In this article we will talk about common wheat, or soft wheat, a cereal from which “00”, “0”, “1”, “2” and “wholemeal” flour is obtained.
The cultivation and consumption of cereals date back to ancient times and, almost certainly, these plants were the first used as food by man. Thus it is very interesting to know the properties of this raw material.
Botanical classification and characteristics of the plant
Cereals are herbaceous plants belonging to the Gramineae family which are cultivated for their fruits (grains or kernels) which, eaten either whole or more frequently ground, are the basis of our diet.
Wheat, Triticum in botanical classification, is a genus of graminaceous plants that includes various species, the most common of which are:
- Soft wheat or Triticum Aestivum, from which flour is obtained and which will be the subject of this article;
- Durum wheat or Triticum Durum, from which semolina is obtained.
Soft wheat grows everywhere except in tropical areas. The plant produces inflorescences called ears (see figure 1), and their fruits are known as kernels or grains. The height of the plant varies between 70 and 100 cm depending on the different cultivars, i.e. the agricultural varieties of the Triticum Aestivum species. As the cultivar varies, the shape of the grain, its starch and protein content and its colour also vary. For more details on these differences, read our article on grain selection and milling. The “productive” part of the wheat is the ear, which is made up of 3 parts: flower, spikelet and caryopsis.
The ear, as found in nature, i.e. attached to the wheat plant, cannot be processed by mills. For this reason, after maturation, when the caryopses have reached a certain level of humidity, we proceed to harvesting and threshing. These operations are now carried out by a single machine, the “combine harvester” which cuts the stalk of the wheat and subsequently selects the kernels, discarding the straw and the chaff. At this point, the grain is ready to enter the mill, where it will be checked and cleaned several times before being ground.
Figure 1. Ears of wheat of Triticum aestivum (soft wheat). Source: “Flora von Deutschland, Österreich und der Schweiz”, Dr. Otto Wilhelm Thomé, Gera, Germany, 1885.
From wheat to flour
After numerous checks and, in the specific case of our mill, three cleaning phases, the grain is finally ready to be ground. Remember that flour, whether it be type “00”, type “0”, type “1”, type “2” or “wholemeal”, is obtained by the grinding and subsequent sieving of soft wheat (you can learn more about sieving technologies in our dedicated article). Similarly, semolina is produced by the grinding and subsequent sieving of durum wheat.
Both soft wheat and durum wheat can be ground in cylinders or stone ground. Since the kernels of soft wheat are very different from those of durum wheat, specific milling systems must be used to obtain the best from each grain. For this reason, soft wheat mills and durum wheat mills, although conceptually similar, exploit different milling diagrams, i.e. they subject their products to different processes. Mulino Padano grinds only soft wheat and produces a wide range of flours (to find out how flours can be classified, you can read our article on choice of flours).
And now, to fully understand where flour comes from, we need to analyze the structure of the wheat grain.
The structure of soft wheat grain, its components and nutritional properties
The caryopsis (or grain) of soft wheat has several overlapping layers, each of which has a different composition. We can easily make out four layers that go from the outside to the centre of the grain (Figure 2):
- bran
- aleuronic layer
- amiliferous endosperm
- germ
Figure 2. Structure of a grain of wheat. Source: Wheat Flour Institute Chicago: “Classification of Triticum species and of wheat varieties grown in the United States”, Dept. of Agriculture, 1963.
Soft wheat bran
Bran constitutes about 14.5% of a grain of wheat and is in turn made up of 7 superimposed layers, it is very rich in fibre, especially insoluble fibre (cellulose and lignin). The mineral salt content is also higher in the bran than in the other parts of the grain, and is mainly made up of phosphorus, potassium and magnesium. Furthermore, most of the antioxidants (such as phenolic acids and anthocyanins) are contained within the bran.
The aleuronic layer and its composition
The aleuronic layer is genetically part of the endosperm but, since it is often separated from this during milling, it is considered to be part of the bran. We can imagine this layer as a small film that surrounds and protects the endosperm and the germ representing about 7-8% of the total weight of the grain. It is very rich in:
- Vitamin B3, also known as niacin, of which 80% of the total contained within the grain is to be found in the aleuronic layer;
- Lysine, an essential amino acid, of which 30% of the total contained within the grain is to be found in the aleuronic layer;
- β-glucans and arabinoxylans, 29% and 65% of the total content of the kernel respectively, make up part of the soluble fibre and help the proliferation of a protective intestinal bacterial flora and also have a hypocholesterolemic and hypoglycaemic benefits (especially β-glucans). Since arabinoxylans tend to soak up a lot of water, their high content in flour can cause problems in the formulation of doughs and products intended to keep over time, such as: crackers, pre-cooked and frozen products;
- Fatty acids. The aleuronic layer contains 20% of the fatty acids contained within the grain, which are mostly saturated;
- Mineral salts. The aleuronic layer contains 40-50% of the mineral salts contained within the grain, they are not only found in free form but also bound to phytic acid. The main ones are phosphorus, magnesium, manganese and iron;
- Phytic acid: binds and inhibits the absorption of mineral salts by the intestine.
The endosperm: its composition and nutritional characteristics
The endosperm represents the largest fraction of the grain of wheat, making up about 83% of its weight. Its primary components are proteins (most of which are gliadins and glutenins, which form gluten during kneading) and starch, which in turn consists of chains of amylose and amylopectin.
The percentage of amylose and amylopectin in wheat grains can vary significantly; kernels rich in amylose lead to more easily digestible flours, and softer and more stretchable dough.
The food value of wheat and the flour obtained from it derives from its high starch, low fat content, which makes this cereal an excellent energy food.
The endosperm contains 1-1.5% of the total lipid content of the wheat grain. Finally, there are tocopherols (vitamin E) and carotenoids, proven antioxidants, as well as albumins and globulins (proteins present in very small quantities).
Wheat germ: nutritional properties
Finally, the germ (or embryo) represents about 2 – 3% of the weight of the grain. Despite its small size, the germ can be considered a real “mine”, rich in nutrients, offering a significant dose of essential unsaturated fatty acids, vitamins, minerals and proteins. Among the substances that make up its composition are:
- Vitamin E, also known as tocopherol, a molecule with strong antioxidant activity. Antioxidants help protect the body from free radicals;
- Folic acid, a vitamin that helps cell regeneration;
- Thiamine, also known as vitamin B1, helps cells convert glucose into energy;
- Magnesium, as a cofactor of various enzymes, helps the functioning of the metabolism;
- Phosphorus that, together with calcium, forms bones and teeth. This mineral is also necessary for the growth, maintenance and repair of body tissue;
- Other mineral salts include potassium, iron, calcium, zinc and selenium.
Wheat germ is also an excellent source of fibre and protein which have a high biological value, as well as unsaturated and polyunsaturated fats (omega 3 and omega 6) which have effective beneficial actions on our bodies.
Soft wheat explained in brief:
let’s recap
- Soft wheat is the variety of wheat used for the production of flour;
- The high starch content and low fat content makes flour an excellent energy food;
- A grain of wheat consists of 4 superimposed layers, each of which contains specific nutrients and has specific characteristics. These, from the outside of the grain inwards, are: bran, aleuronic layer, endosperm and germ.
- Bran, the outermost layer, is very rich in fibre (especially insoluble fibre) and mineral salts.
- Aleuronic layer, a thin layer interposed between the endosperm and the bran, has a very complex composition.
- Endosperm, the predominant part of the grain of wheat, is mainly made up of proteins and starch.
- Germ, present in small quantities, is very rich in nutrients.
The mill is the “tool” that is used to select, through mechanical processes, each of the components of the grain listed above and produce flour.
Anna Leone
Doctor of Nutritional Science – Mulino Padano analysis laboratory
