1. Take a tablespoonful of fully matured dough when making Standard bread.
2. Form it into a ball between the palms of your hands.
3. Allow water from a tap to flood over your hands and rub the dough so as to wash out the starch and any fibrous material, but try to avoid loosing any bulk material.
4. After a few minutes the ball will be reduced in size but it will have become rubbery. This material is the isolated gluten. Continue until it is free of other material.
5. Dry the gluten with a hair drier. It will be very sticky and elastic with yellow, grey or green colour, and no taste.
6. If this experiment fails it is likely that your dough has not matured, see Troubleshooting chart for possible reasons.
This will be used to enable us to calculate the ideal temperature for the water used for making dough. The flour from the store, being cool, will absorb heat from the water and reduce its temperature. The water for the mixture should therefore be at a sufficiently high temperature to yield dough at the required temperature.
Some theory
The quantity of heat involved in a change in temperature of an amount of material is always equal to the mass of the material multiplied by the 'specific heat' of the material multiplied by the change in temperature involved; more concisely expressed thus:
where Q is the quantity of heat, m is the mass, t is the change in temperature. (These quantities must be expressed in appropriate units of measurement.)
Procedure
Given the specific heat capacity of flour, if its mass and initial temperature are known, the temperature for the required mass of water may be calculated. Note that the specific heat of water is 1 and this value would have no effect on the calculation so has been omitted in the following.
In my experiment I used 357gm flour at 14°C and 300ml water at 47°C. When thoroughly stirred, the temperature of the mixture stabilised at 35°C.
The heat equation is as follows.
where s denotes the specific heat of the flour. Note that the values on each side of the quation amount to a quantity of heat; on the left side it is the heat absorbed by the flour and on right side it is the heat lost by the water. They are equal.
This gives s = 0.48, which is convincingly close to the text book value of 0.45.
Now, suppose I wish to produce dough at 40°C, using 350gm flour at 14°C and 300ml water. In the following equality t denotes the required temperature of the water:
Thus
Note that this result is subject to a small percentage error owing to heat lost to the environment.