LOOKING AT WHEAT SEEDS
The food value of a wheat plant lies in the rows of starch-filled grains or
seeds, called the 'ear', at the top of the plant. Each ear of wheat has about 40
grains. A single grain contains about 20,000 particles of flour. This flour can
be used to make a huge range of foods, including bread, cakes and biscuits.
Structure of wheat seeds
The diagram shows a grain of wheat magnified and cut lengthways through the
crease.
A wheat grain is a seed. This means it is designed for
reproducing the wheat plant. Each grain of wheat is made up of three distinct
parts. First there is the coarse outer
bran layer. Inside the bran layer the grain is made up of two
main parts. The smaller part is called the
germ. The larger part is called the endosperm.
The pericarp (part of the outer bran layer) is a tough skin which protects
the inner seed from organisms in the soil which may attack it. The inner seed
coats control the intake of water by the seed.
The germ is the part of the grain which is the embryo plant. It has a radicle
which can grow into a root system and a plumule which can develop into the
stems, leaves and ears of a new wheat plant.
The endosperm is the starchy store of food, which the germ will feed on while
it is growing.
Wheat seeds after the harvest
Storing the grain
After harvest, the wheat seeds (grain) is kept in special stores until it is
needed for making flour. Grain is harvested only once a year, but may be stored
for up to 12 months, so the conditions are very important to ensure the grain
stays in good condition. For example:
- The store must be clean, dry and well ventilated.
- Grain is cooled rapidly (using air) after harvesting. Otherwise its
natural heat makes it an ideal breeding ground for insects.
- The moisture level and temperature must be carefully managed so that the
grain does not spoil.
- The store must be free from pests, such as mice or fungi.
- All equipment must work properly and be checked regularly.
- The stored grain is sampled to check its quality.
Making the flour
Grain from the store is taken to a mill where it is used to make different
types of flour.
White flour is made from the endosperm only. Wholemeal
flour uses all parts of the grain: the endosperm, the wheatgerm and the
bran layer.
Brown flour contains about 85% of the original grain, but some
bran and germ have been removed. Find out more about how flour is made
here.
If you buy flour and use it at home, keep it on a cool, dry, airy shelf in
its bag, or in a clean, dry container. White flour will keep for 6 to 9 months,
and wholemeal or brown flour for 2 to 3 months.
