After harvesting, the grains are transported to storage where the moist grain is dried, in preparation for grinding, or longer storage periods.
The process of reducing the moisture content of the grain using various methods: hot-air drying, ventilation and other means of moisture removal. Grain is safe to store only when the moisture content is 14% or less, although the moisture of grain harvested in Latvia is 18-20%, therefore drying and cleaning must be done as fast as possible. Self-heating starts fast if moist or unclean grains are stored, also the seed and nutritional value diminishes and the activity of microscopic fungi increases .
Firstly all remaining impurities are removed from the grain in the mill. Cleaning is performed using various types equipment: an air-sieve separator removes all large, small and light impurities with the sieves- per geometric properties and in the pneumatic separation channel- per aerodynamic properties. Mineral impurities (sand and dirt particles, rocks) are separated from the grain in rock separators. Any remaining impurities can reduce the quality of the flour; therefore, this stage of flour production is very important- the safety, purity and quality of the final products depend on it. After removing all the impurities from the grain, surface cleaning and processing begins. This process is performed in the sanders, polishing and brushing (peeling) machines. After surface cleaning the grain goes into an aspirator, which removes the resulting pealed-off products and dust.
Then hydrothermal processing of the grains is performed- the grains are moistened with water and are left to settle. During settling the grain acquires the properties required for grinding and the coat separates from the endosperm.
This is one of the final operations of preparing grain for the grinding. In addition, to impurities the grain may contain live insects or microorganisms. Some on these spend all their lives inside the grain. Such grains are not different from normal grain on the outside, but they become less resistant to mechanical effects. This is a secret contamination of the grain, which is eliminated by the grain going through an impact machine- the entoleter. Eaten out, hollow grains are crushed, and the resulting small and light parts are removed with air in the pneumatic channel.
Before grinding the grains undergo hydrothermal processing once again, then they’re weighed and after magnetic control they travel to the grinding section. A single grain can be crushed to an astonishing 20,000 flour particles.
Grinding is classified into simple and complex grinding, but the nature is the same. First, the grains enter a roller machine, where they’re crushed between two corrugated rolls rotating in opposite directions. After that, the sorting of intermediate products (flat sieves), enrichment in sieve fans (sifting in a rising air stream), sanding, grinding and flour control are performed. Crushing in the roller machine and sifting are performed several times, until the desired products is achieved. The grinding plan can be adjusted depending on the properties of the raw grain material and the desired final product. E.g.: while grinding rye some operations are skipped and different grinding parameters are applied than those used for wheat. Specific parameters are also used in the production of pasta flour.
Did you know that baking with freshly ground flour is not recommended? It must be stored for a certain period for the flour to masture. It appears that significant changes take place in the flour while maturing, which may add further properties to the flour. These changes take place on molecular level, when the thiol group undergoes oxidation due to contact with oxygen and diulphide bonds, determining the strength of the gluten. What impact does it have on the baking properties of flour? A very large one, as the volume of baked goods from un-aged flour is lower and the structure is weak. Bread from un-aged flour has poor elasticity, rises poorly and looks soggy, the inside is very crumbly and the crust is rough and hard. Usually flour matures in 304 weeks after grinding. It is very important that it is stored in air-permeable containers (e.g.: fabric sacks or paper packages). This is why flour is packed in air-permeable paper packages and is able to mature and acquire the best baking properties until it reaches our homes.
Gluten content is represented byletters (B,C,D,E,F). Scalded and yeast dough needs as high a gluten content as possible- then it rises better. In such case flour marked with letter closer to the beginning of the alphabet should be chosed- C or D. Flour with a lower gluten content- marked D or F is more suitable for crumbly or sponge dough. Flour marked with E can be used for waffles.
The number (405, 550, 812, 1050, 1600, 1700) indicates the ash content (ash has minerals) and the color of the flour. The lower the figure the whiter the flour. Coarse wheat flour is produced by coarsely grinding soft and dwarf wheat and partially removing the bran and germs.
Rye flour is classified into fine (finely ground, without bran) and sifted (finely ground, by removing dome of the bran). According to ash content fine rye flour is marked with the number 600, and sifted rye flour- with the numbers 700 or 815.
Coarse rye flour flour is produced by coarsely rye grains and removing a part of the bran, or not removing it at all. This flour is classified into partially sifted (average coarsely ground, by removing some of the bran) and not sifted 9coarsely ground, by removing part of the bran or none at all). According to ash content it is marked: partially sifted- 997, 1150, 1370, 1740 and not sifted- 1800.
Baked goods from rye flour remain fresh for longer. Bread baked from rye has a thick crust- it’s distinctive feature. But don’t forget, dough with rye flour needs more water than wheat flour.