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Section 6. Food processing industry
Mannanov Ulug'bek, Institute of Management at UWED (University of World Economy and Diplomacy), Professor, Doctor of Technical Science, director Institute of Management at UWED E-mail: [email protected] Mamatov Sherzod, Tashkent institute of chemical technology (Uzbekistan), Doctor of Technical Science, Department of Food Safety,
Shamsutdinov Bakhadir, Rivne State Humanitarian University (Ukraine), Ph. D., Faculty of Physics and Technology
Research and study mode vacuum infrared drying vegetables
Abstract: The paper studies the process of vacuum infrared drying vegetables as a method of preservation of the product and the impact on its quality. Grounded drying modes — the temperature at which the vacuum infrared drying vegetables and duration of the process, on the example of potatoes, carrots and onions. Special attention is paid to the moisture content and water activity change.
Keywords: infrared drying, water activity, potatoes, carrots, onions.
Introduction. Great influence on the quality of the This indicates the need for alternative methods of
dried product has a drying process. By drying is meant drying, to improve the quality of the product, ensuring
the simultaneous occurrence ofheat and mass transfer to remove moisture contained in the product for the purpose of lengthening the shelf life by eliminating or reducing the intensity of the processes due to the increased amount of available moisture.
An analysis of modes of drying dry products of small size has allowed establishing the minimum process temperature equal to 50 °C. At this temperature, the standard value of moisture content reached a maximum after 3 hours. The processing at a drying temperature of over 70 °C the treatment time is reduced to a minimum of 30 min [1].
The high temperature of the heating agent and longer drying contribute to the development of oxidative processes, reduce food and biological value of the product as a result of changes in the quality of protein, loss of vitamins and biologically active substances, changes in the structure of raw materials, which is the major drawbacks of traditional methods of drying. On the other hand, at a low temperature drying, the product is longer in the temperature range favorable to the growth of microorganisms, which reduces the sanitary quality of the product.
a guaranteed level of safety and reduction of energy consumption, which is especially important in the production of high-value products.
Infrared rays of a certain wavelength oscillation of the water molecules increase. This leads to the release of a large quantity of heat consumed exclusively on evaporation without heating the tissue product, resulting in the evaporation can occur at low temperature 50-60 °C. This promotes intense evaporation of moisture without a significant change in the structure of the surface layer, reduction in processing time, preservation of biologically active components raw death of the microbial cells and inactivation of enzymes. Performing IR drying under vacuum dramatically increases the rate of evaporation by reducing the pressure, no air and consequently oxygen into the drying chamber to minimize oxidation and microbial growth, which is the basis for the preservation of food products. Vacuum drying IR refers to gentle methods of processing, therefore holds great promise in the treatment technology of thermo labile materials.
Methods and research facilities. The analysis process resulted in a review of the research showed that
great interest is the study of vacuum infrared drying as a method of preserving vegetables and the formation of the product.
Justification of the temperature at which the vacuum infrared drying vegetables and duration of the pro-
cess, performed on samples of potatoes, carrots and onions. Moisture content in the feedstock subjected to drying, is: the potato — 78.8%, carrot — 88.7% and onion — 90.3%, the amount of bound moisture is 88% of the total water content.
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Figure 1. The dependence of moisture from the potato being dried sample of temperature IR vacuum drying
Carrot and onion cut into plates with a thickness 0.8 mm and a radius of 25 mm, the potatoes in cubes the size of the faces 10 mm. The main factor determining the temperature and duration of drying is water activity, which decrease to values below 0.35 and suggests minimizing the amount of moisture available for the growth of microorganisms, including toxigenic. By water activity that characterizes the state of water in foods and for
Figure 2. The dependence of the activity of water in a dried sample of potato IR temperature vacuum drying process
determining the availability of its chemical, physical and biological reactions, foodstuffs are divided into three groups: — fresh, with a water activity Aw>0,951; processed with a water activity Aw = 0.9-0.95; processed with a water activity Aw < 0,90. The relationship between moisture content, water activity with a constant temperature characterized sorption isotherms [2].
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Figure 4. The dependence of the activity of water in a dried sample of carrots on the process temperature vacuum drying IR
Figure 3. The dependence of moisture from a dried sample of carrots process temperature vacuum drying IR
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Figure 5. The dependence of the moisture dried up sample of onion on the process temperature vacuum drying IR
Drying performed in a pilot plant, which will be described in Chapter 2, the raw material at temperatures 50C, 60 °C and 70 °C, the residual pressure due to the technical characteristics of the drying plant and in all cases was 40 kPa. The samples were laid out to dry in a single layer.
Figures 1-6 shows the graphs of the physical and chemical indicators of vegetables (potato varieties Santa carrot varieties Shantane Royal and onion varieties Karatal) and activity of water in them on the process temperature vacuum drying, infrared.Fig. 1 shows the experimental curves of the variation of humidity of the sample of potatoes at temperatures of 50, 60 and 70 °C, the main indicator in determining the duration and temperature of drying is water activity, which decrease to values below 0.25 and testifies to minimize the amount of moisture (Figure 2).
For those conditions the curves changes in humidity and water activity for a carrot, which curves are shown in Fig. 3-4 and onion, the curves of which are shown in Fig. 5-6.
Discussion of the results. According to the survey, the most uniform drying takes place when the product is heated to a temperature of 60 °C. Analysis of the dynamics of change of moisture content indicates that in each of the time periods measured relative decrease of moisture content was 37%. The value of water activity, required for the stability properties of the dry product (Aw <0.6), was achieved after 90 min of drying. The consistency of the final dried product was characterized as dense and elastic enough, by applying mechanical stress sample retains its shape, it does not crumble.
Figure 6. The dependence of the activity of water in a dried sample of onion on the process temperature vacuum drying IR
Upon drying under vacuum at a temperature of 60 °C the rate of evaporation of moisture from the material increases significantly. After 60 minutes the treatment residual moisture in the dried raw material was (15,31 ± 1,1)% against (36,03 ± 0,5)%, fixed for the same period of drying the sample to 60 °C. Rapid removal of moisture and micro vessel macro- and most of the moisture adsorption effect on the organoleptic properties of the dried sample. Uneven moisture evaporation led to excessive densification of the upper layer, giving a hardness and brittleness while consistency, upon application of mechanical force sample structure was destroyed to form a crumb. The water activity was higher than the recommended value and amounted to 0.3237, which is consistent with the presence of the compacted surface layer which hinders moisture transfer appearance at constant temperature of the heating medium and the degree of vacuum.
Drying feedstock at a temperature of 70 °C resulted in a more rapid heating of the raw materials and increase the temperature of the central layer, which was the consequence of a reduction of moisture content to 40.53% after 30 min of drying. After 60 min, relative decrease in the drying of moisture content was 73%, which leads to the conclusion that the drying speed was higher than the average of 1.5 times as compared with drying up to 50 °C. The water activity of the dried product was 0.4212 mass fraction of residual moisture 10.85%. With high efficiency moisture evaporation consistency of the dried sample should be regarded as unacceptable, to describe it applies the following characteristics: easily
destroyed by slight mechanical action, overly dry, hard wetted.
In the aggregate data suggest that when infrared heating in a vacuum drying vegetables, cut into thin slices, should lead to 70 °C temperature drying of 2-3 hours (depending on the type of vegetable), and the organoleptic properties of the dried samples correspond to those that adopted for vegetables.
According to the data, the curve of drying potato samples under vacuum and moderate temperature heating looks somewhat different from the curves characteristic of capillary-porous colloidal structures. The curve of the vacuum infrared drying ofvegetables is no warm-up portion of the material that is necessary to explain the mechanism of the impact of infrared heating, which refers to the volumetric heating, and a small thickness of dried samples. The result is a rapid heating of the raw material, reducing its influence on the intensity of heat and moisture evaporation. The residual pressure maintained in the drying chamber, accompanied by a reduction in the boiling point of water, which also contributes to intensive evaporation of moisture in the beginning of drying, when the raw material has a moderate temperature.
If the total duration of 120 min period of drying, flowing at a constant rate of 30 min. Limiting the duration of the drying period with constant high speed, or to explain the increase in the proportion of osmotic ally bound moisture in the sample. The first portion of the drying rate is 0.73%/min. During this period, the mass fraction of moisture in the sample decreased from 73.08% to 51.87%.
Beginning of the period of falling drying rate corresponds to the critical moisture content of the material. At
this time, moisture is removed, the most tightly bound to the product. The drying vegetables falling velocity of 60 m. End of the drying process in the experiment was calculated from measurements of water activity and the achievement of its normative value (0.8). The drying rate in the second stage was 0.27%/min. Moisture content in the sample after drying is 90 minutes (26.87 ± 0.37)%, which is higher than for the sample of unsalted dried under similar conditions. However, the water activity value is 0.8, which corresponds to the standard value.
To evaluate the effectiveness of the vacuum infrared drying, part of the samples prepared in an analogous manner was subjected to convective drying process at a temperature of 90 °C.
The conditions in the absence of convection heating vacuum heating of the product occurs primarily due heat hydraulic conductivity hat under constant pressure in the chamber is determined by molecular thermal diffusion of moisture due to the movement of moisture due to different rates of molecules of different layers of the heated product. Because of the low capacity of heat and moisture at a temperature of 90 °C drying it takes a long time even with a small thickness of the sample evaporation is slow, to be explained, including increased content firmly bound moisture. By the end of drying, that is, to achieve the standard value water activity, the mass fraction of moisture in the dry sample was 23.75%.
Conclusion. Thus, it was found that for the same size of the potato samples, carrots, onions and methods of preparation of raw material the use of a vacuum infrared drying reduces the duration of the process and to achieve a water activity, guaranteeing microbiological stability of the product, the organoleptic characteristics typical of dry products.
References:
1. Ilyasov S., Krasnikov V. Physical basis of infrared irradiation of foods. -M.: Food Industry, 1978. - 359 p.
2. Mamatov Sh. M. Application of mathematical model for optimizing the process of drying vegetables and fruits//IV of the All-Russian conference on chemical technology with the international participation. - Moscow (Russia), 2012. - P. 330-332.
