an optimization of microwave hydrodistillation … · heri septya kusuma, ali altway, mahfud mahfud...

Heri Septya Kusuma, Ali Altway, Mahfud Mahfud

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AN OPTIMIZATION OF MICROWAVE HYDRODISTILLATION EXTRACTION OF VETIVER OIL USING A FACE-CENTERED CENTRAL COMPOSITE DESIGN


ABSTRACT

Several methods of vetiver oil extraction are developed. One of these refers to microwave hydrodystillation. The parameters of each of these methods have a major impact on the extract results. Parameter optimisation is usually applied by classical techniques where one variable changes at a time while another variable remains constant but they do not provide adequate information on the interaction between the experimental variables tested. Besides, they require a huge amount of time and materials. The face-centered central composite design (FCCD) technique of the response surface methodology (RSM) is efficient in comparing the individual effects and the interactions between the variables. Therefore FCCCD technique is used in this study to optimize, model and analyze the effects of each variable and their interactions in the course of microwave hydrodistillation applied to extract vetiver oil from dried vetiver (Vetiveria zizanioides). The variables used as parameters refer to the microwave power (300 W, 450 W, 600 W), the feed to solvent (F/S) ratio (0.3 g/mL, 0.4 g/mL, 0.5 g/mL) and the extraction time (60 min, 120 min, 180 min). The experimental design indicates that a maximum yield of 0.828 % is obtained in case of a microwave power of 600 W, a F/S ratio of 0.358 g/mL and extraction time of 180 min. Based on the design R2 value of 0.7955, it can be concluded that the model obtained can be used to describe the experimental results and determine the yield of vetiver oil. Furthermore, the results of variance (ANOVA) analysis show that the essential factors which determine the oil yield refer to the microwave power, the F/S ratio and the extraction time.

Keywords: Face-centered central composite design, microwave hydro-dystillation, vetiver oil, Vetiveria zizanioides.

Received 15 March 2018Accepted 08 March 2019

Journal of Chemical Technology and Metallurgy, 54, 4, 2019, 803-809

Department of Chemical Engineering, Faculty of Industrial TechnologyInstitute Teknologi Sepuluh Nopember, Surabaya, Indonesia 60111E-mail: [email protected]; [email protected]

INTRODUCTIONThe global essential oils market has developed

steadily within the last few years. The market size is expected to reach USD 11.19 Billion by 2022 and projected to increase by 8.83 % from 2017 to 2022. The demand is increased because of the development of a number of industries such as the perfume, cosmetics, pharmaceutical, food and beverage one. Furthermore, the tendency of consumers converting from a consumption of ingredients containing synthetic compounds to those with natural ingredients also boosts the oil demand. Moreover, the essential oil products cannot be replaced by synthetic materials. In the international market, this commodity is considered to have a strategic role in the production of primary and secondary products, for both

domestic and export needs [1].Currently, about 150 - 200 species of plants, including

the Pinaceae, Labiatae, Compositae, Lauraceae, Myrtaceae and Umbelliferaceae family are estimated to contain essential oils [2]. Indonesia is one of the leading countries of the world in oil production as approximately 45 types of essential oil-producing plants are found growing there. However about 15 species have become export commodities, namely citronella oil, patchouli oil, cananga oil, sandalwood oil, nutmeg and mace oil, clove leaf, stem and bud oil, cullilawan oil, massoi oil, sassafras oil, ginger oil, black pepper oil, agarwood oil, turpentine oil, cajeput oil, kafir lime oil and vetiver oil. From an economic point of view, the cheapest abundant materials and the crop wastes are usually selected as a raw material

Journal of Chemical Technology and Metallurgy, 54, 4, 2019

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for the extraction process influencing thus the price of the product [3].

Vetiver (Vetiveria zizanioides) is a kind of grass-cultivated plant in the tropic and subtropic regions of the world. The volume of the world traded vetiver oil averages 250,000 kg per year. Indonesia is the second largest supplier of vetiver oil on an international level. It cannot still be replaced by a synthetic oil [4], or that of Haiti [5].

Despite its rising demand in the World market, the price of Indonesia’s vetiver oil is at around 58 - 60 US$ per kg which is much lower than that of the Haitian (US$ 93 per kg) and the Brazilian one (US$ 85 per kg). The declining export volume and the low prices of Indonesian vetiver oils are caused by the low production rates. The latter can be attributed to the current mode of production which employs conventional methods of refining of 22 h - 24 h duration. Besides that, the yield of the vetiver oil produced is low, as only about 1.2 % of its 2 % - 3 % potential is realized. This is a result of the accumulated effect of the poor quality of the raw material and the type of the refinery and processing technology used.

Considering the elapse time, it is imperative to enhance the technique used to extract vetiver oil. That is why more effective and efficient technique are developed aiming to hasten the production efficiency while contributing to the environmental conservation. The use of hydro-distillation (HD) for oils extraction using Clevenger and Soxhlet equipment has started several years ago [6]. This procedure requires extraction time of a few hours. The current development is based on ultrasound extraction, subcritical water, supercritical fluid extraction and microwave extraction. They are found a faster, a cheaper and a more efficient alternative. The research conducted proves that the microwaves based extraction technology is capable of being applied to different systems providing a more adjustable process of a lower energy consumption and better environmental impingement [7]. The microwave technology is widely used in the food industry due to the fact that: i) it can be applied to the required biomass without pre-treatment; ii) it allows fast and uniform heating; and iii) it can be easily adapted to become a sustainable process [8]. The microwave hydro-distillation method [9] is one of the successful extraction processes. It combines hydro-distillation and microwave heating. The microwave steam-distillation [10] combines steam distillation and microwave heating. Mahfud et al. [11] conduct a

study which compares the yield of essential oils from rhizomes using hydro-distillation and steam distillation methods. The hydro-distillation provides a yield of 26.77 % compared to 22.52 % product of the steam distillation. Golmakani and Rezaei [12] examine the use of microwave-assisted hydro-distillation (MHD) coupled with a conventional refining method and discover that MHD is more efficient because it provides a high yield at a shorter extraction time.The parameters of each extraction technique have a significant impact on the extract. The parameter optimization is most often used in line with the classic technique where a given variable changes while the rest remain constant. But this technique fails to produce adequate information on the experimental variables tested. On the other hand, it requires a large volume of time and materials [13]. The response surface methodology (RSM) has been often conducted to optimize the research variables used. Danh et. al. [14] find that RSM with Face-centered central composite design (FCCCD) is an effective tool for correlating the individual effects and the interactions among the variables using supercritical CO2 extraction (SCE). With a reference to several literature reviews, this study aims to optimize three variables (the microwave power, the extraction time and the feed to solvent ratio) used in extracting vetiver oil by microwave hydro-distillation. RSM-FCCCD method is applied aiming to obtain the highest yield on the ground of the designed optimal conditions.

EXPERIMENTALMaterials

The materials used referred to dried vetiver (Vetiveria zizanioides) obtained from Garut, West Java, Indonesia and distilled water as a solvent in the distillation process. The chemicals required for this research were obtained from PT. Brataco Chemicals (Surabaya branch).

Microwave Hydro-Distillation This study applied microwave hydro-distillation for

vetiver oil extraction. EMM2308X, Electrolux microwave oven was used. It had a maximal power of 800 W and a wavelength frequency of up to 2450 MHz. Its dimensions referred to 48.5 cm x 37.0 cm x 29.5 cm. It was modified by drilling a hole at its top. A 1000 mL round bottom flask connected to Clevenger condenser through the hole was placed inside. The hole was closed with a PTFE to prevent the entry of any contaminants (Fig. 1).


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Face-centered Central Composite DesignThe extraction of vetiver oil from dried vetiver

with the application of a microwave hydro-distillation technique was optimized using RSM. The FCCCD method was chosen to model, optimize and analyze the interaction and the effects of each variable in addition to the second order terms. Three variables were studied: the microwave power (W), the extraction time (min) and the F/S ratio (g/mL) as illustrated in Table 1. The value of the microwave power used ranged from 300 W - 600 W, the ratio of F/S was changed within the interval of 0.30 g/mL - 0.50 g/mL, while the extraction time was varied between 60 min and 180 min.

Table 1 shows the high (+1 code), the middle (0 code) and the low (-1 code) level of the microwave power treated as variable A, the feed to solvent (F/S) ratio treated as variable B and the time of extraction treated as variable

C. The initial regression model was a second order one comprising 4 factors. Similarly, square and two factor interactions were also obtained. The formula of each experimental response (Y) was presented as follows:

𝑦𝑦 = 𝛽𝛽0 + � 𝛽𝛽𝑖𝑖𝑛𝑛

𝑖𝑖=1𝑥𝑥𝑖𝑖 + � 𝛽𝛽𝑖𝑖𝑖𝑖𝑥𝑥𝑖𝑖2

𝑛𝑛

𝑖𝑖=1+ � � 𝛽𝛽𝑖𝑖𝑖𝑖 𝑥𝑥𝑖𝑖 𝑥𝑥𝑖𝑖 + 𝜀𝜀

𝑛𝑛

𝑖𝑖=𝑖𝑖+1

𝑛𝑛

𝑖𝑖=1

𝑦𝑦 = 𝛽𝛽0 + � 𝛽𝛽𝑖𝑖𝑛𝑛

𝑖𝑖=1𝑥𝑥𝑖𝑖 + � 𝛽𝛽𝑖𝑖𝑖𝑖𝑥𝑥𝑖𝑖2

𝑛𝑛

𝑖𝑖=1+ � � 𝛽𝛽𝑖𝑖𝑖𝑖 𝑥𝑥𝑖𝑖 𝑥𝑥𝑖𝑖 + 𝜀𝜀

𝑛𝑛

𝑖𝑖=𝑖𝑖+1

𝑛𝑛

𝑖𝑖=1

where β0 was a constant, βi, βii βij were coefficients, ε was an error factor, xi and xj were variables (A, B and C), while n stood for the number of variables. The coefficient was determined by the multiple linear regressions approach [15].

RESULTS AND DISCUSSION

Each variable value is introduced to the Design-Expert version 9.0.6.2 (State-Ease Inc., Minneapolis, MN, USA). FCCCD is applied on the ground of 20 experiments aiming to obtain the optimum yield of vetiver oil. The experimental and FCCCD values referring to vetiver oil extraction can be seen in Table 2.

ANOVA (analysis of variance) analysis is carried out to identify the vital factors affecting the yield at P-value = 0,05. ANOVA is an important criterion which demonstrates the model significance [16]. The results of ANOVA analysis can be seen in Table 3. The important factors affecting the yield are identified by P-value less than 0.05. Table 3 shows that the linear parameters, i.e. the microwave power (A), the F/S ratio (B) and the time of extraction (C) have a major impact on the yield (P- value < 0.05). However, the interaction relationships between the variables (AB, AC and BC) have no significant effect as the P-value is greater than 0.05 (the effect is significant in case P-value < 0.05).

Fig. 1. A schematic representation of the microwave hydro-distillation apparatus.

Table 1. Factors of the face-centered central composite design (FCCCD) referring to the extrac-tion of vetiver oil.

Factor Unit Level

Low Middle High -1 0 +1

A: Microwave power W 300 450 600 B: F/S ratio g/mL 0.30 0.40 0.50 C: Extraction time min 60 120 180


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Table 2. Experimental and FCCCD values referring to vetiver oil extraction.

Table 3. Variance (ANOVA) analysis.

Microwave power (W)

F/S ratio (g/mL)

Extraction time (min)

An Yield (%) Experimental Predicted Residual

300 0.4 120 0.3265 0.5456 -0.2191 300 0.5 60 0.1894 0.1375 0.0520 300 0.5 180 0.3604 0.3417 0.0186 300 0.3 180 0.7527 0.6828 0.0699 300 0.3 60 0.3847 0.3062 0.0785 450 0.4 120 0.6391 0.6345 0.0046 450 0.4 120 0.6391 0.6345 0.0046 450 0.4 120 0.6391 0.6345 0.0046 450 0.5 120 0.4462 0.3753 0.0709 450 0.4 120 0.6391 0.6345 0.0046 450 0.4 180 0.7713 0.7363 0.0350 450 0.4 120 0.6391 0.6345 0.0046 450 0.4 60 0.4328 0.4817 -0.0489 450 0.4 120 0.6391 0.6345 0.0046 450 0.3 120 0.5028 0.5876 -0.0848 600 0.5 180 0.4454 0.5204 -0.0751 600 0.3 180 0.7278 0.7763 -0.0485 600 0.4 120 0.9228 0.7176 0.2052 600 0.5 60 0.3215 0.3879 -0.0664 600 0.3 60 0.4562 0.4714 -0.0152

Source Sum of Squares df Mean Square F Value p-value

Prob > F

Model 0.52 9 0.057 4.32 0.016 A-Microwave power 0.074 1 0.074 5.57 0.04 B-F/S ratio 0.11 1 0.11 8.48 0.0155 C-Extraction time 0.16 1 0.16 12.2 0.0058 AB 3.63E-03 1 3.63E-03 0.27 0.6124 AC 2.57E-03 1 2.57E-03 0.19 0.6691 BC 0.015 1 0.015 1.12 0.3151 A2 2.30E-05 1 2.30E-05 1.73E-03 0.9676 B2 0.064 1 0.064 4.85 0.0522 C2 1.79E-03 1 1.79E-03 0.13 0.7212 Residual 0.13 10 0.013 Lack of Fit 0.13 5 0.027 Cor Total 0.65 19


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Fig. 2. 2D and 3D contour plots presenting the effects of the microwave power (A), the F/S ratio (B) and the extraction time (C) on the yield of vetiver oil obtained from a dried plant material using microwave hydro-distillation with FCCCD.

(a) Extraction time of 120 min (data center)

(b) A F/S ratio of 0.40 g/mL (data center)

(c) A microwave power of 450 W (data center)

In addition, the optimization of the vetiver oil extraction using the microwave hydro-distillation method along with FCCCD can also be used to obtain an equation predicting the yield obtained. Based on the experimental design that has been conducted, the yield extracted using the microwave hydro-distillation is expressed by Eq. 2:

Yield = -2.22700+3.59773E-004*Microwave power +11.40518*F/S ratio+7.59155E-003*Extraction time+1.42055E-003*Microwave power*F/S ratio-1.99318E-006*Microwave power*Extraction time-7.18133E-003*F/S ratio*Extraction time-1.28446E-007*Microwave power2-15.30496*F/S ratio2-7.08605E-006*Extraction time2 (2)


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The graphical representation known as a contour plot is used in this study to investigate the effects of several factors on the yield of vetiver oil. These plots are obtained from the regression model described by Eq. (2). They are presented in Fig. 2 (taking only at the data center).

Fig. 2. 2D and 3D contour plots presenting the effects of the microwave power (A), the F/S ratio (B) and the extraction time (C) on the yield of vetiver oil obtained from a dried plant material using microwave hydro-distillation with FCCCD.

Fig. 2(a) shows that the microwave power increase results in yield increase. This is because the higher the power, the faster is the attainment of the required temperature and hence, the higher is the amount of the essential oil produced. The microwave power in the microwave hydro-distillation acts as a driving force as it tends to break down the structure of the plant cell membranes enabling oil’s diffusion and dissolution. Therefore, the addition of microwave power will decrease the extraction time [17]. The maximum results procured for the microwave power variable are used to project a further increase of the yield value if the power is increased to the optimum point. The optimal point in respect to the F/S ratio (variable B) is obtained in the range of 0.3 g/mL - 0.4 g/mL (Fig. 2(b)). This is indicated by the yellow contour. The increase of the yield in the range pointed above is also influenced by the arrangement of the material in the distiller. In this study, the material arrangement in case of F/S ratio of 0.4 g/ml is more regular than that in case of F/S ratio of 0.3 g/mL. This provides an easier diffusion of patchouli oil at a ratio of 0.4 g/mL increasing the yield in comparison to that at a ratio of 0.3 g/mL. This result is in accord with that of Fachrudin and Velayas [18] who state that the phenomenon of yield increase with increase of F/S ratio is caused by the more regular and even spreading of the material in the distiller, which does not hamper the rate of refining and the space in the course of evaporation. But the increase of F/S ratio to 0.5 g/mL does not have the effect expected because the raw material (the dried vetiver) is overused and almost fills the distiller. It does not provide steam penetration and hence hampers the oil molecules diffusion out of the material. Besides, the latter density is closely related to the large space required. When it is too high and uneven, „rat holes“ vapor lines can be formed [18] which can reduce the yield and the quality of the essential oil. In contrast to parameter B,

parameter C (the extraction time variable) increase results in yield increase. The optimal point is determined using the variable range of 60min-180 min (Fig. 2(c)).

The contour plots displayed in Fig. 2 illustrate that using 600 W microwave power, a F/S ratio 0.358 g/mL and an extraction time of 180 min results in an adequate yield of vetiver oil. The maximum yield achieved amounts to 0.828 at the highest variables values. R² can be used to determine the level of conformity between the experimental results and the model values. It is found equal to 0.7955. The obtained model can be used to illustrate the experimental results or analyze the yield. The plot contours in Figs. 2(a) and 2(b) indicate that interaction AB (between the microwave power and the F/S ratio) and AC (between the microwave power and the extraction time) increase the yield value with increase of the two interactions. But the tendency of BC interaction (between the F/S ratio and the extraction time) shows that the ratio increase does not improve the extraction effectiveness at longer extraction time. This is illustrated by the contour plot in Fig. 2(c). A shrinking color degradation change is seen in the F/S ratio range of 0.3 g/mL -0.4 g/mL followed by no further increase.

CONCLUSIONSMicrowave hydro-distillation is used to extract

vetiver oil from dried vetiver. The microwave power, the F/S ratio and the extract time are optimized for this procedure using face-centered central composite design (FCCCD). The experimental design proves that optimum results are obtainable using 600 W microwave power, a F/S ratio of 0.358 g/mL and extraction time of 180 min. The maximum yield reached at these conditions amounts to 0.828 %. In view of the design R2 value (0.7955) it can be concluded that the model obtained can be used to describe the experimental results.

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an optimization of microwave hydrodistillation … · heri septya kusuma, ali altway, mahfud mahfud...

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