RU2252564C1 - Method for producing of dried carrot - Google Patents

Abstract

FIELD: food-processing industry, in particular, production of food concentrates.

SUBSTANCE: method involves washing, inspecting, gauging, cleaning, cutting, blanching and drying carrot. Drying process is provided in two sequentially and repeatedly alternating short-term stages. First stage involves processing carrot cubes in dense 65-mm high layer with overheated steam under atmospheric pressure and second stage involves processing in fluidized bed at predetermined temperature and flow rate of overheated steam.

EFFECT: increased heat effectiveness, intensified drying process and improved quality of ready product.

2 dwg, 4 tbl

Description

The invention relates to the food industry, namely the production of food concentrates, and can be used for the production of dried carrots.

A known method for the production of dried carrots, which includes washing, calibrating, cleaning, sulfitating, cutting, blanching and drying [Handbook technologist food concentrate and vegetable production / V.N. Gulyaev, N.V. Dremin, Z.A. Katz and others; Ed. V.N. Gulyaev. - M .: Light and food industry, 1984. - 488 p., S. 344-337].

The disadvantages of this method are significant energy consumption and low quality of the finished product.

An object of the invention is to increase thermal efficiency and intensification of the drying process, improving the quality of the finished product due to the use of superheated atmospheric pressure steam and alternating modes of processing carrots in dense and fluidized beds as a heat carrier.

The problem is achieved in that in the proposed method for the production of dried carrots, including washing, inspection, calibration, cleaning, cutting, blanching and drying, the new is that the drying is carried out in two successively repeatedly alternating short-term stages: at the first stage, the carrot cubes are processed in a dense layer 65 mm high with superheated atmospheric pressure steam, the duration of the first stage being 120 s, and in the second stage, the processing is carried out in a fluidized bed, duration which is 2; moreover, the temperature of superheated steam during drying for the first 600 s is - 413 K, then from 10 minutes to 18 minutes - 418 K, from 18 minutes to the end of drying - 423 K, and the speed of superheated steam during drying in a dense layer is during the first 12 minutes 2.1 m / s, from 12 minutes to 22 minutes -1.3 m / s and from 22 minutes to the end of the drying process - 0.8 m / s; and when drying in a fluidized bed - during the first 10 minutes 6.7 m / s, from 10 minutes to 22 minutes - 5.6 m / s and from 22 minutes to 28 minutes - 5.4 m / s, from 28 minutes and until the end of the drying process - 3.7 m / s.

The technical result consists in increasing the thermal efficiency and intensification of the drying process, improving the quality of the finished product due to the use of superheated atmospheric pressure steam and alternating modes of processing carrots in dense and fluidized beds as a heat carrier.

Figure 1 shows the kinetic dependences of the drying process of carrot cubes with rational operating parameters: a - diagram of the change in speed ν _n and temperature T of superheated steam over time, b - drying curve U = f (τ) (1) and drying curve dU / dτ = f (U) (2) carrots with superheated steam, where U is the moisture content of carrots, kg / kg, τ is time, s; in - thermogram of the process of drying carrots with superheated steam T _to = f (τ), where T _to - temperature of carrots; figure 2 is a diagram of changes in carbohydrate content in carrots.

A method of manufacturing dried carrots is as follows.

As the object of study used carrots, which met the requirements of GOST 1721-67 “Fresh table carrots." The table carrot used for processing, in its quality, met the following requirements:

in appearance: the root crops are fresh, unfading, disease-free, whole, uncracked, dry, unpolluted, without damage by agricultural pests, uniform in color, characteristic of this botanical variety, ugly in shape; the length of the remaining petioles is not more than 20 mm;

by the size of root crops (by the largest transverse diameter) - 25 ... 60 mm;

the absence of cracked, broken, ugly root (but unbranched) root crops with improperly cut tops (cuts of heads);

lack of rotten, steamed, frost-bitten root crops with foreign odors caused by growing, storage and transportation conditions

the presence of land adhering to root crops did not exceed 1%.

Carrots, previously peeled and washed, were treated with a solution of sodium bisulfite of 0.20 ... 0.25% concentration for 3 minutes and cut into cubes (with side sizes from 5 to 9 mm).

Before drying, carrot cubes were blanched in a chamber at a temperature of 95 ... 98 ° C for 3 ... 5 minutes.

The carrots treated in this way were placed in the working chamber of the dryer and were processed in two successively repeatedly alternating short-term steps (Fig. 1a). At the first stage, carrot cubes are treated in a dense layer 65 mm high with superheated steam of atmospheric pressure, the duration of the first stage being 120 s, and at the second stage, the processing is carried out in a fluidized bed, the duration of which is 2 s; moreover, the temperature of superheated steam during drying for the first 600 s is - 413 K, then from 10 minutes to 18 minutes - 418 K, from 18 minutes to the end of drying - 423 K, and the speed of superheated steam during drying in a dense layer is during the first 12 minutes 2.1 m / s, from 12 minutes to 22 minutes - 1.3 m / s and from 22 minutes to the end of the drying process - 0.8 m / s; and when drying in a fluidized bed - during the first 10 minutes 6.7 m / s, from 10 minutes to 22 minutes - 5.6 m / s and from 22 minutes to 28 minutes - 5.4 m / s, from 28 minutes and until the end of the drying process - 3.7 m / s.

From the analysis of the drying curves and the drying speed of carrots (figb), it is seen that there are three periods: heating, constant and falling drying speeds.

One of the main reasons for the intensification of the process of drying carrots in a pulsed fluidized bed with superheated steam of atmospheric pressure is the rapid heating of the product to a saturation temperature T _s = 373 K, which is due to condensation of vapor on the surface of the particles due to their relatively low initial temperature.

Analysis of the drying curves of carrots (figb) shows that the duration of the warm-up period is very significant and is 9 ... 10 minutes This period was used to conduct the process of cooking carrots. During cooking, not only the physicochemical and structural-mechanical parameters of the feedstock are changed, but also a new qualitatively created product with properties formed under the influence of heat and moisture is created. At the same time, most of the moisture, both condensed from steam and its own product, is actively absorbed by the product. In the process of cooking carrots, qualitative changes in substances occur. So, for example, as a result of denaturation, proteins coagulate, which entails the compaction of flooded gels and the extrusion of a significant part of the moisture contained in them, which is absorbed by carbohydrates. Carbohydrate carbohydrates are high molecular weight carbohydrate compounds characterized by structural characteristics and molecular chain sizes. Swelling of carrots is also due to the swelling of the proteins contained in them, which absorb water and bind it adsorption and osmotic.

The process of cooking carrots is a complex physico-chemical and structural-mechanical change in the substances of the product, causing its qualitative transformation and accompanied by unsteady transfer of heat and moisture.

Due to the high heat transfer coefficients during steam condensation on the surface of the cubes during the heating period, the temperature rises very quickly (Fig. 1c) and with further drying, moisture is removed from the product in the form of steam.

Such combined processing of carrots can increase the energy efficiency of the process, reduce the processing time of carrots and improve its quality.

The method of obtaining carrots is illustrated by the following example.

An example implementation of a method for producing dried carrots. As the object of study used carrots "Nantes - 4". The carrots, previously peeled and washed, were treated with a solution of sodium bisulfite of 0.20 ... 0.25% concentration for 3 minutes and cut into cubes (with a side size of 6 × 6 × 6 mm).

Before drying, carrot cubes were blanched in a chamber at a temperature of 95 ... 98 ° C for 3 ... 5 minutes.

The carrots treated in this way were placed in the working chamber of the dryer and were processed in two successively repeatedly alternating short-term steps (Fig. 1a). At the first stage, carrot cubes are processed in a dense layer 65 mm high with superheated steam, the duration of the first stage being 120 s, and at the second stage, the processing is carried out in a fluidized bed, the duration of which is 2 s; moreover, the temperature of superheated steam during drying for the first 600 s is - 413 K, then from 10 minutes to 18 minutes - 418 K, from 18 minutes to the end of drying - 423 K, and the speed of superheated steam during drying in a dense layer is during the first 12 minutes 2.1 m / s, from 12 minutes to 22 minutes - 1.3 m / s and from 22 minutes to the end of the drying process - 0.8 m / s; and when drying in a fluidized bed - during the first 10 minutes 6.7 m / s, from 10 minutes to 22 minutes - 5.6 m / s and from 22 minutes to 28 minutes - 5.4 m / s, from 28 minutes and until the end of the drying process - 3.7 m / s.

The choice of this height (65 mm) of the layer of carrot cubes is due to the fact that steam condensation flows evenly throughout the entire volume of the layer and a uniform condensate film forms on the surface of the cubes to ensure the normal cooking process.

An increase in the height of the layer of carrot cubes, for example, up to 75 mm, led to excessive waterlogging of the lower layers of carrots and insufficient moisture by condensate of the upper layers of carrots. At the same time, the lower layers of carrots were boiled, while the upper layers were overdried due to lack of moisture. When drying in a fluidized bed, this height of the layer of carrot cubes (75 mm) did not allow uniform boiling: either a bubbly mode of steam movement through a layer of carrot cubes was observed, or a jet regime of steam movement through a layer of carrot cubes.

Reducing the height of the layer of potato cubes, for example, to 55 mm, led to excessive waterlogging of all layers of carrots and their rapid adhesion. In this case, conglomerates of carrot particles formed, which during further processing did not evenly weld.

The choice of the duration of the first stage (120 s) is due to the fact that at the beginning of the drying process, cooking occurs due to steam condensation. With more frequent stirring, i.e. when the duration of the first stage was less than 120 s, for example 100 s, there was a breakdown of the condensate film from the surface of the carrot cubes during processing in a fluidized bed, which led to incomplete and poor-quality cooking. And, on the contrary, with a duration of the first stage of more than 120 s, for example 140 s, there was a deoxidation of the surface of the carrot cubes due to their overmoistening, which also led to poor-quality cooking.

At the second stage, carrots are processed in a fluidized bed, the duration of which is 2 s. When the duration of the second stage was less than 2 s, for example 1 s, there was insufficiently uniform and complete mixing of carrot cubes during processing in a fluidized bed, which led to incomplete and poor-quality cooking and drying. And, on the contrary, with a duration of the second stage of more than 2 s, for example 4 s, there was a breakdown of the condensate film from the surface of carrot cubes during processing in a fluidized bed, which led to drying of the carrot cubes and unreasonably high energy costs.

The choice of the speed regime for processing carrot cubes with superheated steam (the speed of superheated steam during drying in a dense layer is 2.1 m / s during the first 12 minutes, 1.3 m / s from 12 minutes to 22 minutes and from 22 minutes to the end of the process drying - 0.8 m / s) was selected experimentally and depended on the nature of the change in moisture of the product during drying. As drying, the moisture of the carrot cubes decreased, their mass also became less. When carrots were dried, shrinkage was observed, i.e. reducing the size of the cubes. Therefore, for uniform processing of carrot cubes, an adjustable heat supply was required, which was provided by this law for changing the speed of superheated steam. Failure to comply with this time and speed regimes led either to overdrying and burning carrots, or, conversely, to underdrying and to obtain a product with high humidity, which was a violation of the current GOST.

At the second stage, the speed of superheated steam during drying in the fluidized bed was 6.7 m / s during the first 10 minutes, 5.6 m / s from 10 minutes to 22 minutes, and 5.4 m / from 22 minutes to 28 minutes s, from 28 minutes to the end of the drying process - 3.7 m / s (figa).

The choice of the speed regime for processing carrot cubes with superheated steam (the speed of superheated steam during drying in the fluidized bed was 6.7 m / s for the first 10 minutes, 5.6 m / s for 10 minutes and 22 minutes for 28 minutes - 5.4 m / s, from 28 min until the end of the drying process - 3.7 m / s) was selected experimentally and depended on the nature of the change in moisture of the product during drying. As drying, the moisture of the carrot cubes decreased, their mass also became less. Therefore, for uniform processing of carrot cubes in a fluidized bed, a gradual and controlled change in the speed of superheated steam was required. Failure to comply with this time and speed regimes led either to the ablation and overdrying of carrots, or, conversely, to insufficiently uniform boiling and obtaining a product with high humidity, which was a violation of the current GOST.

The temperature of superheated steam during the first 600 s was 413 K, then from 10 minutes to 18 minutes - 418 K, from 18 minutes to the end of drying - 423 K.

The choice of the temperature regime for processing carrot cubes with superheated steam (the temperature of superheated steam was 413 K during the first 600 s, then 418 K from 10 minutes to 18 minutes, 423 K from 18 minutes to the end of drying) was experimentally selected and depended on the nature of the change in humidity of the product during drying. As drying, the moisture of the carrot cubes decreased, their temperature increased. In order for the carrot temperature not to exceed the maximum permissible temperature (above which thermal decomposition of valuable nutrients was observed: melanoid formation, thermolysis, etc.), a gradual and controlled change in the temperature of superheated steam was required to achieve uniform processing of carrot cubes. Failure to comply with this time and temperature conditions led either to overdrying and thermal decomposition of carrots, or, conversely, to underdrying and obtaining a product with high humidity, which was a violation of the current GOST.

Thus, the best option for processing carrots for all quality and energy indicators is the above method with the rationale for each parameter given. This is due to the uniformity of drying over the entire volume of the cubes and the intense evaporation of moisture from their surface. A reduction in the rate of internal heat transfer is achieved in comparison with the rate of movement of moisture and its evaporation from the surface of carrot cubes of this size.

In this case, the cubes heat up more slowly than moisture evaporates from them, which completely eliminates overheating of the product and ensures its high quality. From the energy point of view, the proposed option allows us to provide the most rational energy consumption per 1 kg of the obtained product, which is explained by the hydrodynamics of the process, which changes in time not only by pulsating changes in speed with alternating drying time intervals in a dense and fluidized bed, but also by the chosen equivalent particle size. In this case, the pressure drop in the product layer, corresponding to the mass and heat flux of superheated steam for a given processing mode, provides minimal energy consumption for obtaining a quality product. The drying time of carrots is 35 minutes according to the proposed technology and 4.5 hours according to the factory.

Evaluation of the effectiveness of the proposed method for the production of dried carrots and factory technology was carried out by the value of specific energy consumption per 1 kg of finished product. The value of specific energy consumption per 1 kg of dried carrots cooked according to the factory technology is 4930 kJ / kg. The value of the specific energy consumption per 1 kg of dried carrots cooked by the proposed technology is 3960 kJ / kg.

Thus, the above analysis shows the high thermal efficiency of the proposed technology for the production of dried carrots in comparison with the factory technology.

The study of quality indicators of table carrots was carried out in accordance with GOST 7588-71 “Dried table carrots." It was investigated by organoleptic and physico-chemical indicators. The determination of these indicators allows you to identify structural changes in carrots that occur during its drying, and to assess the quality of the resulting product.

Organoleptic and physico-chemical indicators, microbiological indicators and nutritional and energy value of dried table carrots are given in Table 1-3.

Table 1
Organoleptic and physico-chemical characteristics of carrots cooked according to the factory and proposed technology The name of indicators Characteristics of carrots cooked by factory technology proposed technology Appearance Carrots in the form of cubes of regular shape, with a flat surface, uniform in thickness, whole, without broken edges, keeping shape Shape and size Evenly sliced with a thickness of not more than 3 mm, a width of not more than 5 mm, a length of not less than 5 mm Consistency Hard cubes. Elastic cubes Taste and smell Inherent in carrots, without extraneous smacks and smells Color Orange-yellowish. The core is yellowish in color. Orange. The core is yellowish in color. Moisture content, % 14 14 Mass fraction of fried, greenish cubes with black spots and skin residues,% 5,6 2.9 Digestibility, min 24 5 Mass fraction of metal impurities,% 0,0003 not Mass fraction of mineral impurities (sand),% 0.009 0.004 Mass fraction of sulfur dioxide,% 0,037 not

table 2
Microbiological indicators of dried table carrots, prepared according to the factory and the proposed technology Name of indicator Carrots cooked by factory technology proposed technology Mesophilic aerobic and facultative anaerobic microorganisms in 1 g 1.9 × 10 ⁴ 1.1 × 10 ⁴ Coli-shaped bacteria in 1 g 8 6 1 g moldy mushrooms 4.9 × 10 ² 2.3 × 10 ²

Table 3
Nutritional and energy value of dried table carrots (100 g), prepared according to the factory and proposed technology The name of indicators Characteristics of carrots cooked by factory technology proposed technology Carbohydrates, g 54.8 56.3 Vitamins mg β-carotene 41 44 B ₁ 0.12 0.14 In ₂ 0.31 0.35 PP 2,8 2.9 FROM 10.0 11.2 Energy value, kcal 275 282

To analyze the dynamics of changes in carbohydrate content, thin-layer chromatography (TLC) was used, using computers and standard laboratory equipment. Using the Sorbfil TLC Video densitometer program, the retention order R _f and the area of the obtained spots S (%) were calculated on the basis of chromatograms.

In carrots, carbohydrates are mainly represented by starch, sugars, cellulose and pectin. In the initial (raw) sample of carrots, mono- and disaccharides are 2.35 g / 100 g.

The retention order R _f and the spot area S (%) of carrot carbohydrates are given in Table 4 for samples: 1 - raw carrots, 2 - dried carrots obtained by the factory technology, 3 - dried carrots obtained by the proposed technology.

The carbohydrate content in the product is accurately reflected by the area of the carbohydrate spot. From the analysis of data on the spot area, it follows that the content of high molecular weight carbohydrate compounds (polysaccharides of the 2nd order, tri-, tetra- and pentosaccharides) in the initial (raw) carrot sample is 5.5% of the total carbohydrate composition (Table 4).

Table 4
The retention order R _f and the spot area S (%) carbohydrate carbohydrates Name of carbohydrates R _f Carrot "Nantes - 4" 1 2 3 Monosaccharides Fructose 0.6 ... 0.88 68,452 50,944 39,647 Glucose 0.4 ... 0.6 24.85 43,369 30,452 Disaccharides Sucrose 0.3 ... 0.4 0.907 1,259 6.86 Maltose 0.21 ... 0.3 0.433 1,456 13.13 Other oligosaccharides Tri-, tetra- and pentosaccharides 0.1 ... 0.21 1,855 2,293 9,875 Polysaccharides of the 2nd order Dextrins and Starch 0.01 ... 0.1 3,503 0.679 0,036

* - unidentified monose residue approaching R _f glucose

For carrots, an increase in the content of tri-, tetra-, pentosaccharides and higher dextrins during drying compared to the initial (raw) sample is associated with the reduction of sugars, changes in fiber and pectin substances. For example, for carrots in the factory and proposed samples, the content of monosaccharides is, respectively, 94 and 70%.

The content of mono- and disaccharides (C, g / kg) in carrots before and after processing according to the factory and proposed technology is shown in the diagram (figure 2). An increase in monosugars in carrots, mainly glucose, was noted, when dried by the proposed technology — about 2.5 times and by factory technology — 1.8 times.

The increase in carbohydrate mono- and disaccharides during drying is presumably due to the following factors. This increase is observed as a result of hydrolysis, especially of low molecular weight oligosaccharides under the action of amylolytic enzymes under conditions of increased enzymatic activity with increasing temperature. However, carrots have a higher fiber content (12 g / kg). Due to the greater strength and thermal stability of the cell walls of carrots, it is possible that it is not possible to completely release glucose from the initial samples, primarily glucose, then fructose, and disacchar. Therefore, during the destruction of cell walls under conditions of elevated temperature and moisture, an increase in the identified mono- and disaccharides is observed.

Thus, by the method of thin-layer chromatographic analysis using a computer, the ratio of mono- and polysaccharides, the content of mono- and disaccharides, and the change in carbohydrate carbohydrates during drying were determined by the factory and proposed technology.

The studies revealed the characteristic features of changes in carbohydrates during the drying process: an increase in glucose and disaccharides in carrots when dried with superheated steam.

Drying by the proposed technology with superheated steam compared with drying by the factory technology allows to increase fructose content in carrots by 1.3 times, glucose by 1.35 times, sucrose by 5 times.

Thus, the proposed method for the production of dried carrots has the following advantages:

- a significant reduction in processing time from 4.5 hours in the factory technology to 35 minutes in the proposed;

- obtaining a product with a higher content of valuable nutrients (proteins, carbohydrates, etc.);

- a significant reduction in energy costs for the process.

Claims (1)

A method for the production of dried carrots, including washing, calibrating, cleaning, cutting, blanching and drying, characterized in that the drying is carried out in two successively repeatedly alternating short-term stages; at the first stage, carrot cubes are treated in a dense layer 65 mm high with superheated atmospheric pressure steam, the duration of the first stage being 120 s, and at the second stage, the processing is carried out in a fluidized bed, the duration of which is 2 s, and the temperature of the superheated steam during drying during the first 600 s is 413 K, then from 10 to 18 minutes - 418 K, from 18 minutes until the end of drying - 423 K, and the speed of superheated steam during drying in a dense layer is 2.1 m / s during the first 12 minutes, from 12 to 22 min - 1.3 m / s and from 22 min to con the drying process - 0.8 m / s; and when drying in a fluidized bed during the first 10 minutes, 6.7 m / s, from 10 to 22 minutes - 5.6 m / s and from 22 to 28 minutes - 5.4 m / s, from 28 minutes to the end the drying process is 3.7 m / s.

Images