Joint International Conference on Long-term Experiments ...

The objective of this study was to investigate whether the transport of water towards the
centre actually occurs during the baking process and to establish when the water transport
starts, ends, and what direction it takes. A second objective was to investigate whether the
rise in water content inside the loaf is centred at the coldest region or whether it is
geometrically centred.
MATERIALS AND METHODS
Bread recipe: A standard recipe for white French bread was used in this study with the
following quantities and ingredients for one loaf: wheat flour 370 g, water 200 g, salt 6 g,
sugar 6 g, oil 6 g, dry yeast 4.5 g.
Water content and temperature measurements: During the baking processes the optic fibre
was placed at five different sites in the loaf, in the centre, 1 cm from the base, in the bottom
crust, 1 cm under the top surface and in the top crust. The temperatures in the oven and in
the loaf were measured with copper-constantan thermocouples type T. The thermocouples in
the loaf were placed on the bottom surface, in the centre or 1 mm from the optic fibre. In
two of the loaves the temperature was measured at seven different places during the baking
to locate the coldest region and study the temperature gradient. The thermocouples were
placed, (a) on the top surface, (b) on the bottom surface, (c) on the side surface, (d) a third
of the way to the centre from the bottom surface, (e) half way to the centre from the top
surface, (f) in the centre, (g) two thirds of the way to the centre from the bottom surface.
Oven: The study used a conventional oven with a good temperature stability ±3 0 C and no
forced convection.
Baking procedure: The ingredients were mixed in a dough processor at 80 rpm for 2 min
and at 185 rpm for 3 min. The dough was left to rise for 35 min and mixed again at 185 rpm
for 2 min. It was then divided into three pieces which were rolled out into rectangular slabs.
The rectangular slabs were placed on top of each other in the baking tin, with the
thermocouples and the optic fibre between. The rectangular, 1.5 L baking tin had
dimensions of 9x25x6 cm. At one end of the tin there was an open slot, from the base to the
top, where the optic fibre and the thermocouples could protrude. The dough was allowed to
rise for 45 min in the tin before being placed into the oven, where it was baked for 35 min at
225 0 C.
Separation of crust and crumb: In one loaf the crust was cut off immediately after baking.
The crust pieces were separated into crust in direct contact with the baking tin, and crust in
contact with the air. The crust in contact with the baking tin was separated into side and
bottom crust. The crust was dried and weighed to see how much of the dough had become
crust and how much water had been present as dough. The water content of the crust in
contact with the air was compared with the total water loss of the loaf directly after baking.
The water content of the crust in contact with the baking tin was compared with the rise in
measured water content in the centre of the loaf.
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