RU2800725C1 - Method for cyclic control of structural and mechanical characteristics of the crumb of bakery products - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: invention relates to the field of obtaining and controlling the structural and mechanical characteristics of bakery products and can be used to control the quality of bakery products. When implementing the method, bread crumb samples are prepared. Controllable contact of the indenter with the surface of the sample is provided. The dynamics and kinetics of the loading force is determined on the indenter when the crumb is compressed by 25% of the height of the sample, and then with the reverse movement of the indenter to the final loading force F_f on the indenter, equal to the initial touch force F_t. After 180 seconds, the compression of the same crumb sample is repeated with the same mode of indenter exposure with the repeated determination of the dynamics and kinetics of the loading force of the indenter, the structural and mechanical characteristics of the crumb are determined from the measured values.

EFFECT: invention makes it possible to develop a crumb texture index, which is a dimensionless cohesion criterion (Dcoh), used to assess the degree of hardness of bakery products during storage, as well as a 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 _pl) expended on plastic deformation of the crumb sample under repeated limited compression to the amount of mechanical energy (A^I _pl) expended on plastic deformation of the crumb under primary limited compression.

2 cl, 7 dwg, 1 ex, 2 tbl

Description

The invention relates to the food industry, namely to the field of obtaining and controlling the structural and mechanical characteristics of bakery products and can be used to control the quality of bakery products.

Food products are complex multicomponent heterophase disperse systems with specific physicochemical properties, among which rheological properties are fundamental.

Prescription ingredients, semi-finished products and finished food products are food systems of an organic nature, that is, biologically active systems, the rheological properties of which are determined by physical, colloidal, biochemical and microbiological processes. Establishing the relationship between these processes and changes in the indicators of the texture of finished food products allows you to manage the technological operations of food production and ensure a given level of quality of finished products.

The set of objects of rheological research in the baking industry covers a wide range of properties of raw materials, semi-finished products and finished bakery products, ranging from free-flowing powder and liquid media to elastic-plastic and hard or brittle finished products.

Semi-finished products have complex rheological and structural-mechanical properties: sourdough, sourdough, rye, rye-wheat and wheat dough, as well as the crumb of finished bakery products.

To formalize the technological operations of the production of bakery products, taking into account the influence of various technological factors, it is necessary, first of all, to have modern instrumental methods for determining the structural and mechanical properties of the crumb of finished products. Establishing a correlation between crumb texture indicators and the properties of prescription components and semi-finished products and equipment operation modes will allow developing mathematical models to control technological operations for the manufacture of various types of bakery products.

The development of instrumental methods for monitoring the parameters of the texture of the crumb of bakery products must be carried out taking into account the existing methods of sensory organoleptic assessment of the state of the texture of the crumb during tasting, as set out in the international standard ISO 11036-2017.

One of the most important indicators of the structural and mechanical properties of the crumb are the indicators of hardness and strength, which are determined by the consumer when touching and pressing on a piece of the product, as well as when biting off and chewing, which makes it possible to assess the state of the capillary-porous structure of the crumb by its rheological behavior.

Among the instrumental methods for monitoring crumb texture indicators, the hardness indicator is currently widely used, which models the organoleptic assessment of this indicator by the taster when touching and uniformly pressing the fingers of the palm on a slice of bread, determining the force required for limited compression of the crumb. The hardness index (Fh, gs) of the crumb, controlled using texture analyzers, is the loading force (Fl, gs) that occurs when the crumb sample is compressed by 25% of its height using an indenter connected to a strain gauge.

When chewing the crumb of bakery products, a cyclic effect on the crumb is carried out when it is compressed by human molars, which leads to the loss of the elastic properties of the crumb and the connectivity of its capillary-porous structure. Visualization of the crumb chewing process, modeled using a texture analyzer, will allow creating additional indicators and criteria for evaluating its structural and mechanical properties.

It is known (RU, patent 2085940, publ. 07/27/1997) a device for determining the dimensional stability of bread, containing a base and nodes located on it for measuring the height and diameter of bread, characterized in that it is equipped with a control unit, calculation and registration and a turntable, a measurement unit represents a rod mounted for rotation around an axis fixed together with a spring, an adjusting stop and a switch on a carriage mounted for movement on a lead screw equipped with an electrical impulse sensor, the lead screw is connected to an electric motor by means of a belt drive, a switch, a sensor and an electric motor are connected to the control, calculation and registration unit, and the turntable is mounted with the possibility of rotation around the axis on the skid and connected by means of a rack and pinion with the carriage of the diameter measurement unit.

Also known is the International Method AACCI (American Association of Grain Chemists) 74-09.01 dated 11/08/1995, which regulates the quantitative determination of the force required to compress the bread product to a certain immersion depth, which makes it possible to determine the hardness index as a measure of the freshness and quality of the bakery product. The method determines the determination of the parameters of the device, as well as the calculation of the obtained data. This method is applicable to the research and quality control of white pan bread. This principle of operation is also applicable when examining other forms of bread and similar products such as cakes, for example, if the preparation conditions, indenter size, force sensor parameters are adjusted accordingly.

Until now, the means and methods for determining the structural and mechanical characteristics of the crumb of bakery products are unknown.

The technical problem solved using the developed method is the development of an instrumental method for monitoring the structural and mechanical properties of the crumb of bakery products using the texture analyzer device "Structurometer ST-2".

The technical result achieved by implementing the developed method consists in developing a crumb texture index, which is a dimensionless cohesion criterion (Dcoh), used to assess the degree of hardness of bakery products during storage, as well as a criterion for loss of elasticity of the interpore walls of the crumb, which is the ratio of the amount of mechanical energy (A ^II _pl ) spent on plastic deformation of the crumb sample under repeated limited compression to the amount of mechanical energy (A ^I _pl ) spent on plastic deformation of the crumb under primary limited compression; as well as how to determine them.

To achieve this technical result, it is proposed to use the developed method for cyclic control of the structural and mechanical characteristics of the crumb of bakery products. According to the developed method, samples of bread crumb are prepared, contact of the indenter with the surface of the sample is controlled, the dynamics and kinetics of the loading force on the indenter are determined when the crumb is compressed by 25% of the height of the sample, and then when the indenter is reversed to the final loading force _Fcon on the indenter, equal to the initial touch force _Fcas , after 180 seconds, the compression of the same crumb sample is repeated with the same indenter action mode, with the repeated determination of the dynamics and kinetics of the indenter loading force, the structural and mechanical characteristics of the crumb are determined from the measured values.

Preferably, when preparing bread crumb samples, the bakery product is cut into slices, six slices are taken from the central part of the product, cylindrical crumb samples are cut out of the selected six slices, 20 mm thick.

In some embodiments of the developed method, the determination of crumb cohesion, as its structural and mechanical characteristics, is carried out by dividing the amount of mechanical energy spent on compressing the crumb during re-compression by the amount of mechanical energy spent on primary compression of the same crumb sample.

Monitoring of physico-chemical, including structural-mechanical, properties of the crumb of bakery products was carried out as follows. 15 products were selected from a batch of manufactured and packaged sliced loaves, the duration of storage of which during the expedition was within 5–6 hours. Then the loaves were delivered to the laboratory, and the first three products were analyzed from the moment the products left the furnace after 12 hours. The rest, in packaged form, were placed in storage and then, also for three products, they were analyzed daily every 24 hours for 4 days.

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 rest to the right and left of them, along with the fritters, are removed). Cylindrical samples of the crumb with a diameter of 36 mm and a volume of 20.36 cm ³ are cut out from the selected six slices, 20 mm thick, using a probe. Thus, six cylinders are obtained from one loaf. The slices for analysis from the sliced product are taken gradually so that they do not weather. The application of the loading force to the obtained cylindrical crumb samples during their compression is carried out to the left and to the right from the center of the product.

The use of crumb in the form of a cylinder for research, rather than the entire chunk, makes it possible to eliminate the influence of the variability of the distance from the edge of the indenter to the product crust and increase the convergence of the results obtained, as well as to implement a multi-parameter method for controlling texture indicators. The cylindrical crumb sample makes it possible to calculate the density and, together with the set humidity, to determine the relative indicators of the crumb texture. The diameter of the cylindrical sample, equal to 36 mm, ensures the control of a sufficiently large local area of the crumb in comparison with the area of the slice itself. Before determining the structural and mechanical characteristics of the crumb, the prepared sample is weighed on a balance and then placed on the table of the ST-2 Structurometer instrument. Structural and mechanical characteristics of the crumb were controlled using the method of reversible deformation, implemented in the device "Structurometer ST-2" (Q-lab - Russia).

The method for determining the texture indices of a cylindrical crumb with a known mass and volume is based on controlling the dynamics and kinetics of the loading force on the indenter when the crumb is compressed by 25% of the sample height, and then when the indenter is reversed until the final loading force _Fcon on the indenter is equal to the initial force touch F _cas .

The mode of operation of the device when determining the texture of the crumb during cyclic compression of its sample is given in Table. 1, which shows the algorithm of the device "Structurometer ST-2" for determining the texture of the crumb under cyclic compression deformation of its cylindrical sample.

Determined indicators of structural and mechanical properties of the crumb of bakery products:

• F _h , gs - crumb hardness - loading force (F _l , gs) on the indenter "Piston ∅49", corresponding to crumb compression by 5 mm (25% of the crumb sample height);

• I _h , gs/[(g/cm ³ )⋅%] - hardness index, calculated by the formula:

where: ρ _cru - crumb density, g/cm ³ ;

W _cru - crumb moisture content, %;

• ε - relative deformation - quotient of the crumb deformation h, mm divided by the height of the crumb cylinder H, mm:

• σ, Pa - stress created during crumb compression - quotient from dividing the loading force (F _l , N) by the area of the crumb cylinder (S _cru , m ² ):

• E ^I , Pa - modulus of elasticity of the interpore walls, quotient of dividing the stress in the first section (Δσ ^I , Pa) by the relative strain (Δε ^I ):

• E ^II , Pa - modulus of elasticity of the porous structure, quotient from dividing the stress in the second section (Δσ ^II , Pa) by the relative strain (Δε ^II ):

• _Atotal , J/g - total amount of specific mechanical energy expended on compressing the crumb to the value of _htotal =5 mm:

Where: - crumb sample weight, g

• A _control , J/g - the amount of specific mechanical energy associated with the restoration of the structure of the crumb due to elastic deformation during the reverse movement of the indenter to a final force of 10 gf in position h _pl :

• A _pl , J/g - the amount of specific mechanical energy, leading to a change in the structure of the crumb due to plastic deformation:

• Dcoh - crumb cohesion criterion (loss of cohesion of the crumb structure) of a bakery product during 2-cycle compression of its cylindrical sample by 25% of the height:

• Vch - staleness rate, gf/day:

Mathematical processing of experimental data was carried out using descriptive statistics methods provided by the Microsoft Office Excell software package and in accordance with GOSTs and special literature, which allows you to establish:

• average values of measured hardness indices (F _h , gs);

• standard deviation of hardness (σ, gs), which gives an idea of how widely the values of the hardness index F _h are scattered relative to their average value;

• coefficient of variation (CV, %), reflecting the ratio of the standard deviation σ to the mean value F _h , expressed as a percentage and characterizing the relative degree of deviation of the measured F _h values from the arithmetic mean. If the coefficient of variation does not exceed 10%, then the variability of a random sample is considered insignificant;

• repeatability limit (r, gs) reflecting the repeatability of measurement results obtained by the same method on identical test specimens belonging to the same lot, in the same laboratory, by the same operator using the same equipment and in a short time interval (the value of r is not exceeded by the absolute difference between the two test results obtained under repeatability conditions, expected with a probability of 95% r = 2.77 σ, where: σ is the sample standard deviation of the results of a series of measurements). The method for determining the texture indices of the crumb of bakery products during cyclic - double compression of its sample simulates the organoleptic assessment of the structural and mechanical properties of the crumb during chewing, when it is subjected to repeated compression. Therefore, a family of diagrams of compression of the sliced loaf crumb subjected to sevenfold impacts was previously obtained.

The developed method will be illustrated by the following implementation example.

Example 1. Determination of the texture of the crumb of a sliced loaf of bakery wheat flour of the highest grade, weighing 0.4 kg (GOST 27844-88).

Monitoring of the structural and mechanical properties of the sliced loaf crumb is carried out as follows. 15 products are selected from a batch of manufactured and packaged sliced loaves, the duration of storage of which in the expedition is within 5-6 hours. Then the loaves are delivered to the laboratory and, from the moment the products leave the oven, after 12 hours, the analysis of the first three products is carried out. The rest, in packaged form, are placed in storage and then, also for three products, they are analyzed daily every 24 hours for 4 days.

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 rest to the right and left of them, along with the crusts, are removed). Cylindrical samples of the crumb with a diameter of 36 mm and a volume of 20.36 cm ³ are cut out from the selected six slices, 20 mm thick, using a probe. Thus, six cylinders are obtained from one loaf. The slices for analysis from the sliced product are taken gradually so that they do not weather. The application of the loading force to the obtained cylindrical crumb samples during their compression is carried out to the left and to the right from the center of the product (Fig. 1).

The use of crumb in the form of a cylinder for research, rather than the entire chunk, makes it possible to eliminate the influence of the variability of the distance from the edge of the indenter to the product crust and increase the convergence of the results obtained, as well as to implement a multi-parameter method for controlling texture indicators. The cylindrical crumb sample makes it possible to calculate the density and, together with the set humidity, to determine the relative indicators of the crumb texture. The diameter of the cylindrical sample, equal to 36 mm, ensures the control of a sufficiently large local area of the crumb in comparison with the area of the slice itself. Before determining the structural and mechanical characteristics of the crumb, the prepared sample is weighed on a scale and then placed on the table of the ST-2 Structurometer (Fig. 2).

The moisture content of the crumb of products is determined by the gravimetric method using a moisture meter "Glutork 2020" (Perten-Instruments - Sweden) or a similar device. The structural-mechanical characteristics of the crumb are controlled using the reversible deformation method implemented in the ST-2 Structurometer (Q-lab, Russia), which is shown in Fig. 1 as part of the information-measuring system. 3.

The method for determining the texture indices of a cylindrical crumb with a known mass and volume consists in controlling the kinetics of the loading force on the indenter "Piston ∅49" when the crumb is compressed by 25% of the sample height, and then with the reverse movement of the indenter to the final loading force _Fcon on the indenter , equal to the initial touch force F _cas .

The mode of operation of the device when determining the texture of the crumb during cyclic compression of its sample is given in Table. 1.

Determined indicators of structural and mechanical properties of the crumb of bakery products:

• F _h , gs - crumb hardness - loading force (F _l , gs) on the indenter "Piston ∅49", corresponding to crumb compression by 5 mm (25% of the crumb sample height);

• I _h , gs/[(g/cm ³ )⋅%] - hardness index, calculated by the formula:

where: ρ _cru - crumb density, g/cm ³ ;

W _cru - crumb moisture content, %;

• ε - relative deformation - quotient of the crumb deformation h, mm divided by the height of the crumb cylinder H, mm:

• σ, Pa - stress created during crumb compression - quotient from dividing the loading force (F _l , N) by the area of the crumb cylinder (S _cru , m ² ):

• E ^I , Pa - modulus of elasticity of the interpore walls, quotient of dividing the stress in the first section (Δσ ^I , Pa) by the relative strain (Δε ^I ):

• E ^II , Pa - modulus of elasticity of the porous structure, quotient from dividing the stress in the second section (Δσ ^II , Pa) by the relative strain (Δε ^II ):

• _Atotal , J/g - total amount of specific mechanical energy expended on compressing the crumb to the value of _htotal =5 mm:

Where: - crumb sample weight, g

• A _control , J/g - the amount of specific mechanical energy associated with the restoration of the structure of the crumb due to elastic deformation during the reverse movement of the indenter to a final force of 10 gf in position h _pl :

• A _pl , J/g - the amount of specific mechanical energy, leading to a change in the structure of the crumb due to plastic deformation:

• Dcoh - crumb cohesion criterion (loss of cohesion of the crumb structure) of a bakery product during 2-cycle compression of its cylindrical sample by 25% of the height:

• Vch - staleness rate, gf/day:

The technique for determining the texture indices of the crumb of bakery products during cyclic - two-fold compression of its sample simulates the organoleptic assessment of the structural and mechanical properties of the crumb during chewing, when it is subjected to repeated compression.

In FIG. 4 shows families of curves for changing the loading force during cyclic compression of a cylindrical crumb sample depending on the amount of deformation for sliced loaves with different storage times after baking - 12; 36; 60; 84 and 108 hours. In Figs. Figure 4 shows the different rheological behavior of the crumb during the first and repeated compression, which manifests itself in a different amount of mechanical energy expended on the deformation of the crumb, which can be explained by the loss of connectivity of the crumb structure or the elasticity of the interpore walls of the capillary-porous structure. This phenomenon was used to develop a dimensionless criterion that reflects the degree of staleness of bakery products during storage, which is the quotient of dividing the amount of mechanical energy (А ^II _pl ) spent on the plastic deformation of the crumb during the second compression cycle (2c) by the amount of mechanical energy (А ^I _pl ), spent on the plastic deformation of the crumb during the first compression cycle (1c):

Dcoh \u003d A ^II _pl / A ^I _pl.

Thus, the developed method for determining the texture indices of a cylindrical crumb with a known mass and volume is to control the kinetics of the loading force on the indenter "Piston ∅49" during the first (1c) compression of the crumb by 25% of the sample height, and then during the reverse movement of the indenter up to the final loading force F _con , equal to the initial touch force F _cas . After that, a pause is made for 180 s and then re-compression (2c) of the same crumb sample with the same compression mode is carried out. Then the mathematical processing of the obtained crumb deformation curves is carried out.

In FIG. 4 it can be seen that during the second cycle of compression of a cylindrical sample of the crumb of a sliced loaf with different storage duration, a different character of the change in the loading force is observed, due to the lower resistance to the compression force due to the loss of elasticity of the interpore walls of the crumb and thereby predetermining a smaller amount of mechanical energy expended during re-compression of the cylinder . The increase in the loss of the elastic properties of the crumb is due to the shelf life of the sliced loaf.

All physical and chemical characteristics of the crumb, established by double compression of a cylindrical sample of a sliced loaf of loaves, depending on the duration of storage, are given in Table. 2.

From Table. 2 it can be seen that the change in the hardness index (Ih) of the sliced loaf crumb ranged from 22 to 58 gf / [(g / cm ³ )⋅%] during three days of storage, and the dimensionless criterion - the cohesion criterion (Dcoh) - from 0.87 up to 0.58. Indicator (ΔAtot) - an indicator of the difference between the amount of mechanical energy (A ^I total) spent on the deformation of the crumb in the first cycle and the amount of mechanical energy (A ^II 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. 5.

In FIG. 5, an inflection point "a" is observed, corresponding to a storage period of 72 hours and reflecting the completion of the crumb hardening process.

In FIG. Figures 6 and 7 show graphs of changes in the Ih index and the Dcoh criterion of the sliced loaf crumb during storage for 108 hours.

From FIG. 6 and 7, it can be seen that the dimensionless criterion of crumb cohesion is the most informative indicator of the state of the crumb structure, and on the third day of storage, when the transition of the amorphous structure of starch grains to the crystalline state is actually completed and the interpore walls of the crumb become more “brittle”, then the yield of this indicator is observed. to the level of plateau phase, which unambiguously reflects that the bread becomes stale and it becomes possible to unambiguously assess the compliance of the structural and mechanical properties of the crumb or its rheological behavior with the shelf life specified in the regulatory documentation for this type of product.

Thus, on the basis of the studies carried out, a comprehensive method for determining the texture parameters of the crumb of bakery products has been developed, based on the use of a double loading of a cylindrical crumb sample and a comparative analysis of its measured structural and mechanical characteristics using an information-measuring system, including a texture analyzer device "Structurometer ST-2 ".

The developed method for monitoring the parameters of texture of the crumb of bakery products, based on a cyclic - two-fold method of compressing a cylindrical sample of the crumb by a deformation value of 25% of the height of the sample, allows you to determine the dimensionless cohesion criterion (Dcoh) to assess the degree of staleness of bakery products during storage - the criterion for loss of elasticity interpore walls of the crumb, which is the ratio of the amount of mechanical energy (А ^II _pl ) expended on plastic deformation of the crumb sample under repeated limited compression to the amount of mechanical energy (A ^I _pl ) expended on plastic deformation of the crumb under primary limited compression, while the dynamics changes in the criterion of cohesion of the crumb during storage of a sliced loaf, within 3 days of storage and the range of change of this criterion is from 0.87 to 0.58.

Claims (2)

1. The method of cyclic control of the cohesion of the crumb of bakery products, characterized in that they prepare samples of the bread crumb, controllably provide contact of the indenter with the surface of the sample, determine the dynamics and kinetics of the loading force on the indenter when the crumb is compressed by 25% of the sample height, and then during reverse movement of the indenter to the final loading force F _con on the indenter, equal to the initial touch force F _cas , after 180 seconds, the compression of the same crumb sample is repeated with the same indenter exposure mode with re-determination of the dynamics and kinetics of the loading force of the indenter, the crumb cohesion is determined from the measured values by dividing the amount of mechanical energy expended on compressing the crumb during re-compression by the amount of mechanical energy expended in the initial compression of the same crumb sample. 2. The method according to claim 1, characterized in that when preparing samples of the bread crumb, the bakery product is cut into slices, six slices are taken from the central part of the product, and cylindrical crumb samples are cut out of the selected six slices, 20 mm thick.