Understanding Friction Factor in Dough Mixing/Kneading
Introduction: What Is the Friction Factor in Dough Mixing?
In dough making, the friction factor is a variable used to calculate the final dough temperature, along with the temperatures of the water, room, and flour. The friction factor indicates the amount of heat generated during the kneading process, which results from the dough’s friction with the work surface or bowl sides. In simpler terms, the friction factor indicates the amount of heat that the dough accumulates during kneading/mixing. For example, a friction factor of 10 means that the kneading process increases the dough’s temperature by 10 degrees.
The specific value of the friction factor depends on the kneading method used. Hand kneading tends to generate less heat, while mixers, particularly home mixers, create more friction and therefore heat the dough to a greater extent.
Beyond the kneading method, other variables can also influence the extent to which the dough heats up during kneading. These variables include the kneading speed, the bowl size, the dough weight, and the duration of kneading. All of these factors affect the friction factor, which ultimately indicates the number of degrees the dough gains during kneading as a result of these variables.
As you can see, different kneading methods result in varying amounts of heat being generated during the kneading process; This, in turn, affects the temperature of the dough at the end of kneading, especially when the friction factor is high. To accurately control the final dough temperature (using PizzaBlab’s Final Dough Temperature Calculator), it is crucial to determine the friction factor.
General Friction Factor Values for Different Kneading Methods
Since the friction factor essentially measures the temperature change (how much heat the dough gained during kneading), its values differ for Celsius and Fahrenheit. It is important to note that this is not a standard conversion between Celsius and Fahrenheit, as it relates to a difference in temperature, rather than an absolute temperature.
To convert from Fahrenheit to Celsius, subtract 32 and multiply the result by 5, then divide by 9. When converting a temperature difference, exclude the subtraction of 32 and only multiply the value by 5, then divide by 9. For instance, a friction factor of 10 in Fahrenheit is equivalent to a friction factor of 5.5 in Celsius (10 * 5 / 9 = 5.5).
Hand Kneading:
- When using Celsius, the typical range for the friction factor for hand kneading is between 1-3.
- When using Fahrenheit, the typical range for the friction factor for hand kneading is between 2-5.
Note that the actual friction factor for hand kneading can be higher than these ranges, depending on the temperature of the kneading surface (room temperature). A warmer surface will heat the dough more quickly, increasing the friction factor, and vice versa.
Mixers:
- When using Celsius, the typical range for the friction factor when using a mixer is between 8-16.
- When using Fahrenheit, the typical range for the friction factor when using a mixer is between 15-30.
| Celcius | Fahrenheit | |
| Hand Kneading | 1-3 | 2-5 |
| Mixers | 8-16 | 15-30 |
If you need an initial value for the friction factor, you can start with the following values and make adjustments:
- For hand kneading, start with a friction factor of 2 (for both Celsius and Fahrenheit).
- For a mixer, start with a friction factor of 12 (Celsius) or 20 (Fahrenheit).
Alternatively, for a precise calculation of the friction factor, refer to the next section (recommended).
How to Calculate the Friction Factor
Although you can attempt to determine the friction factor through trial and error, it is more advisable to calculate the specific friction factor for your particular kneading process. This calculation may require some effort, but the positive aspect is that it typically only needs to be done once. Once we have obtained the friction factor, as long as the kneading process remains relatively consistent (using the same equipment, kneading time, and dough quantities), we can continue to utilize this friction factor to calculate the water temperature in the future.
The formula for calculating the friction factor is as follows:
FF = (FDT * 3) – (WT + RT + FT)
FF = Friction Factor
FDT = Final Dough Temperature
WT = Water Temperature
RT = Room Temperature
FT = Flour Temperature
The method for calculating the friction factor involves the following steps: first, prepare the dough using normal procedures, while also recording the temperature of all relevant variables. Then, input these variables into the formula to determine the amount of heat generated during kneading, which represents the friction factor.
The steps for calculating the friction factor:
- Measure the ingredients’ temperature before starting the kneading process, including the room temperature, water temperature, and flour temperature.
- Knead the dough as you usually do to ensure a reliable result for the friction factor.
- Measure the temperature of the dough at the end of kneading. This will be the final dough temperature.
- Input all the collected data into the formula to calculate the friction factor.
For example:
Room temperature = 22C/72F
Flour temperature: 22C/72F (If the flour is stored outside the fridge, its temperature will be the same as the room temperature)
Water temperature: 18C/64F
Final dough temperature: 26C/79F
Friction Factor: ?
Let’s input all the data into the formula.
In Celcius:
16 = (26 * 3) – (22 + 22 + 18)
In Fahrenheit:
29 = (79 * 3) – (72 + 72 + 64)
Note that it doesn’t matter whether the calculation is done in Celsius or Fahrenheit because the result is a temperature difference. If you want to convert the resulting friction factor between Celsius and Fahrenheit, you can follow the steps we discussed in the previous section (e.g. 29 * 5 / 9 = 16).
As can be seen, the friction factor for this specific example is 16C/29F. Now with our friction factor determined, we can easily and quickly calculate the required water temperature for our desired final dough temperature using PizzaBlab’s Final Dough Temperature Calculator.