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Isolation of Volatiles from Oak Wood (Quercus alba)by a Thermomechanical Process: Screening of someProcessing ParametersHamid Mellouk a , Alice Meullemiestre b , Zoulikha Maache-Rezzoug b , Karim Allaf b & Sid-Ahmed Rezzoug ba Laboratoire de Génie des Procédés et de Dépollution, University Hassan II , Mohammedia ,Moroccob LaSIE, FRE-CNRS 3474. University of La Rochelle , La Rochelle , FranceAccepted author version posted online: 10 Apr 2013.Published online: 16 Jul 2013.

To cite this article: Hamid Mellouk , Alice Meullemiestre , Zoulikha Maache-Rezzoug , Karim Allaf & Sid-Ahmed Rezzoug(2013) Isolation of Volatiles from Oak Wood (Quercus alba) by a Thermomechanical Process: Screening of some ProcessingParameters, Separation Science and Technology, 48:12, 1851-1858, DOI: 10.1080/01496395.2013.771671

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Isolation of Volatiles from Oak Wood (Quercus alba) by aThermomechanical Process: Screening of some ProcessingParameters

Hamid Mellouk,1 Alice Meullemiestre,2 Zoulikha Maache-Rezzoug,2 Karim Allaf,2

and Sid-Ahmed Rezzoug21Laboratoire de Genie des Procedes et de Depollution, University Hassan II, Mohammedia, Morocco2LaSIE, FRE-CNRS 3474. University of La Rochelle, La Rochelle, France

Experiments were performed to evaluate an extraction processdeveloped in our laboratory called the instantaneous controlledpressure drop process (‘‘Detente Instantanee Controlee’’ or (DIC))for extracting volatile compounds from oak wood. This processinvolves subjecting oak chips for a short time (10 s to 12min) undera steam pressure (1 to 6 bars or from 100 to 165�C). This first step isfollowed by a rapid decompression toward vacuum (up to 50mbar).Some parameters were evaluated: steam pressure level, processingtime, initial moisture content, chips thickness and velocity of therapid decompression. A preliminary experimental design allowedoptimizing the processing pressure and processing time: 6 bar and 5minutes. Under these conditions, the optimal conditions were asfollows: 20% for initial moisture content, 0.5mm for the chipsthickness. The number of decompressions towards vacuum was alsoinvestigated and it appeared that extraction yield can be enhanced byrepeating the decompressions cycles for a same processing time.Moreover, GC-MS analysis indicated that DIC extract includedthe same molecules that obtained by steam distillation with almostthe same percentages.

Keywords extractives; instantaneous controlled pressure drop(DIC Process); isolation; oak wood; thermomechani-cal treatment; volatiles

INTRODUCTION

The interest of extractives produced by a tree is toprovide a protection from predators that wish to consumethe structural components of the cell wall (1). The amountand type of extractives produced are quite variable withinindividual species. They were until recently considered tobe a waste product of plant metabolism (2). In the literature,a lot of work has focused on extraction and characterizationof non-volatiles wood extractives compounds (3–5) but fewhave reported on extraction of volatiles oils or essential oilsfrom wood (6–8). Essential oil is a complex mixture of

volatile substances which ordinarily includes terpenes,sesquiterpenes, and oxygenated derivatives; it is generallypresent at low concentrations in wood (9). Traditionalextraction processes are unsuitable because of their largeprocessing time, low yield, high-energy consumption, andlow quality of extracts. The steam distillation, as a hightemperature-long time process can cause chemical modifica-tions of the oil components and often a loss of the most vol-atile molecules (10,11). In extraction with organic solvents,in spite of successive and advanced distillation operations,the final essential oils contain unacceptable residual solventrate (12). In contrast, extraction by supercritical fluids leadsto a high-quality and solvent-free extracts (13). However,according to different authors (14,15), the technologicalconditions required for the use of supercritical fluids canbe onerous due to the high processing pressures and thehigh cost of producing specific products has limited its useto pharmacological products. The aim of this work was toprovide an efficient and economically attractive processfor extraction of essential oil from chips of oak wood, whichcan be considered as a waste issued from sawmills, througha thermomechanical extraction technique developed in ourlaboratory: the instantaneous controlled pressure dropprocess. This extraction process, known as ‘‘D.I.C’’, wasdeveloped and patented in our laboratory (16). In this pro-cess, wood undergoes a rapid transition from high steampressure to vacuum which induces a fast evaporation ofwater and volatile compounds. In a previous work (17,18)we showed that processing by instantaneous controlledpressure drop increases the global diffusivity of the productand improves the availability of the liquid in the plant. Theessential oil isolation based on this process is an interestingalternative to standard techniques of essential oil extrac-tion, such as extraction with solvents or steam distillation.This is because it avoids using solvent, and induces coolingwhen the plant is rapidly transferred from a high steampressure to vacuum thus minimizes thermal degradationof the essential oil components. Moreover, compared to

Received 18 May 2012; accepted 28 January 2013.Address correspondence to Sid-Ahmed Rezzoug, LaSIE,

FRE-CNRS 3474. University of La Rochelle, Avenue MichelCrepeau, 17042 La Rochelle, France. E-mail: sarezzou@univ-lr.fr

Separation Science and Technology, 48: 1851–1858, 2013

Copyright # Taylor & Francis Group, LLC

ISSN: 0149-6395 print=1520-5754 online

DOI: 10.1080/01496395.2013.771671

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the classical processes as steam distillation or hydrodistilla-tion, the short time contact between plant and the heatedzones of apparatus avoids the loss and degradation ofvolatile and thermolabile compounds. In fact, authors asChen and Spiro (12) reported that a long time at high tem-peratures could cause rearrangement or polymerization ofsome of essential oil constituents. It is well known thatoak wood essence contains very useful valuable moleculesas eugenol, which is commonly used in the food industry,in aromatherapy, and as a therapeutic agent in dentistry.This molecule showed interesting insecticidal properties(19) and its vasorelaxant effect was pointed (20). The oakwood essential oil contains also 20% of furfural, which isused in agriculture both as a fungicide and a nematicide,as a nontoxic to both humans and environment (21). Parpotet al. (22) argued that furfural can be the source of manyderivatives and among the wide variety of furfural deriva-tives, furfurylic alcohol and furoic acid are very interestingin the pharmaceutical industry, perfumery, or polymerindustry. The oak wood essential oil is composed of about10% of palmitic acid which is classified among the groupof fatty acids with a great interest as antibacterial agent infoods (23) and high antioxidant activity (24).

In this study, oak volatile compounds were isolated byD.I.C process and some processing parameters were opti-mized. The first time, a factorial design was performed tooptimize processing pressure and processing time and thenother parameters, namely initial moisture content, chipsthickness, velocity of the transition between high streampressure and vacuum, and the number of decompressionscycles were also investigated.

EXPERIMENTAL

Raw Material

American Oak wood (Quercus alba) in form of chips(approximately 5mm� 40mm and between 0.5 and 10mmthickness), with a residual moisture content of 8.5% drybasis was used in this study. The moisture content was mea-sured by Mettler LP16 infrared balance at 105�C during 60minutes. The wood chips samples do not undergo anypretreatment before extraction. For the variation of initialmoisture content, distilled water was added to reach thedesired humidity. The percentages in term of cellulose, hemi-cellulose, and lignin were respectively, 42%, 26%, and 25%while the quantity of extractives was estimated to be 5.3%.

Experimental Set-Up

The experimental set-up, largely described in previousstudies (25,26), is composed of three main elements:

1. processing vessel which contains the wood chips totreat.

2. vacuum system which mainly consists of a vacuum tankand a vacuum pump.

The capacity of the vacuum tank (360L) is 30-foldlarger than that of the processing vessel (12 L). The initialpressure in the vacuum container was fixed at 50mbar inall the experiments. 3) a pneumatic valve placed betweenthe processing vessel and the vacuum tank. The openingtime of the valve is very short, less than 0.2 s, thus involvinga rapid decompression within the reactor.

Protocol of Extraction by the Instantaneous ControlledPressure Drop Process

A quantity of 25 g of wood chips are firstly placed in theD.I.C vessel and the pressure inside is reduced to 50mbar(Fig. 1b). This partial vacuum allows a better diffusion ofsteam within wood structure so that the time to reach thedesired processing pressure (or processing temperature) isshortened. The electropneumatic valve between the reactorand the vacuum tank, is then closed and the DIC reactor isfilled with steam up to a processing pressure fixed between 1to 6 bar (Fig. 1c). After a certain time, at a fixed processingpressure (Fig. 1d), the pneumatic valve is instantaneouslyopen thus resulting in a rapid pressure drop within theD.I.C reactor (Fig. 1e). The mixture of condensed steamand extracted volatiles is recovered in a specific vesselplaced under the vacuum tank. The volume of the recoveredliquid mixture was about 400mL for all experiments.

GC/MS Conditions

GC=MS analysis was performed using Varian 3900 gaschromatograph coupled to a Varian Saturn 2100T ion trapmass spectrometer (Varian, France) for characterizingextracts. The chromatographic column is a 30m� 0.25mm,0.25 mm CP-Sil 8 CB Low Bleed MS capillary column(Varian, France). The column temperature is 80�C (3min)�3�C=min �250�C (40min) with helium as carrier gas at1mL=min. Extract samples are injected via a VarianCP-8400 autosampler fitted with a 5 mL syringe. The

FIG. 1. Typical pressure-time profile for DIC processing cycle.

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temperature of the transfer line was 280�C. Electron impactmass spectra are obtained at 70 eV ionization potential andpeaks are identified from the data library NIST 2008.

Steam Distillation

For steam distillation, a quantity of 25 g of oak woodchips was placed on stainless steel grid of a conventionalsteam distillation apparatus and continuously swept during2 hours by steam produced from a flask of boiling water, atatmospheric pressure. The mixture of steam and extractedvolatiles is cooled and condensed after flowing through acooling coil. An organic phase rich in extracted oil is finallyseparated from the aqueous phase by using 10% chloro-form. The experiments of steam distillation aim to comparethe molecules extracted by this conventional process withthose extracted by using the proposed D.I.C thermomecha-nical isolation process.

Scanning Electron Microscopy

Philips-FEI Quanta 200 ESEM=FEG Scanning ElectronMicroscopy operated at 20 kV, with a detector of second-ary electrons Everhardt-Thornley, was used to image somethe treated samples. To improve the quality of the SEMimages, a high vacuum was achieved.

Experimental Design

The relationships between response function and processvariables have been estimated using a full-factorial design aswell as the optimal conditions of the developed process. Thedesign needed 13 experiments with four (22) factorial points,four combinations between the different levels of the twovariables with the central level, and five central points toestimate the experimental error and to prove the suitabilityof the model. The experiments were run in random order tominimize effects of unexpected variability due to extraneousfactors. The two independent variables are coded accordingto the following equation:

xi ¼Xi �Xi0

DXii ¼ 1; 2 ð1Þ

where xi and Xi are respectively the dimensionless and theactual values of the independent variable i, Xi0 the actualvalue of the independent variable i at central point, andDXi the step change of Xi corresponding to a unit variationof the dimensionless value. The processing pressure (p) andprocessing time (t) are chosen as independent variables andthe selected response was the total yield of isolated oil. Theprocessing pressure was varied between 1 and 6 bar andthe processing time between 30 and 300 seconds. The centralpoints were performed at 3.5 bar and 165 seconds, respect-ively, for processing pressure and time. The studiedresponses are related to the coded independent variablesxi, xj according to the second order polynomial expressed

in Eq. (2),

Y ¼ b0 þX

bixi þX

biix2i þ

Xbijxixj ð2Þ

with b0 as the interception coefficient, bi the linear terms, biithe quadratic terms, bij the interaction terms, and xi and xjthe coded values of the independent variables. The Fisher’stest for analysis of variance (ANOVA) affected on experi-mental data make it possible to estimate the statisticalsignificance of the proposed model. Response surface asrepresented by Fig. 2 was drawn by using the analysis designprocedure of Statgraphics Plus for Windows software (5.1

FIG. 2. Estimated Response surface of isolated oil yield as a simul-

taneous function of processing pressure and processing time.

TABLE 1Experimental design of the 3-level design values of the yield

of isolated oil

Runs

Independent variables

Experimentalresponses

Coded values Actual values

x1 x2 X1 (bar) X2 (sec)

1 �1 �1 1 30 0.0942 �1 þ1 1 300 0.0123 þ1 �1 6 30 0.1144 þ1 þ1 6 300 0.2515 0 �1 3.5 30 0.0116 0 þ1 3.5 300 0.1617 �1 0 1 165 0.0978 þ1 0 6 165 0.3509 0 0 3.5 165 0.111

10 0 0 3.5 165 0.11211 0 0 3.5 165 0.11512 0 0 3.5 165 0.09713 0 0 3.5 165 0.099

Mean absolute error for the 5 replications 0.007

Isolation yield is expressed in g of isolated oil=100 g d.m.

ISOLATION OF VOLATILES FROM OAK WOOD 1853

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version) (27). Table 1 shows the full-factorial design matrix,with variables in both coded=non-coded forms as well as theexperimental values of yield of isolated oil.

RESULTS AND DISCUSSION

It is well known that heat treatment of wood changes itschemical composition by degrading cell wall compoundsand extractives. Of all wood polymers, hemicelluloses arethe most unstable with respect to temperature. They arethe first structural compounds to be thermally affected,even at low temperatures (28,29). This highly reactiveheteropolymer is easily depolymerised between 200 and230�C. Since they are also the main source of volatileproducts and to avoid any degradation, the processingsaturated steam pressure was limited to 6 bar (or 165�C).For processing time, it was first fixed at a maximum 5 min-utes. It is assumed that this short duration is not sufficientto allow any reaction of degradation.

EFFECTS OF STEAM PRESSURE AND PROCESSINGTIME ON EXTRACTION YIELD

Results of the regression analysis, that is, the values ofcoefficients in Eq. (2) are listed in Table 2. For yield in iso-lated oil, the linear terms related to processing pressure andto processing time were statistically significant. The strongeffect of the processing pressure and processing time is pro-ven by the low p-value (p< 0.05). The P-value indicates thestatistical significance of each parameter. It is based onhypothesis that a parameter is not significant, thus the clo-ser this probability is to 0, the more an effect is significant.This is also obvious when considering Fig. 2, which showsthe tri-dimensional response surface for the yield in isolatedoil. For a processing time fixed at it central value (165 sec),the yield increased from 0.068 to 0.156 g=100 g wood whenthe processing pressure increased from 1 to 6 bar. On theother hand, when the processing pressure was fixed at a cen-tral value (3.5 bar), the change in the yield was from 0.065 to0.131 g=100 g of wood when the processing time increasedfrom 30 to 300 s. The strong effect of both processing para-meters is probably the result of two simultaneous effects: a

free diffusion phenomenon on wood surface and a mechan-ical strain resulting from the drop of steam pressure with asubsequent degradation of wood cells and subsequentliberation of volatiles. The abrupt pressure drop provokesan adiabatic vaporization of water and volatile molecules.This vaporization induces swelling and alveoles are createdwithin the wood microstructure. Then, the amount of thevaporized quantity and volatiles is proportional to pressurelevel. The higher the steam pressure, the higher and morecomplex is the alveolation, thus requiring shorter heatingtime compared to classical processes as steam distillationor hydrodistaillation. The same observation was pointedout by Spiro and Chen (30), who reported that the essentialoil synthesized in the secretory cells is not released unless anexternal factor damages the microstructure. Several authors(12,31,32) reported that a severe thermal stress such asirradiation with high microwave power, and the build-upwithin the cells, could have exceeded their capacity forexpansion, thus causing them to break. For the proposedthermomechanical extraction process, this expansionphenomena were also observed for food product (33) andfor extraction of essential oil from rosemary leaves (34).Figure 2 also shows that the interaction between time andpressure was statistically significant (p< 0.05). For a fixedprocessing pressure at its lowest level (1 bar), the yield inextracted oil was almost stable and equal to 0.065 g=100 gwhen the processing time increased from 30 to 300 s. Incontrast, with a processing pressure fixed at 6 bar, the yieldin extracted oil varied from 0.065 to 0.24 g=100 g when pro-cessing times increased from 30 to 300 s. The F-test resultsof variance analysis for essential oil yield listed in Table 2revealed that the regression associated to the interactionbetween processing time and steam pressure was statisti-cally significant (p< 0.05). The regression coefficient ofthe model R2 was 0.91. The predicted model seemed toreasonably fit to experimental values, since the fitted modelcould explain 91% of total variation.

Effect of Initial Moisture Content on Extraction Yield

The effect of initial moisture content on the yield of iso-lated oil was investigated for values that ranged between8.5% to 50% d.b. These experiments were performed at3.5 and 6 bar processing pressure and 12 minutes processingtime with the aim to enhance the yield of isolated oil. InFig. 3, it appears that the yield of isolated oil is almost stablebetween 8.5% d.b and 20% and beyond this value, the yielddecreased and remained stable from 30% d.b. This decreas-ing is probably due to two concomittant reasons. The firstone is the fiber saturated point. The matrix between thecellulose fibers consists of non-cellulosic polysaccharides(hemicelluloses), lignin, extractives, and inorganic com-pounds. In the wet state, water molecules interpenetrate thismatrix. Water exists in wood material in three differentphases: free water and water vapor in the lumens as well

TABLE 2Regression coefficients of the second order polynomialequation (with coded variables) for the isolated oil yield

Coefficients Yield F-ratio P-value

b0 0.1012 – –b1 (P) 0.0870a 6.83 0.0348b2(t) 0.0670a 4.13 0.0817b11(P

2) 0.0220 0.21 0.6632b22(t

2) �0.036 0.01 0.9422b12(Pt) 0.1090a 7.14 0.0319

aSignificant (p< 0.1).

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as bound water in the cell walls (35). At higher watercontents, water is stored as free water in the cell lumens.The moisture content, at which the cell walls are saturatedwith bound water, but the cell lumens (i.e., the voids) insidethe wood cells are still empty, is denoted as fiber saturationpoint (FSP). Below fiber saturation point (FSP), watervapor and bound water exist to significant extent. BeyondFSP, the free water could form a thin layer which preventsthe vapor steam to reach the cell. Another reason for thedecreasing in yield of isolated oil is the thermal degradationof xylan which is the main source of extractives. It is wellknown that thermal degradation of wood starts at tem-perature of about 200�C with decomposition of hemicellu-loses, followed by cellulose at 240�C and lignin at 280�C.These conditions are valid in dry atmosphere; undermoist conditions, the degradation even starts at lowertemperatures (36).

Effect of Chips Thickness on Extraction Yield

To investigate the influence of the chips thickness on theyield of isolated oil, some samples with various thicknesses,ranged between 0.5 and 3.5 were prepared by using anelectrical plane. For the higher thicknesses, the sampleswere cut with an electrical saw. From Fig. 4, it is obviousthat the yield of isolated oil is strongly dependent of thesample thickness. It decreased from 0.32% to 0.02% whenthe thickness increased from 0.5 to 10mm. Wood being ahygroscopic and hydrophilic material that can absorbmoisture from its surroundings, it is clear that the diffusionrate play an important role in the driving of condensedwater from outer to inner of wood structure. When steamis in contact with wood, it is ultimately absorbed as liquid

water. Consequently, the latent heat of condensation isabsorbed and the temperature of the product increasesuntil reaching the surrounding steam temperature or equi-librium temperature. Thoemen and Kuelppel (37) reportedthat at low density levels, the larger particles are morepermeable than the smaller particles, but become lesspermeable towards high densities. The shape effect wouldlead to a reduced permeability for the larger particles.The void system in wood structure available for steamgas flow is larger for low thickness samples leading to amore contact between steam and volatile molecules

Effect Number of Decompressions Cycles onExtraction Yield

In order to examine a multi-cycle D.I.C thermomechani-cal process, oak wood was treated in optimized conditionsnamely 6 bar and 12 minutes but this time was dividedaccording to the number of decompressions which wasvaried from 1 to 4. In a multi-cycle process (Fig. 5), steam

FIG. 3. Yield of isolated oil as function of initial moisture content of

oak wood.

FIG. 4. Effect of wood thickness on oak wood isolated oil (6 bar proces-

sing pressure and 12 minutes processing time).

FIG. 5. Pressure history in a multi-cycle thermomechanical D.I.C

process.

ISOLATION OF VOLATILES FROM OAK WOOD 1855

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is injected again after step (e) and the pressure is controlledduring processing time (d). For example 3 cycles correspondto three durations (d) of 4 minutes each. Then n cyclescontain n repetitions of steps (c), (d), and (e). The last cycleis finished by step (f) for wood recovery. For one cycle,obtained yield was similar to that obtained previously,around 0.3% d.m and surprisingly, for higher cycle number,the yield increased to reach 0.82% d.m. (Fig. 6). The yieldwas multiplied by almost 3. It seems that each cycle enhanceextracts available in the microstructure. Kristiawan et al.(38), by working on isolation on Indonesian canaga oil bythe same process, discussed about an enhancement ofthe alveolation of the microstructure which facilitate theliberation and vaporization of volatile molecules and simul-taneously increase their availability, according to thenumber of decompression cycles. The cross section of themicrographs shows that the resulting effect causes woodmicrostructure to lose its tenacious and fibrous structure.From Fig. 7, it is clear that increasing of the cycle number

leads to more deep and large canals. Then steam penetratesmore easily in each next cycle and heats the wood morerapidly.

Comparison between Oils Isolated by Steam Distillationand by D.I.C Process

Table 3 allows comparing the compositions of isolatedoils obtained from a classical steam distillation procedure(reference process) and the proposed thermomechanicalD.I.C process. The yield obtained by D.I.C isolation

FIG. 7. Microstructure (�1000) of oak chips after D.I.C thermomecha-

nical oil isolation at 6 bar and 12 minutes processing time with 1 cycle (a);

2 cycles (b) 3 cycles (c) and 4 cycles (d).

FIG. 6. Effect of cycle number on the yield of isolated oil (processing

pressure. 6 bar; total processing time 12min for the four experiments).

TABLE 3Composition of oak wood extract obtained by steam

distillation (SD) and by instantaneous controlled pressuredrop process (D.I.C). Steam distillation was performed

during 2 hours and the thermomechanical D.I.C isolationprocess was performed at 6 bar processing pressure during

12 minutes including 4 cycles

g of compound=100 g extract

SD DIC

Furfural 15.68 19.17n-tetradecane 1.83 2.48n-dodecane 4.64 3.77m-cumenol 2.60 1.21Linalool 1.00 0.594-ethylguaıacol 1.13 0.92decanoıc acid 1.34 1.01d-nonalactone 11.23 5.25Thymol 1.82 1.51cis-lactone 2.31 11.7Eugenol 4.74 3.022-methyl.1-decanol 0.50 0.623-(1-methylethyl)benzoic acid.

2.39 0.51

carbofuran phenol 4.07 2.013-ethoxy benzamide 6.28 3.59propanoic acid 0.53 2.31dodecanoıc acid – 0.51d -selinene 2.27 2.23a -eudesmol 1.76 1.20Syringaldehyde 0.77 1.27methoxyeugenol – 1.09tetradecanoıc acid 0.56 1.10palmitic acid 3.49 8.72Vanillin 0.75 1.021-hexadecanol. 2-methyl 1.40 0.83hexadecadienoıc acid. methyl ester 1.64 –3-tetradecyloxy. 1.2-propanediol 1.61 0.88ethanol. 2-octadecyloxy 1.28 0.83Isolation yield 0.18 0.82

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process is four times higher than that obtained by steamdistillation. In spite of this difference, the same moleculeswere found in the two processes including a large groupof phenolic compound present in oak wood as 4-ethyl-guaıacol, eugenol or vanillin. It is well known that thisclass of molecules is highly anti-microbial, antiseptic,and anti-oxidant. The compound with the highest percent-age was the furfural which is important renewable,non-petroleum based chemical feedstock resulting fromhemicellulose degradation (39). Furfural represents almost20% in isolated oil for D.I.C isolation process. In a generalway, the majority of oak extractive substances which havea potential to modify the aroma and taste of oaked winesare present. This kind of oil could represent an interestingpotential natural additive for improving wine quality andorganoleptic characteristics because it contains the mainodorant molecules.

CONCLUSION

In this study, some processing parameters of thermo-mechanical isolation process were investigated. Optimalconditions obtained following an experimental design were6 bar during 5 minutes. To investigate the effect of chipsthickness and initial moisture content the processing steampressure was maintained and the processing time increasedto 12 minutes. The optimal conditions were 0.5mmand 20% d.m, respectively. To enhance the yield of isolatedoil, the effect of the number of pressure drop during 12minutes was studied and surprisingly the yield wasincreased from 0.2 g oil= 100 g d.m to 0.8 g oil= 100 g.

Isolation of oak wood oil by the thermomechanicalD.I.C process could be advantageously compared to classi-cal methods as steam distillation in terms of time and energysaving. The energy required to perform the two extractionmethods were respectively 0.13 kWh=g of isolated oil forsteam distillation, and 0.014 kWh= g of isolated oil forD.I.C extraction process. The power consumption wasdetermined according to the quantity of steam requiredand to vacuum pump energy consumption. Regarding theenvironmental impact, the calculated quantity of carbondioxide rejected in atmosphere is largely higher for steamdistillation (from 115.8 to 127.1 g CO2=g of extracted oil)than for the proposed D.I.C. extraction process (from12.5 to 13.7 g CO2=g of extracted oil), for 6 bar as proces-sing pressure. These calculations were preformed accordingto literature provided by the French Nuclear Energy Society(http://www.sfen.org/fr/societe/developpement/edf.htm(downloaded on May 3, 2012).

ACKNOWLEDGEMENTS

The financial support by ‘‘Region Poitou-Charentes’’through ‘‘VALBOIS’’ project is gratefully acknowledged.The authors also acknowledge M. Benoit Saint-Leger

from the ‘‘Archambaud’’ company and ‘‘Futurobois’’association for kindly providing the wood.

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