RU2560947C1 - Method for manufacturing dried pears - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: pears are inspected, sorted, washed, cut and subjected to combined UHF and convective drying. Drying is performed with a UHF electromagnetic field with power equal to 800 W and with convective blowing with air having initial temperature equal to 293 K in three temporal stages. At the first stage pears cut into 10×10×10 mm cubes are heated with UHF field during 3 minutes; then the magnetron is switched off and the product is blown with an air flow with flow rate equal to 0.7 m/s during 3 minutes; then one proceeds with repeated UHF field drying during 4 minutes. At the second temporal stage pre-dried pears are heated with UHF field during 4 minutes; then the magnetron is switched off and the product is blown with an air flow with flow rate equal to 0.5 m/s during 4 minutes. The cycle is repeated three times, the second stage duration equal to 24 minutes. At the third temporal stage pre-dried pear cubes are heated with UHF field during 5 minutes; then the magnetron is switched off and the product is blown with an air flow with flow rate equal to 0.4 m/s during 5 minutes. The cycle is repeated five times until the ultimate moisture content is 23%; the third stage duration is 50 minutes.

EFFECT: invention allows to produce high quality dried pears with high content of valuable nutritive thermolabile substances, to increase thermal efficiency and intensify the drying process as well as reduce the ready product production energy costs.

1 dwg, 1 tbl

Description

The invention relates to the food industry, in particular to technology for processing fruits, and can be used for the production of dried pears.

A known method of producing a food product from pears [US Pat. RF 2484654, IPC A23L 1/212. Method for the production of food product from pears [Text] / O.I. Kvasenkov; applicant and patent holder O.I. Kvasenkov. - No. 2012136291/10; declared 08/27/2012; publ. 06/20/2013], including the preparation of pears, their cutting, convective drying to intermediate humidity, drying in the microwave field until a dry matter content of at least 85% is reached.

The disadvantage of this method are: the low quality of the finished product, the duration of the drying process and high specific energy consumption

An object of the invention is to improve the quality of the finished product and increase the thermal efficiency of the drying process through the use of a stepped regime of microwave convective drying of pears, reducing energy consumption to obtain the finished product, and intensifying the drying process.

The object of the invention is achieved by the fact that in the proposed method for the production of dried pears, including inspection of raw materials, sorting, washing, cutting raw materials, combined microwave convective drying, it is new that microwave convective drying is carried out by a microwave field at a power of 800 W and convective air blowing with an initial temperature of 293 K in three time stages: at the first stage, 10 × 10 × 10 mm pears cut into cubes are heated by the microwave field for 3 minutes, then the magnetron turns off and air blowing begins m flow at a speed of 0.7 m / s for 3 minutes, then again heating with the microwave field for 4 minutes, at the second time stage, the pre-dried pears are heated with the microwave field for 4 minutes, then the magnetron is turned off and the product is blown air flow at a speed of 0.5 m / s for 4 minutes, while the cycle is repeated three times, and the duration of the second stage is 24 minutes, at the third time stage, pre-dried pear cubes are heated with a microwave field for 5 minutes, then the magnetron is turned off and the product blown ozdushnym flow with a velocity of 0.4 m / s for 5 min, and the cycle is repeated five times to a final moisture content of 23% and the duration of the third stage is 50 minutes.

The technical result of the invention is to improve the quality of the finished product through the use of stepwise modes of combined microwave convective drying of pears, increasing thermal efficiency and intensification of the drying process, in reducing energy consumption for obtaining the finished product.

Figure 1 shows the kinetic laws of the stepped regime of combined microwave convective drying of pears: a - drying curve (1) and a drying speed curve (2); b - temperature curve; in - thermogram.

Fresh pears that are processed must be in accordance with the technical specifications of GOST 21713-2000 and meet the following requirements:

in appearance: selected fruits, typical in shape and color for this pomological variety. The stalk is optional. In the absence of a stalk, the skin of the fetus at the place of attachment to the stalk must be intact, not torn off the pulp;

by maturity - fruits are uniform in maturity, but not green and not overripe;

by the size of the largest transverse diameter - not less than 50 mm.

The chemical composition is variable and is closely dependent on climatic conditions, cultivation techniques and variety.

Pears for the production of dried pears must be fresh, healthy, of appropriate color, high in pectin, organic acids and dry soluble substances.

A method of manufacturing dried pears is as follows.

Wash pears in a fan washer. For more intensive washing of contaminated fruits in the washing tub of the machine, drilling is created by means of compressed air supplied to the perforated pipes. The washed fruits from the washing bath are moved by an inclined conveyor, in the upper part of which they are rinsed with water from the shower unit. When processing heavily contaminated fruits, you can increase the time they spend in the washing area by occasionally stopping the conveyor.

Then washed pears are subjected to inspection and sorting, which are carried out manually on the sorting and inspection conveyor. Simultaneously with sorting, an inspection of raw materials is carried out, in which defective specimens (rotten, damaged, broken, moldy, heavily contaminated), foreign impurities and objects are removed.

Then, the processed pears are cut into cubes with linear dimensions of 10 × 10 × 10 mm. Cutting pears into cubes larger than 10 mm, for example 15 mm, significantly increases the drying time and reduces the productivity of the line. Cutting pears into cubes smaller than 10 mm, for example 5 mm, leads to severe shrinkage, which will spoil the presentation of the product.

Then the diced pears are subjected to combined microwave convective drying. Moreover, heating the pear is carried out with a microwave field followed by convective air blowing with an initial temperature of 293 K in three time stages.

The choice of microwave power equal to 800 watts is due to the fact that if the microwave power is more than 800 watts, for example 1000 watts, the product will burn. If the field power is less than 800 W, for example 600 W, then the drying time will be increased and the line productivity will decrease.

Pears are blown with an initial temperature of 293 K to remove water vapor evaporated from the product.

The choice of the initial air temperature of 293 K is due to the fact that air is taken from industrial premises, in which, as a rule, this temperature is maintained.

The use of air as a heat carrier with an initial temperature of more than 293 K, for example 303 K, will necessitate the installation of a heater for additional heating of the air, which may impair the quality of the finished product due to its overheating, increase the cost of production and increase the amount of capital investment due to the installation of an additional heater .

The use of air as a heat carrier with an initial temperature of less than 293 K, for example 283 K, will necessitate the installation of cooling devices for additional air cooling, which during microwave drying can cause unnecessary excessive cooling of the product and lead to an increase in energy consumption and an increase in the cost of production.

The essence of the choice of stepwise modes of combined microwave convective drying of pears consists in dividing the drying process into three stages of different duration, at each of which, depending on the law of change in the current humidity of pears, a rational technological drying mode is selected, i.e. the temperature of heating the pear cubes with a microwave field and blowing them at a coolant velocity (air flow with an initial temperature of 293 K) assumed fixed values, the values of which were determined experimentally. Moreover, their selection at each stage must be carried out in accordance with the restrictions imposed by technological requirements on the quality of the finished product.

At the first time stage, the cut pear cubes 10 × 10 × 10 mm in size are heated with a microwave field for 3 minutes, then the magnetron is turned off and the fan is turned on and airflow starts at a speed of 0.7 m / s for 3 minutes (Fig. 1 ) In this case, physical and mechanical moisture is removed, i.e. moisture micro- and macrocapillaries and wetting moisture. The main parameter affecting the intensity of moisture removal during this period is the coolant speed. Therefore, it is most advisable to use drying at the initial moment of drying with a high coolant velocity and a low heating temperature of the product. Drying at the first stage most fully meets this requirement.

Blowing the product with air flow at a speed of less than 0.7 m / s, for example 0.6 m / s, will reduce the efficiency of removal of evaporated water vapor, and therefore, reduce the efficiency of heat and mass transfer of the drying process. Blowing the product with air at a speed greater than 0.7 m / s, for example 1 m / s, will lead to overdrying of the surface layers of the pear, the formation of a crust on the surface of the pears, which makes it difficult to remove evaporated moisture.

The duration of the first time step (10 min) was determined experimentally by analyzing the obtained drying curves. Using a longer duration of the first time step, for example 12 minutes, will lead to the drying out of the surface layers of the pears and the difficulty of removing moisture contained in the central layers of the pear. Using a shorter duration of the first time step, for example 8.5 minutes, will result in the fact that not all physico-mechanical moisture will be removed from the pears, which will entail an increase in the duration of subsequent temporary stages of drying and a deterioration in the quality of the finished dried pears.

At the second time stage, the pre-dried pears are heated with a microwave field for 4 minutes, then the magnetron is turned off and the fan is turned on and the product is blown with air at a speed of 0.5 m / s for 4 minutes (figure 1). In this case, the cycle is repeated three times, and the duration of the second stage is 24 minutes. With the removal of physical and mechanical moisture, the velocity of the coolant as a determining factor in the intensity of the process loses its significance. Therefore, in the second stage, it is preferable to carry out drying at a decreasing speed and increasing temperature of the coolant. Blowing the product with an air stream at a speed of less than 0.5 m / s, for example 0.4 m / s, will not ensure the complete removal of evaporated water vapor, and therefore, will reduce the efficiency of heat and mass transfer of the drying process. Blowing the product with an air stream at a speed greater than 0.5 m / s, for example 0.6 m / s, will lead to overdrying of the surface pears and the formation of a crust on the surface of the pear, which will complicate the removal of evaporated moisture.

The duration of the second time stage (24 min) was determined experimentally as a result of the analysis of the obtained drying curves. Using a longer duration of the second time step, for example 30 minutes, will lead to the drying out of the surface layers of the pears and the difficulty in removing moisture contained in the central layers of the pear. Using a shorter duration of the second time step, for example 20 minutes, will result in the fact that not all osmotic moisture will be removed from the pear, which will entail an increase in the duration of subsequent temporary drying steps and a deterioration in the quality of the finished chips.

At the third time stage, the pre-dried cubes of pears are heated with a 800 W microwave field for 5 minutes, then the magnetron is turned off and the fan is turned on, and the product is blown with air at a speed of 0.4 m / s for 5 minutes (Fig. 1). The cycle is repeated five times, the duration of this stage is 50 minutes. As osmotic moisture is removed, the velocity of the coolant as a determining factor in the intensity of the process loses its significance, due to the fact that temperature as the factor determining the intensity of internal moisture transfer has the greatest influence on the rate of removal of polyadsorption moisture.

Blowing the product with an air stream at a speed of less than 0.4 m / s, for example 0.3 m / s, will not ensure the complete removal of evaporated water vapor, and therefore, will reduce the efficiency of heat and mass transfer of the drying process. Blowing the product with an air stream at a speed greater than 0.4 m / s, for example 0.6 m / s, will lead to overdrying of the surface layers of the pear and the formation of a crust on the surface of the pear, which makes it difficult to remove evaporated moisture.

The duration of the third time step (50 min) was determined experimentally as a result of the analysis of the obtained drying curves. Using a longer duration of the third time step, for example 60 minutes, will lead to overdrying of the surface layers of pears and the difficulty of removing moisture contained in the central layers of the pear. Using a shorter duration of the third time step, for example 45 minutes, will result in the fact that not all polyadsorption moisture will be removed from the pear, which will entail an increase in the duration of subsequent temporary drying steps and a deterioration in the quality of the finished product.

The moisture content of the dried product is 23% according to GOST 28502-90. Adapted in accordance with the basic kinetic laws of the drying process, the coolant supply at the three stages of drying the product allows you to choose rational drying modes taking into account changes in the moisture content of the product during the drying process.

The table shows the chemical composition of the original pears and dried pears dried according to the proposed three-stage regime of combined microwave convective drying.

A method of manufacturing dried pears is illustrated by the following example.

Wash pears in a washer. Then washed pears are subjected to inspection and sorting, which are carried out manually on the sorting and inspection conveyor. Next, pears are cut into cubes 10 × 10 × 10 mm in size. Then, the diced pear cubes are subjected to combined microwave convection drying, the pear is heated by a microwave field with a power of 800 W, then air blowing occurs with an initial temperature of 293 K in three time steps.

At the first time stage, the pears cut into cubes are heated by the microwave field for 3 minutes, then the magnetron turns off and the fan turns on, the air flow rate was 0.7 m / s for 3 minutes. In this case, physical and mechanical moisture is removed, i.e. moisture micro- and macrocapillaries and wetting moisture.

At the second time stage, pre-dried pear cubes are first heated with a microwave field for 4 minutes, and then blown with air at a speed of 0.5 m / s for 4 minutes, then the cycle is repeated three times. The time of the second stage is 24 minutes. In this case, osmotic (intracellular) moisture is removed.

At the third time stage, the pear cubes are heated with a microwave field for 5 minutes, then the magnetron is turned off and the fan is turned on and the product is blown with air flow at a speed of 0.4 m / s for 5 minutes. In this case, the cycle is repeated five times to a final moisture content of 23%, and the duration of the third stage is 50 minutes. At the same time, poly- and monoadsorption moisture is removed from pears.

Analysis of the data given in the table shows that dried pear has a high content of valuable nutrient thermolabile substances. This indicates the correct choice of soft, gentle temperature-hydrodynamic drying regimes. Such processing of pears can increase the energy efficiency of the process, reduce the drying time of pears and improve its quality.

Thus, the use of the proposed method for the production of dried pears allows you to:

- receive dried pears of high quality with a high content of valuable thermolabile substances (vitamins, monosugar, amino acids, etc.)

- increase the thermal efficiency of the process;

- reduce energy and labor costs for the production of dried pears due to the use of stepwise modes of microwave convective drying.

Claims (1)

Method for the production of dried pears, including inspection of raw materials, sorting, washing, cutting of raw materials, combined microwave convective drying, characterized in that microwave convective drying is carried out by a microwave field at a power of 800 W and convective air blowing with an initial temperature of 293 K in three time Stage: at the first stage, 10 × 10 × 10 mm pears cut into cubes are heated by the microwave field for 3 minutes, then the magnetron is turned off and airflow begins at a speed of 0.7 m / s for 3 minutes, then the microwave is heated again -floor eat for 4 minutes, at the second time stage, pre-dried pears are heated with a microwave field for 4 minutes, then the magnetron is turned off and the product is blown with air at a speed of 0.5 m / s for 4 minutes, while the cycle is repeated three times, and the duration of the second stage is 24 minutes, at the third time stage, the pre-dried cubes of pears are heated with a microwave field for 5 minutes, then the magnetron is turned off and the product is blown with air at a speed of 0.4 m / s for 5 minutes, while the cycle is repeated fiveAz to a final moisture content of 23% and the duration of the third stage is 50 minutes.