strengthening of the network, before the gases have had time to fully expand. When the gases start to
expand, they are unable to stretch the protein network (which is too rigid), and the bread remains fairly
flat. Equally, under kneaded dough will produce bread with a reduced volume, because less air will be
incorporated, so there will be less overall gas expansion during cooking and the bread will remain
fairly flat. This dough will rise less during subsequent cooking, even at an ideal temperature.
If, however, the temperature is too low, the gases will swell before the bread has formed its hard outer
crust, so the gases will expand and the bread will stay flatter.
On cooling, starch that has been released from the starch granules will start to bond to each other,
trapping the water present into a gel. This makes the soft centre of the bread become harder, which
actually makes it easier to slice the bread. After a few days, starch bonding is so great that water is
squeezed out of the network and the bread become so hard it is no longer edible. Therefore, stale
bread can be softened slightly by heating it, because it allows the starch molecules to become mobile
again, releasing trapped water, and softening the dough.
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What we make from culinary ingredients: Cakes
Cakes are another sort of dough, in which the flour is mixed with eggs, sugar and butter. This mixture
is then cooked to produce a light and fluffy cake, filled with gas. The gas bubbles contained in the
cake are not produced by yeast, like in bread, but rather are incorporated into the cake mixture either
by using chemical gas producers (like baking powder), or mechanically by beating in air.
The different ways of introducing gas
Chemical leaveners (eg baking powder and soda) are compounds that give off carbon dioxide when
placed in hot water. Their primary component is the alkali sodium bicarbonate, which is either mixed
with acid already (as in baking powder) or needs the addition of acid to function (as in baking soda).
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