MAJOR COMPONENTS OF WHEAT

Wheat is a seed which has evolved as a means of allowing a new plant to reproduce itself when provided with the right conditions of warmth and moisture.  When consumed by humans or animals, the grain provides a nutritionally balanced blend of carbohydrate, protein, fibre, vitamins and minerals. 
 
THE WHEAT GRAIN CONSISTS OF THREE MAIN COMPONENTS 

Bran – the outer coating of the grain designed to protect the internal contents of the grain until it is activated.  Bran consists of a number of fibrous layers, with the innermost layer, the aleurone layer, being high in non-gluten protein, oil, B vitamins and minerals.   Once milled, the high oil content can make the bran susceptible to rancidity and result in off flavours developing if the product is kept for a long time at higher temperatures.  Because of its tough fibrous nature, bran tends to maintain a large particle size during milling allowing it to be easily removed during milling by passing the ground wheat over sieves.

Endosperm - The major component of the wheat kernel represents about 85% of the grain weight. It is from this part that white flour is milled. The endosperm is high in starch (carbohydrate) and gluten protein, but it also contains small quantities of hemicellulose.  It is almost impossible to obtain pure endosperm in even the whitest flour as there is usually a small amount of contamination with bran and germ.  
Millers use a term called extraction rate which refers to the amount of flour obtained from each unit of wheat milled.  An extraction rate of 75% therefore means that 750kg of flour (mostly endosperm) is obtained from each tonne of wheat milled.

Germ or Embryo - The part of the seed from which the new plant grows. The germ lies at one end of the grain and represents 2 - 3% of the kernel mass.  It is a rich source of oil, B vitamins, vitamin E and has considerable enzyme activity which when activated breaks down the starch contained in the endosperm to provide energy for the growing plant until it is large enough to extract them from the soil and sun. 
In traditional milling processes, a significant amount of the germ is removed from the flour in order to limit the amount of rancidity that can occur.  Germ can also negatively impact flour baking performance in some processes due to the presence of a natural reducing agent called glutathione.  Wheat germ is highly nutritious and has a sweet, nutty flavour making it ideal for addition to many products.