The 3 Main Purposes of Kneading
Mixing of Different Ingredients into a Homogeneous Dough
Water plays a predominant role:
- By performing the enzymatic reactions allowing for the transformation of flour starch into compound sugar (maltose) and simple sugar (glucose); and
- By helping dissolve the salt and dilute the yeast, thus creating the favourable environment to the dough proofing changes…
Development of the Gluten Network
Water is also involved in the agglomeration, softening and extension of certain proteins contained in the flour and insoluble in water: gliadins and glutenins. It is them that form the gluten, a substance that is more or less soft and elastic. Properly hydrated, gluten gives the dough its impermeability and its rheological properties.
The Trapping of Air in the Dough
The stretching of the gluten network creates a fibre which will become stronger through the incorporation and the trapping of air bubbles. The dough becomes smooth, elastic and uniform and its whitening is proportional to the duration and intensity of the kneading.
Mixing and Stretching for Proper Kneading
Kneading is broken down into two phases in sequence to obtain a homogeneous dough:
It promotes the absorption of starch and gluten by water; and
- Stretching and blowing
which promote the structuring of the dough through the reinforcement of its glutinous network.
These 2 phases may be interrupted by a so-called autolysis stage. This phenomenon of relaxation of the gluten network happens under the natural action of enzymes contained in the dough.
Then, the kneading mode and duration are chosen depending on those various elements:
- The basic characteristics of the flour used,
- The recommended bread-making method depending on the type of bread to produce,
- The amount of dough kneaded, and
- The desired
The kneading speeds will vary with the dough’s hydration rate. Firm doughs have a hydration rate below 60% unlike soft doughs which need more water.
The Temperature of the Dough
The dough’s temperature control is of great importance for the bread-making process and must be performed since the mixing phase.
For the fermentation to develop in a satisfactory manner and to manage the development, it is required to have a dough temperature after mixing that is typically between 20°C and 26°C.
The final temperature of the dough differs depending on the temperature of raw materials (flour and water), of room temperature, of the mixing method and of the type of mixer used.
VMI Measures the Energy Used During Mixing
An Empiric Method With Poor Reliability…
For several years, VMI has carried out research on the control of various parameters during kneading operations. In most cases, the baker relies on criteria gathered by the sensorial examination of the dough to determine the optimum length of the kneading process. Relying only on touching or seeing the dough (smoothness, elasticity, colour…) is unreliable.
… Replaced By a More Meticulous Follow-Up.
Productivity and more specifically repeatability factors have recently led some bakers to demand a real time follow-up of the kneading process that takes into account the rheological characteristics of the dough and the operational parameters of the kneaders.
The energy generated by the kneader and transferred to the dough is one of the physical values which meet this goal. It can be of precious help in the follow-up and optimization of a variety of settings.
Experimental works have allowed to establish a correlation between:
- the kneading time,
- the power generated by the mixer, and
- the temperature of the dough during kneading.
The VMI mixers measure in real time the consumption of electrical energy by the motor(s) of the mixer thanks to a wattmeter. Tests have proven that the evolution in the consumption of energy during the mixing is correlated to the curve corresponding to the energy transferred to the dough.
Thus, we can offer a new variable that takes into account the state of the mixer/dough combination as a whole, thanks to its energy balance.
Today, we are working in collaboration with partner researchers to develop a measuring device that would allow to steer the kneading by taking into account a parameter only based on the characterization of the dough (disconnected from the mechanical or thermal phenomena of the kneader itself).