Improvement of Clove Oil Quality by Using Adsorption-distillation Process

The objective of this research was to improve the quality of clove oil by using adsorption-distillation process. Clove oil is one of essential oil products extracted from clove plants and currently considered as the most main product of Essential Oils Cluster in Batang Regency, Central Java. The main problem of essential oil production is low product quality due to high level of Eugenol and dark color of oil which does not met the National Standard. Therefore, process improvement was required to increase product quality as well as yield of product. The results showed that equipment material contributes significantly to the colors due to the availability of Fe ions. The addition of citric acid of 0.6-10% could improve the colors. The stirring process was proved as important variables to yield of products, while optimum time and temperature were optimum at 60 min and 50°C, respectively.


INTRODUCTION
Batang District is one of the largest regions of clove oil productions in Central Java Indonesia.The number of oil refineries in this area is more than 30 units which owned by a Small Medium Entrepreneurship (SME).This SME produces clove oil, clove stem oil and patchouli oil which reaches 20% of production growth (Profil Kluster Minyak Atsiri Kabupaten Batang Propinsi Jawa Tengah, 2011).
Clove oil is an essential oil extracted from clove plants (Eugenia caryophyllata thunb), especially from its flowers, stems and leaves.The quality of clove oil is normally indicated by its eugenol and carryophyllene contents (Badan Standarisasi Nasional, 2006).The content of eugenol in oil is mainly affected by quality of raw materials and oil refining methods.The highest eugenol level is shown by oil extracted from flowers and stem of clove plants (Table 1).
Eugenol is an alkyl bond (C 10 H 12 O 2 ) or 2-methoxy-4-(2-propenyl) phenol and it is a member of the alkyl benzene.Eugenol is very reactive to the strong base such as NaOH and KOH.Apparently, eugenol is liquid form with colourless or slightly yellowish and it is soluble in alcohol, chloroform and ether and slightly soluble in water, smelling clove oil, burning taste and heat in the skin.The boiling point of eugenol is 256°C and flash point of 104°C while the vapor pressure of 10 mmHg at 123°C.The chemical structure of eugenol is shown in Fig. 1 and it has density of 1.064 to 1.068 g/mL, a molecular weight of 164.20 g/mol and a refractive index of 1.541 at 20°C.The eugenol is mostly utilized in the perfume industries, flavor concentrates and in the pharmaceutical industry-as an antiseptic and anesthetic drug.It is also used to produce isoeugenol as a raw material in the manufacture of vanillin.Oyedemi et al. (2009) studied the use of eugenol for the metabolic activity of bacteria types Listeria monocytogenes, Streptococcus pyogenes, Escherichia coli and Proteus vulgaris.Cheng et al. (2008) utilize this compound and sinamaldehid as an anti-fungal for the type of fungus and Laetiporus sulphureus, which is considerable as inhibitory activity.Shelly et al. (2010) used methyl eugenol (eugenol derivative) to increase fertility of insects and the results were quite promising.Sadeghian et al. (2008) have conducted a synthesis of eugenol derivatives and tested to inhibit the activity of the enzyme 15-lipogenase.This enzyme was involved in many diseases such as asthma and lung cancer.The results showed that the compound could inhibit the performance of the enzyme 15-lipogenase.Furthermore, Chami et al. (2004) also have tested eugenol as anti fungus Candida albicans.Vidhya and Devaraj (2011) experienced eugenol for inducing lung cancer, which showed inhibitory phenomena in lung cancer.
The main problem faced by the SME in Batang District are low product quality due to availability of eugenol and darkness of colour (Profil Kluster Minyak Atsiri Kabupaten Batang Propinsi Jawa Tengah, 2011).The solution of this problem has been attempted by several researches by using bleaching agent.This method showed an extraction of eugenol content from 80 to 82% (Silviana and Dan Errysa, 2006).In other hand, citric acid and Na 3 EDTA were also used to improve quality of clove oil (Marwati et al., 2005;Silviana, 2007;Ma'mun, 2008).However, the levels of eugenol were still lower than required by the EOA (Essential Oil Association) of USA (1975).Therefore, the objective of this research was to study process improvement to produce high product quality by using adsorption-distillation process.Adsorption process showed an interesting technology to overcome the problem of dark colour of oil as normally found by conventional process (Silviana and Dan Errysa, 2006;Silviana, 2007;Ma'mun, 2008;Marwati et al., 2005).The distillation was integrated to solve the eugenol content.

Materials:
The clove oil used in this research was obtained from clove oil cluster at Batang District, Central Java.The raw material was analyzed under Indonesian Standard method for its colour and odour, refractive index, density, viscosity, solubility in ethanol and eugenol total.Moreover, raw materials were also analyzed by gas chromatography.Citric acid was utilized for the colour quality improvement.The purification of eugenol has been performed by using NaOH and HCl and done in Laboratory of Process Engineering, Department of Chemical Engineering, Diponegoro University.The equipment used was a laboratory scale and pilot plant scale which was the result of the design and production-scale trials.

Experimental design:
The experiment was carried out at in a laboratory scale under batch processes (Fig. 2).The clove oil volume was set at 200 mL under atmospheric pressure (1 atm), while the citric acid was varied between 3-6% and operation temperature of 40-60°C.The Design of Experiment was used response surface methodology (Box et al., 1978).The response surface methodology was used to formulate the number of experiment which was tabulated in Table 2.
Experimental procedure: The adsorption experiment was performed by using citric acid and heating was applied between 50-70°C in an Erlenmeyer equipped  with a stirrer for 1 h.The effluent of this heating process is then purified by using citric acid in a vacuum pump strainer.The amount of iron bound calculated by the following equation: The responses were density, viscosity, total eugenol, heavy Fe citrate.The data was further processed by using Statistical 6.

RESULTS AND DISCUSSION
Raw material analysis: Clove oil can be obtained from clove plants such as leaves, stems/handle and flower (Guenther, 1987).Clove oil is an essential oil produced from the clusters obtained from the stems and leaves.The results of the analysis as compared to the standard are presented in Table 3.The result showed that clove oil does not meet the standards especially for levels of eugenol and color.Therefore, the next step is to improve the quality of clove oil by using adsorptiondistillation method.The analysis of clove oil was performed by using Gas Chromatography and Mass Spectrometry (GCMS) (Fig. 3).The GCMS result shows 5 pieces of the chromatogram peak with the retention time of 11 to 13 min.The complete results of analysis are presented in Table 4 including Euogenol content.The impurity components in clove oil is dominated by trans caryophyllene and alpha humulene.Clove oil contains two major components, namely eugenol (70 trans-caryophyllene (15-20%) as well as some of small quantities components such as β-carryophylene, cubebene, α-copaene, humulene, γ-cadien and 1, 3, 5 trien cadina.

Clove oil improvement:
The previous research had shown the use of bleaching earth method to reduce colour and eugenol content (Silviana 2006).The results suggested that the clay can be used to reduce the colour of clove oil.Other researches have also been done by Marwati et al. (2005), Silviana (2007) and Ma'mun (2008) in which citric acid was used as a chelating agent to reduce colour of oil.Since citric acid showed more efficient in reducing dark colour, therefore this method was subjected as our further experiment.To compare the adsorption, zeolite was also used.The treatment of natural and impurity in the clove oil Komposisi (%) 0.17 73.10 0.55 22.40 2.64 The analysis of clove oil was performed by using Gas Chromatography and Mass Spectrometry (GCMS) (Fig. 3).The GCMS result shows 5 pieces of the chromatogram peak with the retention time of 11 to 13 min.The complete results of analysis are presented in including Euogenol content.The impurity is dominated by transcaryophyllene and alpha humulene.Clove oil contains two major components, namely eugenol (70-80%) and 20%) as well as some of small carryophylene, αcadien and 1, 3, 5- The previous research had shown the use of bleaching earth method to reduce colour and eugenol content (Silviana and Dan Errysa, 2006).The results suggested that the clay can be used to reduce the colour of clove oil.Other researches have .( 2005), Silviana (2008) in which citric acid was colour of oil.Since citric acid showed more efficient in reducing dark colour, therefore this method was subjected as our further experiment.To compare the adsorption, zeolite natural zeolite was     done through chemical and physical treatments by addition of hydrochloric acid and calcinations.In other hand, the experiment by using citric acid was done by addition of 0.6% citric acid without heating.The heating efficiency was subjected as main consideration.
The experimental results are documented and presented in Fig. 3. Figure 4 show that the addition of citric acid at a concentration of 0.6 and 10% has the ability to improve the colour quality of clove oil.More citric acid used, the clove oil is brighter because of Fe bound to citric acid.However, the citric acid in clove oil is not preferred and therefore must be reduced.The use of 2% zeolite improves this quality (Fig. 4b), however there was a smell problem ranging from typical odor of cloves to smell fragrant vanilla.
Process improvement: In this phase, the experiment was carried out on the basis of 200 g of oil of cloves with a magnetic stirrer stirring system at a speed of 200 rpm.During experiment, it was observed that heavy precipitation was formed.Heavy iron deposition is assumed as citrate, which was then used to calculate the bounded iron.The reaction of Metal binding (Fe) in eugenol with adsorbent citric acid can be described by Fig. 5 as follows.
The variation of citric acid concentration and temperature to Fe bounded is shown in Table 5.
Respond data in Table 6 is then processed by using Statistica 6 for mathematical modeling, model validation, analysis of variation, the response surface graphs.The output of this optimization is non-linear equation of Fe bounded correlated to citric acid and temperature Eq. (3).N From the correlation analysis shows that coefficient of variable temperature (X 2 ) is positive meaning that increasing temperature will also increase the Fe bounded in citric acid.Vice versa, coefficient of X1 is negative that mean increasing citric acid will reduce the Fe bound in the solution: Y = 76.7569-5.1811X 1 + 5.0265X 2 + 8.5358 X 2 1 + 0.7419 X 2 2 -6.9198X 1 X 2 (3) The completed correlation analysis is tabulated in Table 6.Equation (3) has been used to illustrate the surface response.Figure 6 indicate that under range of proposed variable, the optimum condition is still not discovered.Further experiment is needed to evaluate optimal point of this purification process.

CONCLUSION
Clove oil material did not comply with the standard SNI 06 2387 2006, especially from the color and eugenol total.Addition of citric acid up to 10% could reduce the dark colour while the stirring process and temperature of 50ºC will significantly improve the quality of clove oil.
The temperature gives a positive effect to the quality, while the amount of citric acid gives a negative impact to the quality of clove oil.
2012.In addition, the authors also thank to Clove Oil Cluster in Batang District for their support and cooperation.

Fig. 2 :
Fig. 2: Experimental set up with batch process

Fig. 4 :
Fig. 4: Purification of clove oil by using citric acid (a) and combination citric acid-zeolite (b) Fig. 5: The mechanism of Fe bounded to citric acid

Table 2 :
Experimental design

Table 4 :
The eugenol and impurity in the clove oil

Table 5 :
Effect of citric acid and temperature to Fe bounded