rice, barley, oat, millet, and wheat. All these are “cereals”, amongst the most important staple food of
mankind. They have been grown systematically from as early as 5000 BC, and today their production
reaches billions of tons!
The “fruits” of these plants are made of cells (of course!), with different layers, as one can easily see
just by looking at wheat grains. In particular, one can see some envelopes, and also various zones
Using the iodine test, one can easily see that all of them contain starch.
And now it ‘s time to cook them.
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Take rice grains, for example, and cook it in water for a very long time. You get a “paste”.
Take wheat grains (or flour if you cannot get whole grains) and cook them in water for some minutes:
you get a “paste”.
Take pure starch and cook it in water for some time… and you again get a “paste”.
In all these situations, the starch was able to make the “paste”, i.e. it modified the viscosity of water
and “thickened” it.
Let’s cool the “pastes” produced: a gel is formed.
This can be attributed to the two main compounds of starch, called amylose and amylopectin. Imagine
that the amylose molecules are simply like microscopic threads, and that the amylopectin molecules
are simply like microscopic soft trees. They are both packed in the starch granules.
The above experiment has many conclusions. In particular, one is important: starch is not soluble into
cold water, but it can dissolve (more or less) in hot water. Upon cooling, it forms a gel, i.e. a solid that
traps water. But bear in mind that when cooling, or setting, some water is released by this gel. This is
called “syneresis”, derived from a latin word meaning “contraction”.
At a time when one did not know if water was drinkable, milk, stock and wine were very important! And
one should not forget that milk is the very first food that we recieve.
First, milk is a liquid: when poured, it flows. Could we admit that it contains some water? Again, the
experiment of heating it, is not difficult, and indeed if carried out one can observe that milk is made