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Industrial Crops and Products 54 (2014) 122–129

Contents lists available at ScienceDirect

Industrial Crops and Products

jo u r n al homep age: www.elsev ier .com/ locate / indcrop

ressing and supercritical CO2 extraction of Camelina sativa oil

ihomir Moslavaca, Stela Jokic a,∗, Drago Subaric a, Krunoslav Aladic b,osipa Vukojac, Nikolina Prcec

Josip Juraj Strossmayer University of Osijek, Faculty of Food Technology Osijek, Franje Kuhaca 20, 31000 Osijek, CroatiaCroatian Veterinary Institute, Veterinary Department Vinkovci, 32100 Vinkovci, CroatiaUniversity of Mostar, Faculty of Agronomy and Food Technology, Biskupa Cule bb, Mostar, Bosnia and Herzegovina

r t i c l e i n f o

rticle history:eceived 19 October 2013eceived in revised form 8 January 2014ccepted 10 January 2014vailable online 2 February 2014

eywords:amelina sativa oilcrew pressing

a b s t r a c t

The objective of this study was to evaluate the oil extraction process from Camelina sativa (L.) Crantz seedsby screw pressing followed by extraction with supercritical CO2. In pressing experiments, the responsesurface methodology (RSM) was conducted in order to study the effects of temperature, frequency andnozzle size on oil recovery and quality parameters. The optimal condition to obtain the highest oil recoveryand the best oil quality within the experimental range of the variables studied was at temperature of 52 ◦C,frequency of 20 Hz and using nozzle of ID 9 mm. The experimental values agreed with those predicted,thus indicating suitability of the used models and the success of RSM in optimizing the pressing conditionsof investigated system. The cake resulting from pressing at optimal conditions was extracted with CO2 in

xidative stabilityupercritical CO2 extraction homemadeystemesponse surface methodology

a new designed and built a homemade supercritical fluid extraction system. The residual oil in the pressedcake was almost totally extracted by supercritical CO2. The aim of this study was also to investigate theinfluence of natural antioxidant (rosemary extract Oxy.Less CS, Oxy.Less CLEAR and StabilEnhance OSR,green tea extract, olive leaf extract, pomegranate extract) on the oxidative stability of C. sativa oil. Therosemary extract Oxy.Less CS in concentration of 0.3% was the most effective in protecting the oil from

oxidative deterioration.

. Introduction

Camelina sativa (L.) Crantz is a cruciferous oilseed plant with theommon names false flax, German sesame, gold of pleasure, linseedodder, Siberian oilseed or wild flax. The main product of C. sativa ishe oil produced by crushing and pressing the seeds, which containbout 50–60% polyunsaturated fatty acids where the omega-3 fattycid (�-linolenic) makes 35–40%, and omega-6 fatty acid (linoleic)5–20%. Due to these properties, camelina oil is one of the richestegetal sources of essential fatty acids which cannot be synthe-ized by the human body; they can only be obtained from food. Themportant value of the camelina oil is also given by its high contentn natural tocopherols, which makes it very stable from an oxida-ive point of view. Furthermore, the environmental benefits of thisrop and the multipurpose applicability of its oil in certain foodroducts, in dye industry and soap industry, and recently, as bio-uel, make C. sativa a promising oilseed crop. The consumption ofamelina oil can improve the human health, especially in industri-

lized countries (Zubr, 1997; Abramovic and Abram, 2005; Imbreat al., 2011).

∗ Corresponding author. Tel.: +385 98 1666629; fax: +385 31 207115.E-mail address: stela.jokic@ptfos.hr (S. Jokic).

926-6690/$ – see front matter © 2014 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.indcrop.2014.01.019

© 2014 Elsevier B.V. All rights reserved.

Cold pressed oils refer to oils that are extracted by cold pressingplant seed with a screw press or hydraulic press. Cold pressing isused to extract oil from plant seed instead of conventional solventextraction method because cold pressing does not require the useof organic solvent or heat. Cold pressing is able to retain bioactivecompounds such as essential fatty acids, phenolics, flavonoids andtocopherols in the oils (Teh and Birch, 2013). The by-product (oilcake) from processing the seed by pressing represents an importantoutput because of the high percent of residual oil, proteins, fibers,minerals and other substances (Zubr, 1997; Quezada and Cherian,2012). Today, there is a lot of interest in the use of by-products fromthe food industry in different purposes. One of the major problemsduring production, application and processing of edible oils is oxi-dation of lipids, which causes an important change in the chemical,sensory and nutritional properties. Due to high content of unsatu-rated fatty acids in camelina oil its oxidation stability should be animportant parameter in evaluation the oil quality (Abramovic andAbram, 2005). Camelina oil was found to be more stable towardoxidation than fish and linseed oil, but less stable than sunflower,corn, sesame, olive and rapeseed oils (Eidhin et al., 2003).

Oil extraction using supercritical fluids is an alternative method

to replace or to complement conventional industrial process suchas pressing and solvent extraction. Supercritical fluid extractiontechnique presents various advantages over traditional methods,like the use of low temperatures, reduced energy consumption

ops and Products 54 (2014) 122–129 123

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2

2

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2

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2

todiCt

a

2

damOti

Table 1The uncoded and coded levels of independent variables used in the RSM design.

Independent variable Symbol Level

Low (−1) Middle (0) High (+1)

Temperature (◦C) X1 30 60 90

T. Moslavac et al. / Industrial Cr

nd high product quality due to the absence of solvent in extracts.arbon dioxide is most widely used compressed fluid because it

s non-toxic, non-explosive, inflammable, cheap, readily available,asy removable from the product and possesses moderate criticalroperties (Tc = 31.1 ◦C, Pc = 7.38 MPa). The disadvantages of super-ritical fluid extraction are the high investment costs for equipmentcquisition and the high energy demand of the CO2 extraction unitBrunner, 2005; Sahena et al., 2009; Temelli, 2009; Martínez et al.,008). Homemade supercritical fluid extraction system permit tobtain extracts in an inexpensive way, and the obtained extrac-ion yields had been very similar to those obtained by commercialupercritical fluid extraction system (Castro-Vargas et al., 2011).

The objectives of this work were threefold: (i) to investigate theffects of process parameters during the screw pressing of C. sativaeeds on the oil recovery and oil quality using response surfaceethodology (RSM); (ii) to recover the residual oil from pressed

ake using supercritical CO2 in the new designed and built home-ade supercritical fluid extraction system and (iii) to investigate

he influence of different natural antioxidants and its concentrationn the oxidative stability of camelina oil.

. Materials and methods

.1. Chemicals

Rosemary extracts Oxy.Less CS, Oxy.Less CLEAR and StabilEn-ance OSR, green tea extract and pomegranate extract wereupplied from Naturex (France). Olive leaf extract were suppliedrom Exxentia (Spain).

The purity of CO2 used for extraction was 99.97% (w/w) (Messer,sijek, Croatia). All other chemicals and reagents were of analytical

eagent grade.

.2. Plant material preparation

The camelina oil used in this study was produced from seeds of. sativa (L.) Crantz plants obtained from family farm Mikac AnitaLukac, Croatia) in 2013. The camelina oil was obtained by pressingf 1 kg C. sativa seeds per each experiment using different processonditions. The pressing of the seeds were performed in a screwxpeller SPU 20 (Senta, Serbia). After pressing, the volume of screwressed oils and their temperature were measured and after thathe oil was centrifuged. The sedimented solids were recovered andolid percentage of the oils was calculated by weight difference.

.3. Determination of initial oil and water content

The initial oil content in C. sativa seeds was measured by tradi-ional laboratory Soxhlet-extraction with n-hexane as solvent. 5 gf C. sativa seeds was extracted with 150 mL solvent, until totallyepleted. The whole process took 8 h. The measurement was done

n triplicate. The average of the initial oil content was 42.40 ± 0.73%.ake residual oil (CRO) was also determined by traditional labora-ory Soxhlet-extraction.

Moisture content of the seeds (5.92% ± 0.02%) was determinedccording to AOAC Official Method 925.40 (2000).

.4. Oil quality parameters

Free fatty acids (FFA), iodine value and saponification value wereetermined according to AOAC Official Methods 940.28, 920.185nd 920.160 (1999). Peroxide value (PV) of oil samples was deter-

ined according to ISO 3960 (1998). PV was expressed as mmol

2/kg of oil. Insoluble impurities (II) were determined accordingo ISO 663 (1992). p-Anisidine value (AV) was determined accord-ng to ISO 6885 (2006). Totox value was calculated as 2PV + AV

Nozzle (mm) X2 6 9 12Frequency (Hz) X3 20 30 40

(Hamilton and Rossell, 1986). All these determinations were carriedout in triplicate.

2.5. Experimental design

Box–Behnken design which includes three variables and threefactorial levels was chosen in this study (Bas and Boyacı, 2007). Theranges for the variables, namely temperature (30, 60, 90 ◦C), fre-quency (20, 30, 40 Hz) and nozzle size (6, 9, 12 mm) were selected toapproximate the optimal conditions for screw pressing of C. sativaoil. Coded and uncoded levels of the independent variables and theexperimental design are given in Table 1. Coded value 0 stands forcenter point of the variables and repeated for experimental error.Factorial points are coded as ±1.

Second-order polynomial equation was used to express theinvestigated responses (Y) after pressing, namely the volume ofscrew press oil (ml), volume of screw press oil after centrifugation(ml), oil temperature (◦C), peroxide value (mmol O2/kg), free fattyacids (%), insoluble impurities (%), and residual oil in pressed cake(%) as a function of the coded independent variables, where X1, X2,. . ., Xk are the independent variables affecting the responses Y’s;ˇ0, ˇj (i = 1, 2, . . ., k), ˇii (i = 1, 2, . . ., k), and ˇij (i = 1, 2, . . ., k; j = 1,2, . . ., k) are regression coefficients for intercept, linear, quadratic,and interaction terms, respectively; k is the number of variables.

Y = ˇ0 +k∑

i=1

ˇiXi +k∑

i=1

ˇiiX2i +

k−1i = 1∑

i<j

k∑

j=2

ˇijXiXj (1)

Statistical analysis was performed using RSM software Design-Expert®, v.7 (Stat Ease, Minneapolis, USA). The results werestatistically tested by the analysis of variance (ANOVA) at the sig-nificance level of p = 0.05. The adequacy of the model was evaluatedby the coefficient of determination (R2) and model p-value. Mathe-matical models were established to describe the influence of singleprocess parameter and/or interaction of multiple parameters oneach investigated response. Response surface plots were generatedwith the same software and drawn by using the function of twofactors, and keeping the other constant.

2.6. Determination of oxidative stability

The oxidative stability was determined by rapid oils oxidationtest – Schaal or Oven Test (63 ◦C) (Joyner and McIntyre, 1938). Theinfluence of the addition of natural antioxidants, namely rosemaryextracts Oxy.Less CS, Oxy.Less CLEAR and StabilEnhance OSR, greentea extract, olive leaf extract, and pomegranate extract in the con-centrations of 0.1% and 0.3% on the oxidative stability of C. sativaoil were monitored. The result of oil oxidation was expressed asPV during 4 days of the test. All determinations were carried out induplicate.

2.7. Homemade supercritical fluid extraction (HM-SFE) system

The pre-pressed material (100 g of sample was used for extrac-tion) resulting from the calculated optimal oil pressing conditions

124 T. Moslavac et al. / Industrial Crops and Products 54 (2014) 122–129

F k; 3. S( . Cen

wtmau

str

TE

P

ig. 1. Homemade supercritical fluid extraction system. (1. Compressor; 2. CO2 tanB-HV); 7. Manometers; 8. Extraction vessel; 9. Separator vessel; 10. Water bath; 11

as extracted with CO2 in a new designed and built HM-SFE sys-em at pressure of 20 MPa and temperature of 40 ◦C with a CO2

ass flow rate of 4.9 kg/h. The extracts were collected at 1.5 MPand 25 ◦C. The schematic diagram of new constructed apparatussed for supercritical fluid extraction is given in Fig. 1.

Materials used for the construction of HM-SFE system weretainless steel AISI 316Ti and AISI 304. All additional connectionubing parts were also same grade of material. Extractor and sepa-ator vessels were properly tested at safety factor of 1.5. Extraction

able 2xperimental matrix and values of the observed response.

Run Temperature(◦C)

Nozzle(mm)

Frequency(Hz)

Screw press oilvolume (ml)

Oil aftercentrifugat

1 60 6 20 290 280

2 60 6 40 260 235

3 60 9 30 270 255

4 60 9 30 290 260

5 60 9 30 280 250

6 60 9 30 285 255

7 60 9 30 280 250

8 60 12 20 300 270

9 60 12 40 260 230

10 90 12 30 265 235

11 90 6 30 290 260

12 90 9 20 290 255

13 90 9 40 280 250

14 30 9 20 255 215

15 30 9 40 230 210

16 30 12 30 215 178

17 30 6 30 260 225

V, peroxide value; FFA, free fatty acids; II, insoluble impurities; CRO, cake residual oil.

tainless steel coil; 4. Cooling bath; 5. Air driven fluid pump Haskel MS-71; 6. Valvestralized system glass fiber heater; 12. Flow meter).

vessel was tested at working pressure 50 MPa and separator vesselat 3 MPa.

The construction and assemblage of HM-SFE were spent by ÐuroÐakovic Aparati d.o.o. (Slavonski brod, Croatia) which provided testfor material durability and pressure test for vessels. Extraction ves-

sel was made from stainless steel bar (AISI 304) O.D. 100 mm andheight 500 mm. Stainless steel rod is drilled (center hole) with a Ø40 mm bore for a 400 mm. Upper inside part of extraction cell waspolished to plug well gaskets. Cap of extraction cell was designed

ion (ml)Oil temperature(◦C)

PV (mmolO2/kg)

FFA (%) II (%) CRO (%)

35 0.64 0.95 0.39 15.0532 0.45 1.00 0.37 18.0137 0.44 0.91 0.06 17.9534 0.48 0.94 0.23 17.3735 0.48 0.95 0.14 17.7535 0.50 0.94 0.16 18.9935 0.49 0.94 0.22 18.2436 0.44 0.94 0.11 16.9036 0.47 0.94 0.35 20.2040 0.48 0.99 0.05 18.3440 0.50 1.06 0.05 17.5440 0.48 1.03 0.06 16.7540 0.48 1.01 0.06 17.6429 0.50 1.01 0.11 19.1433 0.48 1.01 0.22 19.3827 0.50 1.02 0.21 20.7532 0.50 0.96 0.27 18.87

ops and Products 54 (2014) 122–129 125

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30

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60

75

90

224

240

256

272

288

S

cre

w-p

ress o

il volu

me (

ml)

Nozzle (mm ) Temper ature (° C)

30

45

60

75

90

6

8

9

11

12

186

205.5

225

244.5

264

O

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Tempe rature (°C ) Nozz le (mm)

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75

90

17.10

18.08

19.05

20.02

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Nozzle (mm ) Temper ature (° C)

T. Moslavac et al. / Industrial Cr

o hold plug and it is connected with extraction cell trough trape-oidal thread. Plug was patented by company that assembled theM-SFE system and seals in two places with o-ring. In plug is placedlter element that should prevent withdrawal of material. Filterlement has the ability to filter particles 2 microns nominal and 10icrons absolute (Norman Ultraporous 4202T-6T-2M). Lower part

f extraction cell was also drilled and prepared for quick connectionith R½” connector with o-ring seal. High pressure seamless tubes

re dimension 10 mm × 2 mm and are connected to each other byrmeto couplings (flat, knees, tees). The used high pressure valvesere provided by the same company that produces ermeto cou-lings (model B-HV). Pressure extraction cell is controlled by twoIKA manometers (model 212.20) 60 MPa and one WIKA manome-

er (model 212.20) 4 MPa for pressure in separator.Extraction cell is heated with glass fiber electric heater con-

rolled with centralized system and Solid State Relays (SSR). Theemperature control is achieved using PID regulator with lag delayompensation, due to the large mass of the extraction cell. Tem-erature measurements and regulation of the extraction cell iserformed using an integrated temperature sensor within the cellnd additional temperature sensor measuring output gas temper-ture. The input CO2 line toward the extraction cell is preheatedsing a heat exchanger, powered by a water heating system. Theemperature of the input gas is regulated by measuring threeemperatures: water temperature alongside to the water heater,ater input temperature in the heat exchanger and the outputO2 temperature that exits the heat exchanger. The temperature

s regulated using a standard PID regulation, taking into accounthe differential temperatures of water lines and output gas line.egulation of the pressure in the separator is performed using anlectromechanical solution for controlling pressure valve, with aressure sensor working as a feedback.

Pump used for pressurize liquid CO2 is Haskel® MS-71. LiquidO2 is precooled trough SS coil at temperature −18 ◦C cooled bythylene glycol/ethanol cooling bath. After pump check valve isocated to prevent eventually disorders of CO2 flow. Prior to inputxtraction vessel CO2 is preheated trough stainless steel double coilt the temperature of extraction. After extraction vessel high pres-ure is reduced by high pressure valve (B-HV) to desirable pressure.alves and tubing are heated to a temperature of 0 ◦C due to highressure drop. Flow of CO2 is controlled trough Matheson FM-1050E800) flow meter.

. Results and discussion

.1. Screw pressing experiments

The oil from C. sativa seeds were obtained by screw pressingsing different process parameters. Effects of temperature, nozzleize and frequency on recovery and quality parameters of camelinail were studied by RSM. Experiments were performed accordingo the Box–Behnken design (Table 2). In all 17 experimental runsnly a small percentage (0.024–0.052%) of moisture was found inhe obtained oils. Water contributes to the hydrolysis of oil dur-ng processing, which generates FFA and glycerol products. In thistudy, FFA content was in the range from 0.91 to 1.06% whilebramovic and Abram (2005) published that Slovene camelina oilontains 2.35% of FFA which is quite a high value probably becausef the hydrolytic activity of lipolytic enzymes during the prepara-ion of seeds for oil production. It is very important that cold pressedils are low in moisture content and FFA to maintain the quality and

helf life of the oils (Teh and Birch, 2013). The oil temperature inll experimental runs was in the range from 27 to 40 ◦C. Primaryxidation processes in oil mainly form hydroperoxides, which areeasured by the PV. In general, the lower the PV the better the

630

Fig. 2. Response surface plots showing the effects of investigated variables on oilrecovery.

126 T. Moslavac et al. / Industrial Crops and Products 54 (2014) 122–129

Table 3Estimated coefficient of the second order polynomial equation.

Term Coefficienta Screw press oil Oil after centrifugation Oil temperature PV FFA II CRO

Intercept ˇ0 281.00* 254.00* 35.20* 0.48* 0.94* 0.16* 18.06*

X1 ˇ1 20.63* 21.50* 4.88* −0.005 0.011 −0.074* −0.98*

X2 ˇ2 −7.50 −10.87 0.000 −0.025 −0.01 −0.046 0.84*

X3 ˇ3 −13.13* −11.88* 0.12 −0.023 0.0038 0.041 0.92*

X12 ˇ11 −18.63* −25.38* 0.15 0.001* 0.064 −0.11* 0.75

X22 ˇ22 −4.88 −4.13 −0.60 0.016 0.007 0.089* 0.064

X32 ˇ33 1.38 3.88 0.15 0.006 0.015 0.055 −0.58

X1X2 ˇ12 5.00 5.50 1.25 −0.005 −0.033* 0.013 −0.27X1X3 ˇ13 3.75 0.000 −1.00 0.005 −0.005 −0.030 0.16X X ˇ −2.50 1.25 0.75 0.055* −0.013 0.065 0.085

2x3,. x

qtt(

e

2 3 23

a y = ˇ0 + ˇ1x1 + ˇ2x2 + ˇ3x3 + ˇ11x21 + ˇ22x2

2 + ˇ33x23 + ˇ12x1x2 + ˇ13x1x3 + ˇ23x

* Significant at p ≤ 0.05.

uality of the oil (Frankel, 2005). In this study, PV of all experimen-al runs were low (0.44–0.64 mmol O2/kg) which is lower valuehan PV value of camelina oil obtained by Abramovic and Abram

2006).

Table 3 shows the regression coefficients obtained by fittingxperimental data to the second order response models for

20

25

30

35

40 6

8

9

11

12

0.44

0.4825

0.525

0.5675

0.61

P

V (

mm

ol/kg)

Frequency (Hz) Nozzle (mm)

20

25

30

35

40

6

8

9

11

12

0.13

0.1925

0.255

0.3175

0.38

In

so

lub

le im

pu

ritie

s (

%)

Frequency (Hz) Nozzle (mm)

Fig. 3. Response surface plots showing the effec

1: pressing temperature; x2: nozzle size; x3: frequency.

investigated responses. The coefficients are related to codedvariables. The first-order term of temperature (X1) had significanteffect (p < 0.05) on the volume of obtained oil, oil temperature,

insoluble impurities and on the amount of cake residual oil. Thefirst-order term of nozzle size (X2) and frequency (X3) had signif-icant effects on amount of cake residual oil while first-order term

30

45

60

75

90

6

8

9

11

12

28

31.25

34.5

37.75

41

O

il te

mpera

ture

(°C

)

Temperature (°C) Nozzle (mm)

6

8

9

11

12

30

45

60

75

90

0.93

0.965

1

1.035

1.07

F

FA

(%

)

Nozzle (mm) Temperature (°C)

ts of investigated variables on oil quality.

T. Moslavac et al. / Industrial Crops an

Table 4Analysis of variance (ANOVA) of the modeled responses.

Source Sum ofsquares

Degree offreedom

Meansquare

F-value p-value

Screw press oil volumeThe recoveryModel 7017.87 9 779.76 4.64 0.0277Residual 1176.25 7 168.04Lack of fit 956.25 3 318.75 5.80 0.0613Pure error 220.00 4 55.00Total 8194.12 16Oil volume after centrifugationThe recoveryModel 8757.69 9 973.08 5.69 0.0160Residual 1197.25 7 171.04Lack of fit 1127.25 3 375.75 21.47 0.0063Pure error 70.00 4 17.50Total 9954.94 16Oil temperatureThe recoveryModel 204.39 9 22.71 6.48 0.0111Residual 24.55 7 3.51Lack of fit 19.75 3 6.58 5.49 0.0668Pure error 4.80 4 1.20Total 228.94 16Peroxide valueThe recoveryModel 0.022 9 0.004 3.98 0.0268Residual 0.009 7 0.0009Lack of fit 0.007 3 0.001 2.23 0.2292Pure error 0.002 4 0.0005Total 0.031 16Free fatty acidsThe recoveryModel 0.026 9 0.003 8.91 0.0044Residual 0.002 7 0.0003Lack of fit 0.001 3 0.0005 1.99 0.2574Pure error 0.045 4 0.0002Total 0.0004 16Insoluble impuritiesThe recoveryModel 0.18 9 0.021 4.52 0.0296Residual 0.032 7 0.005Lack of fit 0.012 3 0.004 0.81 0.5490Pure error 0.020 4 0.005Total 0.22 16Cake residual oilThe recoveryModel 24.29 9 2.70 3.76 0.0473Residual 5.02 7 0.72Lack of fit 3.54 3 1.18 3.19 0.1462Pure error 1.48 4 0.37

oooTonwss

Tmrofi0pt

PV before the test and after four days (Fig. 4). Addition of natural

Total 29.31 16

f frequency had also significant effect on oil volume. The second-rder term of temperature (X2

1 ) had significant effect (p < 0.05)n oil volume, free fatty acids content and insoluble impurities.he second-order term of nozzle size (X2

2 ) had significant effectn content of insoluble impurities. The interactions between theozzle size and frequency had significant effect on peroxide value,hile the interaction between temperature and frequency had

ignificant effect on free fatty acids. Other interactions had noignificant (p > 0.05) effect on investigated responses.

The ANOVA results for modeled responses are reported inable 4. Joglekar and May (1987) suggested that for a good fit of aodel, R2 should be at least 0.80. In our study, the R2 values for these

esponse variables were higher than 0.80, indicating the adequacyf the applied regression models. Table 4 shows the test statisticsor the model (F-test and probability) of oil recovery and oil qual-ty. The probability (p-value) of all regression models was below

.05, which means that there was a statistically significant multi-le regression relationship between the independent variables andhe response variable.

d Products 54 (2014) 122–129 127

The best way of expressing the effect of screw pressing param-eters on oil recovery and oil quality within the investigatedexperimental range was to generate response surfaces of the model(Figs. 2–3). From Fig. 2 can be seen that the amount of obtained oilsignificantly increased with the increase of temperature up to about70 ◦C while further increase in temperature did not cause a signifi-cant change in oil volume. Furthermore, the amount of residual oilin cake increased also with the nozzle size from 6 to 12 mm anddecreased with increase of temperature. Fig. 3 shows the influenceof pressing conditions on the quality of obtained oil. It can be seenthat the oil temperature is significantly influenced by used temper-ature for heating the output press head. PV decreases with nozzlesize from 6 to 12 mm and with increases of frequency from 20 to40 Hz. FFA decreases with temperature until 60 ◦C, while furtherincrease of temperature increases FFA. II significantly decreasedwith nozzle size from 6 to 10 mm while using 10–12 mm nozzle itcan be increasing in that investigated matter. The ANOVA showedthat the models were acceptable and could be used for optimizationthe pressing parameters with respect to oil recovery and quality.

3.2. Optimization of screw pressing of Camelina sativa (L.) Crantzseeds

The final goal of RSM is the process optimization. Thus, thedeveloped models can be used for simulation and optimization.Optimization is an essential tool in food engineering for the effi-cient operation of different processes to yield a highly acceptableproduct. During optimization of screw pressing process, severalresponse variables describe the oil quality characteristics and hadinfluence on oil recovery. Some of these variables need to be maxi-mized, while others need to be minimized. The goal of this researchwas to find the best settings for the screw pressing, i.e. the besttemperature, frequency and nozzle size. By applying desirabilityfunction method (Cojocaru et al., 2009), the optimum screw press-ing conditions were obtained: temperature of 52 ◦C, frequency of20 Hz and using nozzle of ID 9 mm. Screw press oil volume wascalculated to be 289.5 ml, oil temperature 32.6 ◦C, peroxide value0.48 mmol O2/kg, free fatty acids 0.95%; insoluble impurities 0.17%;cake residual oil 15.9%, which is in very close agreement with exper-imental obtained data.

In obtained camelina oil at this optimal screw pressing condi-tions, iodine value, saponification value and moisture content werealso determined. Moisture content was determined to be 0.038%.Iodine value was 139.28 g I2/100 g of oil and saponification valuewas 192.19 mg KOH/g of oil which is very similar to obtained valuespublished by Abramovic and Abram (2005). p-Anisidine value (AV)was 0.032. Totox oxidation value, so called Totox value, was calcu-lated to be 1.032. Good quality oil should have p-anisidine value ofless than two, and Totox value less than four (Frankel, 2005).

3.3. Oxidation stability of camelina oil

Lipid oxidation is the main process leading to the deteriorationof edible oils (Frankel, 2005). It produces rancid odors, unpleasantflavors, discoloration and decrease nutritional quality and safety.In order to prevent oxidation of lipids the application of varioussynthetic and natural antioxidants can be used. In the last decades,the use of natural antioxidants over synthetic increased becausenatural food ingredients are safer than synthetic.

Oxidation stability of cold pressed camelina oil and added nat-ural antioxidants, in concentration of 0.1% and 0.3%, determinedby Schaal Oven test (63 ◦C) during four days was expressed by

antioxidants in the tested concentration less than 0.1% in camelinaoil have no affect on the stability of the oil (Gramza et al., 2006) andaddition of natural antioxidants in concentration higher than 0.3%

128 T. Moslavac et al. / Industrial Crops and Products 54 (2014) 122–129

a)

b)

0.75

14

19.8

5.05

1715.03 14.76

16.62

0

5

10

15

20

25

Oil withou tan�oxid ants

Green teaext ract 0.1%

Oxy 'Less CS0.1%

Stabil Enh anceOSR 0.1%

Oxy' LessCLEAR 0.1%

Pom egran ateextract 0.1%

Olive leafextract 0.1%

PV (m

mol

O2/

kg)

0 day 4 day

0.75

1414.87

2.46

16.54

12.25

15.1916.14

0

2

4

6

8

10

12

14

16

18

Oil withou tan�oxid ants

Green teaextract 0.3%

Oxy 'Less CS0.3%

StabilEn.OS R0.3%

Oxy' LessCLEAR 0.3%

Pom egran ateextract 0.3%

Olive leafext ract 0.3%

PV (m

mol

O2/

kg)

0 day 4 day

n (a)

cwttoc

cfrOtatciatoba

cgtl(f

Fig. 4. Influence of natural antioxidants (in concentratio

hange sensory/organoleptic properties of camelina oil, so testsere carried out in upper and lower limits of antioxidant addi-

ions. Heating the sample in the thermostat (Binder) at 63 ◦C duringhe four days increased the PV of samples, which represents thexidative deterioration degree of oil under the investigated testonditions.

Fig. 4a shows the oxidation stability (expressed in PV) foramelina oil without antioxidants and camelina oil with added dif-erent natural antioxidants in concentration 0.1%. According to theesults obtained by Oven test it can be seen that rosemary extractxy’Less CS show the highest protection efficiency of camelina oil

o oxidative deterioration as reflected in low PV (5.03 mmol O2/kg)fter 4 days of the test. Results indicate that the addition of otherested natural antioxidants (0.1%) did not affect the stability ofamelina oil. After four days of the test the higher PV was obtainedn samples compared to pure camelina oil (without the addition ofntioxidants). Particularly poor effect on the oxidative stability ofhe oil was obtained with green tea extract, where after four daysf the test high PV was determined (19.80 mmol O2/kg), so it cane concluded that this extract in camelina oil acts as a prooxidantnd accelerates the oxidation process.

Fig. 4b shows the effect of the addition of natural antioxidants (inoncentration 0.3%) on the oxidative stability of camelina oil. Veryood antioxidant activity of rosemary extract Oxy’Less CS result

he best stability camelina oil during 4 day test and PV was veryow (2.46 mmol O2/kg). PV after 4 days of the test was very low2.46 mmol O2/kg). Slightly lower PV compared to pure oil afterour days of the test showed a rosemary extract Oxy’Less CLEAR

0.1% and (b) 0.3%) on oxidative stability of camelina oil.

where the PV was 12.25 mmol O2/kg compared to pure oil whose PVwas 14 mmol O2/kg. Green tea extract (PV 14.87 mmol O2/kg) androsemary extract StabilEnhance OSR (PV 16.54 mmol O2/kg) gavenot satisfactory results because after the first day of the test wasobserved color changes in both the oil samples. The pomegranateextract (PV 15.19 mmol O2/kg) did not dissolve well in the oil. Theaddition of olive leaf extract (in both concentrations) does not showantioxidant effect on increasing stability of camelina oil. Abramovicand Abram (2006) investigate the effect of added rosemary extract(0.2%) in the protection of camelina oil against oxidation process.It was published that this natural antioxidant reduces PV.

3.4. Extraction of residual oil from pressed cake with CO2

The cake resulting from pressing at optimal conditions (tem-perature of 52 ◦C, frequency of 20 Hz and nozzle ID 9 mm) wasextracted with CO2 in a new designed and built a homemade super-critical fluid extraction system (Fig. 1). The amount of residual oilin press cake at optimal conditions was 15.7% (obtained by Soxhletextraction). From Fig. 5 it can be seen that after 4 h of extractionalmost all residual oil in the press cake was totally extracted bysupercritical CO2.

From the shape of the extraction curve can be seen that theextraction process is divided in three periods: rapid extraction

period, transition period and slow extraction period. The firstperiod is the constant extraction rate period, where the externalsurface of the particles is covered with solute and the convectionis the dominant mass transfer mechanism. The amount of oil is

T. Moslavac et al. / Industrial Crops an

uCiamt

4

tomiaa9acencCc

A

o

Fig. 5. Extraction of cake residual oil with CO2 using HM-SFE system.

ltimately limited by the solubility of the oil in the supercriticalO2. The second is the falling extraction rate period where failures

n the external surface oil layer appear and the diffusion mech-nism starts combined with convection. In the third period theass transfer occurs mainly by the diffusion in the bed and inside

he solid substratum particles (Sovová, 1994).

. Conclusion

The results of this study showed that the screw pressing condi-ions influenced the oil quality and oil recovery. Obtained camelinail indicated desirable quality as it had very small percentages ofoisture and insoluble impurities, free fatty acids and low perox-

de value. The optimal condition to obtain the highest oil recoverynd the best oil quality using response surface methodology wast temperature of 52 ◦C, frequency of 20 Hz and using nozzle of ID

mm. This study showed also that was possible to design and build supercritical fluid extraction system low cost compared to similarommercial systems. Residual oil content in press cake was totallyxtracted with CO2 in HM-SFE system. The influence of differentatural antioxidants (0.1% and 0.3%) on the oxidative stability ofamelina oil was investigated and the rosemary extract Oxy’LessS in concentration of 0.3% was the most efficient in protecting theamelina oil against oxidative deterioration.

cknowledgements

The authors are grateful to the Josip Juraj Strossmayer Universityf Osijek, Republic of Croatia for financial support.

d Products 54 (2014) 122–129 129

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