the desired finished product quality.
- In Sponge and Dough Systems: The sponge is mixed first and then ferments. The second mix is dough mixing, where the objective is to develop the gluten.
- In Straight Dough and No Time Systems: Dough mixing happens only once.
- In Continuous Mixing Dough Systems: The first mixing is a blending step, which is not intensive in nature. The goal here is to distribute and incorporate ingredients evenly. After a set time in a fermentation and holding tank, a second mixing step occurs. This is mechanically intensive, since the goal is to develop the gluten.
How does dough mixing work?
When flour and water are mixed together, water hydrates the gluten-forming proteins naturally present in the wheat flour, gliadin and glutenin. Meanwhile, the other ingredients dissolve and/or start to bond water.
Here is what’s happening in the mixing bowl:
- Wheat flour particles are dense and resist penetration, so, diffusion is slow. The mechanical movement created by mixing, speeds up the diffusion process.
- Dry flour particles slowly become fully hydrated and the dough starts to become cohesive.
- Soon, the dough is transformed into an elastic, extensible, viscous, and cohesive mass. The hydrated gliadin–glutelin network, or gluten, starts interacting via formation of hydrophobic and disulfide bonds
- An optimally mixed dough is a balance of extensibility/stretchability, elasticity, and resistance to flow.3
How can dough mixing be controlled?
Dough mixing control requires actions and strategies followed by production supervisors and bakery managers to consistently produce high-quality doughs that are ready for the next step in production.
Control of dough mixing involves intrinsic and extrinsic variables:
|Intrinsic variables (ingredients)||Extrinsic variables (processing parameters)|
These strategies require:
- Knowledge of the process (know-how)
- Use of technology (e.g., processing and instrumentation equipment)
- Use of appropriate ingredients and correct scaling
Types of commercial dough mixers
- Vertical mixers (agitator has planetary action, both revolving and rotating during mixing)
- Spiral mixers (commonly used in small- to medium-sized bakeries)
- Horizontal mixers (most common mixer in large-scale due to capacity capability)
- Tweedy / Chorleywood mixers (high speed mixers)
- Continuous mixers (require liquid ferment system, premixer or blenders, and developer)
An ideal dough mixing process:
- Minimizes costs
- Minimizes energy consumption
- Optimizes hydration
- Minimizes staling, i.e., starch retrogradation, in the finished product
- Minimizes dough handling issues
- Provides just the perfect development on the gluten network (not under-developed nor over-developed).
- AIB International. Bread Manufacturing Process, Distance Learning Course, “Module 02 – Mixing.” https://www.aibonline.org/Start-Your-Training/Baking/Baking-Foundations/Bread-Manufacturing-Process-Online, 2018.
- MacRitchie, F. “Structure and properties of dough.” Concepts in Cereal Chemistry, CRC Press Taylor & Francis Group, LLC, 2010, pp. 29–35.
- Gisslen, W. “Lean Yeast Doughs: Straight Doughs.” Professional Baking, 7th ed., John Wiley & Sons, Inc., 2017, pp. 119–122.