Cereals  

This group includes plants from the family Poaceae and some other species from other families of similar traits and utilization. These species are also called pseudo cereals. The main cereal products are cereal grains, a by-product is straw (feeding straw, bedding straw, or straw to be ploughed in). Non-mature cereals also used as feed for livestock (“green feeding”), for making heylage and GPS silage. Cereals belong to annual crops, both spring and winter forms are grown

Cereal grain is a dry, single seed fruit. It is either is enclosed in glumes or naked. The glumes consist of flowering glume  and small glume. Usually, barley, oats, rice, millet and some sorghum species have grains with glumes.

 Nutrient contents in grain

 Carbohydrates prevail, consisting mainly of starch (60 to 70%). Starch serves as an energy source during the grain germination and in human and animal nutrition. Crude protein content is low (6-12%), it depends on the weather, growth and level of nutrition. Protein contents influence the grain quality (both nutritional and technological). Requirements for different ways of using grains are different (food grade vs. feed grade grains). Cereals contain only small amounts of fat. Only maize and oats have higher fat contents. Vitamin content is low, only B vitamins and vitamin E are present at higher levels. The content of mineral substances is not constant, to a great extent it is influenced by mineral contents in the soil and by form of fertilization. In general, cereals contain only small amounts of minerals. From macroelements, only phosphorus and potassium are present at higher levels, from microelements zinc, manganese and iron are present.

 Cereal grain structure:

Covering layers include the outer pericarp and the inner episperm that are grown together. The envelopes contain mainly fibre. Lower fibre contents are present in grains with a thin pericarp such as wheat, rye and corn. A higher content of fibre is present in barley, and oats because their pericarp is better developed. The covering layers also contain B vitamins, mainly thiamine, riboflavin, nicotine acid and pantothenic acid.

Endosperm consists of one layer of aleurone cells and a floury core.

Aleurone layer has the highest protein content, however, its physiological value is relatively low since it contains little lysine. There are two types of protein: protoplasmatic protein and reserve protein. Protoplasmatic protein includes albumins and globulins with favourable amino acid profiles. Their contents in cereals are low (an exception is oats in which they prevail). Reserve proteins prevail in cereals in general. They are also called the gluten fraction and consist of prolamin (30-50%) and glutenin (30-50%). They have unfavourable aminoacid profiles, contain a lot of proline and glutamine and little lysine. They are important for the bakery value of flour. The aleurone layer cells also contain fat.

Floury core contains mainly starch in the form of starch grains. Each cereal has a typical shape of starch grains.

Germ (acrospire) takes up the smallest portion of the grain, about 1.5-4%, in maize about 10 %. It contains structures a new plant. The germ contains protein and most of fat present in the whole grain, with vitamin E dissolved in it.