The aleurone layer
The wheat grain is protected from the environment by several closely grown layers- the aleurone layer, the testa and the inner and outer perciarps- which are removed during grinding and bran is produced. The testa is also known as the seed coat, which contains all the pigments- colour producing materials, and the inner and outer percicarps are also known as the seed skin.
This is the most biologically active part of the grain. It is made of living tissue, from which the future plant is formed. The germ has all the materials needed by the fragile sprout: fat, protein, carbohydrates, minerals (potassium, phosphorus, magnesium, iron), E and B vitamins and enzymes. This part of the grain also has a lot of polyunsaturated fatty acids (linoleic, linolenic), phospjatides (lecithin). The fat in the germ is perishable and may become rancid, therefore the germ is removed when producing flour and grit.
Bran is s source of fiber, B vitamins and minerals. Fiber is a means from preventing various types or illnesses. Nutrition specialists advise eating 25-30 grams of bran every day. Therefore, if you eat 220 grams of rye bread, you will get the necessary fiber required by for your health. It should be noted that for you to get the required amount of fiber you would have to eat 2 kg of potatoes, or 7 kg of tomatoes every day.
The inner part of the grain – the endosperm – contains the main nutritional components of the grain – starch and protein. This anatomical part of the grain (also called the flour kernel) makes up 80-85% of the grain. Although from a nutritional standpoint it is way behind the bran, the aleurone layer or the germ, although the gluten proteins and starch in it make it indispensable in the preparation of baked goods. The main aim in the production of flour is to extract as much of the endosperm from the grain as possible.
What is gluten?
The endosperm in the inner part of the grain contains very important nutrients – the proteins gliadin and glutenin, which make up gluten. They are insoluble in water, therefore can be extracted by washing out the associated starch and other materials. Gliadin and glutenin make up 80% of the proteins in a wheat grain.
Gluten is essential for making wheat baked goods, because it makes up the structure of the dough. Gliadin defines the viscosity and pastiness, and glutenin – the elasticity and resistance when stretching the dough.
The baking properties of the flour depend on the amount and quality of gluten. The stronger the gluten the longer the dough can be kneaded.
Other additives of the dough also have an impact on gluten and the quality of baking. Kneading of the dough and high moisture stimulate the formation of a gluten network, and fatty additives decrease it. Therefore in order to get baked goods of a more fragile and milder structure it is advised to mix in some fat into the dough, use less water and not overdo with kneading.
Flour is divided into types according to the amount of gluten and marked by capital letters. The closer a letter is to the beginning of the alphabet, the more gluten the flour has.
Of all the types of grain only wheat has a high gluten content, therefore wheat flour is the most suitable for baked goods. It is recommended to mix in flour from other types of grain and seeds.
Wheat is used in various areas: nutrition, the pastry industry, feed for livestock, cosmetics and pharmaceutical industries. The wheat (Triticum) family is divided into 22 types, from which several have a wide range of applications – it’s the simple (Triticum aestivum L.), hard wheat (Triticum durum Desf.) and Spelt wheat (Triticum spelta L.). Thousands of strains have been designed from these types – strains with various properties.
The common (soft) wheat is the most common type of wheat worldwide. It makes up around 90% of wheat farming. Only this type of winter and summer wheat is traditionally grown in Latvia.
Durum (hard) wheat is characterised by a particularly high protein content which makes them suitable for use in the pasta industry. This type of grain needs a warmer climate than Latvia has, so it is not grown here..
In recent years interest in the unfairly forgotten Spelt wheat has increased in Lithuania. It is a winter, semi-wind grain, one of the oldest grain plants. This type of grain was known since the Stone Age. Unlike other types of wheat, the Spelt grain is covered in petal scales, protecting it from diseases, pests and loss of moisture. This wheat naturally overshadows weeds, is not demanding and is highly resistant to the cold, so it is suitable for Lithuanian climate conditions.