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Gopika Talwari and B.S. Ghuman JAE : 51 (2) Journal of Agricultural Engineering Vol. 51 (2): April-June, 2014 Optimization of Microwave Assisted Process for Extraction of Gopika Talwari1 and B.S. Ghuman2

Manuscript received: March, 2013 Revised manuscript accepted: April, 2014

ABSTRACT

Microwave assisted extraction (MAE) method was developed for extraction of essential oil from celery . A domestic microwave oven was modified and Clevenger apparatus attached to it to make it an extraction unit. Effect of various parameters such as soaking time, temperature and power density during MAE was studied. A multivariate study based on a Box-Behnken design was used to evaluate the influence of three major variables (soaking time, temperature and power density) affecting the performance of MAE on celery seed. Oil yield, time of extraction and energy consumption (MJ.kg-1 oil) by MAE were determined and compared with those obtained by the traditional hydro-distillation (HD). It was found that microwave assisted process gave approximately same oil yield (1.90%) in less time ( 93.5 min) and with low energy consumption (58191.78 MJ.kg-1 oil). Results revealed that the selected parameters had significant effect on the responses.

Key words: Celery seed, essential oil, microwave assisted extraction, hydro distillation

Essential oils are the volatile oils distilled from aromatic an average contains 2.5% volatile oil containing 60-70% material. Essential oils are contained in the glands, d-limonene and 1-20% beta selinene and 15%–17% fixed sacs and veins concentrated in different parts of the plant. oil. Celery seed is mainly cultivated in Amritsar district in All and contain essential oils ( oil), Punjab, Panipat district in Haryana and Saharanpur district which provide characteristic flavour and to it. The in Uttar Pradesh (Bhatia, 2001). Indian celery seed and oil Indian essential oil industry manufactures rose oil, kewda is exported from Bombay and Amritsar market to various oil, grass oil, oil, champa oil, citrus oil, countries like America, Britain, France, Italy, Canada, palmarosa, and celery oils. The major Indian cities Australia, Netherland, , Jawa, Germany, etc. which have essential oil are Mumbai, Mysore and Chennai. In the last decade, there has been considerable rise The main methods to obtain essential oils from the plant in production of essential oils. In 1990-91, the export was materials are hydro-distillation (HD), steam distillation, 892 Mt worth Rs.31.99 crores, which increased to 4,400 Mt steam and water distillation, maceration, empyreumatic (or worth Rs.386.48 crores in 2000-01(Singhal, 2003). destructive) distillation, and expression. Steam distillation, hydro-distillation and simultaneous distillation– extraction Celery seed is the dried of graveleons L. methods are known to be the most common methods for the belonging to the Umbelliferae . Celery is used in extraction of essential oils. It is known that conventional various forms such as fresh , seeds, oil and methods used for the extraction of essential oils from plant for flavouring foods. It is valued as a spice and imparts a materials have some disadvantages, mainly concerned warm and pleasing flavour to foods such as canned soups, with the quality of the final product like losses of some sauces, pickles, tomato products and meats. Celery is volatile compounds, low extraction efficiency, degradation extensively cultivated for their seeds in India, France and of unsaturated or ester compounds through thermal or United States of America. Celery seed oil lends a floral hydrolytic effects and toxic solvent residue in the extract like odour to oriental to which it imparts warm (Ferhat et al., 2006; Kaufmann and Christen, 2002). and clinging notes (Farooqi and Sreeramu, 2001). The ground seed is mixed with table to give “’’ Some recently published studies have successfully utilized which is used in flavouring fish, , and eggs. Celery a microwave oven for the extraction of active components oil is extensively used in meat , and to flavour from medicinal plants/herbs (Lucchesi et al., 2004; Wang soups, gravy, dressings, confections and non-alcoholic et al., 2006; Lucchesi et al., 2007). Solvent free microwave beverages (Agrawal et al., 2001; Anon, 2002).The seed on extraction has been used to obtain essential oils from three

1Assistant Professor ,College of Dairy Science & Technology, GADVASU, Ludhiana, Punjab, India; corresponding author email: engg_gopika@ yahoo.co.in ; 2Senior Research Engineer (retd.), Department of Processing and Food Engineering, PAU, Ludhiana,Punjab.

9 April-June, 2014 Optimization of Microwave Assisted Process for Extraction of Celery Seed Essential Oil

different spices as ajowan, , pumpkins seeds and star used for the experiment was found to be 7.3% (wet basis). (Lucchesi et al., 2004; Jiao et al., 2014), three different aromatic herbs as , garden , and (Lucchesi et Modification of Domestic Microwave al., 2004), and seed (Lucchesi et al., 2007). Presti A domestic microwave oven (T37, MagiCook, National, et al. (2005) compared the traditional hydro-distillation India, 800W; 2.45GHz) was modified for MAE operation (HD), supercritical fluid extraction (SFE), organic solvent with the addition of a water condenser, temperature extraction (SE), and microwave assisted hydro-distillation measurement device-K type thermocouple (−200 °C to (MAHD) techniques and evaluated their effectiveness in +1350 °C, with sensitivity of approximately 41 µV.°C-1), the isolation of essential oil. Acidic pH based time controlling device i.e. PID controller (TZ4ST series, microwave assisted extraction has been tried on yellow Autonics, USA) and voltage regulator (Fig. 1). The horn by Qu et al. (2014). dimensions of the cavity of microwave oven were 22.5cm x 37.5cm x 38.6cm. The microwave oven was modified Microwave-assisted hydro-distillation (MAHD) has been by drilling a hole at the top. Round bottom flask having a developed and used for the extraction of essential oils capacity of 1000 ml was placed in the oven and connected from Xylopiaaromatica (Lamarck) and Lippiaalba (Mill.) to Clevenger apparatus through the hole. The flask was setup (Stashenko et al., 2004). MAHD was also reported for the within the microwave oven cavity, and a condenser was extraction of essential oils from Cuminumcyminum L. used on the top (outside the oven) to collect the extracted and Zanthoxylum bungeanum Maxim (Wang et al., 2006). essential oils (Fig. 1). The hole made in the ceiling was However, no work has been published on the microwave sealed with metal wool and Polytetrafluoroethylene (PTFE)/ assisted extraction (MAE) of essential oil from celery . Teflon material so that no microwave radiations could pass Therefore, the objectives of this study were to develop a out of the cavity (Bayramoglu et al., 2008). modified process using microwave for rapid extraction of essential oils from celery seed (ApiumgraveleonsL.) and optimize the process taking extraction time, oil yield and Oil Extraction energy consumption as responses. For extraction, 100 g of celery seed sample was taken. Celery seed sample was soaked in 1000 ml of water for MATERIALS AND METHODS stipulated time period (4, 8 and 12 h). After soaking of seeds for stipulated time period, excess water was drained off. This Plant Material soaked sample was then put in flask of Clevenger apparatus Celery seeds grown in Punjab was used in the present study. and the microwave was run at particular temperature and Celery seed was purchased from Suran Singh Ram Singh power density as per the selected design. Power density is Pvt., Ltd., Vala Road, Amritsar. Moisture content of seeds expressed as power of microwave per unit mass of material. was measured in triplicate according to AACC (1983) The extracted oil got settled on top of aqueous phase (Fig.1) method, using a laboratory oven at 105oC until constant in Clevenger apparatus. The oil was manually drained by weight was achieved. The moisture content of celery seed operating a valve.

Fig. 1: Experimental set up for microwave assisted extraction process

10 Gopika Talwari and B.S. Ghuman JAE : 51 (2)

The oil thus obtained was checked for quality parameters Based on the above relationship, the independent extraction such as specific gravity and refractive index as also solubility parameters and their levels in the form of coded variables of the essential oil in . The effects of soaking time, are given in Table 1. temperature and power density on extraction time, oil yield and energy consumption were also examined. The results Yield were compared with those obtained with hydro-distillation Essential oil yield was expressed in terms of the weight method used as control. of the oil collected in mg per 100 g of dry plant material.

Experimental Design Physical properties of essential oil For carrying out the study on optimization of MAE, an Specific gravity, refractive index and solubility (in 85% experimental plan was chosen from the family of three- ethanol v/v) of the essential oils extracted by hydro- level designs available in response surface methodology distillation and MAE at different variable levels were (Cox and Cochran, 1964). Three variables taken were measured. soaking time, temperature and power density; and three levels were chosen based on preliminary trials conducted Specific gravity prior to final experimentation (Table 1). A Box–Behnken design of three variables and three levels, each with three Specific gravity was calculated by dividing the weight of centre point combinations, was used (Box and Behnken, 1 ml essential oil by that of 1 ml distilled water. Weights 1960). This design was taken as it fulfilled most of the were measured using a balance with an accuracy of 0.001g requirements needed for optimization of the microwave (CY220, Citizen Scale, India). assisted extraction process. In the above design X , X , 1 2 Refractive index X3 are the coded variables, which are related to un-coded variables using the following relation: Refractive index was measured at 25±0.2oC in triplicate using an Abbe refractometer. Solubility of the essential X = 2 (x − x ) / d oil in 85% (v/v) ethanol was determined using the method i i i i …(1) described by the Indian Standard Institute (BIS, 1982). In Where, this method, 1 ml of oil was repeatedly diluted with 0.1 x = Variable value in actual units of the ith observation, ml of 85% ethanol, and thoroughly shaken each time. The i dilution procedure was continued until a clear mixture x = Mean of highest and lowest variable value of x , and i I was obtained. The volume of alcohol (V) used to obtain di = Difference between the highest and lowest variable a completely clear solution was recorded. Once the clear x value of i. solution was obtained, the dilution process was continued,

Table 1. Process variables and their levels

Independent variable Symbol Level

Coded Un-coded Coded Un-coded

Soaking time (h) X1 t 1 12 0 8 -1 4

Temperature (°C) X2 T 1 110 0 100 -1 90

-1 Power density (W.g ) X3 W 1 6 0 4 -1 2

11 April-June, 2014 Optimization of Microwave Assisted Process for Extraction of Celery Seed Essential Oil

but with 0.5 ml 85% ethanol until the volume of alcohol Y = bo+b1X1+b2X2+b3X3+b12X1X2+b23X2X3+ 2 2 2 added was 20 times the volume added earlier. The solution b13X1X3+b11X1 +b22X2 +b33X3 … (2) was thoroughly shaken each time with 0.5 ml ethanol. No th turbidity or opalescence was observed during the process. Where bn is the coefficient associated with each n

The results were expressed as ‘‘one volume of essential oil factor, and X1, X2, X3 represents the factors in the model. soluble in V volumes or more of 85% ethanol”. Combination of factors (such as X1X2) represents interaction between the individual factors in that term. Time of extraction Obtained model was evaluated for each response function Time of extraction was the period (min) which was sufficient and the experimental data (extraction time, oil yield and to extract all the essential oils from the sample. During the energy consumption) were statistically analyzed applying first 30 min, the collected essential oil was decanted from the analysis of variance (ANOVA) and using Design expert 8.0, condensate at 10 min intervals. Decantation of the essential a DOE software tool by Stat-Ease, Inc. The adequacy of the oil was then continued at 15 min intervals until no more final model was verified by graphical and numerical analysis. essential oil was obtained. Surface plots Energy consumption Series of surface plots of equal responses were generated Energy consumed in the extraction process was measured from the data, which provided useful information to using Watt-hour meter (single phase, 240 V; current rating interpret the contribution of the parameter to each response of 5-20 A; 3200 impulse/kWh and frequency of 50Hz). It is (Cox and Cochran, 1964; Montgomery, 2004; Lee et al., expressed as MJ of energy consumed to yield 1 kg oil. The 2006). As the present study involved three variables, it Watt-hour meter had a small motor whose instantaneous was necessary to fix the value of one variable in order to speed is proportional to the power passing through it. The generate plots. The non-variant parameters were set at the total revolutions in a given time are proportional to the total optimum point and a new relationship between dependent energy (W.h), consumed during that time. and independent variables was developed and plotted. Statistical Analysis RESULTS AND DISCUSSION A three-factor D-optimal design was used to determine the operating conditions for maximizing the oil yield and Physical Properties of Celery Seed Oil minimising the energy consumption and extraction time. Physical properties (specific gravity, refractive index, Based on trials conducted, soaking time (X1), temperature optical rotation and solubility in 85% alcohol) defining the of extraction (X2) and microwave power density (X3) were essential oil extracted by MAE and HD from celery seed chosen as the three factors for investigation (Table 1). These are shown in Table 2. There was no significant difference parameters (X1, X2, X3) were identified as control factors between the physical constants of essential oils obtained (CFs), because the variation of their values results in optimal by MAE and HD. performance. Other parameter i.e. volume of water used for soaking were set at fixed value. The method consisted of For comparison purposes, standard properties obtained (i) defining levels, (ii) selection of the model that fits, and (Singhal et al., 1997) are also shown in Table 2. The (iii) choosing design points. As presented in Table 1, all the refractive indices and specific gravities of essential oils three factors were varied over 3 levels. Oil yield, extraction obtained from celery seed for both MAE and HD fell within time and energy consumption were statistically evaluated the ranges specified by Singhal et al. (1997). Similarly, by analysis of variance (ANOVA).The following quadratic the colours of both essential oils were in the range of the model was selected: standards indicated. The only difference was that the colour

Table 2. Physical properties of extracted celery seed oil

Physical property Standard MAE HD Specific gravity 0.872-0.891 0.86 0.86 Refractive index 1.480-1.484 1.481 1.480 Solubility (v/v) in 85% alcohol Turbid in 90% alcohol 0.4 0.4

12 Gopika Talwari and B.S. Ghuman JAE : 51 (2) of the essential oils extracted by MAE was lighter than that obtained by HD. Oils obtained from both the methods were turbid, and had same value for solubility. Therefore, considering physical properties of the extracted essential oils, MAE as a new extraction technique does not adversely affect the physical properties of the essential oils extracted from the celery seed.

The values of various responses at different experimental combinations for coded variables are given in Table 3. The extraction time was found to vary from 70 min to 195 min as compared to 300 min (5 h) in the conventional hydro- distillation process. Oil yield varied from 1.334% to 1.911% in the developed process. The energy consumption varied -1 Fig. 2: Variation of celery seed oil yield during hydro- from 38182 to 74051 MJ.kg oil in the developed process. distillation and microwave assisted extraction process (MAE) (■: hydro distillation; x: MAE process 2 W.g-1; Figure 2 shows the variation of celery seed oil yield with ●: MAE at 4 W.g-1 ; ▲: MAE at 6 W.g-1) time for MAE and hydro-distillation process. The time taken to reach the maximum yield was significantly higher inside the seeds. Microwave absorption results in significant in hydro-distillation (5h) than in MAE (3h and 15 min). internal heating, thus creating significantly higher internal The reason for the reduction in extraction time in the case pressure which enhances oil extraction (Bayramoglu et of MAE process might be due to high pressure formed al., 2008).

Table 3. Experimental data for the three factors and three level response surface analysis (coded values) of MAE process

Treatment Factor Response Soaking Temperature Power density Extraction Oil yield Energy consumption time (h) (o C) (W.g-1) time(min) (%) (MJ.kg-1 oil) 1 -1 -1 0 195 1.90 55894.74 2 1 -1 0 185 1.89 50322.58 3 -1 1 0 180 1.89 49354.84 4 1 1 0 90 1.66 61807.23 5 -1 0 -1 85 1.78 43484.15 6 1 0 -1 80 1.56 54000.00 7 -1 0 1 70 1.91 62764.40 8 1 0 1 80 1.77 73220.34 9 0 -1 -1 90 1.65 38181.82 10 0 1 -1 170 1.56 39692.31 11 0 -1 1 180 1.77 55525.42 12 0 1 1 75 1.58 74050.63 13 0 0 0 120 1.33 62526.32 14 0 0 0 120 1.46 58191.78 15 0 0 0 110 1.44 49354.84 Control (Hydro distillation) 300 1.91 56188.92

13 April-June, 2014 Optimization of Microwave Assisted Process for Extraction of Celery Seed Essential Oil

The full second order model of the form was fitted to the of temperature and power density, soaking time and for data, and regression coefficients were computed (Table 4). higher powers of temperature and power density. Soaking The sign and magnitude of the coefficients indicated the time was found to have insignificant effect on extraction effect of the variable on the response. Negative sign of the time, which was also supported by surface plot (Fig. 3) coefficient meant decrease in response when the level of showing soaking time effect by a straight line. R2 value of the variable was increased while positive sign indicated 0.96 explained that selected quadratic model had good fit. increase in the response. Significant interaction suggested that the level of one of the interactive variable can be In response to power density, extraction time increased to increased, while that of the other decreased for constant a point of maxima with an increase in power (4 W.g-1), and value of the response (Montgomery, 2004). with further increase it dropped to a value of 90 min. At 5% level of significance, quadratic model was found to be Effect of process parameters on extraction time significant and effect of temperature and power density was As shown in Fig. 2, HD required an initial time period of found to be significant on extraction time, whereas the effect 30 min for heating water soaked celery seed sample (100g) of soaking time was found to be insignificant. until oil extraction started. Additional time required for Extraction time was found to decrease with increase in the full extraction of essential oils was 270 min. However, temperature. This decrease could be attributed to the fact MAE required only 7 min for the initial stage and additional that with increase in temperature, the vapour pressure of 63 min for the final stage. Therefore, MAE resulted in water present inside the celery seeds increased leading to significant saving in extraction time. The modified process leaching out and evaporation of volatile oil along with water retained the advantage (continuous contact of the plant (Chemat et al., 2006). material with clean extract) of the hydro-distillation and offered additional benefits of quicker extraction leading to Effect of Process Parameters on Oil Yield substantial saving in energy and costs. Oil yield response was supported by a quadratic model with Figure 3 indicated that with increase in temperature, R2 value of 0.9724 with non-significant lack of fit (Table extraction time decreased quadratically, as indicated in 4). Oil yield was significantly linearly affected by soaking Table 5. With increase in power density, extraction time time, temperature and power density and higher derivatives increased till it attained a point of maxima at 113 min at 4 of power at 95% level of significance. From surface plots of W.g -1 and with further increase in power density, extraction oil yield response, it was found that the effect of variables time decreased. From Table 5, it is clear that extraction as soaking time, temperature and power density achieved time was significantly affected by temperature, interaction a point of minima. With increase in soaking time, oil yield

Table 4. Regression coefficients (un-coded values) of the responses

Term Coefficient Extraction time Oil yield Energy consumption

Constant βk0 113 1.406 54533.8

Soaking time β1 -5.625 -0.072 3481.5

Temperature β2 -41.875 -0.062 3122.56

Power density β3 2.5 -0.057 11275.3

Soaking time * Soaking time β11 6.625 0.274 -

Temp * Temp β22 21.625 0.003 -

Power density * Power density β33 -14.625 0.018 -

Soaking time * Temperature β12 1.25 0.052 -

Soaking time* Power density β13 -5.0 0.017 -

Temperature* Power density Bk23 -17.5 -0.025 - R2 0.9595 0.9724 0.9679

14 Gopika Talwari and B.S. Ghuman JAE : 51 (2)

Fig. 3: Surface plots showing effect of process variables on extraction time in MAE process

decreased to a point of minima at 8 h. With further increase Effect of Process Parameters on Energy Consumption in soaking time oil yield increased, but to a lesser value than Energy consumption was well expressed by quadratic at 4 h. With increase in temperature, oil yield decreased to a model with R2 of 0.9679 with non-significant lack of o point of minima at 100 C. With increase in power density, fit (Table 5). At centre point, energy consumption was oil yield increased quadratically. Soaking time was found 58191.78 MJ.kg-1 oil at 8 h of soaking, 100o C and 4 to have significant effect on oil yield. Celery seeds were W.g -1 power density. Power density was found to have soaked in water at 25o C to moisten the outer layers, which significant linear effect on energy consumption. With increased the pressure inside the seeds till bursting of outer increase in power density, energy consumption increased layer took place. This bursting led to release of oil, which linearly. Interaction of soaking time and power density increased the oil yield when compared to conventional had significant effect on energy consumption. Soaking hydro-distillation process. time and temperature did not have effect on energy consumption (Fig. 5). In case of temperature, maximum oil yield was found at 110o C, and was low both at 90o C and 100o C. The lower yield of Optimization of Process Parameters o oil extracted at 90 C might be due to the temperature being Responses were optimized individually in combination not enough to burst open the oil glands. Oil yield was also using ‘DX-6’ software (Design Expert 6.0). In response o lower at 110 C because evaporation rate was higher than surface analysis, the selected model was used to locate the condensation rate. the stationary point. A stationary point is a point at which

15 April-June, 2014 Optimization of Microwave Assisted Process for Extraction of Celery Seed Essential Oil

Table 5. ANOVA for response variable extraction time, oil yield and energy consumption

Source P-value P-value P-value (Energy (Extraction time) (oil yield) consumption) Model 0.0004 0.0001 0.0002

X1 0.1770 0.0042* 0.3244

X2 <0.0001* 0.0091* 0.4086

X3 0.520 0.0131* <0.0001*

X12 0.8203 0.0733 0.0491

X13 0.3768 0.5135 0.7784

X23 0.0131* 0.3407 0.0843 2 X1 0.2404 <0.0001* 0.0006 2 X2 0.0041* 0.0003* 0.1680 2 X3 0.0253* 0.0178* 0.8284 Lack of fit 0.0904 0.4102 0.2071

*significant at 5% significance level

Fig. 4: Surface plots showing effect of process variables on oil yield (%) in MAE process

16 Gopika Talwari and B.S. Ghuman JAE : 51 (2)

Fig. 5: Surface plot for effect of process variables on energy consumption in MAE process Fig. 7: Overlay plot by graphical superimposition showing the slope of the response surface is zeroed in all the area (dark) of optimization (power density Vs directions. Since the optimum response for each variable soaking time) was not all in exactly the same region in the space formed by the processing variables, constraints were set such that Table 6. Optimum process parameter values and responses the selected soaking time, temperature and voltage was for MAE process optimum for most important attributes and close to optimum for the others (Lee et al., 2006). Process parameter Value Soaking time (h) 4 3-D plots for each response were generated by varying two process variables and holding the third one as shown Temperature (0C) 90 in Fig.3-5. Superimposing the individual contour plots Power density(W.g-1) 20 resulted in overlay plots, Fig. 6-7, showing the region which satisfied all the constraints. In the overlay plots, Response the dark portion satisfies all the given constraints and by numerical optimization the points optimization was done. Extraction time (min) 93.7 The optimum region was in vicinity of soaking time of 4 Oil yield (%) 1.90 h; temperature of 90o C at power density of 2 W.g-1, which -1 were also confirmed by numerical optimization. The Energy consumption (MJ.kg oil) 54230.76 optimum process parameters and values of responses are given in Table 6. CONCLUSIONS

Microwave assisted rapid extraction of essential oil from celery seeds exhibited that soaking time, temperature and power density had significant effect on responses of extraction time, oil yield and energy consumption. 0ptimum processing parameters identified were soaking time of 4 h, temperature 90o C and wattage of 2 W.g-1 with extraction time of 93.7 min, oil yield of 1.90% and energy consumption of 58191.78 MJ.kg-1 oil.

NOMENCLATURE

MAE Microwave assisted extraction HD Hydro distillation t Soaking time for celery seeds, h Fig. 6: Overlay plot by graphical superimposition showing di Difference between the highest and lowest variable area (dark) of optimization (soaking time Vs value of η temperature) i

17 April-June, 2014 Optimization of Microwave Assisted Process for Extraction of Celery Seed Essential Oil

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X2 Coded independent variable for temperature Food Chem., 147, 17-24.

X3 Coded independent variable for power density Kaufmann B A; Christen P. 2002. Recent extraction

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