Refining of Crude Canola Oil Using PSA Ultrafiltration Membrane

International Journal of Food
Ultrafiltration Membrane
Seyed Mohammad Ali Razavi, Ferdowsi University of
Mashhad (FUM), Iran
Mashhad (FUM), Iran
Recommended Citation:
Rafe, Ali; Razavi, Seyed Mohammad Ali; and Haddad Khodaparast, M.H. (2012) "Refining of
Crude Canola Oil using PSA Ultrafiltration Membrane," International Journal of Food
Engineering : Vol. 8: Iss. 2, Article 2.
DOI: 10.1515/1556-3758.1931
Authenticated | s razavi@um ac ir
Download Date | 6/10/12 4:52 PM

Ultrafiltration Membrane
Ali Rafe, Seyed Mohammad Ali Razavi, and M.H. Haddad Khodaparast
Abstract The aim of this paper was to study the behavior of spiral wound configuration of polysulfone
amide (PSA) membrane with 20 kDa molecular weight cut off (MWCO) in pilot-plant scale
equipment used for refining micella canola oil under different operating conditions. Refining
process parameters including phospholipids (PLs), color and free fatty acids (FFAs) were measured
to express retentions (R%) and the permeate flux, membrane fouling and hydraulic resistances
were determined to analyze the ultrafiltration process performance. The results showed that the
permeate flux was decreased considerably with increasing process time, although it was increased
by increasing temperature from 30 to 50C and transmembrane pressure from 1.5 to 2 bar. The
irreversible fouling resistance (Rif) and percentage of fouling were decreased as the temperature
or transmembrane pressure increased. The concentration polarization resistance (Rrf) was much
higher than other resistances; therefore reversible resistance had an important role in total hydraulic
resistance. The retention of PLs, FFAs and color was so interesting since it can improve greatly
the efficiency of oil refining process. The retention of PLs and FFAs was increased by temperature
and decreased by transmembrane pressure and time; however, there was no significant difference
in removing color under different operating conditions.
KEYWORDS: membrane, crude oil, hydraulic resistance, flux, retention
Author Notes: The authors are grateful to Professor Migel Mattea for his guidance and giving
information to us. Furthermore, the Fazl Neyshabour Company for providing crude canola oil and
industrial hexane.

Considering rapid population growth, the urgency for improving major food sources, seems quite obvious. Oilseeds are after cereals the second major food
supply sources in the world (Shariati and Ghazi, 2000). Canola is one of the most
important oilseed crops of the world, as its production over the last 10 years has grown much faster than any other source of vegetable oil (Shahidi, 1990). In
2005-2006, the world production of rapeseed/canola was about 44.8 million tons
of oilseeds (FAO, 2006). It is now the second most important source of vegetable
oil in the world after soybean. During the past 20 years, this crop has passed peanut, sunflower and, most recently, cottonseed in worldwide production. It
contains approximately 40% oil and yields a meal containing about 38-43%
protein (Raymer, 2002). The ratio of linoleic to linolenic acid in canola oil is 2:1 and this is considered to be a well balanced ratio for human nutrition.
Furthermore, its protein meal is well balanced, and perhaps may commercially be
upgraded for human consumption in near future (Shahidi, 1990). Canola oil is widely used as cooking oil, salad oil, and in making margarine. It is lower in
saturated fats than any other vegetable oil, making it a popular choice among
health-conscious consumers (Raymer, 2002).
Crude canola oil is obtained mainly by crushing canola seeds, followed by solvent extraction. Approximately 20% of oil is extracted in the first stage and
canola oil meal contains 2-3% oil. Crude vegetable oils are constituted mainly of
triacylglycerols, but contain some minor components such as phospholipids (PLs), free fatty acids (FFAs), sterols, coloring pigments, proteins and oxidation
products, which can adversely affect the end-product and the processing
efficiency (Padley, et al., 1994). These substances may impart undesirable flavor and color, and shorten the shelf-life of oil. Therefore, crude vegetable oils
undergo complex refining processes including degumming, neutralization, washing, drying, bleaching, filtration and deodorization to achieve the desired
quality. Due to the multi-step refining process, large amounts of energy are
consumed to heat and cool the oil as well as to provide power to pumps, centrifuges and other equipment. The energy usage can range from 4600 to 9300
KJ for each kilogram of finished oil, depending upon the age of equipments used.
Neutral oils constitute about 25-40% of the soap stocks and phospholipids gums,
which are thus lost (Gupta, 1997). In addition, solid waste and heavily polluted effluents are produced. Oil refining at high temperature favors isomerization of
double bonds. Although, some improvements have been made in process
engineering and equipment design, the basic principles of edible oil refining have not changed in the last 70 years (Koseoglu, 1991). As a result, the refining
process has many drawbacks, such as high-energy demand, loss of neutral oil, use
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Published by De Gruyter, 2012

of large amounts of water and chemicals, heavily polluted effluents and loss of
nutrients (Subramanian, et al., 2001).
Membrane processes can be used in many areas of the vegetable oil industry. Some applications involving the extraction and refining of vegetable oils
are now established– for example, degumming– while others are still under
development. Membrane processes in vegetable oil industry include solvent recovery by reverse osmosis (RO) or nanofiltration (NF), de-acidification by NF,
de-waxing by microfiltration (MF), recovery of hydrogenation catalysts by MF,
nitrogen production for packaging applications by gas separation (GS), and
wastewater treatment by MF, NF and RO. Performance of membrane separation is affected by membrane composition, temperature, pressure, velocity of flow and
interactions between components of the feedstock and with the membrane
surface. The application of membranes in edible oil refining has been investigated for their potential for energy savings as well as their potential for improvement in
the oil quality (Subramanian, et al., 2001), allowing combination of degumming
and bleaching into a single step, thereby reducing energy requirements and making the use of chemicals unnecessary. In addition, membranes could play a
role in the refining of mechanically extracted oil (Ebert and Cuperus, 1999).
Phospholipids and triacylglycerols have similar molecular weights, about 700–
900Da, which makes them difficult to be separated by membrane. However, phospholipids are surfactants, having both hydrophobic and hydrophilic groups,
and form reverse micelles in non-aqueous systems such as vegetable oils and
oil/hexane miscella that enable their separation using appropriate membranes (Lin, et al., 1997). Gupta (1977) reported that the molecular size of the miscella
formed is about 20,000Da or more. In other words, miscella greatly increases the
effective particle size of the phospholipids (In-Chul, et al., 2002). It should be interesting to apply membrane technology immediately after the extraction stage,
where the composition of oil/hexane miscella is usually found in the 1:3 range, which implies gains in terms of permeate flux, due to the lower viscosity of this
solution compared to the desolventized crude oil. The membrane-based crude oil
degumming produces permeate and retentate fractions containing triacylglycerols and phospholipids, respectively. The majority of the coloring materials and some
of the FFAs and other impurities are included in the phospholipids micelles and
removed as well. The investment needed for a new refining plant is very high
compared to the low price of the end product and because these processes are now well established, generally speaking the industry is not looking for another
technology. In spite of this, the diversification of the non food uses of vegetable
oils would ask for technical innovations. As a matter of fact, oil refining could take advantage of emerging technologies such as membrane based processes.
There are several papers dealing with ultrafiltration (UF) of miscella for removing
solvent or for refining of vegetable oils (Gupta, 1978; Koseoglu, and Lusas, 1989;
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International Journal of Food Engineering, Vol. 8 [2012], Iss. 2, Art. 2

Koseoglu, and Engelau, 1990; Raman, Rajagopalan, and Cheryan, 1994). These
processes involve a solvent to solubilize and extract the FFA with or without
using sodium hydroxide or ammonia. Concerning the removal of FFA and PLS simultaneously, a few patents described dead-end microfiltration (MF) based
refining of oils (Segers, and van der Sande, 1990). Ceramic ultrafiltration
membranes are also used for non-solvent sunflower oil degumming (Koris and Marki, 2006). Recently, the development of hexane-resistant membranes have
created opportunities for applying membrane technology to crude vegetable oil
refining to simplify the whole process, reduce energy consumption and reduce
wastewater production (Lin, et al., 1997). The potential energy savings from the implementation of this technology in the US alone was estimated to be 15-22
trillion kJ per year (Koseoglu, and. Engelgau, 1990).
With regarding to, the non-aqueous systems such as oil-hexane- phospholipids have not enough information in the literature and the fastest
growing separation technique in the food industry - the membrane-based
separations; it is still interesting to study these systems. Therefore, the purpose of this study were to (i) investigate polysulfone amide UF membrane for their flux
and selectivity during membrane degumming of crude canola oil and (ii)
determine the separation efficiency under various operating conditions.
2. MATERIAL AND METHODS
2.1 Samples
Canola oil miscella was prepared by mixing 25% (w/w) crude canola oil with 75 % (w/w) industrial grade hexane. Crude canola oil and hexane were supplied by
Seh Gol Khorasn Co., Fazle Neyshabour, Iran, Industrial grade of hexane is a
mixture of alkenes, which composition is approximately 50% n-hexane, 45%
hexane isomers and 5% of other hydrocarbons and is the commercial solvent used in the edible oil industry.
2.2 UF operation and cleaning procedure
Spiral wound configuration of polysulfone amide (PSA) membrane with 20 kDa
molecular weight cut off (MWCO) was used in these experiments (ARS-0.3,
Biocon Company, Moscow, 1999). The characteristics of PSA membrane are pointed out in Table 1.
Experiments were performed in a cross-flow UF pilot-plant system
equipped to stainless-steel feed tank of 15 L, centrifugal pump, flow meter, UF module, two pressure gauges, tubular heat exchanger, digital thermometer and
two control valves. The device requires external heating and cooling that was
controlled by circulating hot/cold water from a tubular heat exchanger. A
3

schematic diagram of the experimental set-up used in refining of canola oil
miscella is shown in Fig. 1.
Table 1. Specification of PSA ultrafiltration membrane used in this study.
ValueUnitMembrane Specification ARS-0.3
0.33m2 Effective surface
2-12- pH range
0-5 barPressure range
In this research work, the water flux of PSA membrane is firstly measured during 15 min operation and the average of fluxes are calculated. Subsequently,
the membrane is cleaned with some hexane to remove the remained water.
Membrane–solvent interactions can be expected to vary with changes in the solvent properties, such as viscosity, molecular size, surface tension and dielectric
constant. It was shown that hexane has the best flux and low fouling by polyimide
ultrafiltration membrane (In-Chul, et al., 2002). Hexane flux is evaluated similar to water flux under different operating conditions (Rafe, and Razavi, 2009). Then,
the feed tank was charged with about 12 liter canola oil miscella, filtration was
carried out and permeate samples were collected and weighed in regular time
intervals (from 1 min to 30 min) by an electronic balance in order to determine the permeate flux.
Canola oil miscella filtrations were performed at different operating
conditions including transmembrane pressure at two levels of 1.5 & 2 bar, temperature at three levels of 30, 40 & 50 C, and process time at two levels of 15
& 30 min. The hexane flux after miscella ultrafiltration process is measured again to evaluate fouling of the membrane.
After each run, the membrane was cleaned to reach the initial flux. The
cleaning process was performed by using alkaline and acidic detergents. First of all, the membrane was rinsed with warm distilled water for about 15 min. The
alkaline agent was a 1% solution of a commercial detergent (Rodan-Plus Ltd Co.,
Denmark) for 45 min, and the acidic agent was a 0.1% solution of nitric acid (lab grade) for 15 min. Between the alkaline and acidic cleaning steps, and at the end
of cleaning process, membrane was rinsed again with warm distilled water for
about 15 min. The temperature during cleaning of the membrane was 50 C in all
experiments.
4

Fig. 1. A schematic diagram of the experimental set-up UF membrane used
2.3 Process performance parameters
One of the main purposes of this research was to evaluate the process
performance of UF PSA membrane in refining crude canola oil that to be replaced
by conventional refining process. Therefore, the following parameters were determined:
1. Refining process performance parameters including PLs, color and
FFAs. 2. Ultrafiltration process performance parameters including permeate flux,
membrane fouling, hydraulic resistances, and retentions of phospholipids, color
and other impurities. Percent of membrane fouling was obtained by replacing the values of
hexane flux before and after miscella UF process in the following equation
(Cheryan, 1998):
J J (1)
Where, Jh was flux of hexane before filtration and Jfh was flux of hexane
after miscella filtration.

) was determined by
measuring the flux and viscosity at different operating conditions and substituting
the values obtained in the following equation (Cheryan, 1998):
mh h
TMP J
µ = (2)
Where, μh was the dynamic viscosity of hexane (Pa.s), Jh was the hexane permeate flux (m
3 /m
2 .s) and TMP is the transmembrane pressure (Pa), which can
be calculated for a crossflow ultrafiltration by the following relationship:
p oi P
P P TMP −
2 (3)
Where, Pi and Po are inlet and outlet pressures, respectively and P p is filtrate (or permeate) pressure.
The total hydraulic resistance (R T, m -1
) to permeate flux was calculated by
applying the resistance-in-series model or boundary layer-adsorption model as follow (Lin, et al., 1997):
p p T
TMP R
µ = (4)
Where, μ p was the miscella permeate viscosity and J p was the miscella permeate flux. In fact, the total hydraulic resistance is sum of membrane hydraulic
resistance and overall fouling resistance (Cheryan, 1998; Pioch, et al., 1998):
F mT R R R += (5)
Therefore:
TMP R −=
µ (6)
The overall fouling resistance (R F) can be represented as sum of the two
components on basis resistance-in-resistance model: resistance due to reversible
6

fouling or concentration polarization (R rf ) and resistance due to irreversible
fouling (R if ). The fouling resistances were determined as:
m
if F rf R R R −= (8)
Where, μhf and Jhf were the viscosity and flux of hexane through a fouled membrane, respectively. At the end of miscella ultrafiltration, the membrane unit
was firstly flushed with industrial hexane at the same conditions of each run. Then
the permeate hexane flux (Jhf ) and viscosity (μhf ) of fouled membrane was measured for calculation of irreversible fouling resistance (R if ) based on equation
(Koseoglu, 1991).
Miscella permeate and hexane are Newtonian fluids, therefore the kinematic viscosity ( ν, m
2 .s
Ostwald-Canon-Fenske viscometer. Density of samples (ρ, kg.m -3
) was
determined by a 25ml pycnometer at the same temperature. Then, dynamic viscosity (μ, Pa.s) was calculated by the following relationship (Darby, 2001):
Kt ==
ρ
µ υ (9)
Where, K was the instrument conversion factor for capillary viscometer and t was efflux time.
The performance of the membrane process was also expressed in terms of
the retention of feed components. Miscella permeate samples were collected in
regular time intervals in order to determine the removal percentage (R%) of phospholipids (PLs), free fatty acids (FFAs) and color pigments according to the
following formula (Cheryan, 1998):
C C R (10)
Where, Cf and C p were the concentration of each component in the feed
and permeate streams, respectively.

2.4 Chemical analysis
2.4.1 Phosphorous content
The phosphorus content was measured by the standard molybdenum blue, AOCS
method Ca12-55 (Firestone, 1989). The total phospholipids content was determined by multiplying phosphorus content by 30. This method determines
phosphorus by ashing the oil sample in the presence of zinc oxide, followed by
the spectrophotometric measurement of phosphorus as a blue phosphomolybdic
acid complex.
The FFAs content was analyzed using AOCS method Ca5a-40 (Firestone,
1989).This method determines the FFAs in oils by alkali neutralization and
percentage of FFAs is usually expressed as oleic acid.
2.4.3 Color measurement
Color was measured using the Lovibond tintometer method of AOCS Cc13e-92 by a glass cell with an optical path length of 10 mm (Firestone, 1989). The results
are expressed as R, Y and B values, which means the value of redness, yellowness
and blueness, respectively.
2.5 Statistical analysis
Three runs were performed with membrane under each experimental condition
considered. All the measurements were carried out at least in duplicate. All of the
charts were prepared by Microsoft Excel software (2003). In addition, all of the regression equations and model validating parameters (correlation coefficient, R;
coefficient of determination, R 2 , and adjusted R square, Adj. R
2 ) were determined
3. RESULTS AND DISCUSSIONS
3.1 Ultrafiltration process performance
The membrane performance parameters of canola miscella oil are including
permeate flux, hydraulic resistances and components retention as function of operating conditions are shown in Figs. 2-5, Tables 2-3 and Figs. 6-9,
respectively.
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3.1.1 Permeate Flux
The results show that permeate flux was decreased considerably with increasing process time, and after almost 10 minutes running, the flux reached to the stable
flux or the fluctuation was less (Figs. 2 & 3). Also, according to these figures the
fluxes are really getting down to zero after 29 minutes. The preliminary time of process to reach this stability is depended on the properties of the feed solution,
the characteristics of membrane and the conditions of operating process. It may be
possible that the transport occurs mainly by convection transport and partly due to
solution-diffusion mechanism (Subramanian et al., 2001). By comparison between Fig. 2 and 3, it is concluded that the permeate
flux was increased by increasing temperature from 30 to 50 C and transmembrane
pressure from 1.5 to 2 bar. Furthermore, the miscella permeate flux was observed much lower than commercial hexane flux (Fig. 4). It may be due to higher
viscosity of miscella and presence of fine particles of canola seed which were
introduced to the oil during the extraction process. On the other hand, oil impurities particularly phospholipids may be increased hydraulic resistance and
membrane fouling. Marenchino, Pagliero and Mattea (2006) have used lab scale
UF module using tubular inorganic membranes in order to refining 25% crude
soybean–hexane mixture and reached to the similar results obtained.
Fig. 2. Permeate flux of canola miscella oil at transmembrane pressure of 1.5 bar and
different temperatures (, T=30oC;, T=40oC &, T=50oC)
The influence of pressure and temperature on average permeate flux under
pseudo-steady state is presented in Fig. 5. It can be seen that the permeate flux
9

rose when the pressure increased from 1.5 to 2 bar, which is expected from
Poiseuille-Hagen law, although the flux increasing was greater at higher
temperature. Therefore, there was no compaction of membrane for the pressure range used in this study. This result has been also reported by Pioch et al. (1998)
and Kartica et al. (1998).
Fig. 3. Permeate flux of canola miscella oil at transmembrane pressure of 2 bar and
different temperatures (, T=30 o C;, T=40
o C &, T=50
L / m
2 . h
Fig. 4. Average hexane flux of canola miscella oil as function of temperature and
transmembrane pressure (, T=30 o C; , T=40
o C;, T=50
10

Fig. 5. Average permeate flux of canola miscella oil in pseudo-steady state as a function of temperature and transmembrane pressure (, T=30oC;, T=40oC &, T=50oC)
Two features are most important for a successful membrane application;
good fluxes and high retentions. Solute-solvent-surface interactions have a significant effect on both of these features. For high fluxes, it is desired to have
maximum solvent-surface (membrane) and minimum solute-surface interactions.
High solute-surface interactions lead to fouling, which results in a continuous flux decline during the separation process (Gupta, and Muralidhara, 2001). This
subject has been studied slightly by others (Belfort, Davis, and Zydney, 1994;
Jonsson, 1995; Song, 1998), and the mechanism was somewhat understood.
3.1.2 Hydraulic resistances
The results obtained for the hydraulic resistances are summarized in Table 2. The inherent membrane resistance was slope of the curve of hexane flux versus TMP
according to the Eq. 2, as shown in Fig. 4. The membrane resistance to fouling
(R m) was 1, 1.12 and 1.11 m -1
at temperatures 30, 40 and 50 C, respectively, and the average value of membrane resistance was obtained 1.079 m
-1 in this study. It
can be also found that the irreversible fouling resistance (R if ) and the percentage
of fouling were decreased as the temperature increased from 30 to 50 o C (Tables 2
& 3). It may be due to lowering the viscosity of canola oil, although the
percentage of fouling was still so high. By increasing transmembrane pressure,
the irreversible fouling and percentage of fouling was decreased a little due to the
more impetus force and get farther the impurities of membrane. Perhaps, in order
11

to increase working life of membrane, it is preferable to operate as much as
possible in the high temperature and pressure. On the other hand, the results
showed that the concentration polarization resistance (R rf ) was much higher than other resistances (about 50% of total resistance), therefore reversible resistance
had an important role in total hydraulic resistance. In this research, the average of
polarization resistance was obtained 2.35 m -1
. By increasing transmembrane pressure, total resistance (R T) was increased, whereas polarization resistance was
lowered as pressure increased. As temperature increased from 30 to 50 o C, both
R rf and R T were increased.
Table 2. The hydraulic resistances of ultrafiltration of canola miscella oil under different
operating conditions
2.0 1 1.15 1.63 4.47
40 1.5 1.12 1.11 2.04 4.74
2.0 1.10 1.08 1.88 5.06
50 1.5 1.11 1.07 2.58 5.14
2.0 1.09 1.04 2.38 5.75
Average - 1.079 1.026 2.35 4.93
Percent - 22% 21% 47% 100%
Table 3. Percent of membrane fouling during ultrafiltration of canola miscella oil under
different operating conditions
40 1.5 62.6
2.0 56.2
The membrane fouling may be related to the much amount of fine
particles in crude canola oil, membrane configuration (which is spiral wound) and
also the low MWCO of membrane. It is also important to note that membrane can be reached to the initial flux by cleaning procedure mentioned in the materials and
methods. In some situations, it is desired to have a minimum solid–surfactant and
maximum solid–liquid interactions and in other situations vice versa. Fouling of membrane separation processes are good examples where a minimum solid–
surfactant interaction is preferred (Gupta, and Muralidhara, 2001).
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3.2 Refining performance parameters
The main goal of membrane application technology in edible oil industry is
refining crude oil, therefore refining crude canola oil parameters by using UF process was evaluated and compared with conventional refining.
3.2.1 Retention of phospholipids
The content of phosphorous of canola oil was approximately 527 ppm. The characteristic of bleached canola oil after caustic refining and acid degumming is
shown in Table 4 (Apple, 1985). As can be found that solvent oil extraction
caused to introduce more phospholipids to oil, wherein pressed oil extraction had lower phospholipids. During the conventional degumming, more content of
phospholipids is removed, but its content did not approach to zero. It is important
to know the phospholipids retention by membrane processing. Therefore, the retention of phospholipids during membrane filtration was determined, and the
amount of phospholipids in permeate flux was measured at different operating
conditions. The obtained results are shown in the Table 5. It can be found that
ultrafiltration process of canola miscella oil was showed high efficiency in removing phospholipids (99.6%). Lin et al (1997) reported high reduction of
phospholipids during membrane filtration of crude vegetable oils. As the
temperature increases, retention is decreased that may be due to dissolution of phospholipids or disruption micelle structure (Figs. 6 & 7). In addition, percent of
PLs retention is increased as operation time and TMP increased.
Table 4. A comparison between bleached canola oil after caustic refining and acid
degumming
00Peroxide value (meq/kg) 1-31-3Anisidine value
1-131-13Sulfur (ppm) 00Soap (ppm)
The correlation between temperature, TMP and time on PLs retention are
given in the following equation, which can be used for prediction of PLs
retention:
R = 0.958, R 2 = 0.917 & Adj. R
2 = 0.886

The mentioned equation implies that temperature had a positive effect on
removing PLs, whereas time and pressure had a negative effect on PLs reduction.
Therefore, it is better to work at high temperature and low pressure for having the high efficiency. The literature in the removing PLs from crude oil has shown its
effectiveness. For example, Lin et al (1997) found that the UF process can remove
approximately 99.6% phospholipids from crude soy oil. Some oils such as sunflower, rapeseed and cottonseed oil were completely degummed and can be
directly refined by physical refining (Patterson, 1992).
Table 5. Amount of phospholipids in the permeate flux at different operating conditions
Phospholipids (%)Elapsed time (min)TMP (bar)Temperature (oC)
15.8115
Temperature, °C
%
Fig. 6. Retention of phospholipids (PLs) at transmembrane pressure of 2 bar and different temperatures (, Time 15 min; , Time 30 min)
14

h o
l i p i d s r e t e n
t i o n ,
%
Fig. 7. Retention of phospholipids (PLs) at transmembrane pressure of 1.5 bar and
different temperatures (, Time 15 min;, Time 30 min)
3.2.2 Retention of free fatty acids (FFAs)
In spite of many investigation and trails carried out for de-acidification of edible
oils (physical, chemical and biological methods), many difficulties still exist for
removing free fatty acids from edible oils. Several researchers have also
attempted the de-acidification of vegetable oils with and without solvents, by using porous as well as nonporous membranes (Bhosle, 2005).
One of the main parameters in refining crude oil is the content of FFA. The more FFA content in oil caused more oil loss during refining process. As an
example the oil has 1% FFA, oil loss was about 1 to 4%. Therefore, decreasing
FFA content is very important and economical factor in refining process. Crude canola oil has 1.36% FFA and its acidity was 2.72%. But after membrane
processing, the percentage of FFA was averagely decreased to 0.8% and it means
the free fatty acids has lowered 40% and by considering two percent oil loss during process, the total oil loss will be 1.6%. Therefore, by using membrane
technology, about 16 kg oil will be lost for 1 ton oil processed. In conventional
process, oil loss was 27 kg oil that it is so much in high volume of production. For finding optimum conditions of UF process for removing FFA, percent
of FFA retention was measured, and can be seen in the Figs. 8 & 9; by increasing
temperature from 30 to 40 C retention of FFA was increased and then decreased.
Percent of FFA retention, as time and pressure progress was increased that may be
15

possible due to the entrapment FFA in the PL micelles. The statistical analysis is
shown that the optimum operating process to reach the proper flux by using 20
KDa PSA membranes was 40 C and 2 bar pressure. But for adopting in industrial scale, the flux and time of process is low and needs more investigation. The
reason of low retention of FFA in 50 C may be found for preferential permeation
that the FFA interlink to the micelle and could not be passed through membrane in this temperature.
10
15
20
25
30
35
40
45
50
55
60
Temperature, °C
%
Fig. 8. Effect of temperature and process time on FFA retention at 1.5 bar transmembrane
pressure (, Time 15 min; , Time 30 min)
45
46
47
48
49
50
51
52
53
54
55
Temperature, °C
%
Fig. 9. Effect of temperature and process time on FFA retention at 2.0 bar transmembrane
pressure (, Time 15 min; , Time 30 min)
16

3.2.3 Color retention
Crude canola oil has a brown to greenish color. One sample of oil is shown in the Fig 10a. Canola oil is one of the most difficult oil in refining for having darker
color and high content of chlorophyll; it needs more bleaching earth and
therefore, imposes more charge for refining. In the other words, the disposal of bleaching earth has the environmental difficulties. The Lovibond has showed the
color of crude canola oil 8.1R+85Y+5.2B, but canola miscella has
7.6R+74Y+3.5B color that it may be for adding solvent to oil and the color
apparently decreased (Fig 10b). By applying membrane technology, the color of canola oil was decreased
as much as possible, but operating conditions did not have a distinct effect on
color. In the other hand, time, pressure and temperature has not important effect on color of canola. Also, the statistical analysis did not show the significance
effect. Typical samples of permeate and retentate of canola miscella is shown in
the Fig. 10c. As can be seen, the effect of UF operation conditions (pressure, time and temperature) on canola oil bleaching (color removing) are not considerable
that may be due to entrapment of color pigment in phospholipids micelles (Lin, et
al., 1997). Any way, color of miscella after UF treatment was decreased to
1.1R+22.4Y+0.1B which is not necessary to bleach the oil or may need little amount of bleach earth.
The presence of chlorophyll in crude edible oils, particularly canola oil, is
a difficulty in the process of refining oil and there are many drawbacks in the bleaching of oils (Apple, 1985). The literature showed that color improvement
was occurred in the degumming and bleaching steps, but complete removal of
chlorophyll is depend on conducting bleaching process. Furthermore, by using membrane degumming, bleaching is not so much necessary and neutralization has
carry out rationally.
4. CONCLUSION
This study shows that membrane separation by PSA 20 kDa membrane is
effective in removing PLs, FFAs and increasing color quality particularly
removing chlorophyll pigment in canola oil. Despite the promising results
reported here, there is still a lot of work to be undertaken and the phenomena responsible for the selectivity of the separation. For example, further works is
necessary to improve the PSA efficiency in permeate flux and color retention of
canola oil.

(a)
(b)
(c)
Fig. 10. (a) Crude canola oil; (b) canola oil miscella; (c) typical samples of permeate
(left) and retentate (right) of canola oil miscella ultrafiltration
18

FFA Free fatty acid PES Polyethersulfone
GS Gas separation PL Phospholipid
kDa Kilo dalton PSA Poly sulfone amide MF Microfiltration RO Reverse osmosis
MWCO Molecular weight cut off UF Ultrafiltration
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Refining of Crude Canola Oil Using PSA Ultrafiltration Membrane

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