Abstract: Structural and mechanical properties of fermenting dough. Structural and mechanical properties of fermenting dough Baking properties of rye flour

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

As the duration of kneading the dough increases, its structure weakens. After prolonged kneading, the dough consistency indicator Kt increases, and the viscosity of the dough decreases. The elasticity, extensibility and magnitude of the deformation force of the dough, determined on an alveograph, decreases (Fig. 13).

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

The hydration capacity of dough gluten increases with additional mechanical processing. This is reflected in its structural and mechanical properties: the duration of pressing on the plastometer decreased by 22 s, and the specific elongation increased by 1.5 times.
Immediately after kneading with enhanced mechanical processing, the dough had 3.7% less washed-out gluten than in the dough kneaded for 5 minutes. The amount of water-soluble nitrogen, on the contrary, was higher.
These data show that in heavily processed dough, formation and ripening processes occur to a significant extent already during the mechanical processing period, which can contribute to a reduction in dough preparation time.
When the dough is fermented, the amount of gluten washed out decreases both in the control dough and in the dough with additional mechanical processing.
Before putting into the oven, the amount of gluten washed from the control dough decreased by 30.8% compared to the amount of gluten from flour, and from the dough with enhanced mechanical processing - by 39.9%. This indicates a more intense process of change in protein substances in dough with enhanced mechanical processing.
The amount of water-soluble nitrogen in the control dough increased by 60.6% relative to the water-soluble nitrogen of flour, and in the dough with enhanced mechanical processing - by 72.7%.
Diagrams for reducing the amount of washed gluten and increasing the amount of water-soluble nitrogen in the dough before placing in the oven are presented in Fig. 14 and 15.

K. N. Chizhova found that the readiness of wheat dough can be characterized by a certain degree of reduction in the content of washed gluten and an increase in the amount of water-soluble nitrogen. Additional processing of the dough causes deeper changes in protein substances, which accelerates its maturation.
The state of gluten proteins in dough changes under the influence of various factors. In this case, the state of the flour proteins themselves and their changes during the dough preparation process under the influence of accumulating acids and proteolytic enzymes are important.
To study changes in gluten under the influence of acids and enzymes during enhanced mechanical processing of the dough, it was exposed to 0.005 n. lactic acid and studied its attack by the protolytic enzyme papain (Table 24).

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

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

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

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

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

Increasing the intensity of dough kneading for Ukrainian new rye-wheat bread with a 60:40% ratio of peeled flour and grade II flour also slows down its changes during storage. In this case, there is an accumulation of volatile carbonyl compounds, which determine the aroma of bread.

The dough is a polydisperse colloidal solid-liquid system, which has both elastic-elastic and visco-plastic properties, on the surface of which adhesion properties appear. The physical properties of rye dough are largely determined by the properties of its very viscous liquid phase. Rye dough is characterized by high viscosity, plasticity, low stretchability, and low elasticity.

The viscosity of rye dough changes during the fermentation process (Table 2.6).

Table 2.6 – Dependence of the viscosity of baking dough (in kPa∙s) on the duration of fermentation and shear rate

Shear rate, s -1	Fermentation duration, min
Shear rate, s -1

As can be seen from Table 2.6, with increasing shear rate, the viscosity of the dough at any duration of fermentation decreases, which is typical for most dough masses. As fermentation time increases, viscosity also decreases. Note that with fermentation durations of 120 and 150 minutes at all speeds, the viscosity is almost the same.

2.1.2.3 Baking properties of rye flour

The baking properties of rye flour are determined by the following indicators:

gas-forming ability;

the power of torment;

the color of the flour and its ability to darken;

grinding coarseness.

Gas-forming ability of flour. The gas-forming ability of flour is the ability of dough prepared from it to form carbon dioxide.

During alcoholic fermentation, which is caused by yeast in the dough, the saccharides contained in it are fermented. Most of all, ethyl alcohol and carbon dioxide are formed in the process of alcoholic fermentation, and therefore it is by the amount of these products that one can judge the intensity of alcoholic fermentation. Therefore, the gas-forming ability of flour is characterized by the amount of carbon dioxide per ml formed during 5 hours of fermentation of dough prepared from 100 g of flour, 60 ml of water and 10 g of yeast at a temperature of 30 ° C.

The gas-forming ability depends on the content of its own sugars in the flour and on the sugar-forming ability of the flour.

The flour's own sugars (glucose, fructose, sucrose, maltose, etc.) are fermented at the very beginning of the fermentation process. And to obtain the best quality bread, it is necessary to have intensive fermentation both during the ripening of the dough, and during the final proofing and during the first period of baking. In addition, monosaccharides are also necessary for the reaction of melanoid formation (formation of the color of the crust, taste and smell of bread). Therefore, what is more important is not the sugar content of flour, but its ability to form sugars during the dough ripening process.

The sugar-forming ability of flour is the ability of a water-flour mixture prepared from it to form a certain amount of maltose at a set temperature and over a certain period of time. The sugar-forming ability of flour is determined by the action of amylolytic enzymes on starch and depends both on the presence and amount of amylolytic enzymes (a- and β-amylases) in flour, and on the attackability of flour starch. Normal ungerminated rye grain contains a fairly large amount of active α-amylase. During grain germination, α-amylase activity increases many times. In rye flour, β-amylase is approximately 3 times less active than in wheat flour, and α-amylase is more than 3 times active.

All this leads to the fact that the crumb of rye bread always has increased stickiness compared to bread made from wheat flour, which is of lower quality. This is due to the fact that active α-amylase easily hydrolyzes starch to a significant amount of dextrins, which, by binding moisture, reduce its connection with protein and starch grains; a large amount of water is in a free state. The presence of some free moisture not bound by starch will make the bread crumb moist to the touch.

Knowing the gas-forming ability of flour, you can predict the intensity of fermentation of the dough, the course of the final proofing and the quality of the bread. The gas-forming ability of flour affects the color of the crust. The color of the crust is due in large part to the amount of unfermented sugars before baking.

The power of flour. Flour strength is the ability of flour to form a dough that has certain structural and mechanical properties after kneading and during fermentation and proofing. Based on strength, flour is divided into strong, medium and weak.

Strong flour contains a lot of protein substances and gives a large yield of raw gluten. Gluten and dough made from strong flour are characterized by high elasticity and low plasticity. The protein substances of strong flour swell relatively slowly when kneading dough, but generally absorb a lot of water. Proteolysis in the dough occurs slowly. The dough has a high gas-retaining ability, the bread has the correct shape, large volume, and porosity that is optimal in size and structure. It should be noted that very strong flour produces bread with a smaller volume. The gluten and dough of such flour are too elastic and insufficiently extensible.

Weak flour forms inelastic, overly extensible gluten. Due to intense proteolysis, dough made from weak flour has low elasticity, high plasticity, and increased stickiness. The formed dough pieces spread out during the proofing period. Finished products are characterized by low volume, insufficient porosity and vagueness (hearth products).

Medium flour produces raw gluten and dough with good rheological properties. The dough and gluten are quite elastic and elastic. The bread has a shape and quality that meets the requirements of the standard.

The color of flour and its ability to darken during the baking process. The color of the crumb is related to the color of the flour. Dark flour will produce bread with a dark crumb. However, light flour can in certain cases produce bread with a dark crumb. Therefore, to characterize the baking quality of flour, not only its color, but also its ability to darken is important.

The color of flour is mainly determined by the color of the endosperm of the grain from which the flour is ground, as well as the color and amount of peripheral (bran) particles of the grain in the flour.

The ability of flour to darken during processing is determined by the content of phenols, free tyrosine in flour and the activity of the enzymes O-diphenoloxidase and tyrosinase, which catalyze the oxidation of phenols and tyrosine with the formation of dark-colored melanins.

Size of rye flour particles. The sizes of flour particles are of great importance in baking production, significantly influencing the rate of biochemical and colloidal processes in the dough and, as a result, the properties of the dough, the quality and yield of bread.

Both insufficient and excessive grinding of flour worsens its baking properties: excessively coarse flour will produce bread of insufficient volume with a coarse thick-walled crumb porosity and often with a pale colored crust; Bread made from overly ground flour results in reduced volume, with an intensely colored crust, often with a darkly colored crumb. Hearth bread made from this flour may be mushy.

The best quality bread comes from flour with the optimal particle size. The grinding optimum, apparently, should be different for flour made from grains with different quantities and especially quality of gluten.

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Posted on http://www.allbest.ru/

Rheologybakery,pasta, confectionery dough

Rheology- the science of deformation and flow of various bodies, rheological properties of raw materials, semi-finished products and finished products.

The word rheology comes from the Greek rheo, meaning flow.

Deformation- change in body size under load.

In a relationship solids deformation leads to change shape or size the whole body or its parts, and in relation to the structure of food masses - to flow(dough, flour, condensed milk, mayonnaise, etc.) or even to their rupture(sweets, bread, etc.).

Rheological properties:

Elasticity - the ability of the body to restore its shape and size after removing the load.

Plastic - the property of a body to retain its shape and size after removing the deforming load.

Viscosity - the property of a medium to resist the movement of foreign bodies in it.

Strength - the property of a body to withstand a certain external load without destruction.

Hardness - the property of a body to resist the penetration of other bodies into it.

Fragility - the property of a body to collapse without the formation of plastic deformations.

Classification of food products by textural characteristics and rheological properties

Product classification	Product Name	Typical rheological properties
	Chocolate, cookies, crackers, waffles, extruded products, caramel, crackers, dryers, pasta, bread	Tensile strength, modulus of elasticity
Elastic-plastic	Bread, wheat dough, pasta dough, marmalade, marshmallows, marshmallows, candies, hard fat, gingerbread, gluten, gelatin	Tensile strength, modulus of elasticity, ultimate shear stress, adhesion
Viscous-plastic	Rye dough, shortbread dough, sour cream, mayonnaise, gelling products, semi-finished confectionery products	Viscosity, adhesion, ultimate shear stress (plastic strength)
Liquid-like	Yeast suspension, salt solution, sugar solution, melted margarine, whole milk, whey	Viscosity, surface tension coefficient
Powdery	Flour, granulated sugar, starch, table salt	Angle of repose, mechanical characteristics during pressing

The content of protein substances in flour, their composition, condition and properties are of paramount importance and largely determine the nutritional value of bread and the technological properties of flour. The properties of the dough such as elasticity, viscosity, and firmness depend on them. The protein substances of wheat flour are represented by 2/3 (3/4) gliadin and glutenin fractions (gluten components), which are the main components of gluten. They are called gluten proteins. Wheat flour contains slightly more gliadin fraction than glutenin.

The more protein there is in the flour, the denser and stronger its structure, the stronger the flour, and the better and more stable the rheological properties of the dough made from it will be. Therefore, the higher the gluten content in flour and the better its rheological properties, the stronger the flour.

The strength of flour determines the amount of water required to obtain dough of normal consistency, as well as the change in the rheological properties of the dough during fermentation and, in connection with this, the behavior of the dough during its mechanical cutting and dough pieces during final proofing.

The strength of the flour determines the gas-holding capacity of the dough, i.e. the ability of semi-finished products to retain carbon dioxide formed during fermentation. To obtain bread of maximum volume from very strong wheat flour, the rheological properties of the dough must be somewhat weakened. This can be achieved by changing the dough preparation mode: increasing its mechanical processing, slightly increasing the temperature, increasing the amount of water in the dough, or adding drugs that accelerate proteolysis in the dough.

In addition, the strength of flour determines the shape-holding ability of the dough, i.e. the ability of dough pieces to retain carbon dioxide and maintain shape during the proofing process and the first baking period. In this regard, the strength of flour determines the spreadability of hearth bread.

In rye bread, they are of great importance rheological(structural-mechanical) properties of the crumb - the degree of its stickiness, kneadability and moisture or dryness to the touch. Rye bread, especially made from wallpaper and peel flour, has a smaller volume, a darker colored crumb and crust, a lower percentage of porosity and a stickier crumb compared to wheat. The differences noted above in the quality of rye bread are due to the specific features carbohydrate-amylase And protein-proteinase complexes rye grains and rye flour.

Rye flour compared with wheat It is distinguished by a higher content of its own sugars, a lower gelatinization temperature (swelling in hot water, transition from a crystalline to an amorphous state) of starch, its greater attackability and the presence of practically significant amounts of the enzyme amylase in flour, even from unsprouted grains.

The action of amylases on rye flour starch, which gelatinizes at a lower temperature and is more easily attacked, can lead to the fact that a significant part of the starch will be hydrolyzed during dough fermentation and bread baking. As a result, starch when baking a dough piece from rye flour may not be able to bind all the moisture of the dough. The presence of some free moisture not bound by starch will make the bread crumb moist to the touch. The presence of b-amylase (alpha-amylase), especially when the dough is insufficiently acidic, leads to the accumulation of a significant amount of dextrins when baking bread, which gives the crumb stickiness. Therefore, the crumb of rye bread is always more sticky and moist compared to the crumb of wheat bread. In order to inhibit the action of b-amylase, the acidity of rye dough must be maintained at a level significantly higher than in wheat dough.

The carbohydrate complex of rye flour also includes mucus (water-soluble pentosans). The content of pentosans in rye flour significantly exceeds their content in wheat flour. Pentosans have a significant effect on rheological properties rye dough, since by absorbing water when kneading the dough, they make it more viscous.

The protein substances of rye flour are close in amino acid composition to the proteins of wheat flour, but are distinguished by a higher content of essential amino acids - lysine and threonine.

An essential feature of rye proteins is their ability to swell quickly and intensely. . A significant part of the proteins swells unlimitedly, passing into the state viscous colloidal solution.

The second feature of rye flour proteins is that, despite the presence of gliadin and glutenin, they are not capable of forming gluten due to a significant amount of dextrins and water-soluble pentosans.

Features of rheological properties wheat and rye dough

The rheological properties of wheat dough depend mainly on the presence of a gluten framework in it, which gives the dough elasticity and elasticity. There is no gluten framework in rye dough. Rye dough is viscous, plastic, elastic and elastic properties are poorly expressed. Rye dough can be considered as a thick liquid in which swollen starch grains, a limited swollen part of the proteins that has not passed into solution, and also particles of bran are suspended.

The shape-holding ability of rye dough depends on the viscosity of the liquid phase. The viscosity of the liquid phase is due to the peptized state of some proteins, the transition to a colloidal solution of mucus, as well as the presence of dextrins. The transition of rye flour proteins in the dough into a soluble state and the swelling of the insoluble part of the proteins depends on acidity. The active acidity of rye dough is pH 4.2 - 4.4, wheat dough is 5.2 - 5.4. Higher acidity inhibits the action of alpha-amylase and reduces its inactivation temperature. This limits the formation of dextrins during baking, reduces the stickiness of the crumb, and improves the process of protein peptization.

In wheat and rye test There are three phases: solid, liquid and gaseous. Solid phase- These are starch grains, swollen insoluble proteins, cellulose and hemicelluloses. Liquid phase- this is water that is not associated with starch and proteins (about 1/3 of the total water used for kneading), water-soluble flour substances (sugars, water-soluble proteins, mineral salts), peptized proteins and mucus. Gaseous phase- dough is represented by air particles trapped test at batch e and a small amount of carbon dioxide formed as a result of alcoholic fermentation. The longer kneading dough, the larger the volume in it is the share of the gaseous phase. At normal duration batch the volume of the gaseous phase reaches 10%, with an increased phase - 20% of the total volume test.

Relationship between individual phases in the test determines its rheological properties. An increase in the proportion of liquid and gaseous phases weakens dough, making it more sticky and fluid. Increasing the proportion of solid phase strengthens dough, making it more resilient and elastic.

In rye test, compared to wheat, the proportion of solid and gaseous is smaller, but the proportion of the liquid phase is larger.

Mechanical impact on dough at different stages batch may have different effects on its rheological properties. At the beginning batch mechanical processing causes flour, water and other raw materials to mix and the swollen flour particles to stick together into a solid mass test. At this stage batch mechanical impact on dough determines and accelerates its formation. For some time after this, the impact on dough can improve its properties by accelerating the swelling of proteins and the formation of gluten. Further continuation batch may lead not to an improvement, but to a deterioration in the properties of the dough, since mechanical destruction of the gluten is possible. Therefore, knowledge of the formation mechanism dough, the formation of its solid, liquid and gaseous phases is necessary for proper kneading

After operation batch should dough fermentation. In production practice, fermentation covers the period after kneading the dough before cutting it. The main purpose of this operation is to cast test to a state in which it will be best for cutting and baking in terms of gas-forming ability and rheological properties, accumulation of flavoring and aromatic substances. rheology food product dough

Rheological properties ripe test should be optimal for dividing it into pieces, rounding, final shaping, as well as for retaining carbon dioxide in the dough and maintaining the shape of the product during final proofing and baking.

Alcoholic fermentation- this is the main view fermentation in wheat test. Caused by enzymes of yeast cells, which ensure the conversion of simple sugars (monosaccharides) into ethyl alcohol and carbon dioxide.

At fermentation of dough The processes of limited and unlimited swelling of proteins continue to develop intensively. With limited swelling of proteins in the dough, the amount of liquid phase is reduced, and, consequently, its rheological properties are improved. With unlimited swelling and peptization of proteins, on the contrary, the transition of proteins into the liquid phase of the dough increases and its rheological properties deteriorate. In dough made from flour of different strengths, these processes occur with different intensities.

The stronger the flour, the slower the processes of limited swelling of proteins occur in the dough, reaching an optimum only towards the end of fermentation. In dough made from strong flour, the processes of unlimited swelling and peptization of proteins occur to a lesser extent.

In dough made from weak flour, limited swelling occurs relatively quickly and, due to the low structural strength of the protein, weakened by intense proteolysis, the process of unlimited swelling of proteins begins, turning into the process of peptization and increasing the amount of the liquid phase of the dough. This leads to a deterioration in the rheological properties of the dough.

Pastry dough

The use of wheat flour of different qualities, a large set of raw materials, changing their ratio and the use of certain technological parameters and techniques makes it possible to obtain dough and products that differ in physical, chemical and rheological properties.

The rheological properties of the dough depend on the degree of swelling of the proteins.

Depending on these properties, confectionery dough is divided into three types:

plastic - viscous(sugar, shortbread, butter, gingerbread dough), takes well and retains its shape;

elastic - plastic - viscous(long-lasting, cracker, biscuit), does not take well and does not retain its shape well;

semi-structured(waffle, biscuit dough for biscuit semi-finished products and cakes), has a liquid consistency.

Plastic dough is formed under conditions of limited swelling of flour colloids, therefore the duration of kneading the dough should be minimal and the temperature lower than the temperature of the dough, which has elastic-plastic-viscous properties.

In accordance with GOST "Confectionery Products. Terms and Definitions", two types of dough are distinguished depending on its structure:

Biscuit - butter, sugar, oatmeal, from which products of various shapes with well-developed uniform porosity are obtained,

Layered dough - for long-lasting cookies, crackers, biscuits, from which products of various shapes with a layered structure are produced.

Rheological properties of dough

The formation of dough with certain rheological properties is associated with:

With the type of product, recipe, with the correct selection of flour grade, with optimal gluten content and quality, grinding coarseness,

With the correct choice of dough moisture content,

With the correct selection and maintenance of technological parameters for kneading dough (temperature, duration, intensity of kneading).

The noted factors influence the degree of swelling of wheat flour and thereby the rheological properties of the dough, its plasticity, elasticity, elasticity, and viscosity.

By increasing the temperature of the dough during kneading, lengthening the duration of the process from sugar plastic dough as a result of more complete swelling of colloids, it is possible to obtain a protracted dough with elastic-plastic-viscous properties. The plasticity of sugar dough is close to 1. In order to be able to mold the dough into blanks, eliminating their deformation, its plasticity must be increased to 0.5. For this purpose, an operation such as aging the dough is used, or enzyme preparations with proteolytic action are used. For a weakly structured wafer dough, the rheological characteristics of the dough are the viscosity and elasticity. The uniformity of dough distribution over the surface of the waffle irons, as well as the fragility of the wafer sheet, depend on them.

Confectionery dough, like all dough-like masses, is structured disperse system and consists of three phases: solid, liquid and gaseous.

Solid phase represent lyophilic flour colloids. These are water-insoluble protein complexes and wheat flour starch.

Liquid phase is a multicomponent aqueous solution of substances provided for in the dough recipe (invert syrup, water, sugar solution, molasses, salt, sodium bicarbonate, ammonium carbonate, milk, etc.). The composition of the liquid phase includes all water-soluble organic and mineral substances of flour.

The ratio between the solid and liquid phases depends on the type of dough, its moisture content, and the quantity and quality of gluten.

Gaseous phase makes up the air that is captured when kneading the dough, dispersed and retained in the dough. In addition, air enters with flour, water and other types of raw materials and semi-finished products. The gaseous phase can reach 10% in the test.

The degree of leavening of the dough depends on the rheological properties of the dough and on the uniform distribution of chemical leavening agents in the dough. The porosity and volume of dough pieces made from plastic dough - sugar and gingerbread - especially increases. Long and biscuit doughs, which have significant elasticity, resist the expansion of gas bubbles. These products have a slight rise and underdeveloped porosity.

Pasta dough

After kneading, the pasta dough is a loose crumbly mass; after passing through the screw chamber and pressing through the holes of the matrix, it is a compacted dough. In this form, it is characterized as an elastic-plastic-viscous colloidal body.

Technological diagram of a screw pasta press

Factors influencing the rheological properties of dough

Quantity and quality of gluten. It determines the basic technological properties of pasta dough and performs two main functions - 1 dough plasticizer, i.e. acts as a lubricant, giving the mass of starch granules fluidity and 2 binding substances. Those. combines starch granules into a single dough mass. Flour gluten consists of two main fractions: gliadin (extensible) and glutenin (elastic). Gliadin plays an important role in pasta production. It is this that determines the fluidity and cohesion of pasta dough. Glutenin determines the firmness and elasticity of raw products. Soft, highly stretchy raw gluten increases the plasticity of the dough and reduces its elasticity and strength. Dough made from flour with a gluten content of about 28% has the greatest strength. As the gluten content increases, the strength of the dough decreases and the plasticity increases. When the gluten content is below 28%, as the strength of the dough decreases, its plastic properties deteriorate.

Granulometric composition of flour. The granulometric composition of flour affects the duration of dough kneading and determines its water absorption capacity (WAP). Flour with a fine particle size (bread flour) has a large IPS and forms a strong dough. Flour with large particles (pasta flour) has a low EPS and forms a more flexible dough.

The rate of penetration of moisture into particles flour is determined primarily by the size of the flour particles. Large particles require longer kneading. Given the same particle size, moisture will penetrate slower into durum wheat milling particles than into less dense soft wheat milling particles.

To produce pasta with a particle size of up to 350 microns, and even more so up to 500 microns, it is necessary to use multi-trough presses, the kneading time of which is 16...20 minutes. When working on presses with a kneading time of 8...10 minutes, it is advisable to use flour with a particle size of no more than 200-250 microns (semi-grain or bakery flour).

As the dough kneading time increases, the strength of semi-finished pasta products increases and reaches its maximum value, and then begins to decrease.

Intensity (duration) of kneading. With increasing kneading time, the strength of the dough decreases and its plasticity increases. The duration of kneading the dough depends on two factors:

Achieving uniform distribution of water throughout the dough,

The rate at which moisture penetrates into particles.

For achieving uniform distribution of water throughout the dough Water is supplied to the kneading trough in a spray form for faster and more uniform distribution throughout the entire dough mass.

Another way to speed up the uniform distribution of moisture is to intensify the mixing of flour and water. For this purpose, multi-trough presses are used, in which the dough mixing shaft of the first trough rotates at a higher frequency than the shafts of subsequent troughs. In modern presses from the Pavan company, flour and moisture are pre-mixed in a centrifugal flour humidifier “Turbospray”, where flour particles and water in a given ratio are quickly and evenly moistened and enter the dough mixer trough.

Humidity . As the humidity of the dough increases, its plasticity increases and strength and elasticity decrease.

Moisture content of pasta dough- the first technological parameter with which the technologist can change, within certain limits, influence the physical properties of the dough, semi-finished pasta and product quality.

With promotion dough moisture content up to 32% the plasticity and fluidity of the dough increases and the process of pressing it through the matrices is facilitated. This leads to a decrease in pressing pressure and an increase in the extrusion speed, i.e. to increase press productivity.

At higher humidity (more than 32%), lumps are formed that do not pass through the inlet of the screw chamber, the strength of the pressed products decreases and the pressing pressure decreases.

Increasing the moisture content of the dough leads to an increase in the thickness of the solvate shells that surround the flour particles in the compacted dough. In this regard, the viscosity of the dough and the strength of semi-finished products decrease, and their plasticity increases.

Temperature As the temperature of the dough increases to approximately 75 o C, its plasticity increases and strength and elasticity decreases.

Pasta dough temperature- the second technological parameter with which the technologist can operate during the dough kneading process.

The traditional mode of kneading and shaping pasta dough involves increasing the temperature of the dough in front of the matrix to 50...55 0 C; when the temperature increases above 60 0 C, the structure of the dough is not fixed - denaturation of proteins occurs, loss of gluten binders, weakening of the structure of products, which leads to a decrease in the strength of products, an increase in the loss of dry substances during cooking products

Mechanism of formation of structures. Types of structures. Indicators of rheological properties. Effective viscosity, plastic viscosity, fluidity. Viscosity anomaly. Thixotropic restoration

Dispersed systems, which include chocolate semi-finished products and praline masses, have structures as a result of the interaction between dispersed particles of the solid phase. According to the nature of the bonds, coagulation structures are formed in them. Coagulation structures are formed by solid particles in a liquid dispersion medium and are characterized by relatively weak contacts between particles in terms of interaction strength.

There are compact and loose coagulation structures.

Loose dispersed coagulation structures occur at low volume concentrations of the dispersed phase (even at a concentration of less than 1%), if the dispersion is sufficiently high and the particles are anisometric. In chocolate masses, the dispersed phase is about 65%, and the particle size in the bulk is 16-35 microns. Among the particles of the solid phase are particles of cell membranes, cocoa shell particles, having the shape of plates, sticks, i.e. elongated shape. The adhesion of particles occurs at corners, edges and other irregularities, in areas of the highest concentration of free molecular forces. This is explained by the fact that in these places the adsorption-solvation shells of the dispersion medium become thinner. In these systems, the dispersion medium is retained inside the structure, and the entire system loses its mobility and does not delaminate over time.

Cocoa liquor contains less dispersed phase - about 45%. Therefore, the resulting loose coagulation structure has lower strength, which is not able to prevent delamination. Under the influence of mechanical action, the structure of cocoa liquor and chocolate masses is destroyed. But after preliminary mechanical destruction, such structures spontaneously recover over time. This phenomenon is called thixotropy, consists in restoring connections between particles after mechanical destruction as a result of a favorable collision of particles in Brownian motion. This is due to the presence of thin plasticizing layers between the particles.

Compact coagulation structures occur in chocolate masses after rolling. Due to the large volume of the dispersed phase - 75-73% and, accordingly, the low content of the dispersion medium, the particles are connected to each other by direct point (atomic) contacts. Such disperse systems do not have thixotropic properties.

In chocolate masses that have gone through all stages of technological processing, coagulation structures of two types are formed:

1.coagulation structures made of sugar microcrystals connected through thin films of water. The sugar content in chocolate masses exceeds 50% and its participation in structure formation is significant,

2.coagulation structures from microparticles of cellular tissues of cocoa beans, connected through layers of fat.

The formation of mixed structures is quite likely.

When cooling chocolate masses after molding, as a result of cocoa butter crystallization, coagulation structures with point contacts turn into condensation-crystallization structures. The main features of such structures are high strength compared to coagulation structures, determined by the high strength of the phase (direct) contacts between particles, the irreversible nature of destruction, i.e. the absence of thixotropic restoration of the structure, and greater fragility due to the rigidity of the contacts.

Posted on Allbest.ru

...

Similar documents

Basic concepts, definitions and tasks of engineering rheology. Mechanical models reflecting the elementary rheological properties of biochemical, biophysical, physicochemical and organoleptic characteristics of food products; rheometers, viscometers.

presentation, added 06/06/2014

Classification and assortment of rye and rye-wheat bread. Organoleptic assessment of bread quality. Study of porosity, crumb moisture, acidity of rye bread. Chemical composition and nutritional value. The main components of any test.

presentation, added 11/12/2014

Making puff pastry. Rheological properties of raw materials. Baking properties of wheat flour. Baker's yeast and its types. Table salt, its classification. Fats for cooking. Organoleptic properties of margarine. Eggs and egg products.

report, added 01/31/2009

Study of the influence of the dosage of soybean fortifier on the rheological properties of gingerbread dough prepared on the basis of bioactivated wheat grain. Calculation of the dosage of food soy fortifier to ensure optimal viscosity properties of the dough.

article, added 08/22/2013

Warehouses and preparatory departments. Dough preparation and dough cutting departments of bakery production. Production and workshop laboratories. Traditional methods of preparing wheat and rye dough using large thick doughs and sourdoughs.

practice report, added 11/15/2012

Recipe and dosage of wheat dough. Its kneading, formation, loosening and fermentation. Standards for loading fermentation tanks with flour. Dosing of raw materials in bakery production. Traditional methods of preparing wheat dough: sponged and straight.

course work, added 02/16/2016

Features of the development of a project for a confectionery shop with a capacity of 10 thousand products per day. Analysis of the stages of calculation of raw materials and food products. Consideration of problems in the selection of mechanical equipment. Characteristics of the production program of the confectionery shop.

thesis, added 02/01/2015

Classification and assortment of products made from air dough. Commodity characteristics of the main and auxiliary raw materials used in the production of the product. Organization of the work of the confectionery shop, technological equipment and labor of workers.

course work, added 04/19/2015

The influence of fatty products on the properties of dough and bread, their nutritional and consumer value. Sugar as a dough component. Technical and economic significance of the deposit, factors influencing its value. Production recipe for bread, dough preparation scheme.

test, added 02/05/2014

Phytocompositions, their functions, a list of plant raw materials for enriching confectionery and baking production. The history of the emergence of phytocompositions, their therapeutic and side effects. Specialized bread with phytocomposition for athletes.

The compacted pasta dough entering the matrix is an elastic-plastic-viscous material.

Dough elasticity is the ability of the dough to restore its original shape after quickly removing the load; it manifests itself under small and short-term loads.

Plasticity is the ability of dough to deform. Under long-term and significant loads (above the so-called elastic limit), pasta dough behaves like a plastic material, i.e. after removing the load, it retains its given shape and is deformed. It is this property that allows raw pasta of a certain type to be formed from dough.

Viscosity is characterized by the magnitude of the adhesion forces between particles (cohesion forces). The greater the cohesion forces of the dough, the more viscous (strong) and less plastic it is.

Plastic dough requires less energy to form and is easier to shape. When using metal matrices, more plastic dough produces products with a smoother surface. With increasing plasticity, the dough becomes less elastic, less durable, more sticky, sticks more strongly to the working surfaces of the screw chamber and screw, and raw products from such dough stick together more strongly and do not retain their shape well.

Rheological properties of compacted dough, i.e. the ratio of its elastic, plastic and strength properties is determined by the following factors.

As the humidity of the dough increases, its plasticity increases and strength and elasticity decrease.

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

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

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

The use of plant additives had a significant effect on the structural and mechanical properties of the farinograph dough (Table 14-15). Thus, water absorption increased in variants using 3-5% MCC by 0.8-1.5 cm3, pumpkin seed cake - by 2.4-4.0 cm3, sesame seed cake - by 0.6-2.3 cm3, and when adding 30% of the “Gifts of Nature” mixture - by 1.1 cm3. The increase in water absorption capacity with the addition of microcrystalline cellulose can be explained by its capillary structure and, as a consequence, increased ability to adsorb water with the formation of colloidal systems. In the case of adding pumpkin and sesame cake, the increase in water absorption is associated with a high protein content, which has hydrophilic properties. This indicates the need to increase the amount of water added when kneading dough if the studied herbal additives are used in bread baking practice.

Table 14

Rheological properties of dough from mixtures of wheat flour with vegetable additives (2011-2012)

	Water absorption,	dough formation,	Dough stability	liquefaction, EF	Quality indicator, mm










2% MCC, 5% KZH, 7% TG
2% MCC, 10% KZH, 3.5% TG
3% MCC, 15% QL, 10% TJ

*MPVS - premium wheat flour

**MCC - microcrystalline cellulose

***KZH - cedar cake

****TJ - pumpkin cake

Table 15

Rheological properties of dough from mixtures of wheat flour with vegetable additives (2013)

	Water absorption	Dough formation time, min	Dough stability	Degree of liquefaction, EF	Quality indicator, mm	Valorimetric assessment, E. Val.




15% mixture "Gifts of Nature"
30% mixture "Gifts of Nature"

*ZhK - sesame cake

Water absorption decreased in variants with the combined use of 2% MCC, 5% cedar seed cake, 7% pumpkin seed cake; 2% MCC, 10% cedar seed cake, 3.5% pumpkin seed cake; 3% MCC, 15% cedar seed cake, 10% pumpkin seed cake by 2.8; 3.5; 2.2 cm3. This can be explained by the competitive interaction of proteins with hydrophilic properties and fats with hydrophobic properties. Therefore, it is necessary to reduce the amount of water added when kneading dough if the studied herbal additives are used in bread baking practice.

In the case of adding 10-15% cedar seed cake, 7-21% pumpkin seed cake, 5-15% sesame seed cake, and the joint addition of herbal additives, the dough formation time increased by 1.3-1.8; 3.0-13.0; 2.7-3.5; 3.3-4.8 minutes, respectively, and when using 30% of the “Gifts of Nature” mixture - by 2.2 minutes compared to the control (Fig. 5-6).

Rice. 5

In variants using 15% pine nut kernel cake, 7-21% pumpkin seed cake, 5-15% sesame seed cake, joint addition of herbal additives, as well as 15-30% of the “Gifts of Nature” mixture by weight of wheat flour, an increase in stability was noted test by 0.9; 0.8-5.0; 2.5-3.8; 1.0-4.3 and 1.8-4.7 minutes, respectively. Thus, the value of dough stability increased as the mass fraction of the introduced components increased. This is explained by an increase in the protein content in flour as the main component that absorbs moisture and forms the solid phase of the dough.

Rice. 6

The noted increase in the time of formation and stability of the dough (indicates an increase in its resistance during mechanized kneading. This allows us to recommend increasing the duration of kneading in variants using the specified amounts of cedar, pumpkin and sesame seed cakes, as well as the “Gifts of Nature” mixture.

A significant improvement in the rheological properties of the dough was observed when using cedar, pumpkin, sesame cake, as well as the “Gifts of Nature” mixture in the studied quantities and in terms of quality. This indicator increased significantly in the above options, its values fluctuated across the options in a wide range of 80.0-270.0 EF and 105.0-115.0 EF.

An important indicator when deciphering the farinogram is the degree of liquefaction of the dough. The values of this indicator ranged from 25.0 to 135.0 EF and from 80.0 to 115.0 EF. In the control samples, the degree of liquefaction was 45.0 EF (Table 14), which corresponds to a good improver, and 80 EF (Table 15), which corresponds to wheat of the most valuable quality. The addition of 10-15% cedar, 5-15% sesame cake, 15% “Gifts of Nature” mixture caused an increase in the degree of liquefaction by 1.4-1.8; 1.25-1.4; 1.4 times respectively. With the combined introduction of herbal additives (MCC, cedar and pumpkin seed cake) in the studied quantities, this indicator increased by 1.9-3.0 times.

A general indicator for determining the rheological properties of a test using a farinograph is a valorimetric assessment (or farinogram area). The valorimetric assessment significantly increased in all variants using pumpkin seed cake (by 8.0-35.0 E.Val.), sesame seed cake (by 7.5-13.5 E.Val.), with the joint addition of 2% MCC, 5% cedar seed cake, 7% pumpkin seed cake, and also when using 15-30% of the “Gifts of Nature” mixture (at 8.0, 5.5 and 11.0 E.Val., respectively).

The results of determining the structural and mechanical properties of the dough using a farinograph are presented in Fig. 7-9, in appendices 4-7, 16-25.

Rice. 7 Farinograms characterizing the rheological properties of dough obtained from mixtures of premium wheat flour (MPWF) with microcrystalline cellulose (MCC), cedar cake (KZh), pumpkin cake (PW): 1 - MPWF (control); 2 - MPVA + 1% MCC; 3 - MPBC + 3% MCC; 4 - MPVA + 5% MCC; 5 - MPVS + 5% QOL; 6 - MPVS + 10% QOL; 7 - MPVS + 15% QOL; 8 - MPVA + 7% TG

Rice. 8 Farinograms characterizing the rheological properties of dough obtained from mixtures of premium wheat flour (MPWF) with cedar cake (CP), pumpkin cake (PCP), microcrystalline cellulose (MCC): 1 - MPWF (control); 9 - MPVA + 14% TG; 10 - MPVA + 21% TG; 11 - MPVS + 2% MCC, 5% KZH, 7% TG; 12 - MPVS + 2% MCC, 10% QL, 3.5% TG; 13 - MPVS + 3% MCC, 15% KZH, 10% TG

Rice. 9 Farinograms characterizing the rheological properties of dough obtained from mixtures of premium wheat flour with sesame cake (FB): 14 -MPVS (control); 15 - MPVA + 5% FA; 16 - MPVA + 10% FA; 17 - MPVA + 15% FA; 18 - MPVA + 15% of the “Gifts of Nature” mixture; 19 - MPVA + 30% mixture “Gifts of Nature”

The results of determining the rheological properties of the test using an alveograph are presented in table. 16 and in Fig. 10.

Table 16

Rheological properties of alveograph test (2013)

According to the data presented in table. 15, the use of 15-30% of the “Gifts of Nature” mixture led to a decrease in the maximum excess pressure (P) by 11-38 mm. aq. Art., and tensile strength (average abscissa value at rupture L) by 14-38 mm. A change in the test deformation index was also noted. With the addition of 30% of the mixture, this indicator decreased by 164 * 10-4 J. The shape of the curve in the variant with the addition of 30% of the mixture indicates a noticeable deterioration in the rheological properties according to the alveograph. Its value increased to 4.52.

Rice. 10

1) MPVS; 2) MPVA + 15% of the “Gifts of Nature” mixture; 3) MPVA + 30% of the “Gifts of Nature” mixture