Uploaded by quimicadascoisas on 15.05.2012

It's part of human history,
it's one of the most important foods in our diet
and it's is delicious warm with butter...
Have you guessed today's theme?
That's right, we will talk about bread.
Today in The Chemistry of Things we analyse
the chemical composition of its ingredients
and some of the chemical reactions responsible for
this healthy, versatile and delicious food.
In our country, a typical bread recipe has:
wheat flour, water, yeast and salt.
Wheat flour consists primarily of starch, i.e. sugar chains
and proteins, i.e., amino acid chains.
Let's start by kneading the dough,
which in terms of chemistry is more than just mixing flour and water.
This process allows the proteins to surrounding the starch granules
and gives the dough its characteristic consistency.
Salt is added to the dough and not just as a matter of taste.
The presence of sodium and chloride ions is essential
to promote the aggregation of protein chains
that contributes to the formation of a stronger and less sticky dough.
Then, the dough ferments.
During this period the yeast, which is a fungus,
causes the decomposition of sugar, with the release of CO2.
It's the formation of CO2 bubbles, trapped in the gluten protein network,
that makes the dough grow
and produce the light open texture of bread.
At this stage there are also a number of important chemical reactions
involving natural oxidants of the flour,
through which the links between the protein chains break
and form in a different place, repeatedly,
enabling the dough to "stretch" without losing its structure.
Finally we just have to bake the dough.
And by the way, the golden-brown colour of bread after baking
is the result of the Maillard reaction,
so named after the chemist who found that the heat of the oven
causes a reaction between amino acids and sugars
which gives a golden colour to baked foods.
Who said chemistry can't enter the kitchen?
If you want to know more about the chemistry of bread
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