Flour is the most important product of grain processing. Crushing and grinding of grain is characterized by a dispersion process. The product of grain grinding - flour belongs to coarse dispersed systems.
In practice, grain grinding consists of two stages: preparing the grain for grinding and the actual grinding of the grain. Preparation of grain for grinding consists in making up grinding mixtures, cleaning it from impurities, removing shells, germ and conditioning. Grain is supplied to flour mills with different quality indicators.
Grinding batches of grain are made up in order to improve the quality of the processed batch of grain by mixing it with grain that differs in properties from the main batch.
You can mix high-grade grain in terms of grain quality: ash content, glassiness, nature, and other indicators. You can mix whole grain and damaged grain. The latter includes sprouted, frosty grain, damaged by a bug-turtle.
Grain cleaning from impurities differing in size and aerodynamic properties is carried out on separators; from impurities not similar to grain in shape (cockle seeds, wild oats, etc.) - on triers, the working bodies are rotating drums or discs with cells on the surface.
Cleaning of grain from metal impurities is carried out in scouring and brushing machines, which polish the surface of the grain, remove dust, particles of shells and embryos.
Grain conditioning is a hydrothermal treatment, which includes two stages: moistening and warming up the grain. It is carried out for varietal grinding of wheat in order to increase the elasticity of the shells of the grain and facilitate their separation from the endosperm and subsequent separation during sieving. Conditioning can be carried out in two ways: cold and hot.
Cold conditioning is carried out when the grain is moistened with water at a temperature of 18-20 ° C and heated to 35 ° C, then the grain is left to warm up for 12-14 hours. This method is used to treat grain with low elongation gluten.
Hot conditioning is carried out at a temperature of 55-60 ° C, followed by cooling and heating, the duration of which is shorter,
compared to the cold process. Hot conditioning is used to treat grain containing weak gluten.
Grain grinding consists of two stages: the actual grinding of the grain and the sifting of the grinding products. By the number of technological operations
grindings are divided into one-time and repetitive (Fig. 1).
SINGLE REPEATED
 |
SIMPLE COMPLEX
 |
WITHOUT ENRICHMENT WITH ENRICHMENT
KRUPOK KRUPOK
 |
WITH A REDUCED PROCESS WITH A DEVELOPED PROCESS
ENRICHMENT ENRICHMENT
Fig. 1 Classification of grain grinding
Single grinding carried out in one go. The flour is obtained together with the shells, then the flour is sieved and the bran - large particles of the shell - is selected. Grinding is carried out on hammer crushers.
Repeated grinds provide for multiple passage of grain through systems, including: grinding (roller machines) and sifting (sifting).
Systems can be torn, which serve to crush grain into grains and dunst, and milling, which turns grains and dunst into flour.
After torn systems during sieving, two grinding fractions are obtained: sieve exit and sieve passage.
The outlet consists of particles that have not passed through the sieve openings, the passage consists of particles that have passed the sieve openings.
The waste contains coarse fractions with a particle size of 1.0 - 1.6 mm, particles with a smaller size of 0.31 - 1.0 mm, called grains, and particles with a smaller particle size of 0.16 - 0.31 mm, called dunst.
Fine fraction - passage from a sieve with a particle size of less than 0.16 mm, forms flour.
Krupki and dunsty are sent to the following systems and this operation is continued until flour is obtained from them.
Repeated grinding is considered simple if you get wallpaper or peeled flour, and complex if you produce varietal flour.
With a simple repeated wallpaper grinding, the yield of rye flour is 95%, the amount of bran is -2%; wheat yield - 96%, the amount of bran -1%.
With complex repeated grinding, single-grade grinding is carried out with a peeled flour yield of 87% and sown flour with a yield of 63%, as well as two-grade flour with a total flour yield of 80%, at which 50-65% peeled flour and 30-15% sown flour are obtained.
Flour classification
Flour is obtained by grinding grain and classified by type, type and grade.
The type of flour is determined by the culture from which it is made. Distinguish between wheat, rye, barley, oatmeal, rice, pea, buckwheat, soy flour. Flour is also obtained from a mixture of wheat and rye.
The type of flour is determined by its intended use. Wheat flour is produced by bakery and pasta, rye flour - only by bakery.
The type of flour is associated with its yield. That is, the amount of flour obtained from one hundred kg of grain. The flour yield is expressed as a percentage, the higher the flour yield, the lower its grade.
They mainly use wheat and rye flour. Wheat is produced in five grades: gritty, premium, first, second grades and wallpaper (GOST 26574); produce wheat flour of four grades: the highest, first, second grades and wallpaper (TU 8 RF 11 - 95 - 91); Podolsk wheat flour (TU 8 RSFSR 11-42-88); baking wheat flour "Osobaya" of the highest and first grades (TU-9293-003-00932169-96).
Grain grinding consists of two operations: the actual grain grinding and sifting the grinding products.
Grinding can be one-time and repetitive.
One-time grinding is carried out in one go. In this case, the grain is crushed into flour completely together with the shells. This flour is of low quality, has a dark color and is not uniform in particle size. To improve the quality of one-time grinding flour, a certain amount of large shells (bran) is selected from it by sieving. One-time grinds are rarely used. They are carried out on hammer crushers.
Repeated grinds are more perfect. Grain is ground into flour by repeatedly passing through grinding machines called roller mills. After each grinding, the resulting products are sorted by size in sieving machines called sieves.
The main working bodies of the roller machines are two cylindrical cast-iron rollers of the same diameter, located at angles and rotating towards each other at different speeds. The surface of the rollers is corrugated. The size of the gap between the rollers is set depending on the intended grinding coarseness. After each roller mill for sorting products by particle size, a sieve is installed with a set of sieves of different numbers located one below the other. When sifting, two fractions of the milling products are obtained: an exit consisting of particles that have not passed through the sieve openings, and a passage consisting of particles that have passed through the sieve openings. The exit from the top sieve is the largest fraction with a particle size of 1.0-1.6 mm, the next largest fractions are called crumbs with a particle size of 0.31-1.0 mm and dunst with a particle size of 0.16-0.31 mm. The finest fraction passing through the passage forms flour with a particle size of less than 0.16 mm. The roller mill and sieving machine is a system. Systems can be torn, which serve to crush grain into grains and dunst, and milling, which turns grains and dunst into flour.
Repeated milling can be simple if you get wallpaper or peeled flour, and complex if you get varietal flour.
Simple re-grinding involves one torn process or a torn and abbreviated grinding process. It is carried out as follows: the grain is successively ground on several (3-4) roller mills. After each machine, the mixture is sieved and the flour is taken as a pass from the bottom sieve. Larger sieves are directed to the next pair of rollers. This operation is carried out until all the particles turn into flour. Flour from all sieves is combined, control sifting is carried out and flour of the same grade is obtained. With wallpaper milling, the yield of rye flour is 95%, the amount of selected bran is 2%, and the yield of wheat flour is 96%, while the bran yield is 1%.
Complex repeated grinding can be without the enrichment of the crumbs and with the enrichment of the crumbs. The first ones are intended for obtaining rye peeled and seeded flour, as well as for grinding triticale grains into peeled flour. In these cases, a single-grade grinding is carried out with a peeled flour yield of 87% and sown flour with a 63% yield, as well as two-grade milling with a total flour yield of 80%, at which 50-65% peeled flour and 30-15% sown flour are obtained. With single-grade grinding, five torn and two grinding systems operate simultaneously. The latter can be with a reduced and developed enrichment process.
The enrichment of crumbs is carried out in terms of size and quality (ash content) on sieve machines, the main working body of which is a sorting sieve, divided into sections. Each section has a sieve with specific mesh sizes. Air is fed from the bottom to the top through the sieve. The finest crumbs, rich in endosperm, pass through the first smallest sieves, which are fed to the first grinding systems to obtain flour of the highest grades. Crumbs containing more shells, as lighter ones, are separated on subsequent sieves. Then they are subjected to repeated crushing, sieving and processing on sieve machines to separate the remnants of the shells and the embryo. After such processing, they are sent to grinding systems to form flour of lower grades.
Complex repetitive mills with a reduced process for the enrichment of grains are used in small-capacity flour mills. They are designed to produce wheat flour of the second grade with a yield of 85% with one-grade grinding. With two-grade grinding, 55-60% of the first grade flour and 23-18% of the second grade flour are obtained.
Complex repeated mills with a developed process for the enrichment of grains are most widely used in the flour-grinding industry. They allow one-grade, two- and three-grade grinding. These types of grinding provide for the simultaneous operation of 4-5 torn and 10-11 grinding systems.
The complex grain structure requires consistent and selective grinding. For example, the shell of a grain is ten times stronger than the endosperm, therefore, before obtaining flour of the required size, it is necessary to carry out grinding in several stages. The whole process of grain grinding is based on these differences, in which flour is divided into grades.
The flour grinding is divided into two groups - single grinding and repeated grinding. Single grinding is used only for agricultural purposes, for example, for feeding animals. Repetitive grinding is carried out using reusable and gradual grinding of grain on roller machines, followed by sieving. Repetitive grinds are also classified into two types - simple flour grind and complex grind. With the help of simple grinding, wallpaper flours are obtained, grinding is carried out in one stage. All the grain is ground into flour, and the rest goes to further operations.
Complex flour is used to obtain the main varieties. Mainly the endosperm is ground, and the shell, the aleurone layer, and the germ of the grain are separated from the bulk of the flour during this grinding. Complex grinding is carried out in two stages - first, the grain is ground into grains on special torn systems. As a result, crumbs are obtained from pure endosperm, variegated crumbs, which were formed from pieces of endosperm and shell, as well as dunsta. Dunst are particles that are finer than grains, but larger than flour particles.
This is followed by the second grinding stage, in which the grinding is divided into three types - three-grade flour grinding, two-grade grinding and single-grade grinding. After three-grade grinding, flour of the first, second and highest grades is obtained. After two-grade grinding, first grade and second grade flour are obtained. With single-grade grinding, you can get the first grade.
Grain grinding is carried out at flour-grinding enterprises with different productivity: at factories - up to 500 tons per day, at mini-mills - up to 1 tons per hour. At flour mills, detailed schemes of varietal grinding with a developed sieve process are used, and at rural mills, most often abbreviated schemes are used.
^ 1.3.1. Preparing grain for grinding.
To obtain a normalized yield of standard quality flour, the grain is subjected to cleaning and conditioning.
The preparatory (grain-cleaning) department of modern enterprises occupies about 1/3 of the entire production area. Grain is cleaned from foreign matter in separators, triers, aspirators, the extraction of mineral impurities (stones, pebbles, etc.) is carried out in stone-separating cars. The residual content of trash should not exceed 0.4%, and grain - 3%.
To separate the embryo, beard, top layer of fruit shells, remove dust, reduce ash content and contamination with microorganisms, carry out dry grain surface treatment. To do this, it is passed through upholstery (hard and soft) and brush cars . Also for these purposes can be carried out wet processing grain by washing it in washing cars.
It is obligatory at the mills to carry out TRP complex(hydrothermal treatment), or conditioning grains. For wheat grain with high glassiness and elastic gluten, it is technologically and cost-effective cold air conditioning, that is humidification cold water (18-20 о С) in the augers of intensive moistening. Grains with weak gluten can be subjected to hot or high-speed conditioning by moistening it with hot water or steam and heating it to 60 ° C, then cooling it. seduction(maturation) of grain in special silos for 8-24 hours, depending on the initial moisture content and glassiness. These techniques can be repeated.
As a result of conditioning (moistening and heating), the moisture content of the grain increases to 15.5-16%, its structural, mechanical, physical and biochemical properties improve, the endosperm becomes more fragile, and the shells become elastic and durable. In this regard, the grain is better crushed during grinding, the shells are easily separated from the endosperm, forming large bran, the power consumption and wear of the mill equipment are reduced by 20-30%, the flour yield increases by 1.5-2%, especially of high grades. Thus, the economic and technological efficiency of grain conditioning is high.
Immediately before grinding can be carried out formation of grinding mixtures, mixing wheat grain of different quality. This allows you to stabilize the quality of the grain (total vitreousness 50-60%, gluten content 23%) for the correct maintenance of the modes and patterns of grinding.
^ 1.3.2. Grinding technology.
Grinding starts with tattered
the process by which the grain is gradually crushed into intermediate products - grains and dunsty... The process is carried out on roller mills
, the working bodies of which are a pair rollers rotating at different speeds. As a result of different speeds of rotation and the grooved surface of the rollers, the grain and its grinding products passing between them are split and crushed.
Several roller systems are involved in the chipping process.
For separation by size (sorting by size), grains and duns are sent to screening machines - sieves ... Each sieve is a cabinet, divided into several sections, consisting of a set of sieve frames with different sizes of holes and collecting bottoms, and equipped with channels for the release of products. After each torn system, its own sifter is installed. The upper sieve outlet, not sifted through the largest sieves, is sent to the next torn systems for further crushing. The passage through the finer sieves is sorted in the form of flour, fine, medium and coarse grains, soft and hard dunst. Each product, after sorting by size, is processed according to different schemes.
After screening, the grains with developed grinding schemes are fed to sieve machines , sorting them by quality (quality factor) and size. This process is called enrichment grains, it allows you to increase the output of premium flour with high-quality milling. Sieve shaker machines sort products using reciprocating sieve frames installed in 2-3 tiers and an air stream passing through the sieves. Created fluidized a layer of suspended grains. The most solid small crumbs with low ash content (group 1), containing mainly endosperm, have a high density and low windage. They overcome the resistance of the air flow, quickly sift through sieves and go to the roller mills, where they are ground into flour. Crumbs with shell particles ( concretions) have increased windage. They usually come off the sieves and are sent to torn shredding systems or to roller grinding machines equipped with non-grooved rollers. In them, the process of processing crumbs with shells takes place, which is called grinding . After that, the ash content of the crumbs is significantly reduced, which are again sorted before grinding.
After sieve machines, small-sized solid crumbs (2-3%) are not ground into flour, but sent to the finished product warehouse and are called manna cereals.
Sorted grains and duns are ground into flour (with sifting it out on sieves) on roller mills with finely grooved or micro-rough rollers. This process is called grinding ... For varietal grindings, several grinding systems are in operation (from 3 to 12). All received flour passes through control sieves and enters pothole mill department. The bran is separated from the top of the sieves of the last torn and grinding systems or on scouring machines for grinding casings.
^ 1.4. Storing flour
Flour is less stable during storage than grain. Positive processes occurring during storage include maturation flour - improving its baking properties (improving the colloidal properties of gluten, whitening flour). Ripening occurs intensively at a temperature of 20-30 o C and hardly manifests itself at a temperature close to 0 o C. However, long-term storage at a high temperature contributes to the overripening of flour and the activation of various negative processes in it. Among them, oxidation and decomposition of fat is observed - rancidity flour. The activity of various groups of microorganisms causes sourness, mold and even self-heating of flour. It becomes unusable for baking and consumption. No less dangerous is the infection of flour with pests of grain stocks.
To preserve flour for several months, a dry, well-disinfected warehouse, without any odors, is needed. Dry flour is placed on wooden pots in stacks up to 6-8 bags high, leaving indents from the walls and control passages. Bulk storage of flour in silos is also used. To prevent tracking flour, at least once a month, it is necessary to change the lower and upper bags in the stack with the help of metas and transfer the flour from one silo to another.
The lower the temperature in the warehouse, the longer the flour retains its quality. Therefore, the recommended temperature for storing flour should not exceed 8-10 o C. Very low temperatures (about 0 o C) are less acceptable, as this creates the preconditions for moisture condensation. The relative humidity of the air in the storage should not exceed 70% in order to avoid humidifying it with water vapor.
Bakery
Bread is a food product baked according to an appropriate recipe from dough made from flour with the addition of water, yeast, salt and other ingredients. Bread is a high-calorie food product that provides a person with a large amount of energy (at least 30% of what is needed). The energy value of white wheat bread made from first grade flour is 950 kJ, or 225 kcal per 100 g. There is no inedible part in the bread. Due to the consumption of the daily norm (400 g) of bread, a person satisfies half of his need for carbohydrates, and one third for proteins. The fine-pored, thin-walled structure of the crumb of bread determines the large area of its contact in the digestive tract with gastric juice, which ensures good digestibility – 92-95 %.
The assortment of bakery products is several hundred varieties of different appearance, taste and nutritional value. ^ Bread called a product weighing more than 500 g; bakeries products - weighing 500 g or less, baked from wheat flour; small-piece bakery products - weighing 200 g or less. Butter bakery products- these are products with a sugar and fat content in the formulation in the amount of 14% or more.
Bread products can be produced mold and hearth... Shaped products are rectangular, square, round. The hearth products can have a round or oval shape, they can be produced in the form of flat cakes, loaves, braids, whitewash, hal, etc. Shaped bread is called
loaf, and the bottom - roll.
Bread products can be intended both for the general population, and for the prevention and treatment of various diseases, can be produced as unpackaged and in packaging... Bread products may vary storage duration... All types of bread, bakery products, baked goods produced unpackaged have a shelf life of 16 to 36 hours. Packaged bakery products have a shelf life of 2 to 7 days. Bread products of low humidity (drying, bagels, crackers, crispbread, straws, bread sticks) have a shelf life calculated in months.
Flour of various yields and varieties is necessary both due to its different nutritional value and digestibility, and for reasons of aesthetic and taste. Flour of the highest and first grade contains less protein than wallpaper and second grade. However, its digestibility is much higher. But wallpaper flour and second grade, along with a high protein content and a decrease in carbohydrates, contains more B vitamins, minerals and provitamin A - carotene. An idea of the digestibility of wheat flour, depending on its yield, is given by V.L.Kretovich's graph.
According to the recommendations of the Institute of Nutrition of the Academy of Medical Sciences, the human diet should include both black and white bread made from wheat and rye flour in the following approximate proportions: rye - 14-16% and wheat 84-86%. The total amount of dark bread should be at least 30% of the daily diet.
To obtain flour that meets the requirements of state rationing, and in quantities corresponding to the outputs, various types of grinding are used using a variety of machines of various capacities, consistently connected to each other. Therefore, grinding is a set of processes and operations carried out with grain and intermediate products formed during grinding. Grinding schemes that characterize the relationship between machines and the movement of products are usually depicted graphically. The degree of complexity of the schemes depends on the type of grinding and the performance of the mill. The simpler is the grinding of grain, the simpler is the grinding scheme.
Classification of grindings used in mills
All grinds are subdivided into one-time and repetitive (see diagram). The former are named so because the transformation of grain into flour occurs after it has been passed once through a grinding mechanism or machine. This type of machine includes burrs and crushers (eg hammer crushers). In this case, the grinding organs (for example, millstones) should be placed one from another at such a close distance that the grain during its passage from the center of the millstones to their circumference was completely ground to the state of flour. This is facilitated by grooves with a depth of 7-12 mm notched on the working part of the millstones according to certain rules. One of the millstones, made of natural or artificial stone, is fixed motionlessly (bed), and the second (slider) rotates at a peripheral speed of 10-12 m / s. The grain is poured into the throat (Fig. 1) and when the slider rotates, it is pulled into the space between the millstones.
After passing through the grinding belt, the product turns into flour, consisting of particles of different sizes. The distance between the millstones is adjustable. They can be installed horizontally (which is more common) or vertically. The productivity of the millstones is 100-125 kg of grain per 1 cm of the diameter of the millstones per day. Millstones are made with a diameter of 55, 76, 100 and 120 cm.Consequently, with a diameter of 1 m, the output reaches about 10-12 tons of flour per day.
Single grindings are carried out with control sifting of products, grinding or without it. Sifting on burata or centrifugals (prismatic or cylindrical frames covered with silk or metal-woven sieves with certain mesh sizes) excludes large unmilled particles from entering the dough and baked bread, which, when sowing, are sent back to the burr for grinding.
On hammer mills, grinding is more intensive. The grinding of grain particles occurs in the crusher without their repeated return.
With one-time milling with preliminary cleaning of grain, wallpaper flour is obtained from established outputs. Lighter flour (gray "seeded") can be obtained by sifting on thick (frequent) sieves.
Repeated grinding, as the name itself indicates, consists in the fact that the entire mass of flour is obtained in more than one pass through the grinding machine. With successive mechanical actions on the grain, its gradual grinding is achieved, in which the endosperm, which is more fragile than the shell, rather turns into flour.
The grain is grinded on special machines - roller mills. Their working part is a pair of cast-iron rolls 1 m long, rotating towards each other at different speeds, the ratio of which is 1: 1.5; 1: 2, 1: 2.5, etc. The distance between these rolls is different at different stages of the grinding circuit. The largest distance between them (grinding gap) is on the first system, which receives the whole grain.
On the first systems, the surface of the rolls (along their length and at an angle) is corrugated, and at the beginning of the scheme the riffles are the largest. The grain enters the grinding rolls through the feeding mechanism (roller), is distributed along the entire length of the rolls, is captured by them and very quickly passes through the grinding slot. Due to the fact that the rolls rotate at different speeds, the grain between the rolls is not flattened, but chipped and turned around. In this case, immediately a small part of the endosperm is crushed to the state of flour.
After passing through a roller machine, the product enters a sieving machine - a sieving machine, which has a set of different sieves, on which the product is sorted by coarseness into several fractions.
The largest fraction consists of membranes with a significant content of endosperm. Other fractions, depending on the size, are called coarse groats, fine groats, dunst and flour. The resulting flour is sent to form a certain grade, and the rest of the product fractions are sent separately to other machines. So, after sifting, the largest fraction goes back to the roller mills, where further endosperm spalling takes place. Following this, the products are sieved again. This technique, repeated 5-7 times, is called a torn process. In the latest torn systems, the product consists mainly of grain shells and a small amount of endosperm attached to them. The resulting flour and cereals also contain a large amount of small shell particles.
Large and small, cereals in most cases consist mainly of endosperm particles with one or another number of membranes. To separate their groats, they are sent to other roller machines, on which the appropriate parameters and grinding modes are set. The amount of flour formed during this is 5-10% of the weight of the product entering the roller mill. This process of processing an intermediate product is called grinding.
After sorting in sieves the products that have passed grinding systems, the number of which reaches 3-5, several fractions of products are obtained, some of which (cereals and dunsty) are sent to sieve machines.
This process is highly branched in complex two- and three-grade and especially in pasta mills, where you need to get as much granular flour of the highest and first grades as possible.
On sieve machines, grains and dunst particles are sorted by coarseness and specific gravity. If the particle consists of pure endosperm, it has a higher specific gravity. Another particle of the same size, but containing a certain amount of shells, has a lower specific gravity. The principle of operation of sieve machines is that through an inclined sieve with a rectilinear-return movement, to which the product enters, air is sucked in from below, which prevents the passage of lighter particles with a low specific gravity through the sieves (they are kept in suspension), but does not retain particles consisting of pure endosperm.
One of the fractions of coarse cereals, obtained on sieve machines, is called semolina. When wheat is milled, it turns out 2-3%.
The particles that have passed through the sieves of the sieve shaker, depending on the size and quality, are sent to the roller machines of grinding and grinding systems for subsequent grinding. At the same time, small cereals and blows are intensively crushed to the size of flour. This stage of grinding intermediate products is called grinding. However, all the product entering the roller mill cannot be ground to flour in one pass through the grinding slot. Therefore, the grinding process is also carried out on several systems.
On the first grinding systems, where the grain particles with the least number of shells are sent, the flour of the highest grade is obtained. On subsequent systems, which receive particles not ground in the first grinding systems, as well as products containing shells, flour of the first or second grade is obtained. When varietal milling of wheat, 8-12 milling systems are used.
Thus, with branched schemes of repeated grinding at the mill, three types of basic machines are used: roller machines, sieves and sieve shakers. In addition, there are very important technological machines (brush, grinding-whip, which scrub the remnants of the endosperm from the shells, etc.). The number of machines and their dimensions depend on the type of grinding and the capacity of the mill. The smallest number of machines is needed for wallpaper grinding, when grinding is more intensive according to a shortened scheme and no strainers are used at all.
Here are the most basic information, giving only a general idea of grindings, yields and flour varieties. Suffice it to say that some intermediate products during high-grade grinding travel several kilometers in machines and transport mechanisms. The graphically depicted diagrams of these grindings are so complex that they can only be read by a well-trained engineer or technician.
For the production of high quality flour for any type of grinding, the following grain preparation is very important:
selection of grain lots in such a way that they have good flour-grinding and baking qualities;
thorough cleaning of grain from impurities and contamination with some removal of its integumentary tissues; this is achieved by dry and wet cleaning: the grain is passed through separators, triers, aspiration columns, scouring and brushing machines that clean the grain from dust, some integumentary tissues (barbs, shells) and remove the embryo; if mills have washing facilities, the grain is washed with water, removing dirt and microorganisms from its surface;
improving the physical and biochemical properties of grain before grinding. This is achieved by moistening the grain, followed by aging at a certain temperature (cold or hot conditioning). The grain prepared in this way is easier to grind, the shells are better separated from the endosperm, and sometimes the baking qualities are improved as a result of the activity of enzyme systems.
The preparation of grain for grinding in large commercial mills is so versatile that a third of the mill body is occupied by equipment designed for this purpose. Two thirds of the room is occupied by the grinding department.
In agricultural mills, mainly the first two types of preparation for grinding are used. Mills without a grain cleaning department or with a far from complete set of machines have also survived. Sending grain for grinding to such mills requires special attention. Cleaning of a batch of grain and its preparation for grinding should be carried out on the farm.
Operations associated with moving, cleaning and grinding grain are accompanied by the release of dust. To catch it directly in the machines, a ventilation system (aspiration) is used.
