In this experiment, you show, like Beccari, that flour is made of two parts, starch (the white powder)
and gluten (the yellow part).
The conclusion given by the Beccari experiment is clear - we can easily see that gluten forms an
elastic network. The starch “granules” present are dispersed within.
And in the form of flour, the gluten network is not yet fully formed some water is needed.
And one last point: depending on the wheat used, and the part of the wheat grains used to make the
flour, flour can be more, or less white: now you can understand that this depends in particular on the
relative proportions of starch and gluten.
Potatoes are tubers, and could therefore be discussed with vegetables and fruits, but we decided to
consider them here because we need some information on starch before we can fully understand
them. A microscope very useful when looking at potatoes – even a very simple one, just like the ones
children may get as Christmas presents.
Take a potato, and cut it into two parts. Then, using a very sharp knife, take a thin layer of potato and
place it on a glass microscope slide.
Put a glass lamella on top of it, and look at it under the microscope. You are able to see delicate and
transparent contours, enclosing spherical shapes. The contours are the cell walls, and the shapes
inside are the starch granules. You can see them better if you pour a droplet of iodine solution onto
the potato slice: the granules turn blue - the iodine is “trapped” by part of the starch, called amylose.
You should not be surprised to learn that potato cells contain starch - when you are cutting potatoes to
make French fries, for example, and you wash the potato pieces before frying, you see the starch
granules washed from the surface of the potatoes in the cloudy liquid. And washing the potatoes is
useful - if not, the starch granules would go into the oil and burn.
Rice, barley, oat, millet
In the same way that we placed potatoes in their own section, we will also make a specific section for