Introduction

Wheat flour - perhaps the most popular flour for baking in the world. It comes in several types. High-grade flour (some packages say the word “extra”) has quite a bit of gluten, and it looks completely white. Such flour is ideal for pastries, it is often used as a thickener in sauces. Flour of the first grade is good for lean pastries, and its products become stale much more slowly. In France, it is customary to bake bread from wheat flour of the first grade. As for second grade flour, it contains up to 8% bran, so it is much darker than first grade. It is used in our country - it is from it that lean products and ordinary white bread are made, and mixed with rye flour - black.

Rye- one of the most important cereal crops. The consumption rate of rye flour (as a percentage of all cereals) is about 30. Rye flour has numerous useful properties. It contains the amino acid necessary for our body - lysine, fiber, manganese, zinc. Rye flour contains 30% more iron than wheat flour, as well as 1.5-2 times more magnesium and potassium. Rye bread is baked without yeast and on thick sourdough. Therefore, the use of rye bread helps to reduce cholesterol in the blood, improves metabolism, heart function, removes toxins, helps prevent dozens of diseases, including cancer. Due to the high acidity (7-12 degrees), which protects against the occurrence of mold and destructive processes, rye bread is not recommended for people with high acidity of the intestines, suffering from peptic ulcers. The 100% rye bread is really too heavy for daily consumption. The best option: rye 80-85% and wheat 15-25%. Varieties of rye bread: from white flour, from peeled flour, rich, simple, custard, Moscow, etc.

Chemical composition and the nutritional value flour

Flour is made from grains ground to a powder. The basic structure of baked bread depends on flour. The most common flour is rye, barley, corn and others, but wheat flour is most often used for making bread, ground to special technology. On average, grain in the process of turning into flour travels a distance of 5 km through various floors of a modern mill. In the composition of flour, starch and proteins enter the bread.

In addition to starch, wheat flour contains substances from three water-soluble protein groups: albumin, globulin, proteose, and two water-insoluble protein groups: glutenin and gliadin. When mixed with water, soluble proteins dissolve, and the remaining glutenin and gliadin form the structure of the dough. When kneading dough, glutenin folds into chains of long thin molecules, and the shorter gliadin forms bridges between glutenin chains. The resulting network of these two proteins is called gluten.

		Carbohydrates %	Cellulose %	Ash content %		Energy value, kJ
Wheat (high grade)
Wheat (I grade)
Wheat (II grade)
Wheat (seeded)

The chemical composition of flour depends on the grain from which it is obtained. Since the chemical composition of grain varies depending on the soil, fertilizer, climatic conditions, the chemical composition of flour is not constant. In addition, flour of different varieties obtained from the same grain has a different composition. This is due to the fact that when grinding grain, different types of flour get an unequal amount of endosperm, aleurone layer, shells and germ. Since the chemical composition of these parts of the grain is not the same, different types of flour have a different chemical composition. The composition of flour includes the same substances as the composition of the grain: carbohydrates, proteins, fats, etc.

The nitrogenous substances of flour are mainly composed of proteins. Non-protein nitrogenous substances (amino acids, amides, etc.) are contained in a small amount (2--3% of the total mass of nitrogenous compounds). The higher the yield of flour, the more nitrogenous substances and non-protein nitrogen are contained in it.

Wheat flour proteins. Flour is dominated by simple proteins - proteins. Flour proteins have the following fractional composition (in%): prolamins 35.6; glutelins 28.2; globulins 12.6; albumins 5.2. The average content of proteins in wheat flour is 13-16%, insoluble protein is 8.7%.

Prolamins and glutelins of various cereals have their own characteristics in amino acid composition, different physicochemical properties and different names. Wheat and rye prolamins are called gliadins, barley prolamin is called hordein, maize prolamin is called zein, and wheat glutelin is called glutenin.

It should be borne in mind that albumins, globulins, prolamins and glutelins are not individual proteins, but only protein fractions isolated by various solvents.

The technological role of flour proteins in the preparation of bread products is very high. The structure of protein molecules and the physicochemical properties of proteins determine the rheological properties of the dough, affect the shape and quality of products. The nature of the secondary and tertiary structure of the protein molecule, as well as the technological properties of flour proteins, especially wheat, largely depend on the ratio of disulfide and sulfhydryl groups.

When kneading dough and other semi-finished products, proteins swell, adsorbing most of the moisture. Wheat and rye flour proteins are more hydrophilic, capable of absorbing up to 300% of water from their mass.

Optimum temperature for swelling of gluten proteins 30 °C. Gliadin and glutelin fractions of gluten, isolated separately, differ in structural and mechanical properties. The mass of hydrated glutelin is short extensible, elastic; the mass of gliadin is liquid, viscous, devoid of elasticity. The gluten formed by these proteins includes the structural and mechanical properties of both fractions. When baking bread, protein substances undergo thermal denaturation, forming a strong framework of bread.

The composition of gluten. Raw gluten contains 30-35% solids and 65-70% moisture. Gluten solids are 80-85% composed of proteins and various flour substances (lipids, carbohydrates, etc.), with which gliadin and glutenin react. Gluten proteins bind about half of the total amount of flour lipids. Gluten protein contains 19 amino acids. Glutamic acid predominates (about 39%), proline (14%) and leucine (8%). Gluten of different quality has the same amino acid composition, but different molecular structure. The rheological properties of gluten (elasticity, elasticity, extensibility) largely determine the baking value of wheat flour. There is a widespread theory about the significance of disulfide bonds in a protein molecule: the more disulfide bonds that occur in a protein molecule, the higher the elasticity and the lower the extensibility of gluten. There are fewer disulfide and hydrogen bonds in weak gluten than in strong gluten.

Rye flour proteins. According to the amino acid composition and properties, rye flour proteins differ from wheat flour proteins. Rye flour contains a lot of water-soluble proteins (about 36% of the total mass of protein substances) and salt-soluble (about 20%). The prolamin and glutelin fractions of rye flour are much lower in weight; they do not form gluten under normal conditions. The total protein content in rye flour is somewhat lower than in wheat flour (10--14%). Under special conditions, a protein mass can be isolated from rye flour, resembling gluten in elasticity and extensibility.

The hydrophilic properties of rye proteins are specific. They quickly swell when mixing flour with water, and a significant part of them swells indefinitely (peptizes), turning into a colloidal solution. The nutritional value of rye flour proteins is higher than that of wheat proteins, as they contain more essential amino acids in nutrition, especially lysine.

Carbohydrates. The carbohydrate complex of flour is dominated by higher polysaccharides (starch, fiber, hemicellulose, pentosans). A small amount of flour contains sugar-like polysaccharides (di- and trisaccharides) and simple sugars (glucose, fructose).

Starch. Starch, the most important carbohydrate in flour, is contained in the form of grains ranging in size from 0.002 to 0.15 mm. The size, shape, swellability and gelatinization of starch grains are different for different types of flour. The size and integrity of starch grains affects the consistency of the dough, its moisture capacity and sugar content. Small and damaged grains of starch are saccharified faster in the process of making bread than large and dense grains.

Starch grains, in addition to starch itself, contain a small amount of phosphorus, silicon and fatty acids, as well as other substances.

The structure of starch grains is crystalline, finely porous. Starch is characterized by a significant adsorption capacity, as a result of which it can bind a large amount of water even at a temperature of 30 ° C, i.e. at the dough temperature.

The starch grain is heterogeneous, it consists of two polysaccharides: amylose, which forms the inside of the starch grain, and amylopectin, which makes up its outer part. The quantitative ratios of amylose and amylopectin in the starch of various cereals are 1:3 or 1:3.5.

Amylose differs from amylopectin in its lower molecular weight and simpler molecular structure. The amylose molecule consists of 300-800 glucose residues forming straight chains. Amylopectin molecules have a branched structure and contain up to 6000 glucose residues. When starch is heated with water, amylose passes into a colloidal solution, and amylopectin swells, forming a paste. Full gelatinization of flour starch, in which its grains lose their shape, is carried out at a ratio of starch and water of 1: 10.

Subjected to gelatinization, starch grains increase significantly in volume, become loose and more pliable to the action of enzymes. The temperature at which the viscosity of the starch jelly is the highest is called the starch gelatinization temperature. The gelatinization temperature depends on the nature of the starch and on the series external factors: pH of the medium, the presence of electrolytes in the medium, etc. Gelatinization temperature, viscosity and aging rate of starch paste in different types of starch is not the same. Rye starch gelatinizes at 50-55°C, wheat starch at 62-65°C, corn starch at 69-70°C. Such features of starch have great importance for bread quality.

The presence of sodium chloride significantly increases the gelatinization temperature of starch.

The technological significance of flour starch in the production of bread is very high. The water absorption capacity of the dough, the processes of its fermentation, the structure of the bread crumb, taste, aroma, porosity of bread, and the rate of staleness of products largely depend on the state of starch grains. Starch grains bind a significant amount of moisture during dough kneading. The water absorption capacity of mechanically damaged and small grains of starch is especially high, since they have a large specific surface area. In the process of fermentation and proofing of the dough, part of the starch under the action of 3-amylase is saccharified, turning into maltose. The formation of maltose is necessary for the normal fermentation of the dough and the quality of the bread. When baking bread, starch gelatinizes, binding up to 80% of the moisture in the dough, which ensures the formation of a dry, elastic bread crumb. During the storage of bread, starch paste undergoes aging (syneresis), which is the main reason for the staleness of bread products.

Cellulose. Cellulose (cellulose) is located in the peripheral parts of the grain and therefore is found in large quantities in flour of high yields. Wholemeal flour contains about 2.3% fiber, and wheat flour of the highest grade contains 0.1-0.15%. Fiber is not absorbed by the human body and reduces the nutritional value of flour. In some cases, a high fiber content is useful, as it accelerates the peristalsis of the intestinal tract.

Hemicelluloses. These are polysaccharides belonging to pentosans and hexosans. By physical and chemical properties they occupy an intermediate position between starch and fiber. However, hemicelluloses are not absorbed by the human body. Wheat flour, depending on the variety, has a different content of pentosans - the main component of hemicellulose. Premium flour contains 2.6% of the total amount of grain pentosans, and grade II flour contains 25.5%. Pentosans are divided into soluble and insoluble. Insoluble pentosans swell well in water, absorbing water in an amount exceeding their mass by 10 times. Soluble pentosans or carbohydrate mucus give very viscous solutions, which, under the influence of oxidizing agents, turn into dense gels. Wheat flour contains 1.8-2% mucus, rye flour - almost twice as much.

Lipids. Lipids are called fats and fat-like substances (lipoids). All lipids are insoluble in water and soluble in organic solvents. The total lipid content in whole wheat grain is about 2.7%, and in wheat flour 1.6-2%. In flour, lipids are both in the free state and in the form of complexes with proteins (lipoproteins) and carbohydrates (glycolipids). Recent studies have shown that lipids associated with gluten proteins significantly affect its physical properties.

Fats. Fats are esters of glycerol and high molecular weight fatty acids. Wheat and rye flour of various varieties contains 1-2% fat. The fat found in flour has a liquid consistency. It consists mainly of glycerides of unsaturated fatty acids: oleic, linoleic (mainly) and linolenic. These acids have a high nutritional value, they are credited with vitamin properties. Hydrolysis of fat during storage of flour and further conversion of free fatty acids significantly affect the acidity, taste of flour and the properties of gluten.

Lipoids. Flour lipoids include phosphatides - esters of glycerol and fatty acids containing phosphoric acid combined with some nitrogenous base.

The flour contains 0.4--0.7% of phosphatides belonging to the group of lecithins, in which choline is the nitrogenous base. Lecithins and other phosphatides are characterized by high nutritional value and are of great biological importance. They easily form compounds with proteins (lipo-protein complexes), which play an important role in the life of every cell. Lecithins are hydrophilic colloids that swell well in water. As surfactants, lecithins are also good food emulsifiers and bread improvers.

Pigments. Fat-soluble pigments include carotenoids and chlorophyll. The color of carotenoid pigments in flour is yellow or orange, and chlorophyll is green. Carotenoids have provitamin properties, as they are able to turn into vitamin A in the animal body.

The best known carotenoids are unsaturated hydrocarbons. When oxidized or reduced, carotenoid pigments turn into colorless substances. This property is the basis for the process of bleaching wheat flour, which is used in some foreign countries. In many countries, flour bleaching is prohibited, as it reduces its vitamin value. The fat-soluble vitamin of flour is vitamin E, the other vitamins of this group are practically absent in flour.

Minerals. Flour consists mainly of organic matter and is not a large number mineral (ash). The mineral substances of the grain are concentrated mainly in the aleurone layer, shells and embryo. Especially a lot of minerals in the aleurone layer. The content of minerals in the endosperm is low (0.3--0.5%) and increases from the center to the periphery, so the ash content is an indicator of the flour grade.

Most of the minerals in flour consist of phosphorus compounds (50%), as well as potassium (30%), magnesium and calcium (15%).

In negligible amounts contains various trace elements (copper, manganese, zinc, etc.). The content of iron in the ashes of different types of flour is 0.18--0.26%. A significant proportion of phosphorus (50--70%) is presented in the form of phytin - (Ca - Mg - salt of inositol phosphoric acid). The higher the grade of flour, the less minerals it contains.

Enzymes. Cereal grains contain a variety of enzymes, concentrated mainly in the germ and peripheral parts of the grain. In view of this, high-yield flour contains more enzymes than low-yield flour.

Enzyme activity in different batches of flour of the same variety is different. It depends on the conditions of growth, storage, modes of drying and conditioning of the grain before grinding. Increased activity of enzymes was noted in flour obtained from unripe, sprouted, frost-bitten or bug-damaged grain. Drying grain under a hard regime reduces the activity of enzymes, while storing flour (or grain) it also decreases somewhat.

Enzymes are active only when the humidity of the environment is sufficient, therefore, when storing flour with a moisture content of 14.5% and below, the action of enzymes is very weak. After kneading, enzymatic reactions begin in semi-finished products, in which hydrolytic and redox flour enzymes participate. Hydrolytic enzymes (hydrolases) decompose complex flour substances into simpler water-soluble hydrolysis products.

It is noted that proteolysis in wheat dough is activated by substances containing sulfhydryl groups and other substances with reducing properties (amino acid cysteine, sodium thiosulfate, etc.).

Substances with opposite properties (with the properties of oxidizing agents) significantly inhibit proteolysis, strengthen gluten and the consistency of wheat dough. These include calcium peroxide, potassium bromate and many other oxidizers. The effect of oxidizing and reducing agents on the process of proteolysis is already felt at very low dosages of these substances (hundredths and thousandths of a % of the mass of flour). There is a theory that the effect of oxidizing and reducing agents on proteolysis is explained by the fact that they change the ratio of sulfhydryl groups and disulfide bonds in the protein molecule, and possibly the enzyme itself. Under the action of oxidizing agents, disulfide bonds are formed due to the groups, which strengthen the structure of the protein molecule. Reducing agents break these bonds, which causes the gluten and wheat dough to weaken. The chemistry of the action of oxidizing and reducing agents on proteolysis has not been finally established.

The autolytic activity of wheat and especially rye flour serves the most important indicator its baking dignity. Autolytic processes in semi-finished products during their fermentation, proofing and baking should proceed with a certain intensity. With increased or decreased autolytic activity of flour, the rheological properties of the dough and the nature of the fermentation of semi-finished products change for the worse, and various bread defects occur. In order to regulate autolytic processes, it is necessary to know the properties of the most important flour enzymes. The main hydrolytic flour enzymes are proteolytic and amylolytic enzymes.

Proteolytic Enzymes. They act on proteins and their hydrolysis products. The most important group of proteolytic enzymes is proteinases. Papain-type proteinases are found in grains and flours of various cereals. The optimal indicators for the action of grain proteinases are pH 4--5.5 and temperature 45-- 47 ° C -

During dough fermentation, grain proteinases cause partial proteolysis of proteins. The intensity of proteolysis depends on the activity of proteinases and on the susceptibility of proteins to the action of enzymes.

Proteinases of flour obtained from grain of normal quality are not very active. Increased activity of proteinases is observed in flour made from sprouted grains and especially from grains affected by the tortoise bug. The saliva of this pest contains strong proteolytic enzymes that penetrate the grain when bitten. During fermentation, the initial stage of proteolysis occurs in dough prepared from flour of normal quality without any noticeable accumulation of water-soluble nitrogen. During the preparation of wheat bread, proteolytic processes are regulated by changing the temperature and acidity of semi-finished products and adding oxidizing agents. Proteolysis is somewhat inhibited by table salt.

Amylolytic enzymes. These are p- and a-amylases. p-Amylase was found both in germinated grains of cereals and in grains of normal quality; a-amylase is found only in sprouted grains. However, a noticeable amount of active a-amylase was found in rye grain (flour) of normal quality. a-Amylase refers to metalloproteins; its molecule contains calcium, p- and a-amylases are found in flour mainly in a state associated with protein substances and are split after proteolysis. Both amylases hydrolyze starch and dextrins. The most easily decomposed by amylases are mechanically damaged grains of starch, as well as gluten starch. The works of I. V. Glazunov established that 335 times more maltose is formed during the saccharification of dextrins with p-amylase than during the saccharification of starch. Native starch is hydrolyzed by p-amylase very slowly. p-Amylase, acting on amylose, converts it completely into maltose. When exposed to amylopectin, p-amylase cleaves maltose only from the free ends of the glucoside chains, causing hydrolysis of 50–54% of the amount of amylopectin. The high molecular weight dextrins formed in this process retain the hydrophilic properties of starch. a-amylase cleaves off branches of the glucosidic chains of amylopectin, turning it into low molecular weight dextrins that are not stained with iodine and lack the hydrophilic properties of starch. Therefore, under the action of a-amylase, the substrate is significantly liquefied. Then dextrins are hydrolyzed by a-amylase to maltose. Thermal lability and sensitivity to the pH of the medium are different for both amylases: a-amylase is more thermally stable than (3-amylase), but more sensitive to substrate acidification (lowering pH). ,6 and a temperature of 45--50 ° C. At a temperature of 70 ° C, p-amylase is inactivated. The optimum temperature of a-amylase is 58--60 ° C, pH 5.4--5.8. The effect of temperature on the activity of a -amylase depends on the reaction of the medium.When the pH decreases, both the temperature optimum and the temperature of inactivation of a-amylase decrease.

According to some researchers, flour α-amylase is inactivated during bread baking at a temperature of 80–85 °C, however, some studies show that α-amylase is inactivated in wheat bread only at a temperature of 97–98 °C. The activity of a-amylase is significantly reduced in the presence of 2% sodium chloride or 2% calcium chloride (in an acidic environment). p-Amylase loses its activity when exposed to substances (oxidizing agents) that convert sulfhydryl groups into disulfide ones. Cysteine ​​and other drugs with proteolytic activity activate p-amylase. Weak heating of a water-flour suspension (40-50 ° C) for 30-60 minutes increases the activity of flour p-amylase by 30-40%. Heating to a temperature of 60--70 °C reduces the activity of this enzyme. The technological significance of both amylases is different.

During dough fermentation, p-amylase saccharifies some of the starch (mainly mechanically damaged grains) to form maltose. Maltose is necessary to obtain loose dough and normal quality of products from varietal wheat flour (if sugar is not included in the product recipe).

The saccharifying effect of p-amylase on starch increases significantly during starch gelatinization, as well as in the presence of a-amylase.

Dextrins formed by a-amylase are saccharified by p-amylase much more easily than starch.

Under the action of both amylases, starch can be completely hydrolyzed, while p-amylase alone hydrolyzes it by about 64%.

The optimum temperature for a-amylase is created in the dough when baking bread from it. Increased activity of a-amylase can lead to the formation of a significant amount of dextrins in the bread crumb. Low molecular weight dextrins bind the moisture of the crumb poorly, so it becomes sticky and wrinkled. The activity of a-amylase in wheat and rye flour is usually judged by the autolytic activity of the flour, determining it by the falling number or by the autolytic test. In addition to amylolytic and proteolytic enzymes, other enzymes influence the properties of flour and the quality of bread: lipase, lipoxygenase, polyphenol oxidase.

Lipase. Lipase breaks down flour fats during storage into glycerol and free fatty acids. In wheat grain, lipase activity is low. The greater the yield of flour, the higher the comparative activity of lipase. The optimum action of grain lipase is at pH 8.0. Free fatty acids are the main acid reacting substances in flour. They can undergo further transformations that affect the quality of flour - dough - bread.

Lipoxygenase. Lipoxygenase is one of the redox enzymes in flour. It catalyzes the oxidation of certain unsaturated fatty acids by atmospheric oxygen, converting them into hydroperoxides. The most intensively lipoxygenase oxidizes linoleic, arachidonic and linolenic acids, which are part of the grain fat (flour). In the same way, but more slowly, lipoxygenase in the composition of native fats acts on fatty acids.

The optimal parameters for the action of lipoxygenase are a temperature of 30–40 °C and a pH of 5–5.5.

Hydroperoxides formed from fatty acids under the action of lipoxygenase are themselves strong oxidizing agents and have a corresponding effect on the properties of gluten.

Lipoxygenase is found in many cereals, including rye and wheat grains.

Polyphenol oxidase (tyrosinase) catalyzes the oxidation of the amino acid tyrosine with the formation of dark-colored substances - melanins, which cause darkening of the bread crumb from high-quality flour. Polyphenol oxidase is found mainly in high yield flours. In grade II wheat flour, a greater activity of this enzyme is observed than in premium or grade I flour. The ability of flour to darken during processing depends not only on the activity of polyphenol oxidase, but also on the content of free tyrosine, the amount of which is insignificant in flour of normal quality. Tyrosine is formed during the hydrolysis of protein substances, therefore, flour from sprouted grain or affected by a tortoise bug, where proteolysis is intense, has a high browning ability (almost twice as high as that of normal flour). The acid optimum of polyphenol oxidase is in the pH zone of 7–7.5, and the temperature optimum is at 40–50 °C. At a pH below 5.5, polyphenol oxidase is inactive, therefore, when processing flour that has the ability to brown, it is recommended to increase the acidity of the dough within the required limits.

vitamins.Flour contains vitamins B 6 , B 12 , PP, etc. The content of these vitamins depends mainly on the type of flour. In the flour of the highest grades of vitamins, there are significantly less vitamins than in the flour of the lower grades. This is due to the fact that vitamins are contained mainly in the germ and aleurone layer of the grain, which are few in the highest grades of flour.

Flour obtained after grinding wheat grains. It is the most common type of flour.

Kinds

In Russia, flour is classified according to the degree of processing into flour of the highest, first and second grade, wholemeal and whole grain.

Wheat flour of the highest grade, or “extra”, is distinguished by its snow-white color, sometimes with a creamy tint, and the smallest grains that are not felt when rubbed with fingers. It is used in the preparation of rich products, airy muffins, biscuits, cakes, thickening sauces. This flour contains few substances useful for the body, therefore it is not recommended for daily use.

Flour of the first grade contains a small amount of grain shells and a lot of gluten, which provides the dough prepared from it with elasticity, shape maintenance, volume and longer shelf life of finished products. It is suitable for making pancakes, pies, shortbread, puff, yeast dough, flour dressings and sauces.

Flour of the second grade contains up to 8% bran and is characterized by a darkish color. It is used for table white bread and lean flour products.

Whole flour, or wholemeal flour, is made by grinding wheat grains to heterogeneous and large grains. In this case, the germ and shell of the grain are sifted out.

Whole grain flour is the result of grinding wheat grain without preliminary purification from the shell and germs. The most useful type of bread is prepared from it, as well as other products that contain a large amount of vitamins, minerals and fiber.

calories

100 grams of the product contains 328 kcal.

Compound

Wheat flour contains carbohydrates, dietary fiber, starch, proteins, fats, saccharides, ash, vitamins B1, B2, B3, B6, B9, H, E, PP, as well as mineral elements: potassium, magnesium, zinc, manganese, calcium, iron, sodium, silicon, phosphorus, chlorine, sulfur, molybdenum, iodine, copper, fluorine, aluminum, cobalt, nickel.

The amount of nutrients in flour varies depending on the variety.

Usage

Wheat flour is used for the manufacture of bakery products, cakes, cookies, pancakes, fritters, dumplings, dumplings, pasta, sauces, breading, etc.

Beneficial features

Products made from wheat flour fill the body with energy, activate mental activity, and have a beneficial effect on the state of the blood and nervous system.

Use restrictions

A large amount of flour products can lead to weight gain.

People suffering from certain diseases of the gastrointestinal tract should give preference to premium flour.

Examination of flour quality.

Purpose of work: assessment of the quality of wheat and rye flour.

Flour is a powdered product with a different granulometric composition, obtained by grinding (grinding) grain. Flour is used for the production of bakery, confectionery and pasta products.

Flour is divided into types, types and varieties.

Types of flour differ depending on the culture from which it is developed. So, flour can be wheat, rye, corn, soy, barley, etc. Wheat flour is the most important, accounting for 84% of the total flour production.

flour type are distinguished within the type of flour, depending on the intended purpose. So, wheat flour can be bakery, for pasta, confectionery, ready for consumption (cooking), etc. In the production of a certain type of flour, grain with the necessary physical, chemical and biochemical properties is selected. For example, for the production of pasta flour, durum or high-glass soft wheat is taken and flour is obtained, consisting of relatively large homogeneous endosperm particles. In the production of baking flour, soft glassy or semi-glassy wheat is used and finely ground flour is obtained, from which it is easy to make soft, moderately elastic dough, to obtain a high yield of lush, porous bread.

Rye flour is produced in only one type - baking.

Flour grade distinguished within each type. The division into varieties is based on the quantitative ratio of endosperm and shell particles. Flour of the highest grades consists of particles only of the endosperm. Inferior grades contain a significant amount of shell particles. Varieties differ in chemical composition, color, technological advantages, calorie content, digestibility, biological value (Table 2.1).

Table 2.1. The chemical composition of wheat flour of different varieties

Content per 100 g of product	Flour grade
higher	the first	second	wallpaper
Water, g	14,0	14,0	14,0	14,0
Proteins, g	10,3	10,6	11,7	11,5
Fats, g	1,1	1,3	1,8	2,2
Mono- and disaccharides, g	0,2	0,5	0,9	1,0
Starch, g	68,7	67,1	62,8	55,8
Fiber, g	0,1	0,2	0,6	1,9
Ash, g	0,5	0,7	1,1	1,5
Minerals, mg
Na
To
Sa
mg
R
Fe	1,2	2,1	3,9	4,7
Vitamins, mgyo
β-carotene		Traces	0,01	0,01
IN 1	0,17	0,25	0,37	0,41
IN 2	0,04	0,08	0,12	0,15
RR	1,20	2,20	4,55	5,50

Nutritional value of wheat flour. Wheat flour of all types and varieties has some common properties due to the properties of the grain of wheat. These include the characteristic features of proteins, carbohydrates, enzymes and other substances that make up wheat flour, as well as the structure of cells, starch grains, etc.

Wheat flour proteins mainly consist of insoluble hydrophilic proteins - glutenin and gliadin (in ratios 1:1.2; 1:1.6). Other proteins (albumins, globulins, nucleoproteins) are contained in small amounts, mainly in low-grade flour. The most important property of glutenin and gliadin is the ability to form an elastic mass - gluten - in the process of swelling. The yield of raw gluten when washed from flour of different varieties is 20 - 40%, and the share of dry matter accounts for about 1/3 of the mass of raw gluten. The composition of dry gluten includes (%): protein -5 - 9, carbohydrates - 8 - 10, fat and fat-like substances - 2.4 - 2.8, minerals - 0.9-2.0.

During kneading, gluten forms a continuous phase of wheat dough, retains carbon dioxide during fermentation, thereby ensuring good leavening of the dough, and during baking, gluten denatures, coagulates, releasing excess water, and fixes the porous structure of bread. In the production of pasta, due to the presence of gluten, wheat dough has high plasticity and cohesion, and it is possible to produce pasta of various shapes. When drying pasta, gluten hardens, fixes the shape of the pasta and determines their glassy consistency.

For the quality of flour, not only the amount of gluten is important, but also its elasticity, resilience and extensibility.

Carbohydrates in wheat flour are mainly represented by starch. Its amount fluctuates between 65 - 80%. Wheat starch, if it consists of whole, undamaged grains, swells well, gives a viscous, slowly aging glue erased. Starch during saccharification is a source of sugars used in the fermentation of the dough.

The sugars of benign wheat flour are mostly represented by sucrose - 2-4% and to a lesser extent directly reducing sugars (maltose, glucose and fructose) - 0.1-0.5%. The amount of sugar is an important factor baking virtues of flour. Due to the fact that the sugars contained in wheat flour are not enough for fermentation, the activity of flour saccharifying enzymes is of great importance. The process of sugar formation proceeds in flour from high-grade grain according to the scheme: starch - glucose and fructose phosphates - sucrose - invert sugar. In flour from defective grains (self-heating, sprouted), starch is hydrolyzed mainly under the action of the enzymes amylase and maltase with the formation of a significant amount of dextrins, maltose and glucose, therefore, such flour is characterized by a markedly increased content of dextrins and directly reducing sugars.

Wheat flour, especially low grades, is an important source of minerals (Ca, Fe, P and some trace elements) and water-soluble vitamins (B l B 2 , PP). The content of ballast substances - fiber and pentosans is small and depends on the type of flour: in the highest grades, the amount of fiber is 0.1 - 0.15%, pentosans - 1 - 0.15; in the lowest - 1.6 - 2 and 7 - 8%, respectively.

Nutritional value and properties of rye flour largely due to the chemical and tissue composition of rye grain, the properties of its constituent substances. Distinctive feature rye flour - the presence in its composition of a large amount of water-soluble substances (13 - 18%), including soluble proteins, carbohydrates, mucus. Rye flour contains slightly less proteins than wheat flour - an average of 10 - 14% (Table 2.2).

Table 2.2. The chemical composition of rye flour

Content, mg/100 g of product	Flour grade
seeded	peeling	wallpaper
Water	14,0	14,0	14,0
Squirrels	6,9	8,9	10,7
Fats	1,4	1,7	1,9
Mono- and disaccharides	0,7	0,9	1,1
Starch	63,6	59,3	55,7
Cellulose	0,5	1,2	1,8
Ash	0,6	1,2	1,6
Minerals:
Na
To
Sa
mg
R
Fe	2,9	3,5	4,1
Vitamins:
β-carotene	Traces	Traces	0,01
IN 1	0,17	0,35	0,42
IN 2	0,04	0,13	0,15
RR	0,99	1,02	1,16

Under normal conditions, rye flour proteins do not form gluten, which can be separated from other substances. The so-called intermediate protein is capable of forming a certain amount of gluten, but this is of no practical importance, since gluten is not washed off from rye flour. Rye flour proteins contain water- and salt-soluble fractions capable of unlimited swelling. The total amount of soluble and soluble proteins reaches 50-52% of their total content; with soluble carbohydrates and mucus, they form viscous colloidal solutions that make up the continuous phase of rye dough.

Rye flour proteins have a favorable amino acid composition; compared to wheat flour proteins, they are relatively rich in amino acids such as lysine, histidine, valine, leucine.

The amino acid tyrosine is involved in enzymatic oxidation and the formation of dark-colored substances - melanins. For this reason, and also due to the interaction of amino acids with reducing sugars and the formation of melanoidins, rye flour of all varieties gives a darkening dough and bread with a dark crumb and crust.

Carbohydrates make up 80 - 85% of the dry mass of flour and are represented by starch, sugars, pentosans, mucus and fiber.

Starch in rye flour, depending on its variety, contains from 60 to 73.5%. For the most part, it consists of large lenticular-shaped grains. Rye starch has the lowest gelatinization temperature (46 - 62 ° C) and the ability to produce a viscous, slowly aging paste. This property, combined with the overall high content of soluble substances, results in a soft texture and slow staleness of rye bread.

Sugars in rye flour are in the amount of 6 - 9%. They contain few reducing sugars - 0.20 - 0.40%, represented by glucose and fructose, a lot of sucrose - 4 - 6% of the mass of flour (or 80% of all sugars), as well as maltose, raffinose and trifructosans.

Fiber in rye flour, despite the presence of a relatively large amount of shell particles (there are 20–26% in wholemeal flour), is about the same as in wheat flour (0.4–2.1%, depending on the variety). This is due to a significantly lower fiber content in the shells and aleurone layer of rye.

A feature of rye flour is the presence of pectin substances, the amount of which is higher than in wheat flour (Table 2.2).

Fat - there is little of it in rye flour - 1 - 2%. Linoleic (43%), palmitic (27%), oleic (20%) acids predominate in its composition, there is linolenic acid (4%); also contains lecithin (9% of fat mass) and tocopherols - vitamin E (258 mg%), which are natural antioxidants, so rye flour fat is highly resistant to rancidity. Coloring substances of flour are represented by flavone pigments, anthocyanins and chlorophyll.

Quality expertise flour is produced according to the following indicators: organoleptic, technical, physico-chemical and technological. General quality indicators characterize the freshness and good quality of flour - color, smell and taste.

flour color mainly due to its type and variety, i.e. the color of the grain and the content of endosperm and bran particles in the flour. It is determined visually in a dry or wet sample or analytically - using special instruments - photoanalyzers.

Flour of each type and grade has its own color: grits - cream, wheat flour of the highest grade - white, the first - white with a yellowish tint, the second - white with a clear brownish tint, wallpaper - with a darker brownish tint, seeded rye - white, slightly bluish, peeled rye and wallpaper - white with a distinct gray or brownish tinge, etc. Abnormal changes in the color of flour can be caused by an increased content of bran, improper grinding of flour, the presence of impurities (maryannik, smut, etc.) that give the flour unusual dark shades, as well as its spoilage and the formation of dark-colored substances (melanoidins) in it.

The smell of flour usually determined in a small (5 - 10 g) amount of flour slightly heated by breathing. Fresh flour has a specific mild pleasant smell. There is no mustiness, moldy smell and any foreign smell. The appearance of an odor that is not characteristic of normal flour can be caused by various reasons: rancidity of fat, the development of penicillium fungi, and other molds (aspergillus, mucor, etc.). In addition, musty and moldy odors result from the adsorption of odorous substances when flour is stored in damp, poorly ventilated areas. Foreign odors (wormwood, garlic, sweet clover) can be caused by the ingress of the corresponding odorous impurities into the flour, the adsorption of odorous substances when packing flour in dirty containers, as well as during storage in warehouses or transportation in wagons with foreign odors.

Taste determined by chewing a small (2 - 3 g) amount of flour Benign flour has a mild pleasant, slightly sweet taste. Flour should not have a sour, bitter or clearly sweet taste, as well as the presence of foreign flavors. Changes in taste can be caused by spoilage of flour (sourness or rancidity), the production of flour from defective grains. Spoiled grain gives a sour or bitter taste, sprouted - sweet, foreign impurities - wormwood, mustard, briar. Flour of any kind, when chewed, should not give a crunchy feeling on the teeth. The crunch is caused by the ingestion of crushed mineral impurities into the flour.

The indicators determined by analytical methods include moisture content, ash content, grinding fineness.

Humidity, i.e. the amount of free and physically bound water, expressed as a percentage of the mass of the product. Usually, flour made from high-quality grain and stored under favorable conditions has a moisture content in the range of 13-15%. Increased moisture content of flour, which occurs in cases of processing of substandard grain, improper conduct of the technological process (washing and conditioning of grain) or as a result of storage of flour in conditions of high relative humidity air (above 70 - 75%), adversely affects the quality of flour. At high humidity, free water accumulates in it, activating the activity of enzymes and contributing to the rapid development of microflora, which sharply reduces the shelf life and often leads to spoilage of flour. In addition, the increased moisture content of flour significantly affects the properties of proteins and starch, reduces its ability to swell and impairs baking properties.

Quantity and quality of raw gluten determined to characterize the baking or pasta properties of wheat flour. This indicator is provided in the standards and quality norms for flour.

Gluten is a protein jelly that remains after washing the dough with water and removing starch, fiber and water-soluble substances from it. The gluten-forming proteins are concentrated in the peripheral parts of the endosperm; therefore, less gluten is formed in the premium flour than in flour of grades I and II. It should be borne in mind that raw gluten contains from 60 to 75% water and its yield depends not only on the protein content in the flour, but also on its ability to absorb and retain more or less water. If the gluten is dried and weighed, it is possible to determine the content of dry gluten, and by the ratio of the mass of raw gluten to the dry mass, its water absorption capacity. For gluten of normal quality, this value is 2.5 - 3%.

For wheat flour different types and grades, limit norms for the yield of raw gluten (%, not less than) are set: for baking flour: semolina - 30, premium - 28, first - 30, second - 25, wallpaper - 20; for pasta flour from durum wheat - 30 - 32, from soft - 28 - 30.

The washed gluten is evaluated organoleptically by color (light, dark), elasticity and extensibility.

According to the current standard for test methods, flour gluten, like grain gluten, is divided into three groups:

I - good - elastic, normally extensible (up to 10 cm or more);

II - satisfactory - less elastic, different extensibility;

III - unsatisfactory - low-elasticity, strongly stretching, spreading, crumbling.

Gluten in bread flour should be of good or satisfactory quality, and pasta flour should be of good quality.

Unsatisfactory in quality is recognized gluten, which spreads when in water. The gluten of this group is usually dark gray or brownish in color.

Ash content in terms of dry matter serves indirect indicator varietal belonging of flour of all kinds.

The determination of the flour grade by its ash content is based on the uneven distribution of minerals in the tissues of cereal grains. For wheat (on average), mineral substances (%) are distributed as follows: ash content of the endosperm - 0.4, aleurone layer - 10, shells - 4, germ - 5; for rye: ash content of endosperm - 0.5, aleurone layer - 6.7, shells - 3.7, germ - 4.5. Therefore, the highest grade flour has an ash content of 0.4-0.6%, and as the grade decreases and the number of bran particles increases, the ash content increases, reaching an ash content in wholemeal flour close to the ash content of the whole grain (1.9 - 2%).

Grinding size determined in a sample isolated from an average sample weighing 50 g. To determine the fineness, sieves are selected installed normative documents for the respective type of product.

A sample of the product is poured onto the upper sieve, covered with a lid, a set of sieves is fixed on the sieving platform and the sieving is switched on. After 8 minutes, the sifting is stopped, the sieve shells are tapped, and sieving is continued again for 2 minutes. At the end of sieving, the remainder of the upper sieve and the passage of the lower sieve are weighed and calculated as a percentage of the mass of the sample taken.

The fineness of grinding determined and normalized in this way gives only an approximate idea of ​​the degree of grinding of the product. Current regulations limit the amount of coarse particles and guarantee a known minimum of fine particles. Norms for all types and grades, except for grains and pasta flour, the degree of flour grinding is not limited. The passage through any thick sieve can be increased to 100%, and the particle sizes are reduced to a high degree of dispersion. Therefore, different grades of flour - the highest, the first, the second - in terms of the degree of grinding in some cases differ little from each other.

Different grain size of flour is closely related to its properties - water absorption and sugar-forming ability, swelling ability and other indicators. Grain and pasta flour is characterized by a reduced water absorption capacity, slowly swells and is capable of additional swelling. This process consists in the fact that when kneading the dough, substances swell on the surface of relatively large particles and, with a small amount of water used, a coherent dough is formed, but then the moisture is absorbed by the internal colloidal system of particles and the consistency of the dough changes. The dough becomes more cohesive and dense. Coarse flour has a lower sugar-forming capacity. Such flour is best used for the production of pasta, where the minimum water absorption capacity, as well as the ability of the dough to additional swelling, makes it easier and cheaper to obtain high-quality pasta.

For baking flour, an increased grain size is undesirable, since the yield of bread, except for some rich products, decreases, the process of dough formation slows down, bread from it is obtained in a small volume and with a coarser porosity.

Baking flour for retail has the best properties if it consists of sufficiently small (70-100 microns) homogeneous particles with a granular structure. Such flour has a sufficiently high water absorption capacity, the dough from it is elastic, well retaining its elastic properties. Sugar-forming ability is also close to optimal.

Heavily crushed (dusty and ground) flour has undesirable properties: an excessively large water absorption capacity (the dough from it quickly liquefies, the bread is reduced in volume, with a dense, often crumbly crumb and a dark crust). Hearth bread made from such flour usually turns out vague. The fraying of flour has a particularly strong effect on its enzymatic activity. Mechanically damaged starch grains are subject to more rapid action of enzymes, which causes its rapid liquefaction and saccharification. Such starch is saccharified several times faster than normal medium grains.

The content of the metal-magnetic impurity in flour is limited by special regulations. Metal particles get into the flour in the form of grains of slag, ore, rust in case of poor grain cleaning or unsanitary condition of the mill. Particles of cast iron and steel get into the product as a result of wear of rollers, steel screens, metal gravity flows. Most of the metal is extracted in mills using magnetic devices installed along the path of the product, but a small part of it remains in the flour. The amount of magnetic impurities in flour is determined by extracting the metal from a 1 kg flour sample. The metal is extracted using strong magnets - magnetic horseshoes or on a special apparatus - a ferroanalyzer. The isolated metal impurity is weighed on an analytical balance. In flour, more than 3 mg of metal-magnetic impurities per 1 kg of flour are not allowed. The size of individual particles of a metal-magnetic impurity in the largest linear dimension should not exceed 0.3 mm, and the mass of individual particles should not exceed 0.4 mg.

The content of harmful and grain impurities in flour is also normalized, but determined by analyzing the grain before grinding. The results of grain analysis are indicated in the documents on the quality of flour and flour is evaluated on them. The following limiting standards for the content of impurities (%) have been established: ergot, smut, mustard, briar - no more than 0.05, including mustard and briar - no more than 0.04; the admixture of heliotrope pubescent and trichodesma incanum is absolutely not allowed; cockle seeds - no more than 0.1; grains of barley, rye (in wheat) and germinated - no more than 4 in total, including germinated grains, the number of which is determined in the grain before cleaning - no more than 3.

Flour with a high content of harmful impurities is unsuitable for human consumption. Grain impurities, especially barley and sprouted grains, reduce the baking properties of wheat and rye flour.

Infestation of flour by pests(beetles and their larvae, butterflies and their caterpillars, as well as ticks) is not allowed according to the current rules and regulations.

To establish the infection, 1 kg of flour is sifted through sieves (varietal flour through a sieve No. 056, and wallpaper flour through two sieves No. 067 and 056). The passage through the No. 056 sieve is used to detect mites, and the residues on the No. 056 and 067 sieves are used to detect other pests, scattering the residue in a thin layer on the analysis board and carefully examining it.

Ticks in flour are difficult to distinguish and therefore they are detected indirectly. Five portions of 20 g each are taken from the flour that has passed through a sieve No. 056. Each sample is placed on the glass and lightly pressed with a piece of paper or glass to make the surface perfectly smooth. Then, after some time, the surface of the pressed flour is carefully examined. The appearance of swellings or grooves indicates the presence of mites.

Bulk yield and dimensional stability of bread set by trial baking. It is used in the evaluation of wheat flour, less often - rye.

For baking, 1000 g of flour is usually taken at a moisture content of 14% (or the mass of flour is brought to this moisture content); when kneading the dough, use 530 - 540 ml of water, 30 g of pressed yeast and 15 g of salt. The dough ferments for 160 minutes with 1 - 2 punches at 32°C. Ready dough divided into three equal parts. Two are placed in iron molds, and the third is molded into spherical hearth bread. The dough is proofed (at 35 0 C and relative humidity 80%) to the maximum volume. The surface of the dough is moistened with water and baked at 225 - 230 0 C for 30 minutes.

After cooling (after 4 hours), the volumetric yield of bread and the ratio of the height of the hearth bread to its diameter are established. The volume is determined in a special device consisting of a vessel of a fixed capacity and a measuring cylinder equal in volume to it, filled with flax seeds or millet. Bread is placed in the first vessel, filled with flax seeds or millet flush with the edges, the volume of bread is determined from the remainder of the seeds in the cylinder, and then it is divided by the mass of flour (g) spent on baking this bread, and multiplied by 100; the result is a volumetric yield of bread (cm 3) per 100 g of flour. The hearth loaf is measured by determining its diameter and height, and the ratio of height to diameter H/D is calculated. According to the volume output of panned bread and the H/D ratio of hearth bread, the baking properties of the flour are judged.

There are many different test baking methods. One of them can be cited as an example: for high-grade wheat flour, the volumetric yield of bread is from 350 (for second grade flour) to 500 cm 3 (for premium flour), and the H / D ratio is from 0.35 to 0, 5 respectively.

Baked bread is used to determine taste, smell, color, crumb structure, porosity and other indicators.

Test baking also reveals flour contaminated with potato disease. To do this, one loaf is wrapped with wet paper or cloth and left for 24 hours. Then it is cut or broken. The appearance of lumps or threads of mucus in the crumb indicates that the flour is infected with potato disease.

Baking bread from rye flour due to the need to use sourdough and multi-phase dough management is used relatively rarely. They are usually replaced with kolobok pastries: 50 g of flour is kneaded with 41 ml of water room temperature, a ball (kolobok) is formed from the resulting dough and baked at 230 ° C for 20 minutes. Then the quality of the baked kolobok is determined. It has been established that the assessment of flour by the quality of the kolobok is quite close to its assessment by autolytic activity.

From flour of good quality with medium autolytic activity, a bun of the correct shape is baked, without noticeable cracks, with a fairly dry crumb. The content of water-soluble substances in the crumb - 23 - 28%.

Flour with reduced autolytic activity also produces a bun of regular spherical shape, but small in volume, very pale in color, with a dense and dry crumb. The content of water-soluble substances in the crumb is less than 23%.

When baking from flour with increased autolytic activity, the bun is flat, spreading, with cracks on the surface, with a sticky crumb. The content of water-soluble substances is more than 28%.

gas holding capacity- is determined simultaneously with gas-forming. It is characterized by an increase in the volume of dough during fermentation and is expressed either as a percentage of the volume of gas released, or as the ratio of the volume of fermented dough to the original volume.

Determining the gas-forming and gas-holding capacity is important. However, the results of this determination depend on many factors - yeast, test conditions, etc. In addition, the experience requires a lot of time. At the same time, the gas-forming ability of flour depends on its sugar-forming ability, and the gas-retaining ability depends on the quantity and quality of gluten and the elastic properties of the dough. For all these reasons, it is more reasonable to resort to the definition of the latter indicators.

Gas generating capacity determined in the following way: from the test flour (100 g) knead the dough with the addition of salt and yeast, place it in a cylinder and let it ferment for a certain time (5 hours) and under certain conditions (30 ° C), setting the amount of carbon dioxide released. This amount varies widely - from 1000 to 2200 ml or more.

Requirements for the quality of wheat baking and rye flour are given in table. 2.8 and 2.9 (applications).

In accordance with SanPiN 2.3.2.1078 - 01, the safety indicators for all types of flour are as follows (Table 2.3):

Table 2.3. Maximum content of hazardous substances in flour

Practical part

Laboratory analysis of flour for quality compliance with the standards of flour mills is carried out according to the scheme shown in Figure 2.1

Rice. 2.1. Scheme of flour analysis

Lesson 1. "Examination of the quality of wheat flour"

1. Determination of organoleptic indicators of flour __________________.

(type of flour)

Color. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .________________

Smell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .________________

Taste. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ________________

2. Determination of moisture content of flour. Humidity is determined by drying the sample. To do this, a portion of 5 g of flour is placed in a weighing bottle with a ground-in lid, weighed on an analytical balance, and then placed in an oven for 50 minutes at 130 °C, after which the weighing bottle is placed in a desiccator for cooling and weighed again. Humidity is calculated by the formula:

where m 1 is the mass of an empty bottle, g;

m 2 - mass of weighing bottle with wet yeast, g;

m 3 - weight of bottle with dried yeast, g.

When calculating the results, fractions up to 0.05 are discarded, and fractions equal to 0.05 or more are rounded up to 0.1.

Moisture determination method. . . . . . . . . . . . . . . . . ________________

Weight of an empty bottle, m 1, g. . . . . . . . . . . . . . . . . . . ________________

Bulk weight in wet flour, m 2, g. . . . . . . . . . . ________________

Weight of bottle with dried flour, m 3, g. . . . . . . .________________

Moisture content of flour, W, %. . . . . . . . . . . . . . . . . . . . . . . .________________

3. Infection determined by sifting 1 kg of high-quality flour through a wire sieve No. 056, wallpaper - through wire sieves No. 067 and No. 056. The residues on the sieves are analyzed for the presence of beetles, pupae, larvae. The passage of sieve No. 056 is used to determine mite infestation.

4. Grinding size of flour determined by sifting on a laboratory sieving a test portion weighing 100 g for sifting flour and 50 g for high-quality flour on sieves established by the standard. The residue on the upper sieve characterizes the presence of large particles in the flour, and the passage on the lower sieve characterizes the presence of small particles. Enter the results in table 2.5.

Table 2.4. Grinding size of flour _____________________

(type of flour)

Sieve	Residue on the sieve, g	Percentage of neither sieve, %

The result of the analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . _________________

5. Determination of baking power wheat flour on sedimentation sediment.

The determination method is based on the ability of flour protein substances to swell in weak solutions of lactic or acetic acids and form a precipitate, the value of which characterizes the amount of protein substances. In a 100 ml measuring cylinder with a ground stopper, graduated with a division value of 0.1 ml, add 3.2 g of flour, weighed on a technical scale. 50 ml of distilled water, tinted with bromophenol blue dye, is poured into the cylinder. Turn on the stopwatch (it is not stopped until the end of the definition). The cylinder is closed with a stopper and shaken for 5 s, sharply moving in a horizontal position. Get a homogeneous suspension. The cylinder is placed in a vertical position and left alone for 55 s. After removing the cork, pour 25 ml of a 6% solution of acetic acid. Close the cylinder and turn it over 4 times within 15 s, holding the stopper with your finger. Leave the cylinder alone for 45 s (up to 2 minutes by the stopwatch from the beginning of the determination). Within 30 s, the cylinder is smoothly turned over 18 times. Leave for the third time alone for exactly 5 minutes and immediately make a visual reading of the volume of sedimentation sediment to the nearest 0.1 ml. If a small part of the sediment floats, it is added to the main sediment. The established volume of sedimentation sediment (ml) is recalculated for flour moisture content of 14.5% according to the formula

where V y exp - actually measured value of sedimentation sediment, ml;

w m - actual moisture content of the studied flour, % for dry-air substance.

To assess the baking power by the amount of sedimentation sediment, the following approximate standards are recommended.

Table 2.5. Sedimentation sediment (ml) at different grinding sizes

Record in the laboratory journal:

Actual measured value of sedimentation sediment, V c.exp, g. .___________

Humidity of the studied flour, W, % . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ___________

Installed volume of sedimentation sediment, V Y, ml. . . . . . . . . . . . . ___________

6. Quantity and quality of raw gluten.

A portion of flour 25 g is weighed on technical scales and placed in a porcelain mortar or cup and 13 ml of tap water is poured at a temperature of 16 ... 20 ° C. Flour and water are mixed with a spatula, getting a dough, which is then well kneaded by hand. Dough particles adhering to the cup and spatula are carefully collected (cleaned with a knife) and attached to a piece of dough.

After rolling the dough into a ball, place it in a cup and cover with glass for 20 minutes so that the flour particles are saturated with water, the proteins swell. Then the gluten is washed from starch and shells under a weak stream of tap water over a thick silk or nylon sieve, slightly kneading the dough with your fingers. At first, washing is carried out carefully, not allowing pieces of gluten to come off together with starch and shells, after removing most of the starch and shells, more vigorously Accidentally detached pieces of gluten are collected and attached to the total mass of gluten.

It is allowed to wash gluten (if there is no running water) in a basin or container containing at least 2 liters of water. Knead the dough in water with your hands. When starch and membranes accumulate in the water, it is drained, filtered through a thick silk or nylon sieve, a new portion of water is poured and so on until the end of washing, which is established by the absence of starch in the water (almost transparent), flowing down when gluten is squeezed out. If the gluten is not washed out, the results of the analysis are recorded as "Not washable".

Having finished washing the gluten, it is squeezed between the palms, which are periodically wiped dry with a towel. At the same time, the gluten is turned out several times with your fingers, each time wiping your palms with a towel. Do this until the gluten begins to slightly stick to your hands.

The gluten is weighed, washed again for 2-3 minutes, squeezed again and weighed again. The washing of gluten is considered complete when the difference in mass between two weighings is not more than 0.1 g. The amount of raw gluten is expressed as a percentage of a flour weighing 25 g. Depending on the gluten content, several product categories are distinguished (Table 2.6).

The result of the analysis __________________________________________.

7. Determination of the quality of raw gluten. The quality of raw gluten is characterized by physical properties, extensibility and elasticity, color (light, gray, dark).

The extensibility of gluten is understood as its ability to stretch in length. To assess the quality of gluten by extensibility, 4 g of raw gluten is placed for 15 minutes in a glass of water at a temperature of 18 - 20 ° C. Further, taking a piece of gluten out of the water and squeezing it out, manually over the course of 10 s it is gradually stretched over the ruler into a tourniquet until it breaks, noticing how long the gluten has stretched. By extensibility, gluten is divided into: short - 10 cm, medium - extensibility 10 - 20 cm, long - extensibility more than 20 cm.

Under the elasticity of gluten is meant its ability to restore its original dimensions after its stretching. The elastic properties of gluten mean resistance to the action of a compression load. For the determination of 4 g of gluten after exposure for 15 minutes in cold water at a temperature of 18 - 20 ° C is placed in the center on the instrument table of the pinetrometer. The working body of the pinetrometer is brought into contact with gluten, then it is loaded with 120 g. After 30 seconds, the load is removed and the amount of deformation is determined on the scale. When the deformation of the gluten is less than 37.5%, the quality of the gluten is very strong; at 37.5 - 55% - strong; 55 - 70% - average; 70 - 87.5% - satisfactorily weak, 87.5 - 100% - unsatisfactorily weak.

Record in the laboratory journal:

Weighing weight of raw gluten, g. . . . . . . . . . . . . . . . . . . . . . . . . . .___________

after the first washing, g. . . . . . . . . . . . . . . . . . . . .___________

after the second washing, g. . . . . . . . . . . . . . . . . . . . .___________

The amount of crude gluten,%. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .___________

Gluten color. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .___________

Extensibility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .___________

Elasticity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .___________

Wheat flour, premium rich in vitamins and minerals such as: vitamin B1 - 11.3%, vitamin PP - 15%, silicon - 13.3%, cobalt - 16%, manganese - 28.5%, molybdenum - 17.9%

What is useful Wheat flour, premium

• Vitamin B1 is part of the most important enzymes of carbohydrate and energy metabolism, providing the body with energy and plastic substances, as well as the metabolism of branched-chain amino acids. The lack of this vitamin leads to serious disorders of the nervous, digestive and cardiovascular systems.
• Vitamin PP participates in redox reactions of energy metabolism. Insufficient vitamin intake is accompanied by a violation of the normal state skin, gastrointestinal tract and nervous system.
• Silicon is included as a structural component in the composition of glycosaminoglycans and stimulates the synthesis of collagen.
• Cobalt is part of vitamin B12. Activates the enzymes of fatty acid metabolism and folic acid metabolism.
• Manganese participates in the formation of bone and connective tissue, is part of the enzymes involved in the metabolism of amino acids, carbohydrates, catecholamines; necessary for the synthesis of cholesterol and nucleotides. Insufficient consumption is accompanied by growth retardation, disorders in the reproductive system, increased fragility of bone tissue, disorders of carbohydrate and lipid metabolism.
• Molybdenum is a cofactor of many enzymes that provide the metabolism of sulfur-containing amino acids, purines and pyrimidines.

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The chemical composition of flour determines its nutritional value and baking properties. The chemical composition of flour depends on the composition of the grain from which it is obtained, and the type of flour. Higher grades of flour are obtained from the central layers of the endosperm, so they contain more starch and less proteins, sugars, fat, minerals, vitamins, which are concentrated in its peripheral parts. The average chemical composition of wheat and rye flour is presented in table 10.

Table 10 Chemical composition of flour, in % of dry matter

Type and grade of flour	Starch	Squirrels	Pentosans	Fats	Sahara	Cellulose	Ash
Wheat flour: top grade first grade second grade wallpaper	79,0	12,0	2,0	0,8	1,8	0,1	0,55
	77,5	14,0	2,5	1,5	2,0	0,3	0,75
	71,0	14,5	3,5	1,9	2,8	0,8	1,25
	66,0	16,0	7,2	2,1	4,0	2,3	1,90
Rye flour: seeded wholemeal	73,5	9,0	4,5	1,1	4,7	0,4	0,75
	67,0	10,5	6,0	1,7	5,5	1,3	1,45
	62,0	13,5	8,5	1,9	6,5	2,2	1,90

Most of all, both wheat and rye flour contain carbohydrates (starch, mono- and disaccharides, pentosans, cellulose) and proteins, the properties of which determine the properties of the dough and the quality of bread.

Carbohydrates. Flour contains a variety of carbohydrates: simple sugars, or monosaccharides (glucose, fructose, arabinose, galactose); disaccharides (sucrose, maltose, raffinose); starch, cellulose, hemicelluloses, pentosans.

Starch- the most important carbohydrate of flour, is contained in the form of grains ranging in size from 0.002 to 0.15 mm. The size and shape of starch grains are different for different types and grades of flour. The starch grain consists of amylose, which forms the inner part of the starch grain, and amylopectin, which makes up its outer part. The quantitative ratios of amylose and amylopectin in the starch of various cereals are 1:3 or 1:3.5. Amylose differs from amylopectin in its lower molecular weight and simpler molecular structure. The amylose molecule consists of 300-8000 glucose residues forming straight chains. The amylopectin molecule has a branched structure and contains up to 6000 glucose residues. AT hot water amylopectin swells and amylose dissolves.

In the process of making bread, starch performs the following functions:

• is a source of fermentable carbohydrates in the dough, undergoing hydrolysis under the action of amylolytic enzymes (a- and p-amylases);
• absorbs water during kneading, participating in the formation of the dough;
• gelatinizes during baking, absorbing water and participating in the formation of bread crumb;
• responsible for the staleness of bread during storage.

The process of swelling of starch grains in hot water is called gelatinization. At the same time, starch grains increase in volume, become looser and easily amenable to the action of amylolytic enzymes. Wheat starch gelatinizes at a temperature of 62-65 ° C, rye - 50-55 ° C.

The starch condition of the flour affects the properties of the dough and the quality of the bread. The size and integrity of starch grains affect the consistency of the dough, its water absorption capacity and the content of sugars in it. Small and damaged grains of starch are able to bind more moisture in the dough, they are easily amenable to the action of enzymes during dough preparation than large and dense grains.

The structure of starch grains is crystalline, finely porous. Starch has a high ability to bind water. When baking bread, starch binds up to 80% of the moisture in the dough. When storing bread, starch paste undergoes “aging” (syneresis), which is the main cause of stale bread.

Cellulose, hemicelluloses, pentosans belong to the dietary fiber group. Dietary fibers are found mainly in the peripheral parts of the grain and therefore they are most abundant in high-yield flour. Dietary fiber is not absorbed by the human body, so they reduce the energy value of flour, while increasing the nutritional value of flour and bread, as they accelerate intestinal motility, normalize lipid and carbohydrate metabolism in the body, promote the excretion of heavy metals.

Pentosans flour can be soluble or insoluble in water.

Part of the flour pentosans can easily swell and dissolve in water (peptize), forming a very viscous mucus-like solution.

Therefore, water-soluble flour pentosans are often referred to as slimes. It is mucus that has the greatest influence on the rheological properties of wheat and rye dough. Of the total amount of pentosans in wheat flour, only 20-24% are water-soluble. There are more water-soluble pentosans in rye flour (about 40%). Pentosans, which are insoluble in water, swell intensively in the dough, binding a significant amount of water.

Fats are esters of glycerol and higher fatty acids. The composition of flour fats includes mainly liquid unsaturated acids (oleic, linoleic and linolenic). The fat content in different varieties of wheat and rye flour is 0.8-2.0% per dry matter. The lower the grade of flour, the higher the fat content in it.

Fat-like substances include phospholipids, pigments, and some vitamins. These substances are called fat-like because, like fats, they do not dissolve in water, but are soluble in organic solvents.

Phospholipids have a structure similar to fats, but, in addition to glycerol and fatty acids, they also contain phosphoric acid and nitrogenous substances. Flour contains 0.4-0.7% phospholipids. Flour dyes (pigments) consist of chlorophyll and carotenoids. The chlorophyll contained in the shells is a green substance, the carotenoids are yellow and orange. When oxidized, carotenoid pigments become colorless. This property is manifested during storage of flour, which brightens as a result of oxidation of carotenoid pigments by air oxygen.