Joint International Conference on Long-term Experiments ...

RESULTS
Temperature distribution: When the loaf is placed in the oven the temperature rises on the
surfaces Figure 1. The temperature is approximately the same on all of the surfaces which
are in contact with the baking tin (i.e. on the base and sides of the loaf). The temperature of
the base rises slightly faster than the side temperatures due to heat conduction through the
base from the ceramic plate in the oven. At the top surface the temperature is slightly lower,
0-10 0 C, than the base temperature, up to approximately 80 0 C. The top surface temperature is
higher than the bottom temperature from 0 0 C to approximately 30 0 C, when removed from
the oven. Throughout the loaf there is a temperature gradient, with the coldest region a little
below the centre Figure 1. When the temperature reaches 100 0 C there is a plateau in the
temperature rise, until all of the water has evaporated. On the surface there is no plateau
whereas behind the crust, in the crumb of the loaf, the temperature remains at the plateau.
Water content distribution: The water content measured in the centre decreases when the
loaf is placed in the oven, until the temperature reaches approximately 70"5 8C. There is
then a change in the measured water content, which begins to increase. Figure 2 shows a
typical graph of the changes in temperature and water content in the centre during the
baking. At 1 cm underneath the top surface the changes in the measured water content are
identical, although the initial rise is approximately 3 g water 100 g bread and the decrease is
approximately 13 g water 100 g bread Figure 3. At the top and absolute bottom the decrease
in water content commences immediately and a crust is formed.
Figure 1: Changes in temperature inside the loaf during baking (a) top surface; (b)
bottom surface; (c) side surface; (d) 1 cm from the bottom surface; (e) 6.8 cm from the
bottom surface; (f) centre, 4.6 cm from the bottom surface; (g) 3.5 cm from the bottom
surface. Total heights 9.0 cm
DISCUSSION
Temperature distribution: During the fermentation of the dough the temperature distribution
in the loaf is fairly constant. The surface temperature of the loaf rises quickly during baking.
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