recovery of rice bran oil using solid-liquid extraction technique

RECOVERY OF RICE BRAN OIL USING SOLID-LIQUIDEXTRACTION TECHNIQUEFARHAN JAVED1,2, SYED WAQAS AHMAD1,3, ABDUL REHMAN1, SHAHZAD ZAFAR1 andSHAHID RAZA MALIK2

1Department of Chemical and Polymer Engineering, Faisalabad Campus, University of Engineering and Technology Lahore, Faisalabad 58000,Pakistan2Department of Chemical Engineering, NFC Institute of Engineering and Fertilizer Research, Faisalabad, Pakistan

3Corresponding author.TEL: + 92 41 2433508;FAX: + 92 412433502;EMAIL: [email protected]

Received for Publication August 16, 2014Accepted for Publication October 9, 2014

doi:10.1111/jfpe.12166

ABSTRACT

Rice bran oil was extracted using five different solvents, namely acetone, SL-M1(75% acetone and 25% ethanol), SL-M2 (50% acetone and 50% ethanol), SL-M3(25% acetone and 75% ethanol) and ethanol. The effect of the solvent type on thepercentage recovery of the oil has been graphically represented and discussedwhen the temperature, contact time, solvent-bran ratio, stirring and pH were fixedat 50C, 30 min, 5:1, 90 rpm and 7.1, respectively. The results indicated that thepercentage recovery of rice bran oil was at the maximum when SL-M2 (50%ethanol and 50% acetone) was used as solvent. Further, the parametric effects onthe extraction process were also investigated and critically discussed. The qualityof the extracted rice bran oil was determined using Fourier Transform InfraredSpectroscopy (FTIR) analysis, saponification and acid values.

PRACTICAL APPLICATION

A significant amount of rice bran (contains 13–18% oil) is being wasted from ricemills of an agricultural country like Pakistan. Further, rice bran oil is an importantintermediate raw material for food and pharmaceutical industries. So, the presentexperimental studies composed of the recovery of the oil from rice bran throughan efficient and cost-effective method. For this purpose, pure ethanol, pureacetone and three compositionally different mixtures of ethanol and acetone wereused as solvents for the extraction process. Parametric effects were also investi-gated on the extraction process to collect the data for the economic processdesign.

INTRODUCTION

Rice bran, the by-product of rice milling process, is anatural source of antioxidants, minerals and oil because ofits complex composition (Oliveira et al. 2012). The compo-sition of the bran depends on the number of factors, namelyrice type, origin, soil composition, climate and the rice pro-cessing procedures (Saunders 1985; Sereewatthanawut et al.2008). On average, rice bran contains 12 to 25% oil, whichcan provide a significant amount of oil in an agriculturalcountry like Pakistan. Rice bran oil can be utilized in bothedible and nonedible industries (Prabhakar and Venkatesh1986; Renuka and Arumughan 2007). Among edible appli-cations, the rice bran oil can be utilized in place of vegetable

oil and also in the pharmaceutical industries (Liu andMamidipally 2005; Zullaikah et al. 2005). On the otherhand, nonedible rice bran oil is an attractive ingredient forcosmetics, soap and paint industries (Amarasinghe andGangodavilage 2004).

The rice bran oil can be separated either mechanically (bypressing) or physically (by solid-liquid extraction tech-nique) (Proctor and Bowen 1996; Pourali et al. 2009).Subcritical water, subcritical carbon dioxide and organicsolvents (Sharma et al. 2001; Pourali et al. 2009; Oliveiraet al. 2012) were used for the extraction of rice bran oil. Itwas reported that the yield of oil from rice bran can bemaximized using hexane as a solvent in the solid-liquidextraction technique (Hu et al. 1996). However, the

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Journal of Food Process Engineering ISSN 1745-4530

1Journal of Food Process Engineering •• (2014) ••–•• © 2014 Wiley Periodicals, Inc.

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hazardous and toxic nature (Herskowitz et al. 1971) ofhexane limits its use as a solvent. Ethanol attracts the atten-tion of the researchers for the extraction of vegetable andsoybean oil (Moreau and Hicks 2005; Franco et al. 2009).Further, the extraction conditions such as pH, temperature,contact time and solvent-bran ratio can alter the yield of therice bran oil in solid-liquid extraction process (Sivala et al.1991; Hu et al. 1996; Oliveira et al. 2012).

In present studies, the effect of the solvent type on therecovery of oil from the rice bran has been investigatedusing five different solvents, namely pure acetone, SL-M1(75% acetone and 25% ethanol), SL-M2 (50% acetone and50% ethanol), SL-M3 (25% acetone and 75% ethanol) andpure ethanol. Further, the effect of extraction conditions(temperature, contact time, stirring, solvent-bran ratio andpH) was also investigated to maximize the recovery of oilfrom rice bran. The effect of the parameter was presentedand discussed in the succeeding section. The quality of theoil was represented using FTIR analysis, saponification andacid values.

MATERIALS AND METHODOLOGY

Materials

Raw rice bran, for oil extraction, was collected from AdamRice Mills, Faisalabad, Pakistan. Laboratory grade ethanoland acetone, 99.5% pure, were purchased from Merck,Darmstadt Germany. Three types of solvent mixture werealso prepared by mixing ethanol and acetone, namelySL-M1 (75% acetone-25% ethanol [v/v]), SL-M2 (50%acetone-50% ethanol [v/v]) and SL-M3 (25% acetone-75%ethanol [v/v]).

Equipment

Extraction was conducted in an isothermal batch extractionunit, which was fitted with a thermostat, a stirrer and rpmcontroller assembly. After extraction, the solvent was recov-ered in a laboratory scale batch distillation unit.

Preparation and Analysis of Feedstock

Foreign materials, broken grains, hull pigments and paddykernels in raw rice bran were removed through screeningprocess using 100 mesh Tyler series sieve. After screening,stabilization of rice bran was carried out, which was per-formed by placing the screened feed stock in a refrigerationunit at 0C for 24 h. It will reduce the enzymatic activity thatcan make the bran rancid (Ju and Vali 2005; Zullaikah et al.2005). The quality of the rice bran sample is presented inTable 1, where the moisture contents were measured byheating the bran sample in an oven at 104C for 1 h while

ash contents were determined by placing the sample in amuffle furnace at 600C for half an hour. The oil and proteincontents in the rice bran sample were determined by usingSoxhlet extractor and Kjeldahl method (AOCS 1995).

Solvent Extraction Procedure

Initially, 200 mL of pure ethanol (solvent) is preheated inthe solvent extraction unit at 50C for half an hour. Afterpreheating, 40 g of stabilized rice bran was then added tothe extractor keeping solvent-bran ratio at 5:1 (v/w), whenthe temperature and pH were maintained at 50C and 7.1,respectively, while stirring was kept at 90 rpm. The extrac-tion process was carried out for half an hour and then filtra-tion was carried out to separate the defatted bran.Afterwards, the mixture was transferred to the batch distil-lation column for solvent recovery. The rice bran oil wascollected at the bottom of the column. Figure 1 presents thesummary of the solvent extraction procedure. Similar pro-cedure was repeated using acetone, SL-M1, SL-M2 andSL-M3 as solvents. The parametric (temperature, pH,contact time, solvent-bran ratio, stirring) effects on ricebran oil recovery were also graphically reported and dis-cussed in next section. The percentage recovery of the ricebran oil can be calculated using Eq. (1):

Percentage oil recoveryWeight of oil extracted

Weight of o=

iil in bran×100 (1)

RESULTS AND DISCUSSION

In the preceding section, the effect of the solvent type on thesolid-liquid extraction of rice bran oil has been determinedusing five solvents, i.e., ethanol, SL-M1, SL-M2, SL-M3 andacetone. Further, the effect of temperature, contact time,pH, rpm and solvent-bran ratio has also been discussedusing ethanol, SL-M2 and acetone.

Effect of Type of Solvent on Extraction

As discussed earlier, five different solvents were used for theextraction of rice bran oil, namely ethanol, SL-M1 (25%

TABLE 1. PROXIMATE ANALYSIS OF RICE BRAN SAMPLE

Constituent Percentage by weight

Moisture 9.9%Crude oil 14%Protein 13.07%Ash 6.53%Others (carbohydrates, fibers, starch) 56.5%

RICE BRAN OIL RECOVERY F. JAVED ET AL.

2 Journal of Food Process Engineering •• (2014) ••–•• © 2014 Wiley Periodicals, Inc.

ethanol and 75% acetone [v/v]), SL-M2 (50% ethanol and50% acetone [v/v]), SL-M3 (75% ethanol and 25% acetone[v/v]) and acetone keeping the temperature, solvent-branratio, contact time, rpm and pH at 50C, 5:1, 30 min, 90 and7.1, respectively. The effect of the solvent on the oil recoveryof rice bran has been determined and is presented in Fig. 2.It can be observed that the oil recovery in the presenceSL-M2 (i.e., 50% ethanol and 50% acetone) and ethanol isat the maximum as compared with other solvents.

Effect of Temperature on Extraction

The effect of temperature on solid-liquid extraction of ricebran oil is presented in Fig. 3. It can be deduced that as thetemperature increases the percentage oil recovery alsoincreases. It can also be observed that the increase in oilrecovery is sharp as temperature increases from 45 to 55C,while beyond that the increase in oil recovery becomes slug-gish. The percentage increase in the oil recovery is mainlydue to two factors: solubility and kinetic energy of mol-ecules. It is due to the fact that the extraction efficiency of asolvent depends on the solubility characteristics between thesolute and the extracting agent. The relative solvency behav-ior of a specific solvent is represented by the Hildebrand’ssolubility parameter; see Eq. (2) (Hildebrand and Scott1964).

δ = −ΔH RT

Vm

(2)

whereδ = Hildebrand’s solubility parameter (J1/2m−3/2)ΔH = heat of vaporization (J/kg)R = gas constant (J/mol/K)T = temperature (K)Vm = molar volume of extraction solvent (m3/mol)

It can be deduced from Eq. (2) that the solubility is thefunction of temperature, i.e., solubility increases with therise in temperature. Similar observations were practicallyreported by Saxena et al. (2011). So, with the rise in tem-perature, the oil-solvent solubility increases which isresponsible for the augmentation of the percentage oilrecovery. Furthermore, the rise in temperature can increasethe kinetic energy of the solvent molecules which may leadto increase oil solubility. Moreover, beyond 55C, the per-centage increase in the oil recovery becomes slugglish; it is

FIG. 1. SCHEMATIC DIAGRAM OF EXTRACTION PROCESS

75

76

77

78

79

80

81

Acetone SL-M1 SL-M2 SL-M3 Ethanol

Perc

enta

ge o

il re

cove

ry

Type of solvent

FIG. 2. EFFECT OF TYPE OF SOLVENT ON PERCENTAGE RECOVERY OFRICE BRAN OIL AT 50C, 90 RPM, SOLVENT-BRAN RATIO 5:1(v/w),30 MIN (CONTACT TIME) AND PH 7.1

70

75

80

85

30 35 40 45 50 55 60 65

Perc

enta

ge re

cove

ry o

f oil

Temperature °C

Ethanol

SL-M2

Acetone

FIG. 3. EFFECT OF EXTRACTION TEMPERATURE ON PERCENTAGE RICEBRAN OIL RECOVERY AT 90 RPM, SOLVENT-BRAN RATIO 5:1(v/w),30 MIN (CONTACT TIME) AND 7.1 PH

F. JAVED ET AL. RICE BRAN OIL RECOVERY


due to the formation of the free fatty acid (Hanmoungjaiet al. 2000) which can undergo saponification reaction in analkaline environment.

Effect of Stirring on Extraction

The influence of stirring on the percentage oil recovery ofthe rice bran in the solvent is presented in Fig. 4, whichindicates the slight increase in the oil recovery when revolu-tion per minute is increased from 100 to 150. It is due to thefact that at low rpm, the particles of the rice bran tend tosettle down and decrease the oil solubility in the solvent;therefore, increasing rpm can lead to better oil recovery.Further, it can also be observed that as rpm is increasedbeyond 150, there is hardly any change in the percentage oilrecovery; it is because at high rpm the rice bran oil tends toform emulsion (Hanmoungjai et al. 2000), which does notfavor the oil-solvent solubility.

Effect of Solvent-Bran Ratio on Extraction

The effect of solvent-bran ratio is presented in Fig. 5, whichshows that as the solvent ratio is increased from 3 to 7, thepercentage oil recovery of rice bran oil also increases from73% to 77.2%, 76.2% to 82% and 76% to 80.5% foracetone, SL-M2 and ethanol, respectively. It can also beobserved that as the solvent-bran ratio is increased from 7,the percentage increase in the oil recovery becomes nonsig-nificant. The increase in the percentage oil recovery with theincrease in the solvent-bran ratio can be explained on thebasis of the availability of fresh solvent surface (Amin andAbdallah 2012), i.e., the initial increase in the percentageoil recovery is due to the availabilty of the fresh solventsurface for the rice bran oil. When the solvent-bran ratioincreases from 7, most of the oil has already been extractedwhich makes this increase nonsignificant for percentage oilrecovery.

Effect of Contact Time on Extraction

The contact time is one of the important parameters thatcan affect the solid-liquid extraction. Figure 6 shows that asthe contact time increases from 30 to 50 min, the percentageoil recovery augments slightly. The increased oil recovery isdue to the fact that initially the concentration gradient ishigh, which acts as driving force in the physical phenom-enon (Amarasinghe and Gangodavilage 2004; Amin andAbdallah 2012). Similar observations can, theoretically, bededuced from Fick’s law, see Eq. (3), i.e., the mass transferrate is higher at high concentration of solute (Coulson andRichardson 1954).

dC

dt

kA C C

bVs= −( )

(3)

wheredC

dt= rate of change of concentration (k/gm3/s1)

k = diffusion coefficient (m2/s1)Cs = concentration of the saturated solution in contact

with solid particles (kg/m3)

70

75

80

85

80 100 120 140 160 180 200 220

Perc

enta

ge re

cove

ry o

f oil

RPM

Ethanol

SL-M2

Acetone

FIG. 4. EFFECT OF RPM ON PERCENTAGE RICE BRAN OIL RECOVERYAT 50C, SOLVENT-BRAN RATIO 5:1(v/w), 30 MIN (CONTACT TIME)AND 7.1 PH

70

75

80

85

2 3 4 5 6 7 8

Perc

enta

ge re

cove

ry o

f oil

Solvent-bran ratio

Ethanol

SL-M2

Acetone

FIG. 5. EFFECT OF SOLVENT-BRAN RATIO ON PERCENTAGE OILRECOVERY AT 50C, 90 RPM, 30 MIN (CONTACT TIME) AND 7.1 PH

70

75

80

85

25 30 35 40 45 50 55

Perc

enta

ge re

cove

ry o

f oil

Contact time (min)

Ethanol

SL-M2

Acetone

FIG. 6. EFFECT OF CONTACT TIME ON PERCENTAGE OIL RECOVERYAT 50C, 90 RPM, SOLVENT-BRAN RATIO 5:1(v/w) AND 7.1 PH)



C = concentration of the solute in bulk of the solution atany time t (kg/m3)

A = area of the solid-liquid interface (m2)b = effective thickness of the liquid film surrounding the

particles (m)V = volume of the solution (m3)

So, as time goes on, the concentration gradient decreaseswhich is reponsible for making the increase in oil recoveryinsignificant.

Effect of pH on Extraction

The effect of pH on the percentage oil recovery is presentedin Fig. 7, which indicates that by increasing pH from 3.8 to9, the percentage recovery of rice bran oil increases from75.8% to 80.9%, 73.4% to 82.3% and 74% to 77.2% forethanol, SL-M2 and acetone, respectively. During present

experiments, the pH of the solution was controlled byadding 0.1 N potassium hydroxide (KOH) solution and0.5 N hydrochloric acid (HCl) solution. It can be observedthat alkaline medium is suitable for oil extraction from ricebran. It is due to the fact that the rice bran oil is mainlycomposed of triacylglycerols (Hanmoungjai et al. 2000),which are alkaline in nature; therefore, at high pH, thesolvent can efficiently entrain the oil from rice bran.

Oil Quality

FTIR analyses were performed for the extracted rice bran oiland presented in Fig. 8, which indicates the sharp peaks at2,924 cm−1 and 1,710 cm−1 showing the presence of the freefatty acids (composed of linoleic acid, oleic acid, palmiticacid and stearic acid); similar analysis were reported byPourali et al. (2009). The saponification and acid value ofthe extracted oil were also determined using titremetricmethods (Einloft et al. 2007; Dimberu and Belete 2011),which were found to be 180 and 23, respectively, showingthat the extracted rice bran oil is suitable as a raw materialfor many industrial processes.

CONCLUSIONS

The present experimental investigations consist of therecovery of rice bran oil using solid-liquid extraction tech-nique. Pure ethanol, pure acetone, SL-M1 (75% acetone and25% ethanol), SL-M2 (50% acetone and 50% ethanol) andSL-M3 (25% acetone and 75% ethanol) were employed assolvents. It was found that the recovery of rice bran oil wasat the maximum when the mixture of 50% ethanol and50% acetone (i.e., SL-M2) was used as a solvent. Further, theeffect of extraction parameters was also studied. It can be

70

75

80

85

3 4 5 6 7 8 9

Perc

enta

ge re

cove

ry o

f oil

pH

Ethanol

SL-M2

Acetone

FIG. 7. EFFECT OF pH ON PERCENTAGE OIL RECOVERY AT 50C,90 RPM, SOLVENT-BRAN RATIO 5:1 (v/w) AND 30 MIN (CONTACTTIME)

FIG. 8. FTIR SPECTRA OF EXTRACTED RICE BRAN OIL

F. JAVED ET AL. RICE BRAN OIL RECOVERY


deduced because of the increasing solubility of rice bran oilin solvent that the recovery of rice bran oil increases withthe increment in the temperature. There was a little aug-mentation in the oil recovery when the contact time or stir-ring was increased. Moreover, solvent to bran ratio is aneminent parameter in solvent extraction process. As thesolvent-bran ratio increases from 1 to 7, the percentagerecovery of rice bran oil also increases because of the avail-ability of fresh solvent surface. Due to further increment inthe solvent-bran ratio, the rise in the value of percentagerecovery of rice bran oil becomes insignificant.

ACKNOWLEDGMENT

The technical and financial support for this research by Uni-versity of Engineering & Technology, Lahore, Pakistan isgratefully acknowledged.

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recovery of rice bran oil using solid-liquid extraction technique

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