Optimization and kinetic modeling of oil extraction from white mustard (Sinapis alba L.) seeds

Industrial Crops & Products 121 (2018) 132–141

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Optimization and kinetic modeling of oil extraction from white mustard (Sinapis alba L.) seeds

T

Olivera S. Stamenkovića, Ivica G. Djalovićb, Milan D. Kostića, Petar M. Mitrovićb, ⁎ Vlada B. Veljkovića, a b

Faculty of Technology, University of Niš, 16000, Leskovac, Bulevar Oslobodjenja 124, Serbia Institute of Field and Vegetable Crops, 21000, Novi Sad, Maksima Gorkog 30, Serbia

A R T I C LE I N FO

A B S T R A C T

Keywords: Cold pressing Press cake Solvent extraction Response surface methodology ANOVA Kinetics

White mustard seed oil (WMSO) was extracted from the ground seed by cold pressing and Soxhlet extraction using n–hexane. A two–step process consisting of cold pressing of white mustard seed (WMS) and extraction of WMSO from press cake (maceration) was also employed to improve the overall WMSO recovery. The main fatty acids of the WMSO were unsaturated oleic, eicosenoic, erucic, linoleic and linolenic acid. The maceration of press cake was modeled on the basis of a 33 full factorial design with replication coupled with the response surface methodology. The analysis of variance and the quadratic equation were used for assessing the significance of the influence of solvent–to–cake ratio, extraction temperature and extraction time on WMSO yield and for optimizing the maceration process. All three individual process factors, the interactions of extraction temperature with solvent–to–seed cake ratio and time as well as the quadratic terms of solvent–to–seed cake ratio and extraction time had a statistically significant influence on WMSO yield at the 95% confidence level. The mean relative percentage deviation of ± 2.3% and the coefficient of determination of 0.923 proved the adequacy of the developed quadratic model for WMSO yield. The predicted and actual WMSO yields under the optimal maceration conditions (70 °C, 6.5:1 mL of solvent per g of seed cake and 5 min) were 7.29 and 7.20 ± 0.13 g/100 g, respectively. With the two–step process, the WMSO yield of 20.48 g/100 g was achieved, which was 99.2% of the WMSO yield obtained by Soxhlet extraction. This indicated that the two-step process could replace the energy- and solvent-intensive Soxhlet extraction of ground WMS. The model of instantaneous washing followed by diffusion described most adequately the kinetics of WMSO extraction from press cake in the applied experimental region. WMSO extraction from WMS press cake was shown to be as spontaneous, irreversible and endothermic.

1. Introduction White mustard (Sinapis alba L.) is an annual plant of the family Brassicaceae, originating from the Mediterranean (Katepa-Mupondwa et al., 2005). It is cultivated in many countries in Europe and North America. In Serbia is grown in flat regions (Erić et al., 2006). Root has a large suction power, so it can be grown on poorer soils. The known uses of the plant are as a fodder crop, a green manure (Krstić et al., 2010) and a spice (Balke and Diosady, 2000). The young seedlings are edible as fresh and tasty (Balke and Diosady, 2000). The plant has a potential of Pb, Zn and Cd extraction from soil (Kos et al., 2003). The largest agronomic value of white mustard is the seed, which is high in protein and oil and low in starch (Balke and Diosady, 2000). In the traditional medicine, white mustard seed (WMS) is used for its antitumor, antiviral and analgesic activities (Peng et al., 2013). Containing 28–45% of ⁎

semi–drying oil, WMS is industrially used as a lubricant and for lightning (Falasca and Ulberich, 2011). Because of a high content of erucic acid, WMS oil (WMSO) has been objected as edible oil but ground WMS, mixed with water or vinegar, can be used as condiment (Issariyakul and Dalai, 2012a; Sanjid et al., 2014). WMSO contains mainly oleic, linoleic, linolenic and erucic acid (Yaniv et al., 1994) but it is also rich in antioxidants (Mejia-Garibay et al., 2015; SzydłowskaCzerniak et al., 2015) and essential oil (Peng et al., 2014). Because of its potent biocidal activity against microorganisms, some researchers tend to develop WMSO into a food preservative (Peng et al., 2014). Low–quality WMSO can be used for biodiesel production (Ahmad et al., 2008; Ciubota-Rosie et al., 2013; Issariyakul and Dalai, 2012a, 2012b; Sáez-Bastante et al., 2016) and as diesel fuel additive (Issariyakul and Dalai, 2011). Even WMSO itself can be an alternative fuel (Alam and Rahman, 2013). Also, press cakes, a by–product of the biodiesel

Corresponding author at: Faculty of Technology, University of Niš, 16000, Leskovac, Bulevar Oslobodjenja 124, Serbia. E-mail address: [email protected] (V.B. Veljković).

https://doi.org/10.1016/j.indcrop.2018.05.001 Received 13 February 2017; Received in revised form 28 April 2018; Accepted 1 May 2018 0926-6690/ © 2018 Elsevier B.V. All rights reserved.

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cake using a Soxhlet extraction apparatus and n–hexane as a solvent (solvent–to–seed cake: 10:1 mL/g; 6 h). After the extraction, the filtrate was evaporated under vacuum by a rotary evaporator (Hei-VAP, Heidolph, Germany) at 50 °C until the constant mass.

industry from WMS, can be used in poultry production (Thacker and Petri, 2009). For recovery of the oil from WMS, both solvent and mechanical oil extraction techniques can be used (Table S1, Supplementary material). For solvent extraction, WMS is dried and ground before extraction, which is then subjected usually to the Soxhlet extraction using n–hexane (Ciubota-Rosie et al., 2013; Sáez-Bastante et al., 2016; Seal et al., 2008; Singh et al., 2014) or petroleum ether (Ali and McKay, 1982; Yaniv et al., 1994), continuous one step oil extraction using n–hexane (Ciubota-Rosie et al., 2009) and supercritical CO2 extraction (Seal et al., 2008). After the extraction, the solvent is usually removed from the oil by vacuum evaporation. Whole seeds are commonly used for mechanical oil extraction by cold pressing (Ciubota-Rosie et al., 2013), hot pressing (Nie et al., 2016) or expelling (Ahmad et al., 2013; Sultana et al., 2014). The pressed oil is then filtered and dried by heating or vacuum evaporation. Sometimes, WMSO is subjected to acid degumming, neutralization and solid separation (Ciubota-Rosie et al., 2013). In order to improve the overall WMSO recovery, the present paper dealt with its extraction from WMS by a two–step process consisting of the cold WMS pressing and the extraction of WMSO from press cake (maceration) by n–hexane. The Soxhlet extraction by n–hexane and cold pressing was also employed. The maceration of press cake was optimized using a 33 full factorial design with replication, with operating temperature, solvent–to–seed cake ratio and extraction time as process variables. Moreover, the kinetics of maceration was modeled and the thermodynamics of the process was analyzed. The oils obtained by different extraction techniques were characterized with respect to fatty acid composition and specific physico–chemical properties. The main goals were: (a) the selection of optimal extraction technique and conditions; (b) the kinetic modeling of the maceration of press cake, (c) the thermodynamic analysis of maceration and (d) the physico–chemical characterization of the extracted WMSOs. According to our best knowledge, there is no study on the optimization, kinetics and thermodynamics of the WMSO extraction using a solvent in the literature.

2.2.3. Maceration of WMS press cake The ground press cake (10 g) and a volume of n–hexane (30, 65 or 100 mL) were added to an Erlenmeyer flask (250 mL), equipped with a condenser and placed in a water bath. No mixing was applied. In order to follow the maceration kinetics, the suspension was collected from the flask after 0.5, 1, 2, 3, 5, 10 and 15 min, the exhausted cake was separated from the liquid extract by vacuum filtration and then washed once with n–hexane (10 mL). The combined filtrates were evaporated to a constant weight in a rotary vacuum evaporator at 50 °C. The oil yield was defined as the amount of the oil extracted from 100 g of press cake. Each experimental run was conducted in duplicate. 2.2.4. Statistical modeling and optimization of WMSO extraction from press cake For statistical modeling and optimization, a 33 full factorial design with replication was employed (54 runs in total), which included extraction temperature, solvent–to–seed cake ratio and extraction time as process factors (Table 1). Solvent–to–seed cake ratio was 3:1, 6.5:1 and 10:1 mL/g, while the temperature was 20, 45 and 70 °C, as it was used in the case of hempseed oil extraction (Kostić et al., 2013). The range of extraction time (1, 3 and 5 min) was chosen to cover the two stages of the extraction process: the lowest level was approximately at the end of the fast extraction (washing) stage, and the highest level was about the beginning of the saturation stage. WMSO yield (Y) was associated with extraction temperature (X1), solvent–to–seed cake ratio (X2) and extraction time (X3) through the following quadratic equation:

Y = b0 + b1 X1 + b2 X2 + b3 X3 + b1 2X1 X2 + b1 3X1 X3 + b2 3X2 X3 + b11 X12 + b22 X22 + b33 X32

2. Experimental

(1)

where b0 was the constant regression coefficient, bi and bii were the linear and quadratic regression coefficients, respectively and bij were the regression coefficients of two–factor interactions (i, j, = 1, 2, 3). Data processing and evaluating were performed using the Design Expert software (Stat–Ease Inc., Minneapolis, USA).

2.1. Materials The seeds of the “NS Bela” variety of S. alba L. were created at the Institute of Field and Vegetable Crops, Novi Sad, Serbia. The starting material for the creation of the mentioned variety was created by crossing local population. The pedigree breeding method has been applied. In intensive production, seed yield over 1200 kg/ha can be realized, with the oil content of over 20%. The WMS was held in paper bags in a dark room. For the use in the Soxhlet extraction, WMS was ground in an electric mill (Iskra, Slovenia) for 1 min before the use. The mean diameter of powder particles was 0.44 mm. Moisture content of the WMS, determined by drying seeds at 105 °C until constant weight, was 3.78 ± 0.16 g/100 g. n–Hexane (HPLC grade, the boiling point of 69 °C), used as the extracting solvent, was purchased from Lab–Scan (Irland).

2.2.5. Kinetic modeling of WMSO extraction from press cake The kinetics of the WMSO extraction from the ground press cake was described by the phenomenological model that involved two main processes occurring simultaneously and exponentially: (a) dissolution of the WMSO from external surfaces of press cake particles (fast extraction or washing), and (b) mass transfer of WMSO from press cake particles into the liquid extract by diffusion and osmotic process (slow extraction). This model was depicted by the following equation (Kostić et al., 2014):

q = q∞ [1 − f ⋅e−k1⋅ t − (1 − f )⋅e−k2⋅ t ]

(2)

where q was the WMSO yield (g/100 g) at time t (min), q was the WMSO yield at saturation (g/100 g), f and (1 − f ) were constants representing the fractions of WMSO extracted from the ground press cake into the solution by washing (washable part of WMSO) and diffusion (diffusible part of WMSO), respectively k1 and k2 were washing and diffusion rate constants (1/min), respectively and t was time. It was assumed that k1 > k2. Eq. (2) could be simplified for k1 > > k2 (instantaneous washing accompanied by diffusion of the oil):

2.2. WMSO extraction 2.2.1. Cold pressing WMSO was extracted from WMS through an oil press (Komet, Germany) using 8 mm nozzles. After pressing, WMSO was filtered under vacuum to remove solid residues. The press cake was first crushed manually and then milled in the electric mill for 1 min. The powdered press cake (mean diameter of 0.47 mm) was used in the study of maceration.

q = q∞ [1 − (1 − f )⋅e−k2⋅ t ]

2.2.2. Soxhlet extraction WMSO was extracted from both ground WMS and powdered press

and further for f = 0 (no washing): 133

(3)

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Table 1 Experimental matrix of a 33 full factorial design with replication and additional runs at the central point of the design space along with actual and predicted WMSO yield. Type of dataset

RSM modeling and optimization

Validation of quadratic model

Run

Coded factors

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 1 2 3 4 5

q = q∞ (1 − e−k2⋅ t )

Uncoded factors

X1

X2

X3

X1

X2

X3

Actual, series 1

Actual, series 2

Predi-cted

−1 0 1 −1 0 1 −1 0 1 −1 0 1 −1 0 1 −1 0 1 −1 0 1 −1 0 1 −1 0 1 0 0 0 0 0

−1 −1 −1 0 0 0 1 1 1 −1 −1 −1 0 0 0 1 1 1 −1 −1 −1 0 0 0 1 1 1 0 0 0 0 0

−1 −1 −1 −1 −1 −1 −1 −1 −1 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 0 0 0 0 0

20.0 45.0 70.0 20.0 45.0 70.0 20.0 45.0 70.0 20.0 45.0 70.0 20.0 45.0 70.0 20.0 45.0 70.0 20.0 45.0 70.0 20.0 45.0 70.0 20.0 45.0 70.0 45.0 45.0 45.0 45.0 45.0

1:3 1:3 1:3 1:6.5 1:6.5 1:6.5 1:10 1:10 1:10 1:3 1:3 1:3 1:6.5 1:6.5 1:6.5 1:10 1:10 1:10 1:3 1:3 1:3 1:6.5 1:6.5 1:6.5 1:10 1:10 1:10 1:6.5 1:6.5 1:6.5 1:6.5 1:6.5

1 1 1 1 1 1 1 1 1 3 3 3 3 3 3 3 3 3 5 5 5 5 5 5 5 5 5 3 3 3 3 3

4.60 5.49 5.56 6.04 6.08 6.31 6.13 6.07 6.46 5.20 5.88 6.83 6.44 6.54 6.99 6.25 6.90 6.96 5.31 6.22 6.85 6.50 6.75 7.29 6.36 7.26 7.19 6.54 6.71 6.90 6.82 6.21

4.86 5.42 5.66 5.90 6.07 6.25 6.07 6.03 6.59 5.63 5.62 6.50 6.48 6.64 6.90 6.36 6.93 7.02 5.83 5.71 6.71 6.51 6.88 7.10 6.49 7.16 7.21

4.89 5.29 5.70 5.80 6.09 6.37 6.05 6.22 6.38 5.41 5.90 6.40 6.30 6.67 7.04 6.52 6.77 7.02 5.53 6.12 6.70 6.39 6.85 7.31 6.58 6.92 7.26 6.67 6.67 6.67 6.67 6.67

2.3. Analytical methods

(4)

Multiple nonlinear regression was applied to determine the parameters of Eqs. (2)–(4) using the measured values of WMSO yield during the maceration.

2.3.1. Characterization of WMSO The density and viscosity of the WMSO were measured at 20 °C using a pycnometer and a viscometer (Fungilab S.A., Barcelona, Spain), respectively. Saponification, acid and iodine values of the WMSO were determined according to the standard methods (AOCS, 1980). The fatty acid composition of WMSO after the oil methylation was determined by gas chromatography, according to SRPS EN ISO 12966-2:2011 and SRPS EN ISO 5508: 2009.

2.2.6. Thermodynamic properties The following equation was applied to calculate the distribution coefficient (K):

K=

q∞ q0 − q∞

(5) 2.3.2. Average chain length and total unsaturation degree The average chain length of WMSO fatty acids was calculated from the number of carbon atoms of the fatty acid chain, nC, and the fraction of each fatty acid, fFA, as follows:

where q∞ and q0 were the WMSO yield at saturation and the amount of WMSO in the press cake determined by the Soxhlet extraction (both in g/100 g of press cake), respectively. The enthalpy and entropy changes (ΔHo and ΔSo, respectively) were calculated using the Van’t Hoff equation:

ln K = −

ACL =

ΔH o ΔS o + RT R

(6)

while the Gibbs free energy change (ΔG ) was determined as follows: (7)

TUD = fMUFA + 2fDUFA + 3fTUFA

where T was the absolute temperature and R was the universal gas constant. The temperature extraction coefficient (γ) was calculated from the linearized form of Eq. (8):

qT = qTo⋅γT

10

∑ nC⋅fFA

(9)

The total unsaturation degree of WMSO fatty acids was calculated from the fractions of mono–, di– and triunsaturated fatty acids (fMUFA, fDUFA and fTUFA, respectively), as follows:

o

ΔGo = ΔH o − T ⋅ΔS o

WMSO yield (Y), g/100 g

(10)

2.4. Statistical analysis (8) The performances of the developed models were evaluated statistically through the coefficient of determination, R2:

where qT and qTo were the WMSO yields (g/100 g) achieved at temperatures T and To (in °C), respectively. 134

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∑ R2 =

cold pressing and Soxhlet extraction are given in Table 3. Yields and fatty acid compositions of WMSO obtained from a number of WMSs of different origin are compared in Table 4.

(qp, i − qa, i )2

i=1 n

∑

(qp, i − qm)2

(11)

i=1

3.2.1. Physico–chemical properties of WMSO In general, the extraction technique had a little influence on the physico–chemical properties of the oils with exception of the acid value, which was higher in the case of WMSO obtained by solvent extraction (Table 2). This could be ascribed to the influence of the higher temperature of solvent extraction on oil acidity that might be caused by the hydrolysis of acylglycerols (Adeeko and Ajibola, 1990). However, the acid and iodine values of the oils depended on the oily feedstock (seed or press cake) and were higher for the oil from press cake. The higher acid value of the oil from the press cake could be attributed to the process of its recovery that included pressing, milling and solvent extraction that increased the FFA formation (Adeeko and Ajibola, 1990). The saponification value did not depend on either extraction technique or feedstock. The physico–chemical properties of WMSO obtained in the present work are in the range of previously published data for WMSO obtained from WMS from different regions and by different methods (Table 4).

and the mean relative percent deviation, MRPD:

MRPD =

100 n

n

∑ i=1

qp, i − qa, i qa, i

(12)

where qp,i and qa,i were the calculated and actual WMSO yields, qm was the average WMSO yield, and n was the number of experimental runs. R2–values as well as other statistical criteria like the adjusted coefficient 2 2 of determination, Radj , the predicted coefficient of determination, Rpred , and the coefficient of variation, C.V., were calculated by the Design Expert software while MRPD–values were calculated by the Microsoft Excel software. All models were tested by the Student’s t–test. The physico–chemical properties and fatty acids contents of the oils obtained from WMS and press cake by different extraction techniques were evaluated by the Duncan’s multiple range test. 3. Results and discussion

3.2.2. Fatty acid composition of WMSO Generally, there are no differences in the WMSOs extracted by different extraction methods as all oils contained the same fatty acids (Table 3). The content of total saturated fatty acids (SFA) was very low (only 1.99–4.14%), compared to the content of total unsaturated fatty acids, and increased by thermal treatment during the Soxhlet extraction. According to the Duncan’s multiple range test, this increase was statistically significant at the 95% confidence level. Total SFA comprised of palmitic (C16:0), stearic (C18:0), arachidic (C20:0), behenic (C22:0) and lignoceric (C24:0) acids but the most abundunt was palmitic acid. The total monounsaturated fatty acids (MUFA) included oleic (C18:1), eicosenoic (C20:1), erucic (C22:1) and nervonic (C24:1) acids. Among them, the most abundunt was erucic acid. Erucic acid was mostly extracted during cold pressing or the Soxhlet extraction as its content in the WMS press cake (about 50–56%) was significantly lower than in the WMS (about 60%). High erucic acid content is an uniq property of WMSO originated from various world’ regions. As can be seen in Table 4, erucic acid content ranges between about 33% and 60% whereby the highest content is characteristic of WMS from Europian countries. The content of oleic acid was the second most abundunt fatty acid with a content about 11.6–14.9% (Table 3), which is in the range observed for the WMSO from all over the world (9.1–43.4%, Table 4). The highest oleic acid content is reported for WMSO from North and South America. The major polyunsaturated fatty acids (PUFA) of WMSO were linoleic (C18:2) and linolenic (C18:3) acids. While the content of the former was higer in the WMSO extracted from press cake than from WMS, the linolenic acid content did not depend on the extraction technique (Table 3) as proved by the Duncan’s multiple range test. The ratio of oleic to linoleic fatty acids (stability index) in WMSOs depended on extraction technique and decresed with thermal treatment during which the content of linoleic fatty acid increased. For the same reason, the ω–6 (linoleic acid)/ω–3 (linolenic acid) ratio increased after thermal treatment.

3.1. WMSO extraction from ground seed and press cake The WMSO yield obtained from WMS and press cake by one– and two–step processes are shown in Fig. 1. The one-step processes were the Soxhlet extraction of WMS and powdered press cake and the cold pressing of WMS while the two-step processes included cold pressing of WMS followed by Soxhlet extraction or maceration of powdered press cake conducted under optimal extraction conditions (70 °C, solvent–to–seed cake ratio 6.5:1 or 8.5:1 and extraction time 5 min; Section 3.3.2.3.). Fig. 1 demonstrates that the best WMSO yield was achieved by Soxhlet extraction. While the extraction degree of cold pressing was only 64.3% of the best WMSO yield, cold pressing of WMS combined with Soxhlet extraction of powdered press cake resulted in the extraction degree of 96.4%. The combination of cold pressing and maceration under the optimal operating conditions was almost as efficient as Soxhlet extraction. 3.2. Characterization of WMSO The physico–chemical properties of WMSO obtained by various extraction techniques like density and viscosity, determined at 20 °C, as well as acid, iodine and saponification values, are given in Table 2. Fatty acid composition of WMSO obtained from WMS and press cake by

3.3. Maceration of ground press cake to recover WMSO 3.3.1. WMSO extraction mechanism First of all, the mechanism of WMSO extraction from the ground press cake was investigated at the maceration temperature of 20, 45 and 70 °C and the solvent–to–seed cake ratio of 3:1, 6.5:1 and 10:1 mL/ g. Fig. 2, where the change of WMSO yield during the maceration is shown, indicates the typical shape of the curves for oil extractions from oily plant materials. At a constant temperature, the WMSO yield rose rapidly within the first minute of the maceration, then decelerated (up

Fig. 1. WMSO yields obtained from various oil sources and by different extraction methods (values above the bars are mean yields). 135

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Table 2 Physico–chemical properties WMSO obtained by various extraction techniques.* Property

Density (20 °C), kg/m3 Viscosity (20 °C), mPa.s Acid value, mg KOH/g Iodine value, g I2/100 g Saponification value, mg KOH/g

Extraction technique Cold pressing of WMS

Soxhlet extraction from ground WMS

Soxhlet extraction from powdered press cake

Maceration from powdered press cake under selected optimal conditions**

913.38a ± 0.41 84.24a ± 2.21 1.95a ± 0.03 100.58a ± 1.62 180.65a ± 2.35

910.71b ± 0.77 80.45b ± 1.29 2.73b ± 0.08 101.78a ± 0.76 180.72a ± 1.79

911.78a,b ± 0.87 86.07a ± 0.93 4.09c ± 0.10 107.49b ± 0.88 178.29a ± 3.05

910.97b ± 0.87 86.00a ± 0.29 4.43d ± 0.05 108.21b ± 0.66 179.65a ± 1.84

* The contents of a fatty acid obtained by different extraction techniques were tested by Duncan’s multiple range test. The values that have no common superscript are significantly different at the 95% confidence level. ** Solvent–to–seed cake ratio 6.5:1, extraction temperature 70 °C and extraction time 5 min.

Table 3 Fatty acid composition of WMSO obtained from WMS and press cake by cold pressing and solvent extraction.* Plant material

Seed

Press cake

Extraction technique

Cold pressing

Soxhlet

Soxhlet

Maceration

C14:0, % C16:0, % C16:1, % C18:0, % C18:1, % C18:2, % C18:3, % C20:0, % C20:1, % C20:2, % C22:0, % C22:1, % C22:2, % C24:0, % C24:1, % SFA, % MUFA, % PUFA, % ALC TUD, % OLR LLR

nd 0.73 ± 0.03 nd 0.30 ± 0.02 13.95a ± 0.33 5.98a ± 0.23 7.37a ± 0.38 0.28 ± 0.02 7.41a ± 0.33 0.17 ± 0.02 0.39 ± 0.05 59.98a ± 0.48 0.32 ± 0.03 0.30 ± 0.02 2.95a ± 0.14 1.99a ± 0.08 84.28a ± 0.63 13.84a ± 0.66 20.0 119 2.33 0.81

nd 0.86 ± 0.06 nd 0.35 ± 0.02 11.63b ± 1.12 6.03a ± 0.47 7.00a ± 0.57 0.33 ± 0.01 7.00a ± 0.05 0.22 ± 0.00 0.57 ± 0.09 60.29a,b ± 2.57 0.40 ± 0.04 0.50 ± 0.02 4.79b ± 0.01 2.60b ± 0.02 83.71a ± 0.94 13.65a ± 1.00 19.7 118 1.93 0.86

nd 1.09 ± 0.03 0.11 ± 0.02 0.38 ± 0.03 12.60a,b ± 0.07 7.46b ± 0.09 8.03a,b ± 0.11 0.35 ± 0.01 7.32a ± 0.11 0.24 ± 0.02 0.56 ± 0.01 56.21a,c ± 0.33 0.42 ± 0.02 0.69 ± 0.03 4.59b,c ± 0.05 3.05c ± 0.03 80.82b ± 0.19 16.14b ± 0.21 19.5 121 1.69 0.93

nd 1.72 ± 0.09 0.14 ± 0.00 0.61 ± 0.03 14.86a,c ± 0.87 8.86c ± 0.53 8.76b ± 0.55 0.52 ± 0.01 9.59b ± 0.51 0.29 ± 0.02 0.78 ± 0.04 49.81d ± 2.31 1.26 ± 0.03 0.52 ± 0.08 2.31d ± 0.21 4.14d ± 0.07 76.70c ± 1.13 19.17c ± 1.07 20.8 119 2.13 0.84

* The contents of a fatty acid obtained by different extraction techniques were tested by Duncan’s multiple range test. The values that have no common superscript are significantly different at the 95% confidence level. SFA − saturated fatty acids; MUFA − monounsaturated fatty acids, PUFA − polyunsaturated fatty acids ALC − average length chain, TUD − total unsaturation degree, OLR − oleic/linoleic ratio and LLR − linoleic/linolenic (ω–6/ω–3) ratio. nd − not detected (detection limit < 0.05%).

to about the fifth minute) and finally reaches a plateau (next 10 min). Practically, the maceration reached the saturation within almost 5 min. The extremely fast rate of the first extraction step (washing) resulted from the efficient breakage of the seed organs containing the oil by WMS grinding. During the later step (slow extraction), the WMSO diffused from the interior of the seed particles and dissolved in the solvent. On the basis of the verified extraction mechanism, the kinetics of the WMSO maceration could be described by the phenomenological model, Eq. (2).

3.3.2.1. ANOVA results and quadratic equation. By applying Eq. (1), the results of ANOVA (Table S2, Supplementary material) showed that the significant terms are all three individual process factors (X1, X2 and X3), the interactions of extraction temperature with solvent–to–seed cake ratio and time (X1–X2 and X1–X3) as well as the quadratic terms of solvent–to–seed cake ratio and extraction time (X22 and X32) at the 95% confidence level while the interaction of solvent–to–seed cake ratio with extraction time (X2–X3) and the quadratic term of extraction temperature (X12) had no statistically significant influence on WMSO yield in the experimental region applied. The corresponding quadratic model equations in terms of coded and actual factors were as follows: - Actual factors

3.3.2. Statistical modeling and optimization of WMSO maceration The experimental matrix of the used 33 full factorial design with replication with actual and coded levels of the three factors along with the achieved and predicted WMSO yields is shown in Table 1. The Kolmogorov–Smirnov normality test verified that the data were significantly drawn from a normally distributed population at the 0.05 level (statistic = 0.079 < p = 0.969). Moreover, no outlier value was observed in the analyzed data set.

Y = 2.77 + 0.018⋅X1 + 0.553⋅X2 + 0.440⋅X3 − 0.0014⋅X1 X2 + 0.0018 ⋅X1 X3 − 0.0043⋅X2 X3 + 0.000002⋅X12 − 0.027⋅X22 − 0.050⋅X32

(13)

- Coded factors

Y = 6.67 + 0.37⋅X1 + 0.43⋅X2 + 0.38⋅X3 − 0.12⋅X1 X2 + 0.088⋅X1 X3 − 0.030 ⋅X2 X3 + 0.0011⋅X12 − 0.33⋅X22 − 0.20⋅X32

136

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Table 4 Variability of oil content and fatty acid composition in WMS of different origin.a Origin

Serbia

Romania

Extraction technique

Soxhlet/ n–hexane

Yield, % C14:0 C16:0 C16:1 C16:2 C18:0 C18:1 C18:2 C18:3 C20:0 C20:1 C20:2 C22:0 C22:1 C22:2 C24:0 C24:1 SFA, % MUFA, PUFA, % Total, % ALC TUD, % OLR LLR AV SV IV CV Reference

20.6 13.2 – – 0.86 0.73 – – – – 0.35 0.3 11.63 13.95 6.03 5.98 7.00 7.37 0.33 0.28 7.00 7.41 0.22 0.17 0.57 0.39 60.29 59.98 0.40 0.32 0.50 0.30 4.79 2.95 2.61 2.00 83.7 84.3 13.7 13.8 100.0 100.1 20.9 20.8 118.0 119.3 1.93 2.33 0.86 0.81 2.73 1.95 180.72 101.78 100.58 – Present work

Cold pressing

Soxhlet/ n–hexane

Cold pressing

43.5 ∼35 – – 1.6 1.5 – – – – 0.7 0.9 12.4 12.0 12.0 12.3 8.7 8.9 0.7 0.6 6.7 6.6 0.3 0.3 0.7 0.6 55.0 55.0 0.5 0.4 0.1 0.1 0.6 0.6 3.80 3.70 74.7 74.2 21.5 21.9 100.0 99.8 20.4 20.4 126.4 126.9 1.03 0.98 1.38 1.38 1.58 1.23 – – 102.3 102.3 – – Ciubota-Rosie et al. (2013)

Spain

Great Britain

Israel

India

Canada

Soxhlet/ n–hexane

Soxhlet/ petroleum ether

Soxhlet/ petroleum ether

Soxhlet/ n–hexane

Soxhlet/ n–hexane

Commercial

Cold pressing

Cold pressing

25 – 2.82 – – – 17.61 7.82 10.99 – 5 – – 55.76 – – – 2.82 78.4 18.8 100.0 20.3 127.0 2.25 0.71 – – – – SáezBastante et al. (2016)

– – 3.1 – – 0.7 9.1 11.7 12.5 0.7 10.8 0.7 Tr 46.5 0.4 Tr 3.6 4.50 70.0 25.3 99.8 20.2 133.1 0.78 0.94 1.23 174 105.4 – Ali and McKay (1982)

19.5 – 3.0 – –

31.6 – 3.36

35.1 0.3 23.7 – – 1.6 43.4 30.1 0.2 0.6 – – – – – – – 26.20 43.4 30.3 99.9 17.5 104.2 1.44 – 2.19175 106.2– Sengupta and Bhattacharyya (1996)

– 0.05 2.80 0.16 0.06 1.09 26.08 11.64 8.61 0.70 10.44 – 0.57 32.81 – – – 5.21 69.5 20.3 95.0 18.6 118.4 2.24 1.35 0.85 – – – Issariyakul and Dalai (2011)

– – 2.81 – – 1.06 24.89 9.21 10.8 – 10.63 – – 34.94 – – – 3.87 70.5 20.0 94.3 18.5 121.3 2.70 0.85 – – – – Nie et al. (2016)

22.3 – 2.10 0.09 – 0.80 19.62 8.43 21.64 0.41 nd 0.25 – 40.80 – nd 1.25 3.31 61.8 30.3 95.4 18.8 144.0 2.33 0.39 – – – – MejiaGaribay et al. (2015)

15.8 9 8.6 5.8 – – 50.8 – – – 3.00 72.4 17.6 93.0 18.8 116.2 1.76 1.05 – – – – Yaniv et al. (1994)

1.12 22.12 10.78 12.52 11.91

38.16

4.48 72.2 23.3 100.0 19.7 131.3 2.05 0.86 – 184.7 112 50.6 Singh et al. (2014)

Mexico

a SFA − saturated fatty acids, MUFA − monosaturated fatty acids, PUFA − polyunsaturated fatty acids, ALC − average length chain, TUD − total unsaturation degree, OLR − oleic/linoleic ratio, LLR − linoleic/linolenic (ω–6/ω–3) ratio, AV − acid value, SV − saponification value, IV − iodine value and CV − cetane value.

additional five center points of the applied design space (Table 1). The MRPD of ± 3.1% indicated a good agreement between the calculated and experimental values, thus verifying reliability of the developed model equation. As it can be seen in Eq. (14), the linear regression coefficients were positive, indicating a positive influence of all three process factors on WMSO yield. As indicated by values of their linear regression coefficients (Eq. (14)) and their F–values (Table S2, Supplementary material), the extraction temperature (X1) and time (X3) had almost the same influence on WMSO yield which was somewhat lower than the impact of the solvent–to–seed cake ratio (X2). Higher WMSO yields were achieved at higher solvent–to–seed cake ratio because of a better oil dissolution capability of the increased amount of the solvent. The positive effect of extraction temperature on WMSO yield was attributed to the increase of the oil mass transfer rate constant and the WMSO solubility in the solvent with increasing the extraction temperature.

The Fmodel–value of 58.36 and the corresponding p–value of < 0.0001 implied the model was significant with only a 0.01% chance that a Fmodel–value this large could occur due to noise. Also, a high R2–value (0.923) and low MRPD–value ( ± 2.3% on the basis of 54 data) proved the adequacy of the quadratic model. Moreover, the 2 2 –value of 0.883 is close to the Radj –value of 0.907 as these two Rpred coefficients of determination differed to each other less than 0.2 (Anderson, 2010), indicating a good prediction of WMSO yield by Eqs. (13) and (14). Besides that, a small value of the coefficient of variation (C.V. = 3.0%) indicated a good model fit. The only problem was the significant F–value of the lack of fit (p–value = 0.007 < 0.050), which was not desirable and hence should physically be explained before deciding on the further use of the model (Veljković, 2014). High F–value of the lack of fit could result from dividing the mean square of lack of fit by the small mean square of pure error (Table S2, Supplementary material). Indeed, the sum of absolute variations of the replicates about their mean values (4.09, i.e. mean value: ± 0.08) that was lower than the sum of absolute variations of the experimental points about their predicted values (5.89, i.e. mean value: ± 0.11). Besides that, the MRPD between the replicates was ± 1.3%, confirming a high precision of the repeated measurements of WMSO yield that caused the small pure error and the significant lack of fit. Since the developed model fitted the experimental data well as indicated by other statistical criteria, its significant lack of fit was attributed to the small variance of replicated runs and was not further considered as a valid test. Furthermore, this model was validated on the basis of the

3.3.2.2. Response surface analysis. The relationship of WMSO yield with the maceration temperature (X1) and solvent–to–seed cake ratio (X2) at the extraction time (X3) of 5 min is graphically presented in Fig. 3 in the form of a response surface 3D plot that resulted from the quadratic model. Generally, this plot visualizes the effects of the process factors and their interactions on WMSO yield and the optimal process conditions. In general, increasing of both extraction temperature and solvent–to–seed cake ratio led to an increase of WMSO yield. However, at the temperature above 60 °C, the increase of solvent–to–seed cake 137

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Fig. 3. Response surface plot for WMSO yield as a function of extraction temperature (X1) and solvent–to–seed cake ratio (X2) at the extraction time (X3) of 5 min.

9.2:1 mL/g, the predicted best WMSO yield achieved in 4–5 min was 7.30–7.35 g/100 g. Under the extraction conditions of 8.5:1 mL/g, 70 °C and 5 min ensuring the maximum predicted WMSO yield of 7.35 g/ 100 g, the actual WMSO yield was 7.22 g/100 g. However, taking the lowest solvent amount as a criterion of choice, the selected optimal extraction conditions were 6.5:1 mL/g, 70 °C and 5 min, where the predicted best WMSO yield was 7.29 g/100 g which agreed quite well with the experimental WMSO yield of 7.20 ± 0.13 g/100 g. This best WMSO yield obtained from the press cake by the maceration under the optimal conditions was 84% of the WMSO yield achieved from the press cake by the Soxhlet extraction. Thus, the two-step process that included cold pressing and maceration would result in the total WMSO yield of 20.48 g/100 g, which was very close to the WMSO yield achieved from the ground WMS by the Soxhlet extraction (20.64 g/100 g) (Fig. 1). 3.4. Kinetic modeling of WMSO maceration 3.4.1. Phenomenological model On the basis of the observed mechanism of WMSO maceration, the phenomenological model, Eq. (2), was first applied for fitting the experimental WMSO yield data. However, because of very few data in the initial stage of the maceration (only two points in the first minute), the value of washing rate constant, k1, could not reliably be determined. In fact, its value could be varied in a wide range while values of other model parameters, q∞, f and k2, stayed constant, indicating the uncertainty of the model. For instance, for the maceration at 45 °C and the solvent–to–seed cake ratio of 6.5:1 mL/g, the variation of the k1–value between 15 and 150 min−1 did not change other model parameters, i.e. q∞, f and k2 were 6.87 g/100 g, 0.78 and 0.5 min−1, respectively. Therefore, the phenomenological model was not considered further.

Fig. 2. The variation of WMSO yield with time during the maceration with n–hexane at the extraction temperature of 20 °C (a), 45 °C (b) and 70 °C (c) and various solvent–to–seed cake ratios, mL/g: 3:1–○, 6.5:1–Δ and 10:1–□ (model, Eq. (3): line).

3.4.2. Model involving instantaneous washing followed by diffusion Since the rate of washing step was so fast, it could be considered as instantaneous, i.e. k1 > > k2. Therefore, the simpler three–parameter model assuming instantaneous washing followed by diffusion, Eq. (3), was tested in the next step. Values of the parameters of this model, q∞ (both experimental and predicted), f and k2, are presented in Table S3 (Supplementary material). As it was expected, the saturation WMSO yield, q∞, increased with increasing both extraction temperature and solvent–to–seed cake ratio due to the increased WMSO solubility at the higher temperature and the increased amount of the solvent that dissolved a larger amount of the oil, respectively. The same was earlier observed with the extraction of hempseed oil (Kostić et al., 2014). The predicted q∞–values slightly differed from the experimental values as indicated by a small MRPD–value ( ± 2.3% based on 18 data). The

ratio above 6.5:1 slightly reduced WMSO yield. 3.3.2.3. RSM optimization on the basis of the quadratic model. For the selection of the optimal operating conditions using the developed quadratic model, the criterion of optimization was to get the maximum WMSO yield with the process factors constrained to the applied experimental region. According to the 3D plot (Fig. 3), the maximum WMSO yield of 7.3 g/100 g or higher can be obtained in 5 min at the extraction temperature close to 70 °C combined with the corresponding solvent–to–seed cake ratio about 6.5:1 mL/g. The used software on the basis of the quadratic model suggested a number of combinations. For instance, at the extraction temperature close to the solvent boiling point and the solvent-to-seed cake ratio from 6.5:1 to 138

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3.4.3. Diffusional model The simpler kinetic model fitted the experimental data nearly as successfully as the more complex model involving instantaneous washing followed by diffusion since the MRPD value was negligibly higher ( ± 3.1%; 120 data). However, the simpler model had a much lower R2–value than the more complex model (0.627–0.877 and 0.790–0.911, Table S5 and Table S4, Supplementary material, respectively). As it was expected, the diffusion rate constant, k2, and the saturation WMSO yield, q∞, increased with increasing both extraction temperature and solvent–to–seed cake ratio, which was explained in the same way as in the case of the more complex model involving instantaneous washing followed by diffusion. The predicted q∞–values well agreed with the experimental values as can be concluded by a small MRPD–value ( ± 3.5% based on 18 data). On the basis of the ANOVA results (Table S4, Supplementary material), the solvent–to–seed cake ratio and maceration temperature influenced significantly the diffusion rate constant, k2 while their interaction was insignificant at the 95% confidence level. The influence of the solvent–to–seed cake ratio was more significant than the influence of the extraction temperature, suggesting that the larger concentration difference facilitated mass transfer.

ANOVA showed that solvent–to–seed cake ratio, maceration temperature and their interaction influenced the maximum WMSO yield at saturation significantly at the 95% confidence level (Table S4, Supplementary material). The fraction of washable WMSO, f, increased with increasing the solvent–to–seed ratio at a constant extraction temperature due to the positive effect of the increased amount of the solvent on the washing process. This differed from the observance of Kostić et al. (2014), who reported a constant fraction of hempseed oil in the maceration of hempseed oil under the same operating conditions. On the basis of the ANOVA results (Table S4, Supplementary material), the solvent–to–seed cake ratio had a statistically significant influence on the fraction of washable WMSO. However, the influences of the extraction temperature and the interaction between both process factors were not significant, thus indicating that the capability dissolution, determined by the solvent amount, was more influential than the WMSO solubility in the solvent in the applied range of extraction temperature. The dependence of the fraction of washable WMSO on the reciprocal solvent–to–seed cake ratio (s, mL/g) was linear (coefficient of correlation, R = 0.920 and p < 0.001) independently of the maceration temperature:

f = −0.6083⋅

1 + 0.8873 s

(15)

3.5. Thermodynamic analysis

The diffusion rate constant, k2, increased with increasing both extraction temperature and solvent–to–seed cake ratio. The liquid viscosity decreased with increasing both extraction temperature and solvent–to–seed cake ratio, which improved the diffusion rate constant. In addition, with the larger solvent–to–seed cake ratio, the concentration difference was larger, which facilitated mass transfer. However, the driving force would not be changed much in the presence too much excess of solvent as the mass transfer limitation was more confined to the interior of plant particles. The ANOVA showed that extraction temperature and solvent–to–seed cake ratio affected the washing rate constant significantly (at the 95% confidence level) but the impact of the extraction temperature was larger than that of solvent–to–seed cake ratio (Table S4, Supplementary material). To model the influence of solvent–to–seed cake ratio and maceration temperature on the kinetics of the maceration, the Arrhenius equation was modified as follows (Kostić et al., 2014):

E k2 = A′⋅s n⋅exp ⎛− a ⎞ ⎝ RT ⎠

3.5.1. Enthalpy, entropy and Gibbs free energy changes The thermodynamic analysis was based on values of the WMSO yield and the content of WMSO in the exhausted WMS press cake particles at saturation. Values of the distribution coefficient at different extraction temperatures and solvent–to–seed cake ratios was calculated by Eq. (5) using the experimental values of the WMSO yield at saturation, q∞,exp, and the amount of WMSO in the press cake determined by the Soxhlet extraction, q0. As expected, the distribution coefficient increased with increasing maceration temperature and solvent–to–seed cake ratio. The dependence of lnK on 1/T at different solvent–to–seed ratios was linear according to the Van’t Hoff equation, Eq. (6). The same behavior was observed for the hempseed extraction under the same extraction conditions (Kostić et al., 2014). The enthalpy and entropy change, ΔHo and ΔSo, respectively were first calculated from the slope and intercept of Eq. (6), respectively and then the Gibbs free energy change was calculated by Eq. (7). Values of the enthalpy, entropy and Gibbs free energy changes are presented in Table 5. The enthalpy and entropy changes for the WMSO extraction using n–hexane were positive in the applied ranges of maceration temperature and solvent–to–seed cake ratio, thus implying this extraction process is endothermic and irreversible, which is characteristic for oil extraction from various oily feedstocks like olive cake (Meziane and Kadi, 2008) as well as hemp (Kostić et al., 2014), cotton (Saxena et al., 2011) soybean (Rodrigues et al., 2010) and sunflower (Topallar and Gecgel, 2000) seeds. The

(16)

where k2 was the rate constant, A’ was the modified pre–exponential factor (mLn/gn min), s was the solvent–to–seed cake ratio (mL/g), n was the constant related to solvent–to–seed cake ratio, Ea was the activation energy (J/mol), R was the universal gas constant (8.314 J/mol K), and T was the absolute temperature (K). Values of the parameters of Eq. (16) were as follows: A’ = 4.251 min−1, Ea = 5.99 kJ/mol and n = 0.242. The value of activation energy was close to the value (5.75 kJ/mol) for the hempseed oil extraction by n–hexane (Kostić et al., 2014). To check the developed kinetic model involving instantaneous washing followed by diffusion, values of the WMSO yield were calculated by combining Eqs. (3), (15) and (16) and using the determined values of all their parameters, and compared with the experimental values of the WMSO yield. The model equation fitted the experimental data successfully since for all experiments, the MRPD was ± 3.0% (120 points in total). The developed kinetic model was additionally checked by comparing the predicted and experimental WMSO yields determined under the optimal conditions defined by the used software (8.5:1 mL/g and 70 °C). A relatively small MRPD value of ± 3.0% (6 data) validated the developed the kinetic model inside the applied experimental region.

Table 5 The thermodynamic quantities for WMSO from WMS press cake extraction by n–hexane. Solvent–to–seed cake ratio (mL/g)

T (°C)

ΔS° (J/ mol K)

ΔH°(kJ/mol)

ΔG° (kJ/ mol)

R2,a

3:1

20 45 70 20 45 70 20 45 70

47.43

12.46

0.963

39.14

8.68

29.05

5.20

−1.43 −2.62 −3.81 −2.79 −3.77 −4.75 −3.31 −4.03 −4.76

6.5:1

10:1

a

139

p < 0.001.

0.953

0.976

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References

Gibbs free energy change for the WMSO maceration was negative, which meant that the process was feasible and spontaneous. Since the Gibbs free energy change was more negative at larger solvent–to–seed cake ratios and higher maceration temperatures, the spontaneity of the WMSO maceration was favored with increasing solvent–to–seed cake ratio and maceration temperature. Values of the enthalpy and entropy changes for the oil extraction from the exhausted WMS press cake are similar to those for the oil extraction from the olive cake (Meziane and Kadi, 2008), hempseeds (Kostić et al., 2014) and sunflower seeds (Topallar and Gecgel, 2000) but much lower than those for cottonseed (Saxena et al., 2011) and soybean flake (Rodrigues et al., 2010) oil extractions (Table S6, Supplementary material). The Gibbs free energy change for the WMSO extraction from the WMS press cake is similar to that for the oil extraction from olive cake (Meziane and Kadi, 2008) and hempseeds (Kostić et al., 2014).

AOCS, 1980. Official and Tentative Methods. American Oil Chemists’ Society, Chicago. Adeeko, K.A., Ajibola, O.O., 1990. Processing factors affecting yield and quality of mechanically expressed groundnut oil. J. Agric. Eng. 45, 3–43. Ahmad, M., Ajab Khan, M., Zafar, M., Hasan, A., Ahmad, Z., Akhter, G., Gulzar, S., Sultana, S., 2008. Base catalyzed transesterification of Brassica alba oil and its association with mineralogy to environment friendly biodiesel. Asian J. Chem. 20, 6402–6410. Ahmad, M., Zafar, M., Rashid, S., Sultana, S., Sadia, H., Ajab Khan, M., 2013. Production of methyl ester (biodiesel) from four plant species of Brassicaceae: optimization of the transesterification process. Int. J. Green Energy 10, 362–369. Alam, M.M., Rahman, K.A., 2013. Biodiesel from mustard oil: a sustainable engine fuel substitute for Bangladesh. Int. J. Renew. Energy Dev. 2, 141–149. Ali, A., McKay, J.E., 1982. The chemical and physical characteristics and fatty acid composition of seed oils extracted from Cruciferous species cultivated in Pakistan. Food Chem. 8, 225–231. Anderson M.J. 2010. Statistics Made Easy_ Blog, June 2010, 10 (6). http://www.statease. com/news/faqalert10-06.html (Accessed 15.02.14). Balke, D.T., Diosady, L.L., 2000. Rapid aqueous extraction of mucilage from whole white mustard seed. Food Res. Int. 33, 347–356. Ciubota-Rosie, C., Diaconescu, R., Volf, I., Macoveanu, M., 2009. Modeling the extraction process of oil from seeds of white mustard (Sinapis alba). Environ. Eng. Manage. J. 8, 1429–1432. Ciubota-Rosie, C., Macoveanu, M., Fernández, C.M., Ramos, M.J., Pérez, A., Moreno, A., 2013. Sinapis alba seed as a prospective biodiesel source. Biomass Bioenergy 51, 83–90. Erić, P., Ćupina, B., Mihailović, V., Mikić, A., 2006. Brassicas in production and utilization of forage: advantages and disadvantages. Ratar. Povrt. 42, 105–114. Falasca, L.S., Ulberich, A., 2011. Argentina,s semiarid lands aptitude to cultivate non?traditional species for biodiesel production. In: Marchetti, J.M., Fang, Z. (Eds.), Biodiesel: Blends, Properties and Applications. Nova Science Publishers, Inc., New York, USA, pp. 123–150. Issariyakul, T., Dalai, A.K., 2011. Evaluating esters derived from mustard oil (Sinapis alba) as potential diesel additives. J. Am. Oil. Chem. Soc. 88, 391–402. Issariyakul, T., Dalai, A.K., 2012a. Biodiesel from mustard oil. In: Thiyam–Holländer, U., Eskin, N.A.M., Mattäus, B. (Eds.), Canola and Rapeseed: Production, Processing, Food Quality, and Nutrition. CRC Press, Boca Raton, London, New York, pp. 217–244. Issariyakul, T., Dalai, A.K., 2012b. Comparative kinetics of transesterification for biodiesel production from palm oil and mustard oil. Can. J. Chem. Eng. 90, 342–350. Katepa-Mupondwa, F., Gugel, R.K., Raney, J.P., 2005. Genetic diversity for agronomic, morphological and seed quality traits in Sinapis alba L. Can. J. Plant Sci. 2006 (86), 1015–1025. Kos, B., Grčman, H., Leštan, D., 2003. Phytoextraction of lead, zinc and cadmium from soil by selected plants. Plant Soil Environ. 49, 548–553. Kostić, M.D., Joković, N.M., Stamenković, O.S., Rajković, K.M., Milić, P.S., Veljković, V.B., 2013. Optimization of hempseed oil extraction by n-hexane. Ind. Crop. Prod. 48, 133–143. Kostić, M.D., Joković, N.M., Stamenković, O.S., Rajković, K.M., Milić, P.S., Veljković, V.B., 2014. The kinetics and thermodynamics of hempseed oil extraction by n–hexane. Ind. Crop. Prod. 52, 679–686. Krstić, Đ., Ćupina, B., Antanasović, S., Erić, P., Čabilovski, R., Manojlović, M., Mikić, A., 2010. Potential of white mustard (Sinapis alba L. subsp. alba) as a green manure crop. Crucif. Newsl. 29, 12–13. Mejia-Garibay, B., GuerreroBeltrán, J.Á., Palou, E., LópezMalo, A., 2015. Physical and antioxidant characteristics of black (Brassica nigra) and yellow mustard (Brassica alba) seeds and their products. Arch. Latinoam. Nutr. 65 128135. Meziane, S., Kadi, H., 2008. Kinetics and thermodynamics of oil extraction from olive cake. J. Am. Oil Chem. Soc. 85, 391–396. Nie, J., Wang, S., Emami, S., Falk, K., Shen, J., Reaney, M.J.T., 2016. Unusually low pour point of fatty acid methyl esters with low saturated fatty acid content. Eur. J. Lipid Sci. Technol. 118, 1486–1494. Peng, C., Zhang, T., Zhao, G., Wang, S., 2013. Analysis on fat–soluble components of Sinapis semina from different habitats by GC–MS. J. Pharm. Anal. 3, 402–407. Peng, C., Zhao, S.-Q., Zhang, J., Huang, G.-Y., Chen, L.-Y., Zhao, F.-Y., 2014. Chemical composition, antimicrobial property and microencapsulation of Mustard (Sinapis alba) seed essential oil by complex coacervation. Food Chem. 165, 560–568. Rodrigues, C.E.C., Aracava, K.K., Abreu, F.N., 2010. Thermodynamic and statistical analysis of soybean oil extraction process using renewable solvent. Food Sci. Technol. Int. 45, 2407–2414. Sáez-Bastante, J., Fernández-García, P., Saavedra, M., López-Bellido, L., Dorado, M.P., Pinzi, S., 2016. Evaluation of Sinapis alba as feedstock for biodiesel production in Mediterranean climate. Fuel 184, 656–664. Sanjid, A., Masjuki, H.H., Kalam, M.A., Abedin, M.J., Ashrafur Rahman, S.M., 2014. Experimental investigation of mustard biodiesel blend properties, performance, exhaust emission and noise in an unmodified diesel engine. APCBEE Proc. 10, 149–153. Saxena, D.K., Sharma, S.K., Sambi, S.S., 2011. Kinetics and thermodynamics of cottonseed oil extraction. Grasas Aceites 62, 198–205. Seal, C.E., Kranner, I., Pritchard, D.H.W., 2008. Quantification of seed oil from species with varying oil content using supercritical fluid extraction. Phytochem. Anal. 19, 493–498. Sengupta, R., Bhattacharyya, D.K., 1996. Enzymatic extraction of mustard seed and rice bran. J. Am. Oil Chem. Soc. 73, 687–692.

3.5.2. Temperature extraction coefficient Values of the temperature extraction coefficient, calculated from the slope of the dependence of ln(qT) on T/10, which is the transformation of Eq. (8), were 1.040, 1.021 and 1.011 for the WMSO extraction at the solvent–to–seed cake ratio of 3:1, 6.5:1 and 10:1 mL/g, respectively in the temperature range of 20–70 °C (R2 values: 0.973–0.993; p < 0.001). These values were similar to those reported for the oil extraction from hempseeds (1.012–1.027) (Kostić et al., 2014) and olive cake (1.02–1.14) (Meziane and Kadi, 2008). 4. Conclusion A two–step process combining cold pressing of WMS and the maceration of WMSO from the obtained press cake using n–hexane was employed for the oil recovery. While cold pressing alone reached only 64.3% of the yield obtained by the Soxhlet extraction, the two-step process that included cold pressing and maceration conducted under the optimal extraction conditions (boiling point, solvent–to–seed cake ratio of 6.5:1 mL/g and extraction time of 5 min) resulted in the total WMSO yield (20.48 g/100 g), which was 99.2% of the WMSO yield achieved from the ground WMS by the Soxhlet extraction. Therefore, the two-step process could replace the energy- and solvent-intensive Soxhlet extraction (boiling point, extraction time of 6 h and solvent–to–seed cake ratio of 10:1 mL/g). The WMSO consisted mainly of unsaturated fatty acids, and its physicochemical properties were similar to the previously reported ones. The quadratic model was proved to be suitable for modeling and optimization of the maceration process while solvent–to–seed cake ratio, maceration temperature and extraction time were found to have a significant impact on WMSO yield at the 95% confidence level. The kinetics of WMSO extraction from press cake occurred in accordance with the model of instantaneous washing followed by diffusion. This maceration process was proven to be spontaneous, irreversible and endothermic. Acknowledgement This work has been funded by the Ministry of Education, Science and Technological Development of the Republic of Serbia, Serbia (Project III 45001). Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at https://doi.org/10.1016/j.indcrop.2018.05.001.

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Singh, B.K., Bala, M., Rai, P.K., 2014. Fatty acid composition and seed meal characteristics of Brassica and allied genera. Nat. Acad. Sci. Lett. 37, 219–226. Sultana, S., Khalid, A., Ahmad, M., Zuhairi, A.A., Teong, L.K., Zafar, M., Hassan, F.U., 2014. The production, optimization, and characterization of biodiesel from a novel. Source: Sinapis alba L. Int. J. Green Energy 11, 280–291. Szydłowska-Czerniak, A., Tułodziecka, A., Karlovits, G., Szłyk, E., 2015. Optimisation of ultrasound–assisted extraction of natural antioxidants from mustard seed cultivars. J. Sci. Food Agric. 95, 1445–1453. Thacker, P.A., Petri, D., 2009. The effects of canola or mustard biodiesel press cake on nutrient digestibility and performance of broiler chickens. Asian–Aust. J. Anim. Sci.

22, 1531–1539. Topallar, H., Gecgel, U., 2000. Kinetics and thermodynamics of oil extraction from sunflower seeds in the presence of aqueous acidic hexane solutions. Turk J. Chem. 24, 247–253. Veljković, V.B., 2014. Comment on Study of fuel properties of rubber seed oil based biodiesel [Energy Convers Manage 78:266-75] by Ahmad et al. Energ. Conv. Manage. 86, 1186–1188. Yaniv, Z., Schafferman, D., Elber, Y., Ben-Moshe, E., Zur, M., 1994. Evaluation of Sinapis alba, native to Israel, as a rich source of erucic acid in seed oil. Ind. Crop Prod. 2, 137–142.

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