The process of drying pasta in dryers. Method for drying pasta

Raw pasta is a convenient environment for various biochemical and microbiological processes to take place. To prevent the development of these processes, products are subjected to conservation by dehydration - drying to a moisture content of not more than 13%.

Drying pasta is the longest stage in the production process. The correctness of its implementation depends on such indicators of the quality of the finished product as strength, vitreous fracture, acidity. Very intensive drying can lead to cracking of products; excessively long, as well as underdrying - to their souring, and when drying in a layer - to the formation of ingots and deformation. Drying is completed upon reaching a moisture content of 13.5-14%, so that after cooling their moisture content is no more than 13%.

In compacted pasta and raw products, a large proportion of moisture is bound osmotically. During drying, the adsorption and osmotically bound moisture is removed, and first the less strongly bound osmotic moisture is removed, and then as the more strongly bound adsorption moisture. First of all, the moisture bound by starch is removed, and then the proteins are dehydrated. The dough, when dried, releases moisture extremely slowly, therefore, to control the dehydration process, it is necessary to take into account the entire set of properties of pasta dough.

There are two reasons why moisture is removed from products:

1) temperature difference between the material to be dried and the environment

2) the difference in humidity between the outer and inner layers of products.

Ways to remove moisture:

1) contact- pasta is placed on a preheated surface, the products are heated and moisture is removed.

2) convective- based on heat and moisture exchange between the dried material (raw pasta) and heated drying air that blows over the products. The drying process consists in the supply of moisture inside the product to its surface, the transformation of moisture into steam and the removal of steam from the surface of the product. According to this scheme, osmotically bound moisture is removed. Adsorption-bound moisture turns into vapor inside the product and moves in the form of vapor to the surface.

3) radiation, i.e. transfer of energy from the emitter, heated to a high temperature, to the product by means of magnetic oscillations.

4) sublimation– drying of pre-frozen product with removal of ice in high vacuum.

In most cases, the drying of pasta is carried out in a convective way..

When drying pasta in a convective way, heated drying air performs the following functions:

Gives the material the energy (heat) needed to turn water into steam

Absorbs steam evaporating from the surface of products

It removes evaporated steam from the surface of the products.

Therefore, the higher the air temperature, the more intense the evaporation of moisture from the material; the lower its humidity, the more intensively it will absorb evaporating moisture. Also, the intensity of drying depends on the speed of air movement over the material: the higher the air speed, the faster the evaporated moisture is removed from the material.

Convective drying modes depending on air temperature:

1) traditional low temperature modes– t of drying air does not exceed 60 0 С

Drying of pasta in cupboard non-calorific dryers of types VVP, 2TsAGI-700, "Diffuser".

Drying of short-cut products in steam conveyor dryers of types KSK-4G-45 and KSK-4G-90.

Hanging drying of long products in dryers of automated production lines B6-LMV, B6-LMG.

The main disadvantage of traditional low-temperature drying regimes is the long duration of the drying process.

2) high temperature regimes- the air temperature at a certain stage of drying reaches 70-90 0 C.

3) ultra-high temperature regimes- t of drying air exceeds 90 0 С

Drying mode is a set of drying air parameters (t, w speed), drying duration, the presence of periods of drying and dampening, their duration and frequency of alternation.

The ideal drying mode is one in which the internal mass transfer of moisture will not lag behind the moisture transfer from the surface of the products. However, it is difficult to implement such a regime, because the drying process is very slow, which can cause souring of the product. To speed up the drying process and obtain good quality products in the initial period (with dough moisture up to 20%), they are dried under strict conditions, i.e. with intensive air blowing with high drying capacity. Then, in order to avoid cracking, drying is carried out under milder conditions, when moisture is slowly removed by air with low drying capacity. This process must be carried out especially carefully in the last stages of drying, when the moisture content of the products is below 16%. In practice, these conditions are observed when drying products in dryers of production lines, where the process is divided into 2 stages - preliminary and final drying.

Drying modes depending on the drying capacity of the air:

1) three-stage or pulsating- consists of 3 stages:

a) pre-drying- lasts from 30 minutes to 2 hours. During this time, from 1/3 to 7% of the moisture evaporates, which must be removed from the products. The process is carried out under hard conditions, because the dough is plastic and there is no danger of cracking. The purpose of this stage is to accelerate drying, stabilize the shape of raw products, prevent them from stretching, molding and souring.

The dough leaving the pre-drying chamber must have a moisture content of at least 20%. The crust formed on the surface can cause cracking of the product during further drying, therefore, to soften it, the products are sent for softening.

b) softening– blowing with hot air with a relative humidity of 90-100%. At the same time, there is practically no evaporation of moisture from the surface, and the supplied heat is spent on heating the products, leveling the humidity in the inner and outer layers of the pasta tube.

c) final drying- lead under mild modes, tk. products acquire elastic properties, and the rate of moisture evaporation from their surface should be commensurate with the rate of its supply from the inner layers to the outer ones. At this stage, the processes of drying and tempering are sequentially alternated, and the ratio of the drying time to the tempering time is approximately 1:2.5.

A similar method is used for drying long products in a suspended state in automatic production lines LMB, B6-LMG and in the lines of foreign firms Pavan and Braibanti. All these lines consist of a press, self-weighting, dryers for pre-drying and final drying, a stabilization chamber and a device for removing products from bastuns.

The parameters of the drying air in the preliminary dryer are t=35-450С, w= 65-75%. The final dryer is a tunnel divided along the length into drying zones and tempering zones. Air heaters and fans are installed in the drying zones. The air temperature in the final drying zone is 35-45 0 С, w= 70-85%. In terms of height, the tunnel of the final dryer is divided into several tiers, along which bastuns with products pass sequentially, crossing the drying and tempering zones in turn.

2) air drying with constant drying capacity

In this mode, the air parameters remain approximately constant from the beginning to the end of drying (t=35-45 0 С, w= 65-75%). A major disadvantage of this mode is that drying has to be carried out at a high drying capacity of the air. This mode can be used for products that are most resistant to deformation: soup fillings and short-cut products. Drying takes place in a shorter time, their size is smaller, they are better amenable to comprehensive blowing when pouring.

This method is used in factories for drying pasta in cassettes in heatless dryers such as GDP, Diffuser, 2TsAGI-700. Drying time 20-24 hours.

3) air drying with variable drying capacity

It is used in continuous belt conveyor steam dryers used for drying short-cut products, such as PKS-20, PKS-40, KSA-80, SPK-45, SPK-90. Dryers are a chamber inside which 5-5 conveyors with products moving in opposite directions are located one above the other. In this case, the product is sequentially poured from the upper belts to the lower ones and is blown with air heated in the heater. Drying time 30-90 minutes depending on the size of the products. Fresh air is heated by the lower heater to 50-60 0 C and has a humidity of 15-20%. Passing through the layer of products on the lower belt, the air gives off part of the heat and is moistened. Rising up, it is heated by the second heater to the same temperature, passes a layer of products on the second belt, etc. As a result, at the exit from the dryer, its temperature reaches 40-50 0 C, and relative humidity - 50-60%, i.e. drying is carried out by air with varying drying capacity.

To mitigate the drying regime and improve the quality of products, 2 dryers are installed in series, the first serves as a preliminary, the other as a final dryer. The total drying time is 1-3 hours, including 0.5 hours in the pre-chamber. A similar mode is used in automatic production lines for drying short products.

4) drying with preliminary heat treatment of raw products

Such drying consists in blowing tubular products with a porous-air mixture with a temperature of 95-98 0 С and a relative humidity of 95% for 2 minutes and short-cut products with dry steam at a temperature of 120-180 0 С for 30 seconds, followed by drying, at a constant drying capacity of air .

Such processing of products before drying significantly reduces the dehydration process, because. allows you to apply harsh drying modes without fear of cracking. In this case, two interrelated processes take place: thermal denaturation and gelatinization of starch.

Currently, the following dryers are used in the pasta industry: for drying short products - cabinet, belt and drum, for drying long products - cabinet and tunnel.

Products are distributed in a layer of 2-3 cm on mesh frames. Cabinet dryers have air heaters. The closet is closed with doors. The fan carries out a continuous movement of air. There are openings with scrapers for regulating the suction of fresh air and the ejection of exhaust.

Drying in cupboard dryers can be carried out with permanent drying capacity of air (for example: t in \u003d 45-50 ° С W in \u003d 70-80%), and with changing drying capacity of the air. For example, drying, consisting of three stages:

1. pre-drying t in = 55-60 ° C W in = 70-80% to a moisture content of products of 20%.

2. Softening for 30-45 minutes, in this case, the moisture content of the products is equalized throughout their mass.

3. Final drying t in = 45-50 ° C W in = 70-75% to a moisture content of products of 13%.

Such dryers are used in workshops of small productivity.

Both short and long pasta can be dried in cupboard dryers.

Below are various technological schemes for drying pasta in cabinet dryers.

Drying short pasta in cupboard dryers involves 2 schemes:

1st: the semi-finished pasta leaves the press with a moisture content of 32-34% and enters the cabinet dryer. In a cupboard dryer, its moisture content is reduced to 13-13.5%. Next, pasta enters the stabilizer bunker, where their moisture content is reduced to 12-12.5%;

2nd: semi-finished pasta leaves the press with a moisture content of 32-34% and enters the trobatto. Trobatto is a cabinet equipped with heaters, fans and five mesh frames that reciprocate during the drying of pasta. In trobatto, the moisture content of pasta is reduced to 29-27%. After trobatto, the pasta enters the cabinet dryer. In the cabinet dryer, its moisture content is reduced to 13-13.5%. Next, the pasta enters the stabilizer bunker, where their moisture content is reduced to 12-12.5%.

Drying long pasta in cabinet dryers provides for 1 scheme: semi-finished pasta leaves the press with a moisture content of 32-34% and enters the cabinet dryer. In a cupboard dryer, its moisture content is reduced to 13-13.5%. Next, the pasta enters the stabilizer-accumulator, where their moisture content is reduced to 12-12.5%.

Drying short pasta on production lines involves 3 schemes:

1st: semi-finished pasta leaves the press with a moisture content of 32-34% and enters the final dryer. In the final dryer, its moisture content is reduced to 13-13.5%. Next, pasta enters the stabilizer bunker, where their moisture content is reduced to 12-12.5%;

2nd: semi-finished pasta leaves the press with a moisture content of 32-34% and enters the trobatto. Trobatto is a cabinet equipped with heaters, fans and five mesh frames that reciprocate during the drying of pasta. In trobatto, the moisture content of pasta is reduced to 29-27%. After trobatto, pasta enters the final dryer. In the final dryer, its moisture content is reduced to 13-13.5%. Next, the pasta enters the stabilizer bunker, where their moisture content is reduced to 12-12.5%.

3rd: semi-finished pasta leaves the press with a moisture content of 32-34% and enters the trobatto. In trobatto, the moisture content of pasta is reduced to 29-27%. After trobatto, the pasta enters the pre-dryer, where its moisture content is reduced to 18-20%, after which the products enter the final dryer. In the final dryer, its moisture content is reduced to 13-13.5%. Next, the pasta enters the stabilizer bunker, where their moisture content is reduced to 12-12.5%.

Drying of long pasta on production lines provides for 1 scheme: the semi-finished pasta leaves the press with a moisture content of 32-34% and enters the preliminary dryer. In the preliminary dryer, semi-finished pasta reaches a moisture content of 18-20%. Next, the semi-finished product of long pasta enters the final dryer. In the final dryer, its moisture content is reduced to 13-13.5%. Next, the pasta enters the stabilizer-accumulator, where their moisture content is reduced to 12-12.5%.

Questions for self-control (training)

1. Briefly describe the process of drying pasta.

2. List the ways of drying pasta.

3 Describe the convective method of drying pasta. Give the main parameters of the drying air

4. Classify the convective drying modes.

5. Describe the pasta drying curve.

6. Tell us how the rheological properties of semi-finished pasta change during low-temperature and high-temperature drying.

7. List the advantages of high temperature and ultra high temperature drying.

8. List the ways to intensify the drying process.

9. Tell us about the purpose of the processes of cooling and stabilizing pasta.

10. Give schemes for drying short and long pasta in industrial dryers.

Control test

1. What are the actions of the technologist or operator if after trabatto or preliminary drying there is a darkening of the products?

2. When the products reach a moisture content of 18-16%, is the drying of the products carried out?

3. The appearance of cracks in products during the drying process is due to?

4. Is cracking of products during storage due to?

5. In the process of stabilization of products after high-temperature drying occurs?

6. Does the stabilization of pasta after high-temperature and ultra-high-temperature drying pass?

7. The moisture content of the pasta after the pre-dryer should be?

8. What humidity should the products be after the final dryer at high temperature drying?

9. What are the steps involved in drying long-cut products?

Raw pasta cannot be stored for a long time due to the biochemical and microbiological processes occurring in them. To exclude these processes, they are subjected to drying to a moisture content of not more than 13%.

Drying pasta is the longest and most important stage in the production process. The correctness of its implementation largely depends on such indicators of the quality of the finished product as strength, vitreous fracture, acidity. Drying is usually completed upon reaching a moisture content of 13.5-14%, so that after cooling before packaging, their moisture content is no more than 13%.

When dried, pasta dough loses its plasticity and becomes brittle at a certain humidity, its structural and mechanical properties change due to the gradual transformation of gluten into a strong, hard vitreous mass. Products are compacted, their size is reduced by
6-8% - shrinkage occurs . Moisture should be removed gradually, as excessive drying leads to uneven shrinkage, causing cracking and distortion of products. Pasta can be dried under hard conditions without fear of cracks in them up to 20% moisture content. When the product reaches this moisture content, in order to avoid cracking, it is necessary to carry out drying under mild conditions, slowly removing moisture. This should be done especially carefully at the last stages of drying, when the products reach a moisture content of 16% or less.

However, too long drying can lead to darkening of products as a result of the action of lipoxygenase and polyphenol oxidase enzymes, the formation of melanoidins, as well as sourness and mold. Therefore, the choice of drying mode is very important for the quality of the finished product.

The drying mode consists of temperature, humidity and air velocity, drying time, alternating drying and softening, and depends on the type of manufactured products. Short-cut products are dried in conveyor belt dryers in bulk at a temperature of 50-70 ° C for 20-90 minutes. Long products are placed in tray cassettes or hung on drying poles ( bastuns) and dried at a temperature of 30-50 ° C for 16-24 hours in cabinet dryers (Fig. 9) with alternating drying and tempering to equalize the moisture of the outer and inner layers of products. The higher the air temperature at the beginning of drying, the higher its humidity should be.

Cooling (stabilization) dried products are carried out in stabilizer-coolers, where they are slowly (at least 4 hours) cooled by air having a temperature of 25-30 ° C and a relative humidity of 60-65%. Products even out moisture and reduce internal shear stresses that can be left behind when a product is quickly cooled, sometimes leading to cracking and the formation of scrap and crumbs after packaging.

When choosing and developing drying modes, it is necessary to take into account two main features of pasta as an object of drying:

with a decrease in the moisture content of products from 29 ... 30 to 13 ... 14%, their linear and

volumetric dimensions by 6...8%:

in the process of drying, the structural and mechanical properties of the products change.

Rice. 4 Pasta equilibrium moisture curves.

The nature of the change in the structural and mechanical properties of dried pasta

largely determined by the parameters of the drying air, primarily its temperature and humidity.

Currently, depending on the air temperature, three main modes of convective drying of pasta are used:

traditional low-temperature (LT) modes, when the temperature of the drying air does not exceed 60 °C;

high-temperature (HT) modes, when the air temperature at a certain stage of drying reaches 70 ... 90 "C;

ultra-high temperature (SHT) modes, when the air temperature exceeds 90 °C.

Consider the features of changes in the structural and mechanical properties of pasta when using these three temperature regimes. Under low-temperature regimes, raw products supplied for drying are a plastic material and retain their plastic properties up to about 20% humidity. With a decrease in humidity from about 20 to 16%, they gradually lose the properties of a plastic material and acquire the properties characteristic of an elastic solid material. At this humidity, pasta is an elastic-plastic body. Starting from about 16% moisture, pasta becomes a hard, elastic, brittle body and retains these properties until the end of drying.

Under mild drying conditions, i.e., when products are slowly dried with air with low drying capacity, the difference in humidity between the outer and inner layers is small, since moisture from the wetter inner layers has time to move to the dried outer layers. The rate of moisture evaporation from the surface of products corresponds to the rate of moisture supply from the inner layers (see Fig. 1, a). All layers of products are reduced approximately evenly: the shrinkage of products increases in direct proportion to the decrease in their moisture content.

Under harsh drying conditions, i.e., intensive drying of products with air with high drying capacity, the difference in humidity between the outer and inner layers reaches a significant value due to the fact that moisture from the inner layers does not have time to move to the outer ones. At the same time, the drier outer layers tend to shorten their length, which is prevented by the wetter inner layers - stresses arise inside the products at the boundary of the layers, which are called internal shear stresses. The magnitude of these stresses is the greater, the more intensively moisture is removed from the surface of the products, the more the rate of moisture supply from the inner layers lags behind, and the greater the moisture gradient. Shrinkage of products during hard drying occurs unevenly (see Fig. 5): in the initial period of drying, intensive shrinkage occurs, and then it gradually fades.

While the dried pasta retains plastic properties, the resulting internal shear stresses are absorbed by changing the shape of the products without destroying their structure (Fig. 5).

When the products acquire the properties of an elastic material, the resulting internal shear stresses, if they exceed a certain maximum permissible, critical value, lead to the destruction of the structure of the products - the appearance of microcracks on the surface of the products, which, with intensive removal of moisture, deepen and connect to each other. Pasta dried in this way is very fragile, often turning into scrap or even crumbs.

From the foregoing, an important conclusion follows that, with a low-temperature drying regime, pasta can be dried under strict conditions without fear of cracks appearing in them, up to about 20% moisture content. When the product reaches this moisture content, in order to avoid cracking, it is necessary to carry out drying under mild conditions, slowly removing moisture. Particular care should be taken to remove moisture in the last stages of drying when the products reach a moisture content of 16% or less.

which use low-temperature drying modes, where the drying process is divided into two stages - preliminary and final drying.

However, even at the first stage of removing moisture from products, the degree of rigidity of the regime has its limitations, since excessively rapid drying of the surface layer of raw products with dry air at a temperature of about 60 ° C can lead to its peeling, to the formation of a scaly surface of products, due to the fact that moisture does not have time to approach to the surface from the inner layers of the dense structure of dough pieces. In addition, with this mode of drying, a sharp transformation of the moisture of the products into steam can lead to the formation of bubbles in the thickness of the still plastic products. Therefore, the higher the air temperature at the beginning of drying, the higher its humidity should be.

At the outlet of the dryer, the pasta has a temperature approximately equal to the temperature of the drying air. Therefore, before packaging, they must be cooled to the temperature of the packaging compartment, otherwise the uncontrolled process of further evaporation of moisture from warm packaged products will continue in the package, and when using sealed packaging, such as plastic bags, moisture will condense on the inner surface of the package.

It is preferable to use slow cooling for at least 4 hours, during which the products are washed with air at a temperature of 25 ... 30 "C and a relative humidity of 60 ... 65%. stabilization products: the final leveling of moisture throughout the entire thickness of the products, the absorption of internal shear stresses that could remain after intensive drying of the products, as well as a slight decrease in the mass of the cooling products due to the evaporation of 0.5..1.0% of moisture from them.

Rapid cooling of dried products by intensive blowing in coolers of various designs or their cooling on belt conveyors when feeding to packaging is less desirable: despite the fact that finished products have time to cool to the workshop temperature in a short time (about 5 minutes) and their subsequent shrinkage in the package does not occur , for such a short period of time, the internal shear stresses in unstabilized products not only do not have time to disappear, but increase due to the evaporation of moisture from the surface of the products and an increase in the moisture gradient. And if the products were subjected to hard drying, then cracking and turning them into scrap and crumbs can occur after packaging.

Thus, an increase in internal shear stresses during rapid cooling of products is due to the fact that a sharp decrease in the temperature of the surface layer of products leads to rapid evaporation of moisture from it. And although the resulting temperature gradient is directed in the same direction as the humidity gradient - inside the product, moisture does not have time to get from the inner layers to the surface due to the low moisture conductivity of the dense structure of the dried products (see Fig. 48, b).

At high-temperature and ultra-high-temperature drying modes, when the air temperature exceeds 70 and 90 °C, respectively, pasta remains in a plastic state up to 16 ... 13% humidity (depending on temperature). In this case, the critical moisture content of products W*(see Fig. 49), i.e., the moment of transition of the material from the plastic state to the elastic state, the transition from a constant drying speed to a falling speed, decreases almost to the moisture content of the finished pasta. Therefore, it becomes possible to use such modes throughout the drying process, significantly reducing its duration. However, in this case, in order to avoid cracking of the dried products, it is especially necessary to carefully stabilize and cool the products - without further evaporation of moisture from them. For this, the temperature and humidity conditions for stabilization and the cooling of dried products must correspond to the same equilibrium moisture content, i.e., at the level of 13%. For example, if the stabilization of dried products is carried out at 70 ° C, then the relative humidity of the air should be about 85% (the equilibrium moisture content of the products at these parameters is 13% - see Fig. 51), and after stabilization, the products can be immediately cooled with air in the workshop with temperature of 20...25 °C and relative humidity of about 65%: these parameters correspond to the same value of equilibrium humidity (13%), so there will be no evaporation of moisture from the surface of the products during cooling.

Based on the foregoing, it can be concluded that the main reason for the occurrence of stresses inside the dried pasta, which lead to a change in shape or to the formation of cracks in the products (depending on the ratio of the plastic and elastic properties of the dried products), is the lag of the internal moisture transfer from the evaporation of moisture from the surface product layers. This causes the appearance of a significant moisture gradient, the magnitude of which can serve as a measure of the risk of cracking of dried products.

The nature of the dependence of the moisture gradient on two main factors: relative humidity and temperature of the drying air, shown in fig. 54 shows that at a constant temperature, an increase in air humidity leads to a decrease in the humidity gradient, and at a constant air humidity, slight changes in the humidity gradient occur at low and high temperatures.

Drying pasta in cupboard dryers.

Drying pasta in cabinet dryers. Tray cassettes are used for drying pasta in cupboard dryers. Drying is usually carried out in cupboard non-calorific dryers of the types of GDP, 2TsAGI-700, "Diffuser".

The GDP dryer consists of a wooden cabinet 4 1600 mm deep, 1260 mm wide and 2010 mm high. The frame of the cabinet is made of wooden bars, which are sheathed with plywood. A casing is attached to the lid of the cabinet 3 and electric motor 1 with an axial fan mounted on its shaft 2. The fan blades are located inside the shroud that directs airflow into the cabinet, while the motor is located outside the shroud, in front of the fan.

156 double cassettes 5 are installed in the dryer cabinet: two Rows in depth, three in width and 26 cassettes in height. The capacity of the cabinet for dry products is 600 kg. When using single cassettes, they are installed in four rows in depth.

The pasta is dried by blowing air through the pasta tubes in the cassettes. In this case, the air of the drying compartment is used, the parameters of which are maintained at a constant level (drying with a constant drying capacity of the air), namely: temperature 30 ... 35 ° C, relative humidity 65 ... 70%. The air in the drying room is heated either from a battery of radiators or a heater, through which fresh air is blown into the room instead of part of the humidified exhaust air sucked out of the room.

For more uniform drying, periodically, after 1 hour, change the direction of air movement in the dryers to the opposite, switching the electric motor to work in the opposite direction, i.e., by reversing the electric motor.

The drying time at the specified air parameters should be from 20 (for pasta of large diameter) to 24 hours (for pasta of small diameter). The desire to reduce the drying time by using drier air or increasing the speed of air movement leads to a large amount of cracked pasta. On the other hand, it is necessary to ensure that the air humidity in the drying compartment does not increase more than 70 ... 75% in order to avoid souring and molding of pasta, especially in the inner rows of cassettes.

When drying in tray cassettes, pasta is blown with air from the inner and outer surfaces of the tubes. However, due to uneven contact of pasta, uneven removal of moisture from their surface occurs, a consequently, uneven shrinkage of products. This leads to a strong curvature of the products during drying, which significantly reduces their quality, increases the consumption of containers for packaging. In addition, the close contact of the tubes in the cassette and the inability to quickly remove moisture in the initial stage of drying often lead to the sticking of the tubes to each other, the formation of ingots.

Significant disadvantages of this drying method are also the cost of a large amount of manual labor and severe climatic conditions for working in the drying department - high humidity and temperature. However, this method of drying pasta does not require complex expensive equipment and large production areas.

In order to eliminate manual labor, a number of pasta enterprises created mechanized production lines for the production of pasta with drying in tray cassettes.

Dryers of mechanized production lines are constructed from several cabinet units installed in one or two rows. On both sides of the apparatus (in single-row dryers) or between the rows of apparatus (in double-row dryers), stacks of cassettes with dried pasta move slowly. Dryers are usually enclosed in a casing, which makes it possible to intensify the drying process by using higher air temperatures - up to 40 ... 45 ° C with a simultaneous increase in humidity up to 70 ... 75 %.

The most commonly used dryer design with ten ventilation units, which does not provide sufficient drying time and requires the use of drying air with increased drying capacity. Therefore, to produce strong pasta, a dryer with a large number of ventilation units is needed.

Drying of short-cut products in cabinet dryers. For drying short-cut products, the above non-calorific cabinet dryers can also be used. In this case, the products are distributed in a layer of 2 ... 3 cm on mesh frames, which are placed one above the other in the dryer. However, for these purposes, cabinet dryers of various designs with individual air heaters are now widely used in workshops of small productivity: more often - electric ones with a battery of heating elements with a capacity of 3 ... 8 kW, less often - steam heaters.

The principle of drying remains the same: the fan carries out a continuous movement of air inside the cabinet, driving it over the surface of the products scattered on the frames. However, in this case, the cabinet is closed with doors, and due to the presence of an air heater (usually in front of the fan) and openings with dampers to control the intake of fresh air and the ejection of part of the exhaust air in the cabinet, it is possible to set the necessary drying modes with an air temperature of up to 60 ... 65 ° C and relative humidity up to 80% (due to moisture evaporated from the products). In this regard, it is possible, on the one hand, to vary the drying parameters over a wide range and, on the other hand, to maintain them at a given level with a sufficient degree of accuracy.

For drying short-cut products in closed cabinet dryers, a variety of modes can be used, for example:

drying with a constant drying capacity of air at a temperature of 45 ... 50 "C and a relative humidity of 70 ... 80% to a moisture content of products of 13.5 ... 14.4%;

three-stage drying mode: the first stage - pre-drying at a temperature of 55...60 °C and a relative air humidity of 70...80% to a moisture content of products of 20...21%; the second stage - softening for 30 ... 45 minutes when heating and ventilation are turned off and with the dryer doors closed: the moisture from the products does not evaporate, the moisture content of the products is equalized throughout their mass; the third stage is the final drying at a temperature of 40...45 "C and a relative air humidity of 70...75% to a product moisture content of 13.5...14.5%.

In both cases, the duration of drying depends on the shape of the products, the thickness of the layer of products on the frames, the speed of air movement and is determined experimentally.

After drying, it is advisable to stabilize the products by slow cooling in the cabinet for 2-3 hours with the heating and ventilation turned off and the doors closed.

Some firms, in particular "Pavan" (Italy), offer the supply of cabinet dryers for short-cut products complete with a primary drying unit - trabatto. The purpose of this installation is to create a dried crust on the surface of raw short-cut products, which prevents the products from sticking together during their further drying in a layer on the frames.

The semi-finished product moves sequentially through all grids. By adjusting the speed of rotation of the drive drums with a variator, it is possible, within certain limits, to change the thickness of the layer of products on the conveyor belts and the duration of the products in the dryer.

Conveyor dryer C-109-04 is designed for high-temperature drying of pasta with hydrothermal treatment. This drying technology makes it possible to obtain high quality pasta in terms of composition, color, cooking properties and appearance.

Dryer S-109-2 tray

Designed for high-temperature drying of pasta with hydrothermal processing. This drying technology makes it possible to obtain high quality pasta in terms of composition, color, cooking properties and appearance.

The line carries out convective drying of pasta, automatically maintaining the set parameters (temperature, humidity) inside each section. The cost of electricity per kilogram of products is 0.2 kW.

Stabilizer-cooler С-109-1

The stabilizer-cooler is designed to cool pasta for 30 minutes, with a moisture content of 12-13% at the outlet, which makes it possible to produce instant packaging of products. Provides:
- reduction of the stabilization time of products from 4-6 hours to 30 minutes;
– elimination of defects associated with the fragility of products during pneumatic transportation from the drying line to the stabilizing hopper.

Designed for drying short-cut pasta, as well as for drying vegetables, fruits and other products. Drying cabinet made of thermostabilized panels. Carries out convective drying of products with minimal energy consumption.

Water treatment system

In the production of pasta, water is used for technical needs for kneading dough, creating steam, cooling the press chamber and for operating a vacuum station. Industrial water is used to cool the press chamber and operate the vacuum station; there are no special requirements for the quality of this water. But to create steam and knead the dough, you must use only drinking water. Moreover, the quality of water according to sanitary standards must comply with GOST - R 51232-98, San PiN 2.14.1074-01.