AJOCT-Vol-1-Iss-4-P-1.pdf

American Journal of Oil and Chemical Technologies;

ISSN (online): 2326-6589; ISSN (print): 2326-6570

Volume 1, Issue 4, June 2013

1

Extraction of Olive Oil from Olive Cake using Soxhlet Apparatus

Banat, F1,2*, Pal, P1, Jwaied, N2 , Al-Rabadi, A2 1Department of Chemical Engineering, The Petroleum Institute, Abu Dhabi, U.A.E.

2Department of Chemical Engineering, Jordan University of Science and Technology, Jordan

[email protected]

Abstract:

Chemical extraction of olive oil from natural and dried olive cake (obtained from Alyarmouk

press, Irbid, Jordan) using organic solvents like hexane, ethanol, petroleum ether, isopropyl

alcohol and carbon tetrachloride was carried out in a Soxhlet extractor. Olive cake samples were

dried in an oven at 70°C and 105°C for 3.5 hours before being used in the extraction experiments.

Hexane was found to be the best extracting solvent with an oil yield of 12.7%. Oil yield increased

from 10% to 16% when olive cake was soaked with aqueous sodium chloride solution for 24

hours. Sorbitan monoleate surfactant enhanced the extraction of oil. Particle size of olive cake and

solvent volume had significant effect on oil extraction.

Keyword: Olive oil, extraction, choice of solvent, particle size, solvent-to-solid ratio

1. Introduction

World production of olive oil has constantly risen over the last ten years and Mediterranean

countries account for more than 90% of all the olive oil produced in the world [1]. Olive oil is

obtaining from olive fruit a natural product containing the wide range of bioactive compounds and

key component of the traditional Mediterranean diet. The olive fruit generally contains 50% water,

20% oil, 20% carbohydrates, organic acids, pigments, phenolic compounds and minerals as rest

[2]. The oil contains high levels of typical phenolics and 70% unsaturated fatty acids which are

believed to be associated with a relatively long life and good health [3]. Olive oil is usually

extracted by either mechanical pressing or chemical extraction processes. Mechanical pressing is

used to extract oil from olives on hydraulic presses which resulted in relatively high pure oil,

though it does not extract all of the oil and left the oil residue of about 8-20 weight %. The

chemical extraction requires organic solvent for oil extraction. The most widely used procedure

for oil removing from the solid matrix remains conventional Soxhlet extraction which is straight

forward and inexpensive [4]. In this process solvent extract olive oil by extraction using organic

solvent and the oil is separated from the solvent by distillation. For solvent extraction, the oil

recovered is not extra virgin oil and results in crude olive-pomace oil. It undergoes a refining

process to eliminate impurities and substances using soda, deodorants and bleaching agents at

high temperature. The extraction of oil depends on moisture content, nature of the solvent, time of

extraction, particle size and amount of solvent [5, 6]. Hexane is extensively used for oil extraction

because of its high stability, low greasy residual effects, boiling point and low corrosiveness [7].

Jordan contains huge reserves of energy sources as olive cake. In recent years; rising

environmental awareness in the Jordanian society has brought about concerns regarding the

handling and management of the large amounts of olive cake. Under the current regulatory statutes

mailto:[email protected]




2

and disposal practices, these amounts in many cases pose a disposal problem and constitute a

threat to the country’s very limited water resources [8].

The basic objective of this research was to determine most suitable solvent for olive oil yield using

Soxhlet extractor. To study the effect of oil yield with hexane as solvent dried olive cake at two

different temperatures and pretreated olive cake with sodium chloride were studied. The effect of

surfactants on oil extraction was also touched in this work. The work extends to examine the effect

of various process parameters like extraction time, volume of solvent, and particle size.

1. Materials and Methods

1.1. Materials

All the solvents (hexane, ethanol, petroleum ether, isopropanol and carbon tetrachloride) and the

surfactants (sorbiton monoleate, sorbiton trioleate and polyethylene glycol nonylphenyl ether

(synperonic NP10)) were purchased from Sigma-Aldrich Chemie GmbH, Germany.

1.2. Methods

1.2.1. Oil extraction using different types of organic solvent

Chemical extraction of olive oil from dried olive cake at 70ºC was carried out using hexane,

ethanol, petroleum ether, isopropanol and carbon tetrachloride to determine the best solvent for

oil extraction. 250 ml of solvent and 10 gram olive cake sample was used in each experiment to

maintain a solvent-to-solid ratio of 25:1. The total extraction process was completed within one

hour. The extracted phase was then distilled to separate the oil from the solvent.

Of all the solvents, petroleum ether, ethanol and hexane were used to study the oil yield with olive

cake (dried at 70oC) at different intervals of time to understand the oil extraction steps involved in

the process.

1.2.2. Drying of olive cake

To establish the optimum drying conditions of olive cakes, samples were dried at 70ºC and 105ºC.

10 gram of olive cake samples was then charged to Soxhlet extractor with 250 ml of hexane as

solvent to make a solvent-to-solid ratio 25:1 for 1 hour.

1.2.3. Pretreatment of olive cake with sodium chloride

Dried olive cakes were soaked in aqueous solution of sodium chloride with varying concentrations

(0.1M, 0.5M, 2M and 4M) for 24 hours and then filtered, rinsed with distilled water and dried in

an oven for 3.5 hours at 70°C. 10 gram of each soaked sample was taken and charged to a Soxhlet

extractor with hexane as a solvent for 1 hour. The extracted phase was then distilled to separate

the oil from hexane.

1.2.4. Effect of surfactants

To investigate the effect of surfactants (sorbitane monoleate, sorbitane trioleate and synperonic

NP10) on oil yield, 1.5 ml of surfactant was added to hexane solution. The solvent-to-solid ratio

was maintained at 25:1 for 1 hour of extraction time. The extraction processes was followed by

simple distillation processes to recover the oil.

2. Results and Discussions




3

Soxhlet extraction is a classical extraction technique to remove oil from biomass particle. It is

important to study the choice of solvent, extraction time and other process parameters for

measuring the % yield of the extracted oil.

The % yield of olive oil (y) is obtained as:

y = (Mass of olive oil extracted)*100/ (Initial weight of olive cake) (1)

2.1. Choice of solvents

The selection of solvent for oil extraction from olive cake is an important factor. The solvent

should have good extraction capacity, low viscosity and higher solubility with oil. Proper

penetration of the solvent inside the olive cake is necessary to extract oil effectively with nearly

equal polarity of the solvent and the oil. Generally, organic solvents possess all the above criteria

and are used for oil extraction since long years. Hexane, ethanol, petroleum ether, isopropanol and

carbon tetrachloride were used as organic solvents in this study to find the best solvent for oil

extraction. It was observed that amongst all the organic solvents used, hexane is the best extracting

solvent with a 10.6% yield as shown in Figure1.

Figure1. Effect of solvents on the yield of olive oil

Figure 2 shows the effect of extraction time over the oil yield on the Soxhlet extractor for three

different solvents (petroleum ether, ethanol and hexane). It was observed that oil yield increased

as time progressed and reached maximum after 1 hour. There are two steps involved in the oil

extraction from biomass. The first step involving the extraction of oil from the external surface of

the particle (solubility-controlled phase) is a very fast physical process while the second step

involving the extraction of oil from the inner particle (diffusion-controlled phase) is comparatively

slower [9]. Further increase in extraction time approached the oil extraction curve to a limiting

value of oil yield. This is an indication that the extraction process had almost reached completion.

For the extraction of oil from olive cake it was found that the extraction completion time was 1

hour.

0

2

4

6

8

10

12

Hexane Ethanol Petroleum

ether

Isopropanol Carbon

tetrachloride

% y

ield

Solvents




4

Figure2. Effect of Extraction time on the yield of oil using different types of solvents

2.2. Effect of drying olive cake

Drying caused removal of the moisture content from the olive cake samples and thus the resistance

to oil extraction was reduced. Also, drying before extraction helps rupture the olive cake walls

and thus the solvent can more readily dissolve into the oil. It was observed that by increasing the

drying temperature from 70ºC to 105ºC all the moisture content from olive cake was removed and

the yield of oil was increased from 10.6% to 12.7 % as compared to 7.5% from natural olive cake

(Figure3).

Figure3. Effect of drying of olive cake on the yield of olive oil

0

5

10

15

0 15 30 45 60

% y

ield

Extraction time, minute

Petroleum ether

Ethanol

Hexane

0

2

4

6

8

10

12

14

Natural Dried at 70°C Dried at 105°C

% y

ield




5

2.3. Effect of pretreatment with sodium chloride

Pretreatment of olive cake with aqueous sodium chloride solution had a significant effect on the

yield of oil as shown in Figure4. The oil yield increases with the increase of sodium chloride

concentration and reached a maximum of 16% at 2 (M) sodium chloride solutions. At lower

concentrations, sodium chloride had a strong tendency to rupture the olive cake cells which causes

easier mass transfer of oil and thus extraction of oil increases. A further increase of sodium

chloride concentration leads to decrease in the oil yield. The main reasons postulated are that

during osmotic processing to rupture the biomass cell, the rate of diffusion of solvent depends on

the concentration of the osmotic solution [10].

Figure 4. Effect of pretreatment with sodium chloride on olive oil yield

2.4. Effect of adding surfactants to hexane

Different non-ionic surfactants (sorbiton monoleate, sorbiton trioleate and synperonic NP10) were

used to investigate the effect of surfactant on yield of olive oil. It was observed that the percentage

yield was improved by adding various surfactants, especially to hexane with sorbitan monoleate.

The mobilization of oil molecules depends on the tendency of surfactants to reduce the capillary

forces (i.e. surface tensions) in olive cake and oil tends to adhere to the structure due to surface

tension. The effect of surfactants is to allow the aqueous phase to wet the solid surface

preferentially. The reduction in surface tension of surfactant solution can displace oil molecules

trapped in olive cake that cannot be displaced by pure hexane. As shown in Figure5, increasing

the sorbitan monoleate concentration increases the olive oil yield significantly.

13.5

14.5

15.5

16.5

0 1 2 3 4 5

% y

ield

Salt concentration, molar




6

Figure 5. Effect of surfactant concentration on the yield of oil

2.5. Effect of solvent-to-solid ratio

The effect of solvent-to-solid ratio on the oil extraction from olive cake is shown in Figure6. The

solvent-to-solid ratio was varied from 5:1 to 25:1 on olive oil extraction studies with 0.855 mm

particle size. As the solvent-to-solid ratio increased from 5:1 to 25:1 the oil yield also increased

from 5.4% to 15.6%. With further increase in solvent-to-solid ratio above 25:1 the oil yield

remains constant for olive oil extraction process. In an earlier work [11] much less olive oil yield

(9.4%) was obtained for solvent-to-solid ratio of 4:1 from olive cake using hexane as solvent.

Figure 6. Effect of solvent-to-solid ratio on oil yield

0

5

10

15

20

25

30

0 0.005 0.01 0.015 0.02

% y

ield

Surfactant concentration, molar

0

5

10

15

20

0 5 10 15 20 25 30

% y

ield

,

Solvent-to-soild ratio, ml/gram




7

2.6. Effect of Particle Size

Particle size is an important parameter in extraction of oil process. Smaller the size of solid

particles, the greater the interfacial area between the solid and the liquid and therefore increases

the oil extraction yield [12]. The maximum olive oil extraction of 18.6% was obtained at 0.212

mm of olive cake having solvent-to-solid ratio of 20:1 for 1 hour. It was observed that oil

extraction yield was gradually increased from 15.3% to 18.6% with decrease in particle size from

0.855 mm to 0.212 mm. Different researchers have studied the effect of particle size for the

extraction of oil from different biomass [13, 14] and it has been observed that oil yield increases

with decrease in particle size. As the particle size increases it is difficult for the solvent to reach

core of the biomass to leach oil and the oil yield decreases.

Figure7. Effect of particle size on the yield of oil

3. Conclusion

Different solvents were used to observe the yield of olive oil using Soxhlet apparatus. Hexane was

found to be the best extracting solvent with an oil yield of 7.5 % from natural olive cake and 12.7

% from dried samples. Oil yield can be increased by soaking olive cake samples with aqueous

sodium chloride solution with optimum concentration of 2.0 M with 16% oil yield. Extraction of

oil using surfactant solution like sorbitan monoleate with hexane enhanced the extraction process

at high concentrations of surfactant (0.019 molar). Solvent-to-solid ratio has significant effect on

oil yield and with 20:1 hexane-to-olive cake ratio maximum yield of oil was obtained. As the

particle size of the olive cake decreases oil yield increases.

4. Acknowledgement

The work has been carried out at Jordan University of Science and Technology.




8

5. References:

[1] FAOSTAT, 2009. Crops Processed Data for olive oil. Available at:

faostat.fao.org/site/636/DesktopDefault.aspx , PageID¼636#ancor accessed March 2011.

[2] F. Visioli, C. Galli, Olive oil phenols and their potential effects on human health, Journal of

Agricultural and Food Chemistry, 46, 4292–4296, 1998.

[3] S. Gurbuz, N. Kiran-Ciliz and O.Yenigun, “Cleaner production implementation through

process modifications for selected SMEs in Turkish olive oil production’’, Journal of cleaner

production ,12, 613-621, 2004.

[4] L. Najafian, A. Ghodsvali, M.H. Haddad Khodaparast, L.L. Diosady, Aqueous extraction of

virgin olive oil using industrial enzymes, Food Research International, 42, 171–175, 2009.

[5] R. Chaiklahana, N. Chirasuwana, V. Lohab and B. Bunnagc, “Lipid and fatty acids extraction

from the cyanobacterium Spirulina” ScienceAsia, 34, 299-305, 2008.

[6] M. N. Siddiquee and S. Rohani, “Lipid extraction and biodiesel production from municipal

sewage sludges: A review”, Renewable and Sustainable Energy Reviews, 15, 1067–1072, 2011.

[7] ISO 659-1988 (E) International Organization for Standardization (ISO); Geneva, Switzerland:

1988.

[8] Al-Widyan, Al-Jalil, Abu-Zreig and Abu-Hamdeh,’’Physical durability and stability of olive

cake briquettes’’, Canadian biosystem engineering, 40, 41-45, 2002.

[9] A. N. Mustapa, Z. A. Manan, C. Y. M. Azizi, N. A. N. Norulaini, A. K. M. Omar, “Effects of

parameters on yield for sub-critical R134a extraction of palm oil”, Journal of Food Engineering,

95, 606-616, 2009.

[10] N.K. Rastogi, M. N. Eshtisghi, D. Knorr, “Accelerated mass transfer during osmotic

dehydration of high intensity electrical fieldpulse pretreated carrots”, Journal of Food Science,

64, 1020–1023, 1999.

[11] H. Kadi and H. Fellag, “Modeling of oil extraction from olive foot cake using hexane”,

Grasas y Aceites, 52, 6, 369-372, 52, 2001.

[12] T. Suganya and S. Renganathan, “Optimization and kinetic studies on algal oil extraction

from marine macroalgae Ulva lactuca”, Bioresource Technology, 107, 319–326, 2012.

[13] J. Qian, F. Wang, S. Liu, Z. Yun, “In situ alkaline transesterification of cottonseed oil for

production of biodiesel and nontoxic cottonseed meal”, Bioresource Technology, 99, 18, 9009-

9012, 2008.

[14] X. Han, L. Cheng, R. Zhang, J. Bi, “Extraction of safflower seed oil by supercritical CO2”,

Journal of Food Engineering, 92, 370-376, 2009.

http://www.faostat.fao.org/site/636/DesktopDefault.aspx

Documents

AJOCT-Vol-1-Iss-4-P-1.pdf