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Section 5. Food industry
D OI: http://dx.doi.org/10.20534/AJT-17-1.2-59-63
Gafurov Karim Khakimovich, Bukhara Engineering-Technology Institute E-mail: kgafurov@yahoo.com
Ibragimov Ulugbek Muradilloevich E-mail: culugbek@list.ru
Fayziev Shavkat Ismatovich E-mail: shavkatfayz@gmail.com
Statistical-mathematical model of the process of extraction of pumpkin seeds by CO2-extraction
Abstract: An experimental study of the process of obtaining of oil from pumpkin seeds by CO2-extrac-tion is carried out. Statistical analysis of experimental results is carried out; statistical and mathematical model of the process is obtained, rational parameters of influencing factors are defined.
Keywords: CO2 extraction, liquid and supercritical gas, pumpkin seeds, pressure, temperature, extratant.
Development of methods of energy-saving technologies, allowing getting new high-quality products in the pharmaceutical, cosmetics and food industry is due to a pressing social need for high-quality medicines and food products as well as cleaner production.
One of the solutions of this problem is the use of liquid and supercritical carbon dioxide as the extractant. CO2 extraction is just spread in the world. This is due primarily to the fact that this process is highly cost-effective, more technological, allows processing not only high-quality raw materials, but also the production of waste in order to extract from them the main components to give a better quality of lower grade product. Extraction is carried out with liquefied gases under pressure, where removing extractant evaporates and extractives remain in pure form. Extraction with carbon dioxide in liquid and supercritical form significantly expands the range allocated to the active compounds, and also allows to obtain the concentrations of biologically active substances in the final product, which cannot be obtained by any other known extraction techniques [1, 2-5; 2, 1-2].
Structural features of vegetable raw of the Uzbekistan — fruit seeds, grape seeds, pumpkin, melons, etc. are suggest technological development mode liquid extraction using supercritical carbon dioxide and the kinetics and dynamics of the extraction process, the determine
extraction process effects on the yield and quality of the product [3, 5-6].
In this case, there is a need to develop technics and technology of CO2-extraction designed for local raw materials.
Research of the extraction process of ingredients from plant raw material with liquefied and supercritical carbon dioxide was carried out on laboratory installation (fig. 1), which consists of the following elements: a high-pressure extractor with the cassette to accommodate the sample plant material, extracting supply system, the product collection system, condensation system, heat pump systems, control equipment.
High pressure extractor with sample cassette VII for placing plant raw is a thick-walled vessel made of stainless steel. The cassette, which has a design shape close to the internal volume of the extractor (cylinder of thin sheet material with a perforated bottom sieve) is also made of stainless steel. The extractor has a pressure sensor which transmits signals for controlling the flow of the extractant in the extraction, controlling the operation of the control valve 4. For controlling the temperature of the extractant supplied into the extractor, temperature sensor is put on inlet of the extractor, a signal from which is supplied to the electric heater thermoregulatory system extractant VI.
Fig.1. Schematic diagram of the laboratory equipment for the research of CO2-extraction process from vegetable raw materials
Extractant feed system consists of a cylinder with CO2 I, Compressor II, tanks for gas extracting V, an electric heater extractant VI, 1,2,5 stop valves and control valves 3,4. The capacity for extract V has a pressure sensor and level sensor, which transmit signals to control valve performance 3.
Condensation extractant system consists of a condenser with a cooling jacket IV, in which the inlet pressure gauge, and at the outlet — the thermometer that perform control functions.
Product collection system consists of an evaporator-separator with a coil heater extract IX, the throttle valve 6 and valves 7 and 8.
The heat pump system consists of a compressor heat pump VIII, the throttle valve of the heat pump III. A working agent for the heat pump system is a Freon R-21. which serves as a refrigerant condenser for IV and thermal evaporation agent separator IX.
The laboratory setup is as follows (fig. 1). The crushed plant material pre-loaded into a mesh tape that
is installed in the extractor VII. After sealing the extractor, technology system with the product is purged with gaseous CO2 in order to remove air.
Carbon dioxide from the tank I is transferred to the compressor II at an open valve 1 and closed 2 (during the first installation startup). CO2 compressed by the compressor II passes through the condenser IV, wherein the agent is cooled by the working heat pump and becomes liquid (P1 = 8...10 MPa. and t1 = 25.. .30 °C) and stored in tanks for extractat V at the open valve 3. In this case the pressure of the extractant at the entrance to the condenser and the temperature at the outlet of the condenser measured by pressure gauge and a thermometer, respectively. Pressure and level in the tank V measured pressure and level sensors, and the signals are transmitted to the control system for controlling the operation of the valve 3.
For carrying out the process of extraction the liquid extractant at the open valve 4 passes through the electric heater VI, which passes into a supercritical state
(P2 = 8...10 MPa. and t2 = 35 ...70 °C) and fed to the top of the extractor VII, where a temperature sensor provides a signal to the controlled electrical heater system for controlling the temperature of the extract-ant. Consumption extractat regulated by valve 4. After passing through the layer of vegetable raw material extracting agent extracts the soluble components (eg, pumpkin seed oil) and excreted from the bottom of the extractor, ie, extraction is carried out by infusion for a time (the time depends on the type of infusion extract-able feed) in the closed valve 5. If extraction technology requires extraction flow, then the process takes place at an open valve 5.
After reaching of process time the valve 5 opens and closes the throttle valve 6. When passing through the throttle pressure and temperature of the miscella is reduced below the critical parameters (P3 = 5.0.5.5 MPa. and t3 = 25 „30 °C) and carbon dioxide passes to a gaseous state.
In the separator-evaporator IX is deposited dissolved in the extractant extract, which is necessary to maintain the temperature (t4 = 25.30 °C). The temperature is maintained by means of the heat pump working agent serving to coil heater-evaporator heat separator agent. Thus precipitated extract removed from the bottom of the evaporator-separator with the valve 8 open, the gaseous carbon dioxide output from the top separator at the open-valve evaporator 7. A gaseous CO2 passes through the valve 2 is compressed to the operating pressure of the compressor and the cycle is repeated.
The main operating parameters of the process are the pressure and temperature of the extractant in the extraction circuit, and a simple variation of these operating parameters can be used in the pre- and supercritical state extractant and thus to carry out directional change in the composition of the final extract.
The technological scheme is further coupled to a heat pump condenser IV in the cooling extractant and to maintain the desired temperature of the extract in the separator-evaporator IX. Operating agent — R-21 -freon is compressed in the compressor of the heat pump VIII, passes through the evaporator coil separator-IX, gives up its heat and is cooled, exits the evaporator-separator coil and passes through the expansion valve III,
which loses pressure. Cooling agent is included in the jacket of the condenser IV, where taking heat from the extractant evaporates and comes in a gaseous state to the compressor and the cycle is repeated. Thus, as the heat pump condenser enters the coil-evaporator separator IX, here working agent, giving its heat, maintains the desired temperature for the separation of the extractant from the extract and condensed, and as the heat pump evaporator enters shirt capacitor IV, where the working agent, taking extratant heat from vaporized.
The purpose of the experiments was to determine the influence of the main influencing factors: pressure and temperature of extratant for CO2 extraction on residual oil content meal (oil output).
As a fat-containing plant material are selected pumpkin seeds (SEMINA CUCURBITAE). The pumpkin seeds contain fatty oil (40 %), which includes linolenic glycerides (45 %), oleic (25 %), palmitic and stearic (30 %) acids; essential oil, phytosterols — kukurbi-tol, resinous substances, organic acids; vitamin C, B1 (0.2 mg/ %); carotene and carotenoids together — 20 mg/ %, amino acids [4].
Grinding of all raw materials used in the experiments carried out in the same mode type percussion grinder mill at 16 000 rev/min for several seconds. The fineness of the material was determined by sieve analysis. At a sieve with a mesh size of 2 mm. was whole seeds ("leakage"), and their share was 9.2 %. As a result, the calculation of the weighted average amount of ground seeds was 0.9 mm.
On the basis of the available information and analysis as influencing factors selected pressure and extracting temperature (supercritical CO2). Processing time 60 min.
Varying levels of the two factors (x1 — pressure and x2 — temperature) are the following:
• The upper level (+): the pressure of 8 MPa, the temperature of 40 °C.
• The lower level (-): the pressure of 7 MPa, the temperature of 30 °C.
Coding of the factors is carried out (Table 1).
Since we have two influencing factors, and they change on two levels, get planning experiments to 22. Thus, it is necessary to carry out the experiment 4. Experimental design matrix is shown in Table 2.
Table 1. - Coding of the factors
Factors Upper level x+ Lower Level x~ Center Spacing variation, X encoded variable Dependency on natural
xi 8 7 7.5 0.5 (x1-7.5)/0.5
X2 40 30 35 5 (x2-35)/5
Table 2. - Experimental Design Matrix for 22
№ of experiment Factors The effects of the interaction of factors Results of the experiments Average results
*1 X2 X1X2 y 2 y3
1 - — + 5.2 5 4.6 4.933
2 + — — 4.2 3.8 4 4.000
3 — + 1 — 3.5 3.7 3.3 3.500
4 + + + 2.8 3.2 3 3.000
S y, 15.433
The regression equation in this case is as follows:
y = b0 + bxxx + b2x2 + bi2xix2. The regression coefficients are calculated according to the formulas:
ZN
N
ZN
b _ i=iy,Xkod 1 N
etc.
Table 3. - The calculated values of the regression coefficients
Coefficients b2 K
Meaning 3.8583 —0.3583 —0.6083 0.1083
We determine the significance of these factors: The dispersion reproducibility Sv made under the formula [5, 72-73]:
V NN (y° - y
S2 = Vy > , (1)
NN -1
where: NN—number of replicates; y0 — average value ofy, obtained in parallel experiments; y°u — values obtained when setting each of the additional experiments in the center of the plan.
The standard deviation of the coefficients: S
S f . (2)
Estimated value of the t-test is given by [5, 73-74]:
\b.\
t- = M. (3)
s
cotf
The calculation results are shown in Table 3.
Table 4. - The calculation of the
The calculation results are shown in Table 4. dispersion of reproducibility
j y¡ y2 y3 y j [y, !- y¡) [y, 2- y>) [y, 3- y>) S2 repr.
1 5.200 5.000 4.600 4.933 0.0711 0.0044 0.1111 0.0933
2 4.200 3.800 4.000 4.000 0.0400 0.0400 0.0000 0.0400
3 3.500 3.700 3.300 3.500 0.0000 0.0400 0.0400 0.0400
4 2.800 3.200 3.000 3.000 0.0400 0.0400 0.0000 0.0400
S 0.2133
The standard deviation of the coefficients determined by the formula (2): Scof = 0.0667.
From the distribution tables of Student [5, 283-284] according to the number of degrees of liberty: n (m -1) = 4 • 2 = 8. With a level of significance of a = 0.05 we find t = 1.86.
cr.
Estimated value of the t-test is determined by the formula (3):
\b\= t • S . = 1.86 • 0.0667 = 0.124.
| j | cr. coef
Comparing this value with 0.124 coefficients of the regression equation that all factors except b12 are bigger in absolute value of |bj |. Therefore all the coefficients except b12 are significant. So this factor is excluded from the regression equation.
The regression equation is as follows:
7 = 3.8583 -0.3583Xj -0.6083x2. (4)
Adequacy of obtained regression equation is checked by using Fisher's exact test on formula [5, 74-75]
Si
F = -°.
s2
(5)
where the residual dispersion is calculated using the formula:
S2 =
_Zr=. (y,- yr )2
N - L
(6)
where L — number of significant coefficients in the regression equation.
In our case S2o = 0.14083 . At the significance level a = 0.05 degrees of freedom and k = n - r=4 - 3 = 1 and k2 = n (m - 1) = 8; Ftabl = 5.32 [5, 280-281]. Estimated value of Fisher's exact test on formula (5): F = 2.64.
According to the results of calculations F , < F , so
C» calc tabl/
that the resulting model adequately describes the process.
Upon receipt of the equation (4) we construct a graph of the residual oil content of pumpkin seeds (meal) from influencing pressures and temperature on MathCAD program (fig. 2).
The graph shows that with increasing pressure and temperature oil content of meal decreases. According to fig. 4, rational values of the influencing factors are: pressure P = 7.75 MPa, t = 35 °C temperature. In this extraction mode the residual oil content of meal is 3.13 %.
Fig. 2. Dependence of the residual oil content of pumpkin seeds (meal) from influencing pressures and temperatures
References:
1. Extraction with carbon dioxide in the food technology/E. P. Koshevoy, H. R. Blyagoz - Maikop: Maikop State technological institute, 2000. - 495 p.
2. The supercritical CÜ2-extraction - opportunities and prospects//A. G. Lepeshkov, A. R. Vodyanik, K. M. Averin. SIC of environmental resources "GORO". - Rostov-on-Don//[Electronic resource]. - Available from: http://www.extract.ru/index.php?id=91
3. Safarov A. F., Gafurov K. Kh. Modern technology in the extraction industry//Journal "Development of Science and Technology". - 2015 - №1. - P. 5-9.
4. [Electronic resource]. - Available from: https://ru.wikipedia.org/wiki/Semena_tykvy
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