wavelengths of light. The red fruits will take on an attractive red-orange colour.
Why not use galvanised copper (the copper is covered with a tin layer? The tin will prevent the copper
from being removed from the bottom of the pan, so it will not be able to play its roles in favouring
pectin extraction and keeping the bright red colour. The tin ions that are released will instead bind to
the pigments, changing their configuration and therefore absorption spectrum, and thus giving the jam
an unattractive purplish colour.
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More about culinary ingredients: Flour
Ordinary flour is produced from crushing up the grains of a wheat plant.
To prepare flour, the outer layer of the wheat grain is removed. Although this layer is edible, it contains
lipids which reduce the shelf-life of the flour. The grain is then ground to produce flour.
Flour is mainly composed of starch molecules – the amylose and amylopectin molecules, which are
organised together into starch granules. These starch granules contain circular layers of amylopectin
and amylose molecules held together by hydrogen bonding.The starch content of flour constitutes
between 70 to 80% of flour weight.
Flour also contains proteins (approximately 10% of the flour weight). Flour contains many different
types of proteins – the majority of these proteins are insoluble in water (the gliadines and the
glutenins), the rest are soluble in water (the albumines and globulins). It is the insoluble proteins that
have an important role in the food preparation – they form coagulated networks that are responsible
for holding the shape of flour based foods such as bread, pasta and gnocchi.
The composition of flour can be demonstrated by simply adding flour to water. Some of the flour will
form a soft sticky dough with the water, whereas the rest of the flour will be washed into the water,
which will become cloudy. The part of the flour that is washed into the solution include some of the
starch granules (which make the solution cloudy) as well as the remaining flour components (soluble