The amount of soy flour introduced into the shortcrust pastry recipe is justified. The use of soy flour increases the suitability of the dough for machine processing, in particular for precise dosing of piece products. The presence of fat in soy flour is important for the texture and softness of shortbread products, and the proteins contribute to the entrainment of air and the formation of fine porosity in the dough. Based on the organoleptic characteristics of shortbread cakes with different contents of soy flour, the best sample was identified, containing 5 % of the added additive from the total amount of wheat flour used in the recipe. The influence of the amount of soy flour added to the recipe on the rheological properties of shortcrust pastry is shown. The introduction of a 5 % amount of soy flour slightly increases the hardness of the shortbread dough, which has a positive effect on the shape stability of shortbread muffins with fruit and berry fillings and does not impair the organoleptic characteristics of the finished products.
soy flour
shortbread dough
organoleptic evaluation
rheology
1. Koryachkin V.P., Koryachkina S.Ya., Rumyantseva V.V. Development of technologies for the production of flour confectionery products from shortcrust pastry on rye flour, taking into account the rheological properties of semi-finished products // Advances in modern natural science. – 2006. – No. 7 – P. 68–74.
2. Kuznetsova L.S., Sidanova M.B. Technology for preparing flour confectionery products. – M.: Mastery. 2002. – 320 p.
3. Peretyatko T.I. Flour confectionery products. – Rostov-n/D.: Phoenix, 2005. – 384 p.
Products made from shortcrust pastry are among the most common types of flour confectionery products, the specific weight of the recipes of which is about 17%.
However, the number of recipes for produced semi-finished products, on which the entire variety of shortcrust pastry products is based, according to the current regulatory and technical documentation, is limited and can only satisfy consumers with conservative tastes, without taking into account the physiological characteristics, national traditions of the population, as well as regional production conditions.
In order to improve the range and develop new recipes for flour confectionery products made from shortcrust pastry, as well as to give them additional taste characteristics, the influence of soy flour on the rheological properties of shortcakes with fruit and berry filling was studied.
The chemical composition of soy flour is considered the main distinguishing feature of the product. It contains a large amount of proteins, as well as vitamins A, B and E. In addition, soy flour is enriched with potassium, phosphorus, as well as magnesium and calcium. Therefore, soy flour is used in the food industry as a vitamin food supplement of natural origin. Soy flour has an increased emulsifying ability, which makes it possible to prepare thermally stable emulsions and use soy flour as a functional additive in the confectionery and baking industries to reduce recipe standards for powdered milk, eggs, animal fats, to long-term preserve the freshness of finished products, as well as improve their color . The use of such flour increases the suitability of the dough for machine processing, in particular for precise dosing of piece products. The presence of fat in soy flour is important for the texture and softness of shortbread products, and proteins promote air entrainment and the formation of fine porosity. This explains the manufacturability of using soy flour in shortcrust pastry.
Purpose of the study
The purpose of this study is to improve the structural properties of shortcrust pastry and enrich shortbread products with protein, dietary fiber, vitamins and minerals contained in soy flour.
The subject of the study was shortbread muffins with fruit and berry filling, replacing part of the wheat flour with semi-skimmed deodorized soy flour. Cupcakes are a closed basket with fruit and berry filling inside.
Research results and discussion
For shortbread dough, flour with a reduced gluten content is used to make the baked products more porous and crumbly. For this category of cupcakes, the sand basket and lid need to be slightly stiff so that the fruit filling does not leak out during baking and the products retain their shape better during storage.
Due to the fact that the excessive content of soy flour in shortcrust pastry has a negative effect on the organoleptic characteristics of shortbread products, an attempt was made to add soy flour to shortcrust pastry in amounts of 5, 8, 12% of the total content of wheat flour in order to improve the plastic-viscous properties shortcrust pastry for this category of cupcakes.
As a result of the organoleptic evaluation of model samples, it was revealed that products containing 5% soy flour had the best organoleptic characteristics. The baked products had a perfectly baked, thin-walled structure with good fragility, uniform porosity, uniform golden color, and a very pleasant, clearly expressed taste. The sand basket had better dimensional stability compared to the classic sample.
Shortbread cakes containing 8% soy flour also had a thin-walled structure, with uniform porosity, regular shape, uniform color, but an unexpressed taste.
Shortbread cakes containing 12% soy flour had a slightly thickened structure, without fragility, the taste was not sufficiently expressed, the shape and color of the product met the standards.
Based on the organoleptic characteristics of shortbread cakes with different contents of soy flour, we can conclude that the samples with 5% replacement of wheat flour with soy flour have the best characteristics. This is evidenced by the studied structural and mechanical properties of shortcrust pastry.
Soy flour does not contain gluten, but it has a high content of protein, starch and dietary fiber. It is these substances that give the shortbread dough firmness and elasticity, as they bind moisture, giving the finished products a less crumbly structure, which is an important indicator for giving the correct texture and dimensional stability to shortbread baskets.
A CT3 Brookfield laboratory texture analyzer was used to conduct experiments to determine the rheological properties of shortcrust pastry with the addition of soy flour. It allows fundamental tests to be carried out to study the rheological properties of solids, which include shortcrust pastry.
The graphs (Fig. 1-4) clearly show the influence of the amount of soy flour added to the recipe on the rheological properties of shortcrust pastry.
From Fig. 1 and 2 it can be seen that the sample with 5% addition of soy flour has a modulus of elasticity and modulus of elasticity 1.5 times higher in comparison with the classic sample. But such an increase is positive for this category of shortbread cakes, since a small amount of soy flour gives additional strength to the shortbread basket of the cake and increases its elasticity. As a result, the filling is better retained inside the cupcakes.
Rice. 1. The value of the modulus of elasticity and the modulus of elasticity of shortcrust pastry using classical technology
Rice. 2. The value of the modulus of elasticity and the modulus of elasticity of shortcrust pastry with 5% replacement of wheat flour with soy flour
From Fig. 3 and 4 it can be seen that the modulus of elasticity and modulus of elasticity of the sand semi-finished product after adding 8% and 12% soy flour increases by 3.5-4 times. The dough becomes very hard and inelastic. It is difficult to undergo further technological operations, including the formation of cupcake baskets. This also negatively affects the organoleptic characteristics of baked products.
Rice. 3. The value of the modulus of elasticity and the modulus of elasticity of shortcrust pastry with 8% replacement of wheat flour with soy flour
Rice. 4. The value of the modulus of elasticity and the modulus of elasticity of shortcrust pastry with 12% replacement of wheat flour with soy flour
Conclusion
Based on the effect of different amounts of added soy flour on the rheological properties of shortcrust pastry, it was proven that the optimal amount of replacement of wheat flour with soy flour is 5% replacement. This amount of soy flour has the best effect on the structure of shortcrust pastry, making it more elastic, and also gives the finished baked muffins the necessary dimensional stability, which affects the quality and their appearance.
Bibliographic link
Kuznetsova A.A., Chesnokova N.Yu., Levochkina L.V., Golubeva Yu.I. THE INFLUENCE OF SOYA FLOUR ON THE STRUCTURAL AND MECHANICAL PROPERTIES OF SHORT DOUGH // International Journal of Applied and Fundamental Research. – 2015. – No. 12-7. – pp. 1174-1177;URL: https://applied-research.ru/ru/article/view?id=8109 (access date: 09/17/2019). We bring to your attention magazines published by the publishing house "Academy of Natural Sciences"
| Sample number |
Duration of exposure, h |
E 10 , Pa |
η 10 Pa With |
η/E, s |
P, % |
E, % |
TO , % |
TO , % |
|
1 2 |
0 2
0 2 |
8,5/6,0 3,5/2,9
12,0/7,6 6,4/3,8 |
5,9/5,4 1,9/6,2
6,4/5,4 3,2/8,4 |
69/89 53/220
50/71 50/221 |
72/67 78/45
77/73 78/45 |
74/64 82/65
78/67 76/70 |
59/52 47/50 |
68/-15 50/-55 |
Note. The numerator shows data on non-fermenting dough, and the denominator shows data on fermenting dough.
Dough made from grade I wheat flour has 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 unfermented dough made from grade I flour should be most distinct.
As the results of Table 1 show. 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 less than that of fermenting dough. After 2 hours of fermentation, the viscosity of the dough and η/E did not decrease, as in non-fermented dough, but on the contrary, increased, and plasticity decreased. For this reason, the indicator TO had a negative value, characterizing not liquefaction, but an increase in the viscosity of the structure.
The results of comparison of the mechanical properties of unfermented and fermented wheat dough from two samples of grade II flour are given in Table. 3.1, basically completely confirm the patterns established for dough made from grade I flour; they, however, are of undoubted interest because the process of aging lasted up to 24 hours. It is known that the fermentation of pressed baker's yeast at its usual dosage (about 1% of flour) usually ends within a period of 3-4 hours (the duration of fermentation of the dough) . After this time, the dough is replenished with a fresh portion of flour and mixed, after which fermentation in it resumes. In the absence of flour additives and stirring, alcoholic fermentation is inferior to acidic fermentation. Such dough, acquiring excessive amounts of ethyl alcohol and acids, dissolves gluten proteins (liquefies), losing carbon dioxide - reduces the volume and becomes denser. From the table 3.1 it is clear that fermenting dough after 6 hours and especially after 24 hours of fermentation in terms of shear modulus, 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 fermented dough from its non-fermented structure. Experiments have established that samples of fermented wheat dough from flour of grades I and II have a structure that has more advanced elasticity properties (lower shear modulus), greater viscosity and dimensional stability (η/E), as well as greater stability over time compared to the structure of unfermented dough. 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 MECHANICAL PROPERTIES OF FERMENTING DOUGH AND QUALITY OF BREAD ON THE TYPE AND GRADE 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 rated by GOSTs.
The structure of fermenting dough is the direct material from which bread products are produced by heat treatment in the oven. It was of interest to study the biochemical and structural-mechanical properties of fermented wheat dough depending on the type of flour. For this purpose, seven samples of soft red grain wheat were ground in a laboratory mill using three-grade grinding with a total yield of 78% on average. Then we investigated the gas-forming and gas-holding ability of flour, the structural and mechanical characteristics of fermented dough after proofing, as well as raw gluten proteins and their content in flour, specific volume (in cm 3 /d) molded, as well as HID round hearth bread baked according to GOST 9404-60. The results obtained are shown in table. 4.2. They showed that the yield of varietal flour, even under laboratory experimental grinding conditions, fluctuates significantly and the more strongly, the higher its grade. Thus, the grain grinding technology should influence the chemical composition, and therefore the structure of the dough. It is one of the significant numerous factors influencing 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, the denominator contains data on the test.
The technological properties of grain and flour of each variety 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 movement of fermenting dough, overcoming the inertia of its mass. Determination of the gas-forming ability of flour is accompanied by taking into account the amount of CO released 2 . The amount retained by the test determines it. gas retention by volume increase. This physicochemical indicator characterizes by its inverse value the gas permeability of the test to carbon dioxide. The latter depends on the structure and size of the main elastic-plastic (E, η, η/E) test characteristics. Experiments showed 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-holding capacity of the dough is directly dependent on the gas-forming ability; despite this, it did not increase in absolute and relative (% of gas formation) values, but noticeably and naturally decreased with decreasing 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 Andη/E) test. The latter depend mainly on the corresponding properties of raw gluten proteins and their content in the dough.
Experiments have shown that the content of crude gluten proteins naturally increased with a decrease in grain strength and moisture-holding capacity (viscosity) of flour and its variety. The protein structure of premium flour had higher values of shear modulus and, on average, viscosity than the structure of proteins of first grade flour. This indicates their higher statistical molecular weight. The proteins of grade I flour had a shear modulus and viscosity lower than these characteristics of proteins of grade II flour, but exceeded them in value η/E. This characterizes their greater 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 stress relaxation period of gluten proteins and dough, or η/E . The ratio of viscosity to modulus of gluten proteins of grade II flour was significantly lower than that of premium and grade I flour proteins.
The gas-holding capacity of dough made from high-quality wheat flour depended on the corresponding values of its shear modulus and viscosity. These characteristics decreased with decreasing flour grade, similar to the gas retention ability.
It was established that fermenting dough from premium flour with a moisture content of 44%, like the raw gluten proteins of this flour, had the most significant values of shear modulus, viscosity and viscosity-to-modulus ratio, and the lowest relative plasticity. From this dough, bread products with the highest porosity, specific volume of molded bread, and 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 are obtained from this flour. High viscosity values and η/E contributed to the production of hearth bread with the highest N/A .
Dough made from grade I flour with a moisture content of 44% was slightly inferior in gas retention, mechanical characteristics and bread quality to the quality of dough made from premium flour; it had a viscosity reduced by 14-15%, η/E dough, N/A . This indicates that a decrease in the viscosity of dough made from grade I flour contributed to both the development of the specific volume of molded bread and the increase in the spreadability of hearth bread.
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 first grade flour in terms of gas retention and viscosity. The viscosity-to-modulus ratio of this dough, like that of gluten proteins, was lower, and the relative plasticity was higher than that of dough made from premium and grade I flour. The quality of the resulting bread products was much lower than the quality of products made from premium and first grade flour.
In order to clarify the influence of the structural and mechanical characteristics of fermenting dough on the physical properties of bread products, we differentiated the experimental results into two groups. The first group of samples of each variety had, on average, higher shear moduli and viscosity than the arithmetic mean, while the second group had lower ones. The characteristics of gas retention of the dough and elastic-plastic properties of raw gluten proteins were also taken into account (Table 4.3).
Table 4.3
Average characteristics of dough with high and low viscosity
From the table 4.3 it is clear that the specific volume of bread made from premium flour does not depend on the value of 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 made from flour of grades I and II depended on the slightly higher 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 bread quality indicators.
The viscosity of dough made from premium flour of both groups of samples turned out to be inversely related, and the ratio of viscosity to modulus was directly dependent on the corresponding indicators of their raw gluten proteins; for dough made from flour of grades I and II of both groups of samples, it was the opposite.
Structural-mechanical, or rheological, properties of food products characterize their resistance to external energy, determined by the structure and structure of the product, as well as the quality of food products and are taken into account when choosing the conditions for their transportation and storage.
Structural and mechanical properties include strength, hardness, elasticity, elasticity, plasticity, viscosity, adhesion, thixotropy, etc.
Strength- the property of the product to resist deformation and mechanical destruction.
Under deformation understand the change in body shape and size under the influence of external forces. The deformation can be reversible and residual. With reversible deformation, the original shape of the body is restored after the load is removed. Reversible deformation can be elastic, when there is an immediate restoration of the shape and size of the body, and elastic, when recovery requires a more or less long period of time. Residual (plastic) deformation is the deformation that remains after the cessation of external forces.
Food products, as a rule, are characterized by a multicomponent composition; They are characterized by both elastic deformation, which disappears instantly, and elastic, as well as plastic deformation. However, for some, elastic properties predominate over plastic ones, for others, plastic properties predominate over elastic ones, and for others, elastic properties predominate. If food products are not capable of permanent deformation, then they are fragile, for example refined sugar, dryers, crackers, etc.
Strength is one of the most important indicators of the quality of pasta, refined sugar and other products.
This indicator is taken into account when processing grain into flour, when crushing grapes (in the production of grape wines), when crushing potatoes (in the production of starch), etc.
Hardness- the ability of a material to resist the penetration of another harder body into it. Hardness is determined when assessing the quality of fruits, vegetables, sugar, grains and other products. This indicator plays an important role in the collection, sorting, packaging, transportation, storage and processing of fruits and vegetables. In addition, hardness can be an objective indicator of their degree of maturity.
Hardness is determined by pressing a hard tip shaped like a ball, cone or pyramid into the surface of the product. The hardness of the product is judged by the diameter of the hole formed: the smaller the size of the hole, the harder the product. The hardness of fruits and vegetables is determined by the amount of load that must be applied in order for a needle or ball of a certain size to enter the pulp of the fruit.
Elasticity- the ability of bodies to instantly restore their original shape or volume after the action of deforming forces ceases.
Elasticity- the property of bodies to gradually restore shape or volume over some time.
Indicators of firmness and elasticity are used to determine the quality of dough, gluten content of wheat flour, and the freshness of meat, fish and other products. They are taken into account in the manufacture of containers and in determining the conditions for transportation and storage of food products.
Plastic- the ability of a body to deform irreversibly under the influence of external forces. The property of raw materials to change their shape during processing and retain it later is used in the production of food products such as cookies, marmalade, caramel, etc.
As a result of prolonged external influence, elastic deformation can transform into plastic deformation. This transition is associated with relaxation - the property of materials to change stress at a constant initial deformation. The production of some food products, such as sausages, is based on relaxation. From meat characterized by elastic deformation, minced meat is prepared, and from it sausage, which has the properties of a plastic material. Certain relaxation values are characteristic only for products with a solid-liquid structure - cheese, cottage cheese, minced meat, etc. This property of food products is taken into account during the transportation and storage of bakery products, fruits, vegetables, etc.
Viscosity- the ability of a liquid to resist the movement of one part of it relative to another under the influence of an external force.
There are dynamic and kinematic viscosities .
Dynamic viscosity characterizes the force of internal friction of the medium that must be overcome to move a unit surface of one layer relative to another with a displacement velocity gradient equal to unity. The unit of dynamic viscosity is taken to be the viscosity of a medium in which one layer, under the action of a force equal to 1 Newton per square meter, moves at a speed of 1 m/s relative to another layer located at a distance of 1 m. Dynamic viscosity is measured in N-s/m 2 .Kinematic viscosity is called a value equal to the ratio of dynamic viscosity to the density of the medium, and is expressed in M 2 / C.
The reciprocal of viscosity is called fluidity.
The viscosity of products is affected by temperature, pressure, humidity or fat content, solids concentration and other factors. The viscosity of food products decreases with increasing humidity, temperature, fat content and increases with increasing concentration of solutions and the degree of their dispersion.
Viscosity is a property characteristic of food products such as honey, vegetable oil, syrups, juices, alcoholic beverages, etc.
Viscosity is an indicator of the quality of many food products and often characterizes the degree of their readiness during processing of raw materials. It plays an important role in the production of many products, as it actively influences technological processes - mixing, filtering, heating, extraction, etc.
Creep- the property of a material to continuously deform under the influence of a constant load. This property is typical for cheeses, ice cream, cow butter, marmalade, etc. In food products, creep appears very quickly, which has to be taken into account during their processing and storage.
Thixotropy- the ability of some dispersed systems to spontaneously restore a structure destroyed by mechanical action. It is characteristic of dispersed systems and is found in many semi-finished products and food industry products.
A special place among the structural and mechanical properties is occupied by surface properties, which include adhesion, or stickiness.
Adhesion characterizes the force of interaction between the surfaces of the product and the material or container with which it comes into contact. This indicator is closely related to the plasticity and viscosity of food products. There are two types of adhesion: specific (adhesion itself) and mechanical. The first is the result of adhesive forces between material surfaces. The second occurs when the adhesive penetrates the pores of the material and retains it due to mechanical jamming.
Adhesion is characteristic of food products such as cheese, butter, minced meat, some confectionery products, etc. They stick to the knife blade when cutting, to the teeth when chewing.
Excessive adhesion complicates the technological process, and losses during product processing increase. This property of food products is taken into account when choosing the method of processing, packaging material and storage conditions.
The structural and mechanical properties of food products perform a dual function: they are intended not only for quantitative, but also for qualitative characteristics of food products. Structural m mechanical (rheological) properties - features of goods that appear when they are deformed. 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 noticeably when they are destroyed 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 external tensile and compressive forces are 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, cookies, crackers. If food products are not strong enough, the amount of scrap and 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 a body, which is characterized by resistance to the penetration of another harder 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 when assessing the degree of ripeness of fresh fruits and vegetables; the hardness of crackers and lamb products is used to judge the staling processes .
Deformation - the ability of an object to change its size, shape and structure under the influence of external influences that cause displacement of individual particles relative to each other. The 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 removing the load, but with irreversible deformation, they are not restored. Reversible deformation can be elastic, when the shape and size of the object is instantly restored, and elastic, when restoration requires a more or less long period of time. Residual deformation is the deformation that remains after the action of external forces ceases. 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 during the deformation process lose their mutual connection, 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 action of deforming forces ceases. This indicator is used to determine the elasticity of dough, gluten content of wheat dough, bread products and other products. This property characterizes products such as, for example, rubber inflatable products (tires, toys, etc.).
Elasticity- the property of bodies to gradually restore their shape or volume for some time after the cessation of the action of deforming forces.
This property is also used in assessing the quality of bread (crumb condition), meat and fish, and dough gluten. Thus, the elasticity of the crumb of bread, meat and fish serves as an indicator of their freshness, since when the crumb becomes stale, it loses its elasticity; When meat and fish become overripe or spoil, the muscle tissue softens greatly and also loses its elasticity.
Plastic- the ability of an object to undergo irreversible deformation, as a result of which the original shape changes, and after the cessation of external influence, the new shape is retained. A typical example of plastic materials is plasticine. The plasticity of food raw materials and semi-finished products is used in the molding of finished products. Thus, thanks to the plasticity of wheat dough, it is possible to give a certain shape to bakery, flour confectionery, lamb and pasta products. Hot caramel, candy, chocolate and marmalade masses have plasticity. After baking and cooling, the finished products lose their 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 the temperature of the product. Thus, edible fats, margarine products, cow butter, and bread have relatively high strength at low temperatures, and plasticity at elevated temperatures. Therefore, transporting, 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. Each material or product exhibits different types of deformations, but some are more characterized by reversible deformations, elasticity, and elasticity, while others are plastic. Elastic deformations are most characteristic of goods that have a crystalline structure, elastic - of goods consisting of high-molecular organic compounds (proteins, starch, etc.), plastic - of 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 external force. During elastic and elastic deformations, the distance between particles changes, and during plastic deformations, their relative position changes.
As a result of prolonged external influence, elastic deformation can transform into plastic deformation. This transition is associated with relaxation - stress drop inside the material at a constant initial deformation.
An example is the deformation of fruits and vegetables under the influence of gravity of the upper layers, freshly baked bread under impact 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 part of it relative to another under the influence of an external force.
The viscosity of liquid goods is determined using a viscometer device. Viscosity is used to assess the quality of goods with a liquid and viscous consistency (syrups, extracts, honey, vegetable oils, juices, alcoholic beverages, etc.). Viscosity depends on the chemical composition (water content, solids, fat) and the temperature of the product. With an increase in water and fat content, as well as temperature, the viscosity of raw materials, semi-finished products and finished products decreases, which facilitates their preparation; viscosity increases with increasing concentration of solutions and the degree of their dispersion.
Viscosity indirectly indicates the quality of liquid and viscous products, characterizes the degree of their readiness during processing of raw materials, and affects losses when they are moved from one type of container to another.
Stickiness (adhesion)- the ability of products to exhibit interaction forces with another product or with the surface of the container in which the product is located. This indicator is closely related to the plasticity and viscosity of food products. Adhesion is characteristic of food products such as cheese, butter, minced meat, etc. They stick to the knife blade when cutting, to the teeth when chewing. 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 continuously deform under the influence of a constant load. This property is typical for cheeses, ice cream, cow butter, marmalade, etc. In food products, creep appears very quickly, which has to be taken into account when processing them for storage.
Thixotropy- the ability of some dispersed systems to spontaneously restore a structure destroyed by mechanical action. It is found in many semi-finished products and products of the food industry and public catering, for example, jellies.
For sticky, “lingering” shortbread dough with high humidity (35.5% instead of 19%), underestimated values of structural and mechanical characteristics were obtained: elastic modulus 7.6 103 Pa, viscosity 6.5 105 Pa s.
Thus, from the data obtained it follows that the quality of semi-finished dough products can be judged by their structural and mechanical properties.
For products made from rye dough, rheological properties, along with others, are of particular importance. The structure of the dough and the quality of the finished products depend on the characteristics of the protein-carbohydrate composition of rye flour. Rye dough is characterized by the absence of a spongy gluten framework and the presence of a liquid phase, the basis of which is peptized protein, mucus, soluble dextrins, sugars, a limited swelling part of proteins, and bran particles.
N. A. Akimova and E. Ya. Troitskaya conducted rheological studies using mathematical modeling methods, the purpose of which was to find the optimal concentration of the components included in the recipe (including applesauce), determine the best ratio between them, and describe the nature of the flow of rye dough using mathematical equations, and consequently, identifying the quality of model and control samples and establishing optimal structural and mechanical indicators of the test semi-finished product under study.
The studies were carried out using a rotational viscometer “Reotest-2” at a temperature of 20 0 C. During the experiment, taking into account the nature of the test under study, the working measurement ranges were selected within the existing operating parameters and the values of the indicators were found (viscosity, ultimate shear stress), the equations were determined test flow.
The study of the structural and mechanical parameters of the test is shown in Fig. 13.8 and 13.9.
Rice. 13.8. Dependence of the effective viscosity of model dough recipes on the speed gradient:
1 - sample containing 5% apple component;
2- sample containing 15% apple component;
3 - sample containing 25% apple component
From Fig. 13.8 clearly shows the influence of the apple component on the structural and mechanical properties of the dough, with the introduction of an additional amount of which a sharp decrease in its viscosity is observed; in the mode of shear rates of 0.33... 16.2 s -1 this value is in the range of 0.928...0.029 mPa-s. And, conversely, with a reduced amount of crushed apples in the dough structure, the viscosity increases from 0.083 to 1.940 mPa-s.
Rice. 13.9. Dependence of the effective viscosity of the dough on the speed gradient:
1 - control sample; 2 - optimal sample
When processing the obtained data on a computer, a regression analysis of the found dependencies was carried out, which showed that among the mathematical models (linear, power, hyperbolic, exponential), the processes occurring can be described with the greatest degree of reliability by power equations. The correlation coefficients for the studied model samples were, respectively, r 1 = -0.9859, r 2 = -0.9928, r 3 = -0.9840.
The found power-law dependences η = f(γ), which describe the nature of the flow of model test samples, showed that the objects under study belong to viscoplastic structures that obey the following flow equations:
η 1 = 6.737γ -0.766; η 2 = 6.590γ -0.791; η 3 = 6.013γ -0.828.
The nature of the flow of model samples 1 and 3 differs from the nature of the flow of sample 2. The optimal curve of the dependence of viscosity on shear rate (sample 2) is between the two model samples, its viscosity varies within the range of 1.771...0.062 mPa*s.
Disadvantages of sample 1 - dense, heterogeneous consistency, a little crumbly, a “windy” crust quickly forms; sample 3 has a spreading, loose consistency, inclusions of unmixed components are noticeable; When molded, products do not retain their shape well; the design is not preserved.
When fruit additives are introduced into the sugar-fat egg mass in the dough, the structure liquefies as a result of a relative increase in the dispersion medium.
In this case, we can say that when fruit additives are introduced together with eggs into the fat mass, a system with reduced water mobility is formed, and therefore the adsorption of moisture by flour proteins during subsequent kneading of the dough decreases.
The change in the strength properties of the dough when an additional amount of apple component is introduced into it has a power-law character. A decrease in the effective viscosity of the dough as the content of the apple component in it increases indicates a liquefaction of its structure. This phenomenon can be explained by the weakening of the system as its water content increases.
When choosing the optimal test model from the study, we took into account not only rheological, but also other indicators included in the complex quality indicator, as well as the organoleptic properties of baked products.
The graph shown in Fig. 13.9 shows that in the flow equations given below that adequately describe the process, the structure of the samples studied by comparing the control and optimal samples is destroyed at different rates:
The correlation coefficients are r cont = -0.981, r opt = -0.985.
The rate of destruction of the structure has been established, which is m counter = 2.163, which is significantly greater than m opt = 1.791.
The viscosity of the control test sample is in the range of 2.27...0.043 mPa-s. The dough sample of the developed recipe has a less viscous consistency than the control one, which is explained by the introduction of vegetable fats, as well as carbohydrates and water contained in apples, into the recipe. In addition, the lower viscosity values of the resulting dough can be explained by replacing wheat flour with rye flour.
Thus, the conducted research made it possible, using mathematical modeling methods, to clarify the optimal recipe for a fundamentally new semi-finished dough product made from rye flour, to comprehensively study its structural and mechanical properties and to obtain power equations for the flow of the dough being studied as a viscoplastic dough, and also to further give a comprehensive integrated assessment of the quality as the resulting semi-finished dough product, as well as a wide range of finished products from it.
Under the influence of high temperatures (baking, sauteing), high-molecular substances of flour undergo profound physical and chemical changes. These changes come down to thermal denaturation of gluten protein substances, losing their ability to stretch and destructive changes in starch. The change in proteins under the influence of different heating temperatures can be judged by the nature of the shear deformation curves obtained for non-fermentable flour dough from flour preheated to different temperatures (according to L.V. Babichenko) (Fig. 13.10).
Rice. 13.10. Shear deformation curves of dough made from air-dry flour and heated to various
temperatures (humidity in brackets)
The nature of the curves for dough samples made from air-dried flour heated to 65, 105 and 120 0 C indicates a rather slow development of highly elastic deformation and flow at a decreasing speed, while the unloaded system is characterized by a high value of elastic aftereffect. An increase in the heating temperature of flour is accompanied by a decrease in the elasticity of the dough. Particularly sharp changes in the curves are observed for dough made from flour heated to 130 °C and above. They show the rapid development of elastic deformations (the values of shear modulus and viscosity of dough with a moisture content of 45% are given in Table 13.7).
As can be seen from the table, as the heating temperature of the flour increases, the shear modulus of the dough increases. For dough made from flour heated to 150 0 C, it is almost 30 times greater than for dough made from unheated flour.