Structural and mechanical properties food products perform a dual function: they are intended not only for quantitative, but also for the qualitative characteristics of food products. Structural- m mechanical (rheological) properties - features of goods, manifested during their deformation. They characterize the ability of goods to resist applied external forces or change under their influence. These include strength, hardness, elasticity, elasticity, plasticity, viscosity, adhesion, thixotropy, etc.

These properties depend not only on the chemical composition of the products, but also on the structure, or structure. Indicators of structural and mechanical properties characterize the quality (consistency) of food products, change markedly during their destruction and are taken into account when choosing the conditions for their technological processing, transportation and storage.

Strength - the ability of a solid body to resist mechanical destruction when an external force of tension and compression is applied to it.

The strength of a material depends on its structure and porosity. Strength is important for the quantitative characteristics of food products such as pasta, refined sugar, biscuits, crackers. If food products are not strong enough, the amount of scrap, crumbs increases. This indicator is taken into account when processing grain into flour, when crushing grapes, when chopping potatoes, etc.

Hardness- local surface strength of the body, which is characterized by resistance to the penetration of another more solid body into it.

The hardness of objects depends on their nature, shape, structure, size and arrangement of atoms, as well as intermolecular cohesion forces. Hardness is determined by assessing the degree of maturity of fresh fruits and vegetables, by the hardness of crackers and lamb products judge the processes of staleness .

Deformation - the ability of an object to change its size, shape and structure under the influence of external influences that cause the displacement of individual particles in relation to each other. Deformation of goods depends on the magnitude and type of load, structure and physical and chemical properties of the object.

Deformations can be reversible and irreversible (residual). With reversible deformation, the original dimensions, shape and structure of the products are completely restored after the load is removed, and with irreversible deformation, they are not restored. Reversible deformation can be elastic, when there is an instant restoration of the shape and size of the object, and elastic, when the restoration takes a more or less long period of time. Residual deformation is the deformation remaining after the termination of the action of external forces. Residual irreversible deformation is also called plastic.

If the external forces applied to the body are so great that the particles of the body moving in the process of deformation lose their mutual connection, the destruction of the body occurs.

Food products, as a rule, are characterized by a multi-component composition; they are characterized by both elastic deformation and elastic, as well as plastic deformation.

Elasticity - the ability of bodies to instantly restore their original shape or volume after the termination of the deforming forces. This indicator is used in determining the elasticity of dough, gluten in wheat dough, bread products and other goods. This property characterizes goods such as, for example, rubber inflatable products (tires, toys, etc.).

Elasticity- the property of bodies to gradually restore shape or volume for some time after the termination of the deforming forces.

This property is also used in assessing the quality of bread (crumb condition), meat and fish, dough gluten. Thus, the elasticity of the crumb of bread, meat and fish serves as an indicator of their freshness, since the crumb loses its elasticity when staling; when meat and fish are overripe or spoiled, the muscle tissue becomes very softened and also loses its elasticity.

Plastic- the ability of an object to irreversible deformations, as a result of which the original shape changes, and after the cessation of external influence, the new shape is preserved. Plasticine is a typical example of plastic materials. The plasticity of food raw materials and semi-finished products is used in the molding of finished products. So, due to the plasticity of wheat dough, it is possible to give a certain shape to bakery, flour confectionery, lamb and pasta products. Plasticity is possessed by hot caramel, candy, chocolate and marmalade masses. After baking and cooling, finished products lose plasticity, acquiring new properties (elasticity, hardness, etc.).

When transporting, storing and selling products, one should take into account its ability to deform and its dependence on mechanical loads and temperature of the goods. Thus, edible fats, margarine products, cow butter, bread low temperatures have relatively high strength and elevated temperatures- plasticity. Therefore, the transportation of, for example, hot (not cooled) bread can lead to deformation of products and an increase in the percentage of sanitary defects.

It should be noted that there are practically no bodies capable of only reversible or irreversible deformations. In each material or product, different types of deformations are manifested, but some are more characterized by reversible deformations, elasticity, elasticity, while others are plastic. Elastic deformations are most inherent in goods that have a crystalline structure, elastic deformations - in goods consisting of high-molecular organic compounds (proteins, starch, etc.), plastic - in goods with weak bonds between individual particles.

The fundamental differences between elastic, elastic and plastic deformations lie in the structural changes that occur under the influence of an external force. With elastic and elastic deformations, the distance between the particles changes, and with plastic deformations, their relative position changes.

As a result of long-term external action, elastic deformation can transform into plastic. This transition is associated with relaxation - stress drop inside the material at a constant initial strain.

An example is the deformation of fruits and vegetables under the influence of gravity of the upper layers, freshly baked bread under shock or pressure. In this case, the product may partially or completely lose the ability to restore its shape due to a change in the relative position of the particles.

Viscosity(internal friction) - the ability of a fluid to resist the movement of one of its parts relative to another under the influence of an external force.

The viscosity of liquid goods is determined using a viscometer. Viscosity is used to assess the quality of goods with a liquid and viscous consistency (syrups, extracts, honey, vegetable oils, juices, spirits, etc.). Viscosity depends on the chemical composition (water content, solids, fat content) and the temperature of the product. With an increase in the content of water and fat, as well as temperature, the viscosity of raw materials, semi-finished products and finished products decreases, which facilitates their preparation, the viscosity increases with an increase in the concentration of solutions, their degree of dispersion.

Viscosity indirectly indicates the quality of liquid and viscous products, characterizes the degree of their readiness during the processing of raw materials, and affects losses during their movement from one type of container to another.

Stickiness (adhesion)- the ability of products to exhibit forces of interaction with another product or with the surface of the container in which the product is located. This indicator is closely related to the plasticity, viscosity of food products. Adhesion is characteristic of foods such as cheese, butter, chopped meat etc. They stick to the blade of a knife when cut, to the teeth when chewed. The stickiness of products is determined in order to control this property during the production and storage of goods.

Creep The property of a material to deform continuously under a constant load. This property is typical for cheeses, ice cream, cow butter, marmalade, etc. In food products, creep appears very quickly, which must be taken into account during their processing in storage.

Thixotropy- the ability of some dispersed systems to spontaneously restore the structure destroyed by mechanical action. It is found in many semi-finished products and products. Food Industry and Catering, for example, at jellies.

FEATURES OF THE STRUCTURE AND MECHANICAL PROPERTIES OF THE WAGING DOUGH

Non-fermenting flour dough should be considered a material designed to evaluate the technological properties of grain and flour. Fermenting dough is less suitable for this purpose, since it contains yeast, sourdough, gaseous substances, mainly carbon dioxide, and organic acids formed during fermentation. It is a structural analogue and predecessor of the bread crumb structure, unfixed by heat treatment. The amount of carbon dioxide formed in a unit volume of dough depends on the content and distribution of yeast cells in it, the energy of their fermentation, determined by the mass of yeast, and the conditions of their vital activity. The size of carbon dioxide bubbles and their number in the volume are determined by the gas permeability of the dough (according to CO 2), which depends on its structural and mechanical properties.

Gaseous substances, as is known, differ significantly from solids and liquids in their lower density, greater compressibility, and also in the dependence of their volumetric expansion coefficient on temperature. Their presence in the structure of the dough increases the volume, reduces its density, complicates the structure. Elastic-plastic deformations of the fermenting dough occur in the walls of the pores of its structured mass. In order to consider the influence of the gaseous phase on the mechanical properties of the fermenting dough, let us consider the diagram of its structure shown in Fig. 21. In it, surfactants, proteins, lipoids, etc. are schematically shown with round-ended rods. Their rounded part represents the polar, and the straight "tail" - the non-polar group of atoms in the molecule.

The most probable centers for the formation of primary bubbles of CO 2 in the fermenting dough are the points of adhesion of non-polar groups of surfactant molecules bound by the weakest forces of dispersion interactions. The gaseous products formed in the dough during its fermentation (CO 2 and others) dissolve in free water and are adsorbed on the surfaces of hydrophilic polymer molecules. Their excess forms gas bubbles in the fermenting dough. The walls of the bubbles form surfactants. An increase in the amount of gaseous products causes a corresponding increase in the number and volume of gas bubbles, a decrease in the thickness of their walls, as well as a breakthrough of the walls, diffusion and leakage of gas from the dough surface.

This difficult process the formation of the fermenting dough structure is naturally accompanied by an increase in the volume of its mass and shear deformations. The accumulation of many bubbles of gaseous products leads to the formation of a foamy fermenting dough structure having double walls formed by surfactants. They are filled with a mass of hydrated hydrophilic substances of the test, associated with the polar groups of surfactants of the walls of the bubbles by secondary chemical bonds. The dough has a significant viscosity and elastic properties, providing its foam structure with sufficient strength and durability, a certain ability to flow and retain gaseous substances (air, steam, carbon dioxide).

Elastic-plastic shear deformations of such a structure as a result of a permanent increase in the volume of gas bubbles and dough lead to a decrease in the thickness of the walls, their rupture and merging (coalescence) of individual bubbles with a decrease in the total volume.

The development of elastic-plastic shear deformations in the mass of dough starting to ferment rapidly, which lowers its density, occurs at corresponding reduced stresses, therefore, the initial moduli of elasticity-shear elasticity and the viscosity of such a dough should not be higher than that of a non-fermenting dough. However, in the process of its fermentation and an increase in the volume, deformation of the spherical walls of its gas pores should be accompanied by the orientation of proteins and other polymers in the direction of shear and flow, the formation of additional intermolecular bonds between them, and an increase in dough viscosity. Decreasing the density of the fermenting dough during fermentation allows proteins to more fully realize their elastic properties - to lower the modulus of elasticity-shear elasticity. With increased viscosity, reduced modulus, the fermenting dough should have a significantly greater ratio of these characteristics, have a more solid system than the non-fermenting one.

Owing to the permanent formation of carbonic acid and the increase in volume in this way, the fermenting dough, in contrast to the non-fermenting one, is a doubly tense system. The gravitational forces of its mass during fermentation are inferior, equal to or greater than the energy of chemical reactions of CO 2 formation, which creates forces that develop and move gas bubbles upwards according to the Stokes law (motion of spherical bodies in a viscous medium). The number and size of gas bubbles in the dough are determined by the energy and rate of yeast fermentation, the structural and mechanical properties of the dough, and its gas permeability.

The size of the carbon dioxide bubble formed during fermentation at any given moment will depend on the balance of its tensile forces.

P=π rp (4.1)

and compressive

P =2π rσ (4.2)

where π, r , R , σ - respectively, the ratio of the circumference to the diameter (3, 14), the radius of the bubble, excess pressure and surface tension.

It follows from the equality conditions for equations (4.1) and (4.2) that

P =2 σ / r (4.3)

Equation (4.3) shows that at the initial moment of formation of a gas bubble, when its dimensions, determined by the radius, are very small, the excess pressure must be significant. As the bubble radius increases, it decreases. Neighborhood of gas bubbles of different radii should be accompanied by CO 2 diffusion through the walls in the direction from higher to lower pressure and its equalization. In the presence of a certain excess pressure and the average size of gas bubbles, it is easy to calculate, knowing the viscosity of the dough, the rate of their rise according to the Stokes law mentioned.

According to this law, the force that lifts gas bubbles is

P =4/3π rg ( ρ - ρ ) (4.4)

overcomes the force of their friction

P =6 prηυ (4.5)

where g is the gravitational constant;

and ρ are the densities of the gas and dough;

η-effective structural viscosity of the dough;

υ - the speed of the vertical movement of gas bubbles in the dough

arising in the dough mass when a spherical body (gas bubble) moves in it.

From the equality of equations (4.4) and (4.5) it is easy to determine the value of the velocity

V =2 gr ( ρ - ρ )/9 η (4 .6)

This equation is of great practical importance, making it possible to establish the dependence of the rate of increase in the volume of fermenting dough on its density and viscosity, the size of individual pores, which is also determined by the energy of fermentation of microorganisms. Calculated by the equation, the rate of increase in the volume of wheat dough from flour of grade I with a density of 1.2 with an average pore radius of 1 mm and a viscosity of about 1

10 4 Pas is about 10 mm/min. Practical observations show that such a dough has an average rise rate of 2 to 7 mm/min. The highest rate is observed in the first hours of fermentation.

If there are neighboring pores in the test, having different sizes and gas pressures, their walls break and the pores merge (coalescence); this phenomenon also depends on the rate of fermentation and the mechanical properties of the dough; apparently, most of the pores of the dough and bread crumb are not closed, open. Due to the phenomena of diffusion of CO 2 through the walls of the pores and their rupture by excess pressure, the fermenting dough loses carbon dioxide with its surface: taking the cost of dry substances (sugar) for the fermentation of the dough, equal to an average of 3% of the mass of flour, with alcoholic fermentation per 1 kg of flour (or 1, 5 kg of bread) releases about 15 g, or about 7.5 liters of CO 2 . This amount at atmospheric pressure is several times greater than the volume of gaseous products in the specified volume of bread and characterizes their loss during the fermentation of the dough.

In the fermenting dough, many other organic acids and alcohols are also formed that can change the solubility of grain compounds. Thus, all of the above shows that the structure of the fermented dough is more complex than that of the non-fermented one. It should differ from the latter in smaller: density, elasticity-elasticity modulus, higher viscosity and η / E (greater ability to retain shape), a permanent increase in volume and acidity during fermentation.

The compacted pasta dough supplied to the matrix is ​​an elastic-plastic-viscous material.

The elasticity of the test is the ability of the test to restore its original shape after a quick removal of the load, it manifests itself under small and short-term loads.

Plasticity is the ability of dough to deform. Under prolonged and significant loads (above the so-called elastic limit), pasta dough behaves like a plastic material, i.e. after removal of the load, it retains the shape given to it, deforms. It is this property that makes it possible to form raw pasta a certain kind.

Viscosity - is characterized by the magnitude of the forces of adhesion of particles to each other (cohesive forces). The greater the value of the cohesive forces of the dough, the more viscous (strong) it is, the less plastic it is.

Plastic dough requires less energy for molding, it is easier to mold. When using metal matrices from a more plastic dough, products with a smoother surface are obtained. With an increase in plasticity, the dough becomes less elastic, less durable, more sticky, adheres more strongly to the working surfaces of the screw chamber and the screw, and raw products from such dough stick together more strongly and do not retain their shape well.

The rheological properties of compacted dough, i.e. the ratio of its elastic, plastic and strength properties are determined by the following factors.

With an increase in the moisture content of the dough, its plasticity increases and strength and elasticity decrease.

With an increase in the temperature of the dough, an increase in its plasticity and a decrease in strength and elasticity are also observed. Such a dependence is also observed at temperatures above 62.5 °C, i.e. above the gelatinization temperature of wheat starch. This is because the pasta dough does not have enough moisture to fully gelatinize the starch at that temperature.

With an increase in the gluten content, the strength properties of the dough decrease and its plasticity increases. The dough has the highest viscosity (strength) when the flour contains about 25% of raw gluten. When the content of raw gluten is below 25%, with a decrease in the plastic properties of the dough, its strength also decreases. Sticky, highly stretchy raw gluten increases the plasticity of the dough and significantly reduces its elasticity and strength.

With a decrease in the size of the flour particles, the strength increases and the plasticity of the dough from it decreases: the dough from baking flour is stronger than from semi-grains, and from semi-grains is stronger than from grains. The optimal ratio of strength and plastic properties is typical for particles of the original flour with a size of 250 to 350 microns.

FEATURES OF THE STRUCTURE AND MECHANICAL PROPERTIES OF THE WAGING DOUGH

Non-fermenting flour dough should be considered a material designed to evaluate the technological properties of grain and flour. Fermenting dough is less suitable for this purpose, since it contains yeast, sourdough, gaseous substances, mainly carbon dioxide, and organic acids formed during fermentation. It is a structural analogue and predecessor of the bread crumb structure, unfixed by heat treatment. The amount of carbon dioxide formed in a unit volume of dough depends on the content and distribution of yeast cells in it, the energy of their fermentation, determined by the mass of yeast, and the conditions of their vital activity. The size of carbon dioxide bubbles and their number in the volume are determined by the gas permeability of the dough (according to CO 2), which depends on its structural and mechanical properties.

Gaseous substances, as is known, differ significantly from solids and liquids in their lower density, greater compressibility, and also in the dependence of their volumetric expansion coefficient on temperature. Their presence in the structure of the dough increases the volume, reduces its density, complicates the structure. Elastic-plastic deformations of the fermenting dough occur in the walls of the pores of its structured mass. In order to consider the influence of the gaseous phase on the mechanical properties of the fermenting dough, let us consider the diagram of its structure shown in Fig. 21. In it, surfactants, proteins, lipoids, etc. are schematically shown with round-ended rods. Their rounded part represents the polar, and the straight "tail" - the non-polar group of atoms in the molecule.

The most probable centers for the formation of primary bubbles of CO 2 in the fermenting dough are the points of adhesion of non-polar groups of surfactant molecules bound by the weakest forces of dispersion interactions. The gaseous products formed in the dough during its fermentation (CO 2 and others) dissolve in free water and are adsorbed on the surfaces of hydrophilic polymer molecules. Their excess forms gas bubbles in the fermenting dough. The walls of the bubbles form surfactants. An increase in the amount of gaseous products causes a corresponding increase in the number and volume of gas bubbles, a decrease in the thickness of their walls, as well as a breakthrough of the walls, diffusion and leakage of gas from the dough surface.

This complex process of formation of the fermenting dough structure is naturally accompanied by an increase in the volume of its mass and shear deformations. The accumulation of many bubbles of gaseous products leads to the formation of a foamy fermenting dough structure having double walls formed by surfactants. They are filled with a mass of hydrated hydrophilic substances of the test, associated with the polar groups of surfactants of the walls of the bubbles by secondary chemical bonds. The dough has a significant viscosity and elastic properties, providing its foam structure with sufficient strength and durability, a certain ability to flow and retain gaseous substances (air, steam, carbon dioxide).

Elastic-plastic shear deformations of such a structure as a result of a permanent increase in the volume of gas bubbles and dough lead to a decrease in the thickness of the walls, their rupture and merging (coalescence) of individual bubbles with a decrease in the total volume.

The development of elastic-plastic shear deformations in the mass of dough starting to ferment rapidly, which lowers its density, occurs at corresponding reduced stresses, therefore, the initial moduli of elasticity-shear elasticity and the viscosity of such a dough should not be higher than that of a non-fermenting dough. However, in the process of its fermentation and an increase in the volume, deformation of the spherical walls of its gas pores should be accompanied by the orientation of proteins and other polymers in the direction of shear and flow, the formation of additional intermolecular bonds between them, and an increase in dough viscosity. Decreasing the density of the fermenting dough during fermentation allows proteins to more fully realize their elastic properties - to lower the modulus of elasticity-shear elasticity. With increased viscosity, reduced modulus, the fermenting dough should have a significantly greater ratio of these characteristics, have a more solid system than the non-fermenting one.

Owing to the permanent formation of carbonic acid and the increase in volume in this way, the fermenting dough, in contrast to the non-fermenting one, is a doubly tense system. The gravitational forces of its mass during fermentation are inferior, equal to or greater than the energy of chemical reactions of CO 2 formation, which creates forces that develop and move gas bubbles upwards according to the Stokes law (motion of spherical bodies in a viscous medium). The number and size of gas bubbles in the dough are determined by the energy and rate of yeast fermentation, the structural and mechanical properties of the dough, and its gas permeability.

The size of the carbon dioxide bubble formed during fermentation at any given moment will depend on the balance of its tensile forces.

P=π rp (4.1)

and compressive

P =2π rσ (4.2)

where π, r , R , σ - respectively, the ratio of the circumference to the diameter (3, 14), the radius of the bubble, excess pressure and surface tension.

It follows from the equality conditions for equations (4.1) and (4.2) that

P =2 σ / r (4.3)

Equation (4.3) shows that at the initial moment of formation of a gas bubble, when its dimensions, determined by the radius, are very small, the excess pressure must be significant. As the bubble radius increases, it decreases. Neighborhood of gas bubbles of different radii should be accompanied by CO 2 diffusion through the walls in the direction from higher to lower pressure and its equalization. In the presence of a certain excess pressure and the average size of gas bubbles, it is easy to calculate, knowing the viscosity of the dough, the rate of their rise according to the Stokes law mentioned.

According to this law, the force that lifts gas bubbles is

P =4/3π rg ( ρ - ρ ) (4.4)

overcomes the force of their friction

P =6 prηυ (4.5)

where g is the gravitational constant;

ρ and ρ are the densities of gas and dough;

η-effective structural viscosity of the dough;

υ - the speed of the vertical movement of gas bubbles in the dough

arising in the dough mass when a spherical body (gas bubble) moves in it.

From the equality of equations (4.4) and (4.5) it is easy to determine the value of the velocity

V =2 gr ( ρ - ρ )/9 η (4 .6)

This equation is of great practical importance, making it possible to establish the dependence of the rate of increase in the volume of fermenting dough on its density and viscosity, the size of individual pores, which is also determined by the energy of fermentation of microorganisms. Calculated by the equation, the rate of increase in the volume of wheat dough from flour of grade I with a density of 1.2 with an average pore radius of 1 mm and a viscosity of about 110 4 Pas is about 10 mm/min. Practical observations show that such a dough has an average rise rate of 2 to 7 mm/min. The highest rate is observed in the first hours of fermentation.

If there are neighboring pores in the test, having different sizes and gas pressures, their walls break and the pores merge (coalescence); this phenomenon also depends on the rate of fermentation and the mechanical properties of the dough; apparently, most of the pores of the dough and bread crumb are not closed, open. Due to the phenomena of diffusion of CO 2 through the walls of the pores and their rupture by excess pressure, the fermenting dough loses carbon dioxide with its surface: taking the cost of dry substances (sugar) for the fermentation of the dough, equal to an average of 3% of the mass of flour, with alcoholic fermentation per 1 kg of flour (or 1, 5 kg of bread) releases about 15 g, or about 7.5 liters of CO 2 . This amount at atmospheric pressure is several times greater than the volume of gaseous products in the specified volume of bread and characterizes their loss during the fermentation of the dough.

In the fermenting dough, many other organic acids and alcohols are also formed that can change the solubility of grain compounds. Thus, all of the above shows that the structure of the fermented dough is more complex than that of the non-fermented one. It should differ from the latter in smaller: density, elasticity-elasticity modulus, higher viscosity and η / E (greater ability to retain shape), a permanent increase in volume and acidity during fermentation.

For almost a long time, bakers have characterized the baking properties of fermented dough by its ability to exhibit elastic-elastic deformations after stress relief: “live” (or elastic-elastic) “moving” dough after deformation always gave bread products of good volume, shape and structure of the porosity of the crumb, in contrast from a motionless (plastic) dough, devoid of these properties.

The structure of the fermenting dough, its mechanical properties are mutually dependent on the sugar-forming ability of the flour, as well as the gas-forming and gas-retaining (gas permeability) abilities of the dough. They also depend on the type, age and fermentation ability of microorganisms - fermentation generators.

This is confirmed by the data on the values ​​of gas formation and retention of dough from varietal wheat flour, given in table. 3.10. With equal average gas-forming capacity of wheat flour of the first and second groups, the lower absolute and relative gas-retaining capacity of the dough (and the volumetric yield of bread) of the first is explained by its higher elastic-plastic properties. At the same time, the lower gas-holding capacity of the dough (and the volumetric yield of bread) from the wheats of the third group in comparison with these characteristics of the dough (and bread) from the wheats of the second and first groups can partly be attributed to their lower gas-forming capacity.

Their relative (in % to gas formation) gas-retaining capacity was higher than that of wheat dough of the second and first groups, which can be attributed to the highest content of gluten proteins in wheat of this group. Thus, when considering the gas-holding capacity of the dough and the volumetric yield of bread, it is necessary to take into account not only the mechanical characteristics of the dough, but also the named properties of the flour. It seemed appropriate to investigate and compare the structure of non-fermenting and fermenting dough. The latter is the actual material from which bread products are made from flour of different varieties, differing in physical quality indicators. It was of interest to compare the mechanical properties of non-fermenting and fermenting flour dough. different sort, and also to carry out an approximate normalization of them for the latter.

Structural and mechanical properties of non-fermenting and fermenting dough prepared from two samples of commercial wheat flour I and II varieties are given in table. 3.1 and 4.1.

Table 4.1 Structural and mechanical characteristics of dough made from wheat flour of the 1st grade with a moisture content of 44% Sample number Holding time, h Note. The numerator shows the data on the non-wandering test, the denominator - on the roaming one.

Dough made from grade I wheat flour is a less complex labile structure than dough made from grade II flour: it contains less active hydrolysis processes, contains less sugars and other compounds that change the elastic properties of the structure over time. For this reason, the differences in the structure of the non-fermenting dough made from grade I flour should be the most distinct.

As the results of Table. 4.1, immediately after kneading, the non-fermenting dough of both samples had shear moduli and viscosity, relative plasticity and elasticity were large, and η/E was smaller than that of the fermented dough. After 2 hours of fermentation, the dough viscosity and η/E did not decrease, as in a non-fermenting dough, but, on the contrary, increased, and plasticity decreased. For this reason, the index TO had a negative value, characterizing not liquefaction, but an increase in the viscosity of the structure.

The results of comparing the mechanical properties of non-fermenting and fermenting wheat dough from two samples of grade II flour are given in table. 3.1, basically fully confirm the patterns established for the dough from flour of grade I; however, they are of undoubted interest because the aging process lasted up to 24 hours. It is known that the fermentation of pressed baker's yeast at their usual dosage (about 1% to flour) usually ends at a time interval of 3-4 hours (duration of fermentation of dough) . After this time, the dough is replenished with a fresh portion of flour and mixed, after which the fermentation in it resumes. In the absence of flour additives and mixing, alcoholic fermentation is inferior to acid fermentation. Such a dough, acquiring excessive amounts of ethyl alcohol and acids, dissolves gluten proteins (dilutes), losing carbon dioxide - reduces volume, becomes more dense. From Table. 3.1 it can be seen that the fermented dough after 6 hours and especially after 24 hours of fermentation in terms of shear moduli, viscosity, relative plasticity and elasticity approaches these indicators of non-fermenting dough. This shows that yeast fermentation processes lasting up to 6 hours are the main reason for significant differences in the structure of the fermenting dough from its non-fermenting structure. Experiments have established that samples of fermenting wheat dough made from flour of I and II grades have a structure that has more perfect properties of elasticity-elasticity (lower shear modulus), greater viscosity and dimensional stability (η / E), as well as greater stability over time in comparison with the structure non-fermenting test. The main reason for these differences should be considered the process of alcoholic fermentation of baker's yeast in fermenting dough, the formation of gas-filled pores in it, causing a permanent increase in volume, the development of elastic-plastic deformations, and strengthening of the structure due to the orientation of polymers in shear planes. Acid fermentation in it is less significant and, as shown below, affects these properties by changing the processes of swelling and dissolution of flour compounds.

DEPENDENCE OF THE MECHANICAL PROPERTIES OF THE FEMINATION DOUGH AND THE QUALITY OF THE BREAD ON THE TYPE AND TYPE OF FLOUR

The quality of bread products - their volumetric yield, shape, porosity structure and other characteristics, are determined by the type of flour and are accordingly nominated by GOSTs.

The structure of the fermenting dough is the direct material from which bread products are obtained by heat treatment in an oven. It was of interest to study the biochemical and structural-mechanical properties of fermenting wheat dough depending on the type of flour. For this purpose, seven samples of soft red wheats were ground in a laboratory mill with a three-grade grinding with a total yield of 78% on average. Then we studied the gas-forming and gas-holding ability of flour, the structural and mechanical characteristics of the fermented dough after proofing, as well as raw gluten proteins and their content in flour, the specific volume (in cm GOST 9404-60. The results are shown in table. 4.2. They showed that the yield of high-quality flour, even under conditions of laboratory experimental grinding, fluctuates significantly and the stronger, the higher its grade. Thus, the grain grinding technology should influence the chemical composition and, consequently, the structure of the dough. It is one of the significant numerous factors affecting the quality indicators of flour, dough and bread products.

Table 4.2

Biochemical and structural-mechanical characteristics

gluten proteins of fermented dough and bread

(average data)

Note. The numerator contains data on proteins, in the denominator - on the test.

Technological properties of grain and flour of each grade are characterized primarily by their gas-forming ability. This property characterizes the ability of grain and flour to convert the chemical energy of carbohydrate oxidation into thermal and mechanical energy of the movement of the fermenting dough, overcoming the inertia of its mass. The determination of the gas-forming ability of flour is accompanied by taking into account the amount of released CO 2 . Its amount, delayed by the test, determines it. gas retention by volume increase. This physico-chemical indicator characterizes by its inverse value the gas permeability of the test for carbon dioxide. The latter depends on the structure and magnitude of the main elastic-plastic (E, η, η/E) test characteristics. Experiments have shown that the gas-forming ability of flour increased significantly from the highest to the first and second grades, while the volumetric yield of bread, on the contrary, decreased.

The gas-retaining ability of the dough is directly dependent on the gas-forming ability; despite this, it did not increase in absolute and relative (in % to gas formation) values, but noticeably and regularly decreased with a decrease in the flour grade. There is a close direct relationship between the absolute value of CO retained by the dough and the volumetric characteristics of bread (volume Yield, specific volume). The foregoing allows us to conclude that these characteristics of bread quality are determined mainly not by biochemical, but by physicochemical (gas permeability) and mechanical properties (η, E and η/E) of the dough. The latter depend mainly on the respective properties of the raw gluten proteins and their content in the dough.

Experiments have shown that the content of raw gluten proteins naturally increased with a decrease in grain strength and moisture capacity (viscosity) of flour and its varieties. The protein structure of premium flour had higher shear modulus and, on average, viscosity than the protein structure of grade I flour. This indicates their higher statistical molecular weight. Flour proteins of grade I had a shear modulus and viscosity lower than these characteristics of flour proteins of grade II, but exceeded them in value η/E. This characterizes their great elasticity and dimensional stability.

The gas-holding capacity of the dough and the volumetric yield of bread products directly depend on the duration of the relaxation period for the stresses of gluten proteins and dough, or η/E. The ratio of viscosity to the modulus of gluten proteins of grade II flour was significantly lower than that of proteins of premium and grade I flour.

The gas-holding capacity of dough made from varietal wheat flour depended on the respective values ​​of its shear modulus and viscosity. These characteristics with a decrease in the grade of flour decreased similarly to the ability of gas retention.

It has been established that fermenting flour dough premium moisture content of 44%, like raw gluten proteins of this flour, had the most significant values ​​of shear moduli, viscosity and viscosity-to-modulus ratio, and the lowest relative plasticity. From this test, bread products of the highest porosity, specific volume of molded bread, as well as the ratio of height to diameter of hearth bread were obtained. Thus, despite the significant viscosity, the least gas formation due to the high η / E, dough and bread of high volumetric yield were obtained from this flour. High values ​​of viscosity and η/E contributed to the production of hearth bread with the highest N/A.

Dough made from flour of grade I with a moisture content of 44% in terms of gas retention, mechanical characteristics and bread quality was slightly inferior to the quality of dough made from flour of the highest grade; This indicates that the decrease in the viscosity of the dough made from grade I flour contributed both to the development of the specific volume of the molded bread and to the increase in the spreadability of the hearth bread.

The dough made from grade II flour had a higher moisture content (45%). Despite the greatest gas formation, it was significantly inferior to the dough of the highest and I grades of flour in terms of gas retention and viscosity. The ratio of viscosity to modulus of this test, like that of gluten proteins, was lower, and the relative plasticity was higher than that of the test from flour of the highest and I grades. The quality of the resulting bread products was much lower than the quality of products made from flour of the highest and I grades.

In order to clarify the influence of the structural and mechanical characteristics of the fermenting dough on the physical properties of bread products, we differentiated the results of the experiments into two groups. The first group of samples of each grade had, on average, higher than the arithmetic mean, shear moduli and viscosity, the second group had lower ones. The characteristics of the gas retention of the dough and the elastic-plastic properties of raw gluten proteins were also taken into account (Table 4.3).

Table 4.3

Average characteristics of high and low viscosity dough

From Table. 4.3 it can be seen that the specific volume of bread made from premium flour does not depend on the gas-holding capacity of the dough, which turned out to be almost the same for both groups of samples. The specific volume of bread from flour of I and II grades depended on a slightly higher value of the gas-holding capacity of the dough of the second group of samples. The amount of raw gluten in both groups of samples for all types of flour turned out to be approximately the same and could not affect the quality of bread.

The viscosity of the dough from flour of the highest grade of both groups of samples turned out to be inversely related, and the ratio of viscosity to modulus was in direct proportion to the corresponding indicators of their raw gluten proteins, for dough from flour of I and II varieties of both groups of samples - on the contrary.

From this we can conclude that the main characteristics of the fermenting dough - viscosity and the ratio of viscosity to modulus - depend not only on the corresponding characteristics of gluten proteins, but also on the influence of other grain compounds.

The volumetric yield of the tin bread as well as the H/D of the hearth bread within each of the three types of wheat flour depend on the viscosity and the ratio of the viscosity to the modulus of the fermented dough. Viscosity has an inverse effect on the volumetric yield and a direct effect on the H/D value. The ratio of viscosity to modulus has a direct impact on both of these characteristics of bread quality.

The degree of influence of viscosity and the ratio of viscosity to modulus on the physical and mechanical indicators of the quality of bread can be unequal and mutually directed. It depends both on the value of these characteristics of the dough structure and on the modes of its technological processing. Despite this, the data in Table 4.3 allow us to explain the results obtained not only by the type of flour, but also by the dependence on the values ​​of viscosity and the ratio of viscosity to dough modulus. Thus, a significant difference in the specific volume of pan and H/D hearth bread made from flour of the highest, I or II grades with approximately the same dough viscosity should be explained primarily by the unequal values ​​of their ratios of viscosity to modulus. The results obtained by us allow us to state that the type of grain, ground even according to the same technological scheme, affects the gas retention and structural and mechanical properties of the dough obtained from each type of flour of three-grade grinding. Viscosity and viscosity-to-modulus ratio of fermenting dough made from varietal wheat flour can be used as characteristics that predetermine the physical and mechanical properties of pan and hearth bread. Therefore, it seemed expedient to determine and normalize them for simple test from commercial flour of the main varieties obtained at Moscow enterprises under the conditions of existing technological production modes.

By mass measurements of the elastic-plastic characteristics of the fermented, ready-to-cut dough and statistical processing of the results, the average optimal (M ± δ) values ​​of viscosity and the ratio of viscosity to modulus were established for three varieties of wheat and rye marketable flour (Table 4.4).

Table 4.4

Average optimum viscosity and η/E fermenting dough (D=0.003 s)

	Dough moisture,%
Wheat I grade
peeling

Comparing the data in Table. 4.4. and 3.14, it can be seen that the fermenting dough made from grade I wheat flour has, as in Table. 3.1 and 4.1 are much larger, and rye dough both grades are lower than those of the non-fermenting dough, the values ​​of viscosity and the ratio of viscosity to modulus.

The main reason for the decrease in viscosity and the ratio of viscosity to the modulus of fermented dough from rye wholemeal flour should be considered the dissolution of its compounds by dough acids.

Studies of the effect of lactic acid acidification of non-fermenting dough from three samples of rye wholemeal flour showed that all samples of the acidified (to the norm of fermenting) dough had a lower viscosity and viscosity to modulus ratio than that of the unacidified one. This should be attributed to the partial peptization of swelling proteins and other rye compounds with solutions organic acids.

INFLUENCE OF MODERN METHODS OF TESTING ON THE MECHANICAL PROPERTIES OF THE DOUGH AND THE QUALITY OF BREAD PRODUCTS

PRODUCTS

In recent years, in the USSR and abroad, work has been carried out that has shown the possibility of reducing the consumption of flour and time for the preparation of bread products. This is achieved by using technological schemes, providing for a mechanical effect on the dough and dough, activating their fermentation. Such schemes are based on the use of large liquid (about 70% moisture) or thick (40-50% moisture) doughs.

Liquid sponges have a viscosity that is 1-2 decimal orders lower than thick ones; the latter are difficult to pump up; they are diluted with water after fermentation. It has been established that diluted sourdoughs have a viscosity significantly lower than undiluted ones of the corresponding moisture content; during fermentation, the viscosity of the dough decreases.

Reducing the duration of the fermentation of dough and dough is achieved by a longer intensive effect in the kneading process. At the same time, the amount of gluten proteins washed out of the dough decreases, the content of water-soluble nitrogenous compounds and carbohydrates increases, the attackability of starch by amylase and the fermentation activity of yeast increase. These processes increase the volumetric yield of dough and bread, improve the structure of the porosity of the crumb, the shape of the hearth products.

These characteristics of bread products are also improved by additional machining test in the process of cutting it. However, excessive machining can lead to a deterioration in the physical and mechanical characteristics of products, so its optimization is necessary. As a criterion for the degree of mechanical impact on the dough during kneading, the value of specific work is proposed. It varies depending on the moisture capacity of flour from 12 to 50 J/g.

Based on the foregoing, the following conclusions can be drawn.

The fermenting dough, in contrast to the non-fermenting one, is a more complex doubly strained colloidal dispersed system, which includes a gas phase, which therefore has a reduced density. Its foamy porous mass, continuously forming CO 2 , increases the volume - coalesces due to equalization of the pressure of neighboring pores of various sizes, forming an open structure; in it, according to the Stokes law, the movement of the largest pores upwards to the surface of the dough and the release of carbon dioxide continuously occur. In the process of formation of pores, increase in volume by small stresses and slow shear deformations, the structure of the fermenting dough is elasticized, increases the viscosity and η/E.

Fermented dough made from wheat flour of grades I and II differs from non-fermenting dough in lower shear moduli, relative plasticity (higher elasticity), higher viscosity and viscosity-to-modulus ratio, as well as stability and increase in these characteristics during fermentation after kneading. More significant differences were established for dough made from grade I flour, which has a moisture content lower by 3-4% than dough made from grade II flour, and other chemical composition.

Fermenting dough from rye flour the wallpaper and peeling milling differs from the non-fermenting milling in larger shear moduli, lower viscosity and viscosity-to-modulus ratio. This is due to the influence of a significant concentration of organic acids in it, which partially dissolve swelling proteins and other grain polymers.

Structural and mechanical properties of fermenting wheat dough and raw gluten proteins from flour of the highest, I and II grades, obtained from one grain by three-grade grinding, viscosity, as well as the ratio of viscosity to modulus differ significantly: they determine the gas-retaining ability of the dough, the volumetric yield of the tin, as well as H/D of hearth bread. With a decrease in the flour grade, the viscosity and the ratio of viscosity to the modulus of gluten proteins and the gas retention of the dough, the volumetric yield of bread, its porosity and H / D decrease. The most significant differences in the indicated characteristics of dough, gluten proteins and bread are observed between I and II flour grades.

Within each grade, the viscosity of the fermenting dough has an inverse effect on the development of its volume (gas retention), the volumetric yield of the bread and a direct effect on the H/D of the bread. The ratio of viscosity to dough modulus has a direct effect on both indicators of bread. Grain variety in some cases affects the structural and mechanical properties of the dough from flour of each variety.

The listed properties of the fermenting dough in order to control and manage them, it is advisable to normalize and regulate. As approximate norms for dough made from grade I wheat flour, rye wholemeal and peeled flour, you can use the results of Table 4.4.

THE EFFECT OF HEATING ON THE MECHANICAL PROPERTIES OF THE DOUGH. MECHANICAL PROPERTIES OF BREAD

The process of production of bread products is completed by heating the mass of fermenting dough from 30 to 100°C under conditions of large gradients of heat and mass transfer.

Heat treatment when baking in the specified temperature range, it significantly affects the activity of biochemical processes, changes the conformations of the molecules of the main grain polymers, their hydrophilic properties, as well as the mechanical properties of the dough; the content of free water in the structure decreases, the dough loses its ability to flow under the tension of the gravitational forces of the mass. Then the plastic-elastic structure of the dough turns into an elastic-brittle plastic jelly-like structure of the bread crumb. It should be assumed that its plastic deformations take place mainly at low strain rates due to stress relaxation, and at high rates as a result of brittleness, destruction of the continuity of the walls of the pores of the concentrated protein-starch jelly - crumb in the elastic region. In this regard, when studying the mechanical properties of a bread crumb, one should limit oneself to possibly small values ​​of its deformations and their speeds. Instead of shear deformations, it is advisable to use deformations of uniaxial compression of the porous foamy structure of the crumb.

Heating enhances the thermal movement of the molecules of chemical compounds. In polymer solutions, it reduces the coefficient of internal friction (viscosity). The inverse dependence of the viscosity of polymer solutions on temperature is determined by the well-known empirical Arrhenius equation

η=Ae

where A is a constant depending on the properties of the substance;

e is the base of the natural logarithm;

T is the absolute temperature;

K - gas constant;

E - activation energy (work expended on moving particles).

However, this equation is valid only for solutions of low concentration and provided that there are no significant changes in the shape of polymer molecules. The concentration of the main grain polymers - gluten proteins and starch - in bread dough is very high, and its heat treatment changes the shape of the molecules, as well as the ability of these main grain polymers to interact with the solvent - water. The sizes and shapes of their molecules also change during hydrolysis and fermentation by enzymes of grain and dough microorganisms.

All of these processes can affect the structure, change the mechanical properties of the dough. Therefore, one would expect that the application of the Arrhenius equation for the structure of the dough is valid in a very limited temperature range. The dependence of these dough properties on temperature over a wide range is more complex. Let us consider in more detail its possible influence on these properties: heating the dough during baking and turning it into a bread crumb proceeds in two main stages. In the initial stage of heating the dough to 50-60°C, the enzymatic systems of the dough are activated, the content of water-soluble compounds in it increases, which can plasticize the structure and, simultaneously with an increase in molecular-thermal movement, reduce viscosity, enhance its adhesive properties. At this stage, the main processes of bread baking also begin: starch gelatinization and denaturation of grain proteins, which proceed most actively and end in the second, final stage of heating the dough from 60 to 100 ° C, when its enzyme systems are also inactivated.

With increased mechanical action, the structural and mechanical properties of the dough change. The properties of the dough were characterized by the consistency of Kt on a penetrometer, on an alveograph, and the viscosity was determined on a Tolstoy-Nikolaev device. The duration of the control dough kneading was 5 minutes, with enhanced mechanical processing 30 minutes. The dough was examined after kneading and before cutting (Table 22).

With an increase in the duration of the dough kneading, its structure is weakened. After a long kneading, the dough consistency indicator Kt increases, and the viscosity of the dough decreases. The elasticity, extensibility and magnitude of the dough deformation force, determined on the alveograph, decrease (Fig. 13).

Strengthening the mechanical impact on the dough reduces its viscosity and increases its ability to stretch. At the same time, the dough can significantly increase in volume during proofing and baking, becomes elastic, extensible, and its gas-holding capacity increases.
At the end of intensive kneading, the dough becomes noticeably lighter than with slow and incomplete kneading, which is explained by the capture of air during kneading, its inclusion in the dough and subsequent oxidation of the coloring flour pigments.
Intensive kneading of the dough for 7 minutes destroys about 31% of flour pigments. With increased mechanical processing of the dough, aeration of its components occurs, which affects the redox system of flour. After an appropriate fermentation time, dough with an increased degree of mechanical processing has more elastic properties compared to dough without processing.
During the fermentation of the dough with enhanced mechanical processing, the process of its liquefaction is inhibited (it is assumed that due to the partial restoration of the structure). An important role in this is played by oxidative processes that contribute to the "crosslinking" of protein macromolecules by cross disulfide and other bonds.
With an increase in the intensity of processing, the sorption of water? dough increases and with an increase in dough moisture by 1-1.5%, it has the same structural and mechanical properties as with conventional kneading. This is confirmed by the determination of the structural-mechanical properties of the dough according to the ultimate shear stress τ (in Pa) with an increase in the duration of mechanical processing of the dough from 6 to 20 minutes. It is assumed that with the intensification of dough processing, globules of gluten proteins unfold more fully and their hydration capacity increases.
In order to explain the increased water absorption capacity of the dough during its enhanced mechanical processing, the sorption properties of the dough were studied at different ways batch. The physicochemical properties were compared yeast-free dough, which was kneaded in the L-106 machine for 6 and 20 minutes at 70 rpm and in a rotary type machine at 1400 rpm for 3-5 s.
The drying rate of dough samples was determined on a Mac-Ben adsorption-vacuum installation with continuous steam evacuation and the desorption of water vapor by samples dried in vacuum and then moistened to constant weight.
It has been established that enhanced mechanical processing of the dough accelerates its drying and it quickly reaches a constant mass.
Homogenization of the dough (dough of rotational and 20-minute kneading) with enhanced mechanical processing helps to accelerate the removal of moisture during drying - the drying speed increases. The drying rate increases with the increase in the porosity of the dried samples. The pore volume is 104% for the 20-minute test, 94% for the rotary test, and 86% dry matter for the conventional sample.
When analyzing the desorption isotherms, it was found that in the equilibrium desorption process, the water-holding capacity of the dough increases with increasing mechanical processing of the dough, i.e., the binding energy of moisture increases.
On the basis of experiments, it is noted that an increase in the degree of mechanical processing of the dough contributes to an increase in the amount of water firmly associated with the dough, which improves its structural and mechanical properties, and hence the quality of the bread.
Protein substances of the test. During kneading, protein substances undergo certain changes as a result of their peptization, as well as under the action of flour enzymes.
To study the protein part of the dough with increasing mechanical impact on it, the quantity and quality of the washed gluten and the amount of water-soluble nitrogen were determined (Table 23).

The hydration capacity of dough gluten increases with additional mechanical processing. This is reflected in its structural and mechanical properties: the duration of extrusion according to the plastometer decreased by 22 s, and the specific extensibility increased by 1.5 times.
Immediately after kneading with enhanced mechanical processing, the dough had 3.7% less washed off gluten than the dough kneaded for 5 minutes. The amount of water-soluble nitrogen, on the contrary, was higher.
These data show that in heavily processed dough, the formation and maturation processes to a large extent occur already during the mechanical processing period, which can help to reduce the dough preparation time.
During dough fermentation, the amount of washed gluten decreases both in the control dough and in the dough with additional mechanical processing.
Before planting in the oven, the amount of gluten washed out from the control dough decreased by 30.8% compared to the amount of flour gluten, and from the dough with enhanced mechanical processing - by 39.9%. This indicates a more intensive process of changing protein substances in the dough with enhanced mechanical processing.
The amount of water-soluble nitrogen in the control test increased by 60.6% in relation to the water-soluble nitrogen of flour, and in the test with enhanced mechanical processing - by 72.7%.
Diagrams of the decrease in the amount of washed gluten and the increase in the amount of water-soluble nitrogen in the dough before placing in the oven are shown in fig. 14 and 15.

KN Chizhova found that the readiness of wheat dough can be characterized by a certain degree of reduction in the content of washed gluten and an increase in the amount of water-soluble nitrogen. Additional processing of the dough causes deeper changes in protein substances, which helps to accelerate its maturation.
The state of gluten proteins in the dough changes under the influence of various factors. At the same time, the state of the flour proteins themselves and their changes in the process of preparing the dough under the influence of accumulating acids and proteolytic enzymes are important.
To study changes in gluten under the action of acids and enzymes during enhanced mechanical processing of the dough, it was exposed to 0.005 N. lactic acid and investigated its attackability by the protsolytic enzyme papain (Table 24).

As the mechanical processing of gluten intensifies, its solubility in lactic acid changes: when the dough is kneaded for 5 minutes, 20% of the gluten dissolves, and when the kneading time is increased to 30 minutes, approximately 40%.
Experiments with the addition of papain also show that the attackability of gluten increases with an increase in the degree of its mechanical processing. In a comparative assessment of the dough kneading in a bowl mixer and in a vibratory mixer, it was found that when the dough is exposed to the vibratory mixer for 2 minutes, the solubility of the protein in 0.05 M. acetic acid rises in the same way as with a 15-minute dough kneading in a bowl mixer. Increasing the duration of dough processing on a vibratory mixer to 15 minutes increases the solubility of proteins more than a 45-minute batch in a conventional type dough mixer. The protein substances of the dough were studied by gel filtration on Sephadex G-100. When separating the protein substances of the dough, four fractions were obtained. An analysis of the chromatograms showed that an increase in the duration of the dough kneading increases the percentage of the first and second high-molecular fractions. It is believed that the first fraction characterizes proteins with a molecular weight of more than 150,000, corresponding to glutenin, the second fraction - proteins with a molecular weight of about 100,000 and corresponds to a mixture of molecular glutenin with gliadin. The third and fourth fractions correspond to albumins and globulins.
Transformation of gluten protein during kneading is associated with stretching and breaking it with the formation of thin films of gluten, which are cleaved by breaking non-covalent bonds - hydrogen, hydrophobic and salt bridges, as well as by breaking dpsulfide bonds between peptide chains.
Dough carbohydrates. Intensive mechanical processing of the dough leads to a change in starch grains, increases their attack by flour amylases, which increases the content of water-soluble carbohydrates, including sugars.
Dough carbohydrates were characterized by the content of directly reducing sugars and water-soluble carbohydrates. reducing after hydrolysis for 3 hours (Table 25).

As the mechanical impact on the dough increases, the amount of sugars in it increases.
When kneading a non-fermenting dough a for 30 minutes, the content of directly reducing sugars increases compared to the control test (kneading time 5 minutes) by 18%, water-soluble carbohydrates that restore after a three-hour hydrolysis - by 27%
When a non-fermenting dough rests under the action of flour amylases, the increase in water-soluble carbohydrates continues. In bread baked from such a dough, an increased content of sugars is observed compared to their amount in a dough with conventional processing. In the fermenting dough, the amount of water-soluble carbohydrates before placing in the oven is quite close both in the sample without processing and in the dough with enhanced mechanical processing. This can be explained by the large consumption of sugars during the fermentation period of the dough with an increased degree of mechanical processing, which is confirmed by the data on determining the gas-forming ability of the dough and the volume of bread.

Studies of the influence of the degree of mechanical processing of dough on its gas-forming and gas-retaining ability on samples of wheat flour of grade I with medium strength gluten and sugar-forming ability of 275 and 204 mg of maltose per 10 g of flour (Table 26 and Fig. 16) show that enhanced mechanical processing of dough (kneading time 30 minutes) increases gas formation, determined during the proofing period, by 14-21% compared to the control test (kneading time 5 minutes). This is important when processing flour with a low sugar-forming capacity (204 mg of maltose per 10 g of flour).

An increase in the gas-forming ability of the dough during enhanced mechanical processing is associated with the accumulation in it of water-soluble carbohydrates and disaggregation products of protein substances, which are nutrition for yeast.
These changes in the dough contribute to the production of bread with a larger volume, with a finer and more uniform porosity, with a tender and elastic crumb.
When studying the effect of enhanced mechanical processing of dough on the degree of staleness of bread ( sliced ​​loaves weighing 0.4 kg from wheat flour of grade I) baked at the experimental bakery VNIIKhPa, it was found that the indicators characterizing the freshness of products from this dough change compared to the control. The compressibility and viscosity of the loaf crumb suspension after 3, 24 and 48 hours of storage is higher for bread, the dough for which is kneaded for a longer time (Table 27 and Fig. 17).

The viscosity of the crumb suspension decreased as the loaves were stored, but was higher for loaves from dough that was kneaded for a longer time (see Fig. 17).
Data organoleptic evaluation show that loaves from dough with a longer kneading time (20 min) from the very beginning (after 3 hours) had a more delicate, soft crumb than loaves baked from dough with a kneading time of 4.5 min. The difference in the state of the crumb remains throughout the entire storage period (within 48 hours). These data show that an increase in the degree of mechanical processing of the dough leads to an improvement in the quality of bread and helps to slow down the process of its staleness.

Increasing the intensity of dough kneading for new Ukrainian rye-wheat bread with a ratio of medium and II grade flour of 60:40% also slows down its changes during storage. At the same time, the accumulation of volatile carbonyl compounds, which determine the aroma of bread, is observed.