Methodology of instrumental control of bakery crumb characteristics

. The article uses a comprehensive approach to instrumental control of the parameters of the texture of the crumb of bakery products: hardness, hardness index, elasticity, strength, cohesion, as well as the amount of mechanical energy expended during the deformation of the crumb sample. Measured texture indicators allow you to evaluate the degree of staleness and the rate of staleness of bakery products during storage. The use of the texture analyzer "Strukturometr ST-2" makes it possible to control the hardness of the crumb, its strength and cohesion by methods of reversible and irreversible deformation. When using reversible deformation, the relative change in the height of the crumb sample occurs within 25%, and when using irreversible - 75-80%. A dimensionless cohesion criterion has been developed, which is the result of division of the amount of mechanical energy spent on the plastic deformation of the crumb during secondary compression by the amount of mechanical energy spent on the plastic deformation of the crumb during primary compression. Such cyclic pressure on the crumb simulates the determination by the taster of cohesive properties during chewing.


Introduction
Bakery products are mainly classified as products with a limited shelf life, with the exception of products with a moisture content of less than 19%. These are crackers, dryers, sticks, straws and other products that belong to canned bread. After baking, physical and colloidal processes occur in bakery products due to cooling, drying and redistribution of moisture from the center of the crumb to the crust of the product. When the temperature in the center of the crumb reduces to 28-30°C, the bread is packaged, which at the initial stage slows down the shrinkage process, and then the process of staleness, due to the retrogradation of starch -its transition from an amorphous state to a crystalline one.
According to existing standards, the quality control of bakery products after baking and during storage is carried out according to organoleptic and physico-chemical indicators.
In the organoleptic evaluation, indicators are determined that characterize: the external appearance of products (marketable condition); the state of the crumb; the internal state of the structure; taste and smell.
From the physical and chemical indicators of the quality of all types of bakery products, the following are determined: humidity, titratable acidity and porosity; the content of sugar and fat in terms of dry matter (for rich bakery products, which recepie includes white sugar and fat products); mass fraction of the filling, % to the mass of the product (for rich products with fillings); wetness (for crackers, baranka-type products and other types of products with a moisture content of less than 19%); the content of salt, iodine, sorbitol, protein and other substances (for dietary products, in particular salt for achloride bakery products).
When organoleptically determining the quality of bakery products, a complex integral assessment is used, which includes the determination of the structural and mechanical characteristics of the crumb under: pressure; biting off; chewing and swallowing. When pressed, the following are evaluated: hardness and elasticity of the crumb; when bitinghardness, strength and brittleness (for certain types of bakery products); when chewing, the characteristics of the further destruction of the product are determined -hardness, strength, fragility and structuring of the chewed mass -wetting, stickiness, lumpiness; when swallowed, the rheological behavior of the viscous-plastic mass after chewing is evaluatedplasticity and then elastic aftereffect when swallowed. This assessment is carried out close to those indicators recommended by the international standard ISO 11036-2017 [1].
For instrumental control of the rheological properties of food products under various types of deformation effects in order to objectively assess the texture indicators, penetrometers and texture analyzers are used. The development of this direction for assessing the quality of bakery products is associated with an increase in the number of controlled texture indicators, which are elements of a unified system for the integral assessment of the rheological behavior of the crumb. This approach makes it possible to more accurately and comprehensively assess the course of structural changes in the crumb of bakery products after their baking, due to changes in the properties of polysaccharides and protein substances of bread, and to establish a rational duration for the sale and storage of finished products.
Recently, to measure the structural and mechanical characteristics of the crumb, instruments are used -texture analyzers, which include the ST-2 Structurometer, manufactured in Russia (Fig. 1). It comes with various types of indenters and accessories that allow you to control the rheological behavior of virtually all food products. Fig. 1. Information-measuring system for determining the indicators of the texture of the crumb of bakery products, which includes "Strukturometr ST-2" "Strukturometr ST-2" allows you to determine the deformation characteristics -general, elastic and plastic deformation, work of plastic deformation, stiffness, ultimate strength, modulus of elasticity, ultimate loading force, adhesive stress, ultimate shear stress, viscosity, duration of stress relaxation, elastic aftereffect, loss of elasticity, strength, hardness and other indicators, as well as to study the dynamics and kinetics of the rheological behavior of food media according to the measured conditional and classical rheological characteristics using various loading methods and modes. The operation of the device is based on two main methods of loading the object of measurement: by setting the strain rate (mm/s) or the loading rate of the food medium (G/s).
The purpose of this work is to develop a methodology for instrumental control of the parameters of the texture of the crumb of bakery products using the ST-2 Structurometer device.

Materials and Methods
An analysis of the methods for organoleptic evaluation of texture indicators given in the ISO 11036-2017 standard: hardness, elasticity, cohesion, strength, chewability and stickiness shows that they are determined using the methods of reversible and irreversible deformation of the crumb both with single and repeated (cyclic) deformation impact on its sample [1,2,3].
At the same time, it should be noted that the single or multiple deformation of a crumb sample, based on a controlled indicator, can be carried out by choosing a tactile effect mode by the taster, while ensuring constant either the speed of movement of the fingers of the palm or jaws, or the speed of loading by them when the sample is compressed. The choice of the loading mode is due to the hardness of the product, which is designed to provide the necessary relaxation of the resulting stress and eliminate excessive physical exertion and discomfort when biting and chewing [4,5].
Therefore, the formed instrumental methodology for monitoring the parameters of the texture of the crumb of bakery products, using the texture analyzer "Structurometer ST-2", provides for the use of reversible and irreversible deformation of the crumb, a specially prepared sample of it in the form of a cylinder with a diameter of 36 mm and a height of 20 mm, which is subjected to one or two deformation effects with the ability to select the required loading mode [6].
When using reversible deformation, the relative change in the height of the crumb sample occurs within 25% [1], and when using irreversible deformation, it is 75-80% [6].
Reversible deformation makes it possible to determine the hardness of the crumb and its elasticity [7]. Irreversible deformation is the most informative, since the kinetics of changes in the loading force of the crumb sample makes it possible to determine both the hardness and strength of the crumb. Cyclic exposure reveals the cohesive properties of the crumb -the connectivity of its porous structure.
Preparation of a crumb sample in the form of a cylinder, unlike a slice, makes it possible to eliminate the influence of the variability of the distance from the crust of a slice of bread to the edge of the indenter and increase the convergence and reproducibility of the results obtained, and also, which is very important, to establish the density or porosity of the analyzed sample (when weighing it with known volume), which can be used in the calculation of the integral relative indicators of the texture, predetermining the objectivity and information content of the control being carried out.
The procedure for preparing crumb samples for determining texture indicators is as follows. In advance, but not earlier than 5 hours after baking, according to GOST 5667-65, a representative sample of the investigated bakery product is selected from the batch, so that 12 hours after its baking, the determination procedure begins.
A representative sample must contain at least 3 products to carry out one procedure for determining the structural and mechanical characteristics of the crumb. The total number of products is set taking into account the number of determination procedures, i.e. taking into account the duration of storage of products after baking. The first determination procedure is carried out after 12 hours of storage of the product after baking, and subsequent procedures -every 24 hours during the shelf life or long shelf life of products, depending on the tasks being solved.
The products removed from the package are cut with a slicer into slices 20 mm thick, and then six slices are removed from the central part, and the remaining slices and crusts are removed. One cylindrical sample is cut out from the center of each slice using a cylindrical probe. From one product, six cylindrical samples are obtained with dimensions: diameter dc=36 mm; height hc=20 mm and volume 20.36 cm 3 . When carrying out one determination procedure, 18 pcs. cylindrical samples are taken. Fig. 2 shows the preparation of a sample of a cylindrical crumb for a sliced loaf. The moisture content of the crumb is determined by the gravimetric method using the K.N. Chizhova "PCh-MTST" or moisture meter "Glutork 2020" by Perten-Instruments (Sweden). A cylindrical sample of the crumb is cut in half (two samples 10 mm thick are obtained), weighed, placed on the lower plate of the device and pressed with the upper plate. Drying takes place within 5 minutes at a temperature of 160ºС.
When using texture analyzers, which are part of the information-measuring system, it became possible to visualize the deformation behavior of the crumb when determining its texture indicators. As a result of the tests, the kinetics of the loading force (Fl, G) is established for reversible ( Fig. 3, a) and irreversible deformations ( Fig. 3, b) of the crumb of bakery products, which are then subjected to mathematical processing.  Fig. 3. it can be seen that the curves consist of two sections: the loading section and the unloading section. When the material is loaded at a constant strain rate, the force on the indenter increases unevenly. When using the reversible deformation method (Fig. 3, a) at the beginning of the process, the rate of change of the loading force is greater than at the end, and when using the irreversible deformation method (Fig. 3, b), at the beginning, the force rate increases, then decreases, and then is growing again. Such rheological behavior of the crumb of bakery products is typical for capillary-porous materials, which manifest themselves as non-linear elastic bodies.

Results and Discussion
Determination of crumb texture parameters using the reversible deformation method.

3.1
Determination of the structural and mechanical characteristics of the crumb of bakery products is demonstrated on the example of the analysis of sliced loaves of wheat baking flour of the highest grade, weighing 0.4 kg, stored from 12 to 108 hours after baking.
Monitoring of the structural and mechanical properties of the sliced loaf crumb is carried out as follows. From a batch of manufactured and packaged sliced loaves, 18 products are selected, which time spent in transit was within 5-6 hours. Then the products are delivered to the laboratory and analyzed after 12 hours from the moment they leave the oven. For one procedure, three products are taken. The remaining fifteen in packaged state are placed in storage, and are then analyzed three products daily, for 4 days with 24-hour separation.
Preparation of product crumb samples for analysis. The product is cut into slices using a slicer and six slices are taken from the central part of the loaf and subjected to analysis (the remaining slices to the right and left of them, along with the fritters, are removed). Cylindrical crumb samples with a diameter of 36 mm and a volume of 20.36 cm 3 are cut out from the selected six slices with a thickness of 20 mm using a probe. Thus, six cylinders are obtained from one loaf. Chunks for analysis from a sliced product are used gradually so that they do not weather. The application of the loading force to the resulting cylindrical samples of the crumb during compression is carried out from the center of the product towards the tops.
The operation algorithm of the "Structurometer ST-2" in determining the texture parameters of the sliced loaf crumb in accordance with the implementation of the reversible deformation method [8]: 1. Moving the indenter "Piston Ø49" with a movement speed of 0.5 mm/s down to contact with the crumb breakdown with a force of Fcontact = 10 G; 2. Compression of the crumb sample using the indenter "Piston Ø49" with a movement speed of 0.5 mm/s by the amount of total deformation h= 5 mm; 3. Reverse movement of the indenter "Piston Ø49" with a movement speed of 0.5 mm/s to the final force Ffinal = 10 G; 4. Return of the indenter "Piston Ø49" to the base point at a speed of 3 mm/s.   Fig. 4 it can be seen that the loading force (Fl, G) during crumb compression varies in different ways, depending on the duration of storage of sliced loaves after baking. When storing products for 12 hours, the measured indicator Fl changes almost according to a linear law, and then a break appears on the curves, which is a consequence of the different rheological behavior of the porous structure of the crumb. The loading force corresponding to the compression of a cylindrical crumb sample by 5 mm is taken as the crumb hardness index Fh in units of gram-force (G).  fig. 4 and 5, it can be seen that the change in the hardness index Fh during the storage of a sliced loaf for 108 hours ranged from 134 G to 647 G.
Further, a complete mathematical processing of the obtained experimental data is carried out and the values of physicochemical, including structural and mechanical characteristics are established, which are given in Table. 1: • Crumb hardness, Fh (G) -the loading force Fl, (G) on the indenter "Piston Ø49", corresponding to the compression of the crumb by 5 mm (25% of the height of the crumb sample).
• Hardness index, Ih, (G/[(g/cm 3 ) %]) calculated by the formula: where: pc is the crumb density, g/cm 3 ; Wc is the moisture content of the crumb, %. • Crumb elasticity ∆h: ∆h = helastic / htotal (2) where: helasticelastic and htotal -total deformation, mm; • Relative deformation εquotient of the crumb deformation htotal, mm divided by the crumb cylinder height H, mm: • The stress created during crumb compression σ (Pa) is the quotient of the division of the loading force Fl (N) by the area of the crumb cylinder Sc (м 2 ): • The elastic modulus of the interstitial walls Е I (Pa), the quotient of the division of the stress in the first section ∆σ I (Pa) by the relative deformation ∆ε I : • Elastic modulus of a porous structure, E II (Pa) quotient of the division of the stress at the second site ∆σ II (Pa) by the relative deformation ∆ε II : • The total amount of specific mechanical energy Atotal (J/g) spent on compressing the crumb to the value htotal = 5 мм: where: gc -is the mass of the crumb sample, g.
• The amount of specific mechanical energy Aelastic (J/g) associated with the restoration of the crumb structure due to elastic deformation during the reverse movement of the indenter to the final force of 10 G in position helastic: • The amount of specific mechanical energy Aplastic (J/g), which leads to a change in the crumb structure due to plastic deformation: • The rate of staling Vcr, G/24h: An objective classical rheological characteristic reflecting the deformation behavior of the crumb during compression is the modulus of elasticity. To determine it, a graph of the dependence of the stress change σ on the relative deformation ε is plotted (Fig. 6). As can be seen from Fig. 6, on the curve of stress change during crumb compression, two linear sections are clearly visible during storage of bread in the range from 36 to 108 hours of storage. The first section ∆ε I is in the range of values of relative deformation ε = 0.025-0.075, the second section ∆ε II -in the range of 0.15-0.25. The slope of each linear section to the abscissa axis visually characterizes the current modulus of elasticity.
The modulus of elasticity of the crumb in the first segment Е I reflects the rheological behavior of the interpore walls, which exhibit their properties at the initial stage, when the pores of the upper layer of the crumb were cut with a slicer knife when preparing a cylindrical sample of the crumb, and in the second segment, the modulus of elasticity Е II reflects the deformation behavior of the undisturbed porous structure of the crumb, further from the surface.
For the complete formation of the texture profile of the crumb of a bakery product, such integral characteristics of the crumb were established as the total amount of specific mechanical energy expended in compressing the sample by 25% of its height, the amount of specific mechanical energy leading to a change in the structure of the crumb due to plastic deformation and the amount of specific mechanical energy associated with the restoration of the crumb structure due to elastic deformation.
From the data presented in table. 1, it can be seen that the crumb staling rate Vcr, which is determined within 3 days of storage after baking (during the shelf life), was 134 G/day. The rate of staleness in this case is determined from the moment the process of starch retrogradation begins, i.e. 12 hours after baking (or 0.5 days of storage) up to 84 hours of storage -this is in the range of changes in the hardness index from 134 to 535G.
On fig. Figure 7 shows the dynamics of changes in hardness indices Fh and hardness index Ih of sliced loaf crumb during storage.  Fig. 7 it can be seen that the rate of change in the hardness and hardness index of the sliced loaf crumb in the first day of storage is greater than in the subsequent time -this can be seen from the angle of inclination of the corresponding sections of the curves (from 12 to 36 h) to the abscissa axis.
The values of the hardness index Ih are used to assess the degree of staleness of bakery products in accordance with the requirements of GOST 70085-2022 "Baking products from wheat flour". 4 Method for determining the degree of callousness.

Determination of crumb texture indices using the irreversible deformation method.
After an objective determination of the texture of the crumb using the method of reversible deformation, similar to the organoleptic assessment by a person when touched and pressed, it is necessary to have an instrumental method for controlling the strength of its capillaryporous structure, which can be established by compressing a cylindrical sample to a nonporous state. Irreversible deformation in this case can be 75% or more of the height of the prepared crumb sample.
Preparation of the crumb sample is carried out in the same way. The difference is that after weighing, the crumb cylinder is inserted into a fluoroplastic ring with an inner diameter of 36 mm. The ring is installed on the table of the device under the indenter "Cylinder Ø36", also made of fluoroplastic, the use of which makes it possible to exclude the occurrence of adhesive stress during crumb compression (Fig. 8.).

Fig. 8. Cylindrical crumb sample of known mass and volume, placed in a PTFE ring and compressed by a PTFE indenter "Cylinder Ø36"
The fluoroplastic ring is used so that when the crumb is significantly compressed, its area does not change. In this case, the value of the irreversible total deformation (htotal) is set taking into account the porosity of the controlled cylindrical sample of the crumb. Methodically, this happens in the following way. A cylindrical sample of the crumb gc, g with a height of Hc = 20 mm and a volume of Vc = 20.36 cm 3 is weighed and its porosity Pm, %, is calculated in accordance with the requirements of GOST 5669-96, and then the crumb deformation value (mm) is set during its compression: This methodological approach ensures that the crumb is compressed to a constant density of 1.31 g/cm 3 . In this case, the controlled loading force, which ensures obtaining such a density, is taken as an indicator of the strength of the crumb Fs, G.
The algorithm of operation of the device "Strukturometr ST-2" in determining the indicators of the texture of the crumb in accordance with the implementation of the method of its irreversible deformation: 1. Moving the indenter "Cylinder Ø36" with a movement speed of 0.5 mm/s, down to contact with the crumb breakdown, with a force of Fcontact = 10 G.
2. Compression of the crumb sample using the indenter "Cylinder Ø36" with a movement speed of 0.5 mm/s by the amount of deformation htotal, corresponding to the nonporous crumb density equal to 1.31 g/cm 3 for bakery products made of wheat flour and 1.26 g/cm 3for bakery products made of rye flour 3. Reversible movement of the indenter "Cylinder Ø36" with a movement speed of 0.5 mm/s to the final force Ffinal = 10 G.
4. Return of the indenter "Cylinder Ø36" to the base point with a movement speed of 3 mm/s. Fig. 9 shows a characteristic curve of the change in the loading force during compression of the crumb of a sliced loaf to a non-porous state. Fig. 9. Kinetics of the change in the loading force of the crumb when its structure is compressed to a density of 1.31g/cm 3 This method allows you to additionally determine the following parameters of the crumb texture ( Table 2): • Fs, Gcrumb strengthloading force (Fl, G) on the indenter "Cylinder Ø36", corresponding to crumb compression to a density of 1.31 g/cm 3 ; • E III , Pathe hardening modulus of the nonporous crumb in the III section (Fig. 9), the quotient of the division of the stress in the third section (∆σ III , Pa) by the relative deformation (∆ε III ): • A III total, J/g -the amount of energy spent on compressing the crumb to a density of 1.31 g/cm 3 ; On Fig. 10 shows the families of curves for changing the average values of the loading force during compression of a cylindrical sample of the crumb of a sliced loaf when using the irreversible deformation method for products with different storage periods after baking: 12; 36; 60; 84 and 108h. Fig. 10. The kinetics of the loading force on the indenter "Cylinder Ø36" during compression, to a nonporous state, the crumb of sliced loaves with different storage times after baking: 12; 36; 60; 84 and 108 hours Presented in Fig. 10 curves make it possible to determine texture parameters associated with the crumb deformation of 5 mm and with the deformation corresponding to the pore-free structure of the crumb under compression, i.e. at a density of 1.31g/cm 3 . The obtained indicators are summarized in table. 2. From Table. 2 it can be seen that the products have an increased rate of crumb staling, which is 155 G/day. The initial value of the hardness index is 21 units. The change in the crumb strength index occurs from 4174G to 6055G, while it should be noted that the curve of this indicator on the 3rd day has an extreme value equal to 6087G, which marks the end of the hardening process. Large initial value of the hardness index 21 units. and the high value of the rate of staling 155G/day may indicate a low autolytic activity of the flour's own amylases, i.e. about the low depth of starch hydrolysis, which led to a high rate of its retrogradation.
On Fig. 11 shows graphs of changes in indicators: hardness index (Ih, G/[(g/cm 3 ) • %]) and strength (Fs, G) of the sliced loaf crumb during storage for 108 hours.  Fig. 11 it can be seen that with a general trend towards an increase in the crumb texture indicators: hardness and strength during storage of sliced loaves for 108 hours, the crumb strength indicator more clearly demonstrates the end of the product shelf life by reducing its value after the extreme point "a", when the process of retrogradation of starch grains makes the crumb more "brittle".
The statistical characteristics of the fundamental indicators of texture -hardness (Fh) and strength (Fs) of the sliced loaf crumb obtained after mathematical processing are given in Table. 3. Thus, the method for controlling the crumb texture index -strength, based on the irreversible deformation of its cylindrical sample, placed in a ring and compressed to a nonporous state, corresponding to the density of the crumb from wheat flour for bakery products 1.31 g/cm 3 and for bakery products from rye flour and its mixture with wheat -1.26g/cm 3 makes it possible to assess the strength of the crumb, as tasters do in sensory organoleptic evaluation by squeezing the crumb with molars until they close.
The implementation of the irreversible deformation mode makes it possible to determine the following indicators of the crumb texture: Fh -hardness, Ih -hardness index; E I , E II and E IIIare moduli of elasticity and hardening at different stages of compression of the crumb of the curve; Fs -strength; A I total, A II total -the amount of specific mechanical energy expended in determining the hardness and strength indicators, respectively.

Determination of crumb texture indices using the reversible deformation method with cyclic (two-fold) sample compression
The method for determining the texture indices of the crumb of bakery products by double compression simulates the organoleptic assessment of the structural and mechanical properties of the crumb during chewing, when the crumb is subjected to repeated compression. In this regard, a family of compression diagrams for a cylindrical sample of the crumb of a sliced loaf subjected to a seven-fold impact was obtained (Fig. 12).

Fig. 12.
Kinetics of change in the loading force during cyclic -sevenfold compression (1c -7c) of a cylindrical sample of the crumb of a sliced loaf From Fig. 12 (a and b) it can be seen that the greatest difference between the crumb compression curves is observed between the first and second compression of the cylindrical sample. Further, with subsequent compressions, this difference grows insignificantly. Since during the cyclic compression of the crumb before each subsequent measurement there is a pause for 180 s to relax the mechanical stress, the implementation of such a seven-cycle technique will take a lot of time and the technique in this case becomes quite routine. In order to increase the efficiency of assessing the indicators of the texture of the crumb, only a twofold compression of the cylindrical sample is used.
Algorithm of movement of the indenter during the implementation of two cycles of loading a cylindrical sample of the crumb with a pause between them equal to 180 s.
1. Moving the indenter "Piston Ø49" at a speed of 0.5 mm/s down to contact with the crumb sample with a force Fcontact =10 G.
2. Compressing the crumb sample with the help of the "Piston Ø49" indenter at a speed of 0.5 mm / s by the amount of deformation htotal = 5 mm 3. Reverse movement of the indenter "Piston Ø49" with a speed of 0.5 mm/s until the final force Ffinal =10 G.
4. Return of the indenter "Piston Ø49" to the base point with a movement speed of 3 mm/s. Fig. 13 shows the characteristic curves of changes in the loading force of the crumb of sliced loaves with double (1 c and 2 c) compression of the crumb.  fig. 13 shows the different rheological behavior of the crumb during the first and repeated compression, which manifests itself with a different amount of mechanical energy expended on the deformation of the crumb. When re-compressing the crumb, as can be seen, less energy is expended. This can be explained by the loss of elasticity of its capillary-porous structure after the first compression.
This phenomenon was used to develop a dimensionless cohesion criterion (Dcoh), which reflects the degree of hardness of bakery products during storage, which is the quotient of the amount of mechanical energy (A II plastic) spent on plastic deformation during recompression (2c) divided by the amount of mechanical energy (A I plastic) spent on plastic deformation during the first compression (1c):  From Fig. 14 and Fig. 15 it can be seen that during repeated compression of the cylindrical sample of the crumb, a different character of the change in the loading force during compression of the crumb sample is observed, due to the loss of elasticity of the crumb during its repeated compression, which predetermines a smaller amount of mechanical energy expended in compressing the crumb by the same value.
Physico-chemical characteristics of the crumb, established during the first and repeated compression are given in table. 4.  Table. 4 it can be seen that the change in the hardness index (Ih) of the sliced loaf crumb during three days of storage ranged from 22 to 58 G/[(g/cm 3 )•%], and the dimensionless criterion -the cohesion criterion (Dcoh) -from 0.87 to 0 .57. The indicator (∆Аtotal) -the difference between the amount of mechanical energy (А І total) expended on the deformation of the crumb in the first cycle and the amount of mechanical energy (А ІІ total) -in the second cycle, increased depending on the duration of storage of a sliced loaf by more than 17 times -from 0.127 to 2.255 J/g × E -3 . The dynamics of this indicator is shown in Fig. 16.  Fig. 16. Influence of the duration of storage of a sliced loaf on the change in the difference in mechanical energy spent on compressing the crumb between the 1st and 2nd deformation cycle On fig. 16 there is an inflection point "a", corresponding to a shelf life of 72 hours and reflecting the completion of the process of staling the crumb.
On fig. 17 shows graphs of changes in the hardness index (Ih, G/[(g/cm 3 )•%]) and cohesion criterion (Dcoh) of the sliced loaf crumb during storage for 108 hours.  Fig. 17 shows that the dimensionless crumb cohesion criterion is the most informative indicator of the state of the crumb structure. On the 3rd day of storage, when the transition of the amorphous structure of starch grains to the crystalline state is completed and the interpore walls of the crumb become more "brittle", one can see the output of this indicator to the plateau phase level, which clearly reflects that the bread becomes stale and it becomes possible to unambiguously assess compliance structural and mechanical properties of the crumb or its rheological behavior, the shelf life, reflected in the regulatory documentation for this type of product.
Due to the fact that the initial indicator of the texture of the sliced loaf crumb is the hardness index (Fh, G), for a complete assessment of this indicator, statistical characteristics are given (Table 5). An integrated method for determining the texture parameters of the crumb of bakery products, based on the use of a double loading of a cylindrical crumb sample and a comparative analysis of the obtained structural and mechanical characteristics, allows us to establish the value of the dimensionless cohesion criterion Dcoh -the criterion for the loss of elasticity of the interpore walls of the crumb, which is the ratio of the amount of mechanical energy A II plastic expended on plastic deformation of the crumb sample under repeated limited compression, to the amount of mechanical energy A I plastic expended on plastic deformation of the crumb under primary limited compression. This criterion, together with the indicators of texture -hardness and hardness index, allows you to more objectively determine the degree of hardness of the crumb of bakery products, and the dimensionless status makes it universal for assessing the state of the structure of the crumb of various types of bakery products.

Conclusion
Instrumental control of the structural and mechanical characteristics of the crumb of bakery products contributes to the improvement of an objective assessment of consumer indicators of the quality of manufactured products. The presence of such control at bakery enterprises will make it possible to predict changes in the degree of freshness of bakery products in the distribution network.
The indicators of crumb texture obtained as a result of mathematical processing using various control methods are considered as elements of a single system for assessing the structural-rheological state of the crumb. They are numerical (digital) characteristics of the texture of the crumb of baked goods. The use of these indicators makes it possible to more accurately and comprehensively assess the influence of various technological factors on the quality of finished products and the course of the hardening process, due to a change in the structure of starch grains and protein substances of the crumb of various types of bakery products.
The considered texture indicators are complementary to each other, like coordinates in three-dimensional space, i.e. the more such indicators, the more reliable the accuracy will be in assessing the quality of bakery products in relation to technological factors and in determining the degree of staleness of products during storage.
The use of methods of reversible and irreversible deformation of the prepared crumb sample in the form of a cylinder, with its single and double compression, allows you to set the following texture indicators: hardness, hardness index, elastic moduli, rate of hardening, the total amount of mechanical energy spent on compression, taking into account the manifested plastic and elastic deformation, cohesion, strength and, according to these indicators, determine the rate of staleness and the degree of freshness of bakery products during storage.