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Palm Oil: Processing, Characterization and Utilization in the Food Industry – A Review

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The oil palm tree is an ancient tropical plant that originated from West Africa. Palm oil has centuries’ long use as food and medicine. This review covers the recent significant materials found in the literature on palm oil processing, refining, and use in frying especially in blends with other vegetable oils. Crude palm oil (CPO) is obtained from the fruit of the oil palm tree (Elaeis guineensis). The oil is rich in palmitic acid, β-carotene and vitamin E. CPO has been fractionated mainly into liquid palm olein and solid palm stearin in order to diversify its food applications. Palm oil is highly stable during frying especially due to the synergistic activity of β-carotene and tocotrienol. In recent years there has been a shift from the use of animal fats and hydrogenated vegetable oils in frying and other food applications. The use of naturally stable oils such as palm oil and composite oils like blends of palm oil and other fats and oils is practiced to ensure that maximum benefits are derived from the oils. Blending offers functional, nutritional and technical advantages, such as tailoring the oil to suit frying applications. The objective of this review is to combine and condense the body of research on the processing, characterization and use of palm oil especially in frying as well as suggest areas that need further research.
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Available online at www.sciencedirect.com
Palm oil: Processing, characterization and utilization
in the food industry A review
Ogan I. Mba, Marie-Jose
´e Dumont
n
, Michael Ngadi
nn
Department of Bioresource Engineering, Macdonald Campus of McGill University, 21,111 Lakeshore Road
Sainte-Anne-de-Bellevue, Montreal, Quebec, Canada H9X 3V9
article info
Article history:
Received 4 August 2014
Received in revised form
30 December 2014
Accepted 4 January 2015
Available online 14 January 2015
Chemical compounds studied in this
article:
Palmitic acid (PubChem CID: 985)
Oleic acid (PubChem CID: 445639)
Linoleic acid (PubChem CID:
5280450)
Linolenic acid (PubChem CID:
5280934)
Beta-carotene (PubChem CID:
5280489)
Vitamin A (PubChem CID: 445354)
Alpha-tocopherol (PubChem CID:
14985)
Gamma-tocotrienol (PubChem CID:
5282349)
Alpha-tocotrienol (PubChem CID:
5282347)
Vitamin E (PubChem CID: 1548900)
Keywords:
Palm oil
Characterization
abstract
The oil palm tree is an ancient tropical plant that originated from West Africa. Palm oil has
centuries' long use as food and medicine. This review covers the recent signicant
materials found in the literature on palm oil processing, rening, and use in frying
especially in blends with other vegetable oils. Crude palm oil (CPO) is obtained from the
fruit of the oil palm tree (Elaeis guineensis). The oil is rich in palmitic acid, β-carotene and
vitamin E. CPO has been fractionated mainly into liquid palm olein and solid palm stearin
in order to diversify its food applications. Palm oil is highly stable during frying especially
due to the synergistic activity of β-carotene and tocotrienol. In recent years there has been
a shift from the use of animal fats and hydrogenated vegetable oils in frying and other food
applications. The use of naturally stable oils such as palm oil and composite oils like
blends of palm oil and other fats and oils is practiced to ensure that maximum benets are
derived from the oils. Blending offers functional, nutritional and technical advantages,
such as tailoring the oil to suit frying applications. The objective of this review is to
combine and condense the body of research on the processing, characterization and use of
palm oil especially in frying as well as suggest areas that need further research.
&2015 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.fbio.2015.01.003
2212-4292/&2015 Elsevier Ltd. All rights reserved.
n
Corresponding author. Tel.: þ1 514 398 7776; fax: þ1 514 398 8387.
nn
Corresponding author. Tel.: þ1 514 398 7779; fax: þ1 514 398 8387.
E-mail address: marie-josee.dumont@mcgill.ca (M.-J. Dumont).
Food Bioscience 10 (2015) 26–41
Nutrients
Antioxidants
Frying
Blending
Contents
1. Introduction. .................................................................................. 27
2. Processing and rening .......................................................................... 28
3. Characterization . . . ............................................................................ 30
3.1. Physicochemical characterization of palm oil . . . ................................................. 31
3.2. Fatty acid characterization ................................................................... 31
3.3. Micronutrients characterization . . ............................................................. 33
4. Use in frying .................................................................................. 34
5. Blending...................................................................................... 36
6. Conclusion. . .................................................................................. 37
Acknowledgments ................................................................................. 38
References ....................................................................................... 38
1. Introduction
Palm oil is extracted from the ripened mesocarp of the fruits
of oil palm tree (Elaeis guineensis). The oil palm fruit is a drupe
formed in spiky tight bunches. The ve leading producing
countries are Indonesia, Malaysia, Thailand, Colombia and
Nigeria. The oil palm tree gives the highest yield of oil per
unit area of cultivated land, an estimated 58.431 million
metric tons (MT) per year. One hectare of oil palm plantation
is able to produce up to 10 times more oil than other leading
oilseed crops. Palm fruit produces two distinct types of oils:
crude palm oil (CPO) from the mesocarp and palm kernel oil
(PKO) from the inside kernel (Gourichon, 2013;Robbelen,
1990). Both CPO and PKO are important in world trade
(Schroeder, Becker, & Skibsted, 2006). In 2012, CPO and PKO
accounted for 32% of global fats and oils production. Palm oil
has overtaken soybean oil as the most important vegetable
oil in the world (Oil World, 2013). A chart showing the recent
supply of vegetable oils in the world's market is shown in
Fig. 1. CPO is also called red palm oil because of its high
content of carotenoids. It is a rich source of vitamin E (600
1000 ppm); coenzyme Q10 (ubiquinone) (1825 mg/kg) and
sterols (325365 mg/kg) (Tyagi & Vasishtha, 1996). The edible
food industry utilizes about 90% of palm oil, while the
remaining 10% nds application in soap and oleochemical
manufacturing (Oil World, 2013).
Palm oil has a unique fatty acid (FA) and triacylglycerol
(TAG) prole which makes it suitable for numerous food
applications. It is the only vegetable oil with almost 5050
composition of saturated and unsaturated fatty acids. CPO is
used for cooking, frying, and as a source of vitamins.
Fractionation of CPO yields mainly palm olein, the liquid
fraction and palm stearin, the solid fraction. These fractions
have distinct physical and chemical properties. CPO, palm
olein and palm stearin are important constituents of several
food and industrial products such as shortenings, ice cream,
cosmetics, candles lubricants, toothpaste and biodiesel
(Barriuso, Astiasarán, & Ansorena, 2013). Palm stearin is
helpful in providing the solid fat functionality without the
use of hydrogenation, thus reducing trans-fat intake in the
diets (Kellens, Gibon, Hendrix, & De Greyt, 2007). Interester-
ication of CPO also widens its scope of food applications.
Interesterication can be used to incorporate essential poly-
unsaturated fatty acids in order to obtain oil rich in essential
fatty acids and enhanced antioxidant properties. Customized
blends of CPO and fractions with other oils are used in
different food products ranging from margarines to soup
mixes and infant formulae (Manorama & Rukmini, 1992).
Palm oil is top prime among frying oils. In addition to its
unique fatty acid composition, it has a high smoke point of
about 230 1C. Frying is an ancient cooking method that
started probably around the 6th Century BC (Gupta, 2004;
Kochhar, 2001;Morton, 1998). Frying heats the food through
to the middle, cooking the interior and creating a cruston
the surface of the food plus a characteristic fried food avor
(Marrikar, Ghazali, Long, & Lai, 2003;Rossell, 2001). The hot oil
serves as a medium of heat and mass transfer. During frying,
some of the oil is absorbed by the product, while moisture in
the form of vapor is given off. Thus, frying combines cooking
and drying. Important chemical and physical changes occur
during frying. Examples are starch gelatinization, protein
denaturation, water vaporization and crust formation
(Krokida, Oreopoulou, & Maroulis, 2000;Saguy & Dana,
2003). Fried food quality is a function of oil quality. The
degradation of cooking oils affects the texture, taste, and
overall avor perception of the food (Stier, 2013).
Berger (2005) reviewed the performance of palm oil and
palm olein in frying. The focus of the review was the
suitability and stability of palm oil in restaurant batch fryers
and continuous frying in the manufacture of snack foods.
Matthaus (2007), in his review, concluded that palm oil and
the byproducts of palm oil have similar frying performance
Food Bioscience 10 (2015) 26–41 27
when compared to high oleic oils. This review aims at high-
lighting and evaluating the physicochemical characteristics,
nutritional, functional and frying qualities of palm oil. It also
focuses on the processing, rening and characterization of
palm oil. The suitability and sustainability of blending CPO
with other unsaturated vegetable oils for use in the food
service and processing industries as a cost effective and
healthy alternative to partial hydrogenation will be explored.
2. Processing and rening
The mesocarp of palm fruits contains about 5670% edible oil
when fully ripened. This oil can be extracted using different
methods. These methods are grouped into four categories
based on their throughput and degree of complexity. They are
the traditional methods, small-scale mechanical units,
medium-scale mills and large industrial mills (Poku, 2002).
The basic unit operations associated with palm oil processing
include fruit sterilization, fruit loosening/stripping, digestion,
oil extraction and clarication. Fruit sterilization denotes
heat rendering and moisture absorption. The aim is to
inactivate the lipolytic enzymes in the fruit mesocarp. The
two major extraction procedures are mechanical pressing
and solvent extraction. Oil extraction efciency range of 75
90% has been reported for mechanical screw presses
(Owolarafe, Faborode, & Ajibola, 2002;Poku, 2002). CPO
obtained by either mechanical pressing or solvent extraction
contains desirable and undesirable compounds. Desirable
compounds include triacylglycerols (TAGs) (neutral lipids)
and health benecial compounds such as the vitamins E
(tocopherols and tocotrienols), carotenoids and phytosterols.
The desired compounds serve as nutrients, antioxidants and
health benecial compounds. Free fatty acids (FFAs), phos-
pholipids (PLs) or gums, and lipid oxidation products are the
major undesirable compounds. The impurities are objection-
able from a sensory point of view (Čmolík & Pokorný, 2000;
Dunford, 2012). The impurities are removed during oil ren-
ing process (Sambanthamurthi, Sundram, & Tan, 2000).
The most common methods of palm oil extraction are
either the wetor the dryprocesses. In the wetprocess a
liquid, usually water, is used to extract the oil from the milled
palm fruits. Hot water or steam is used to leach out the oil
from ruptured oily cells of the palm fruits. The hot water
treatment also hydrolyzes gums, resins and any starch
present as well as coagulates proteins. The gums and resins
cause the oil to foam during frying. The hydrolyzed and
coagulated products are removed during oil clarication. The
extracted oil is recovered after evaporating the moisture
(Obibuzor, Okogbenin, & Abigor, 2012;Poku, 2002). In the
drymethod, a hydraulic press or a screw press or centrifu-
gation is employed. The screw press is generally more
applicable in continuous extraction systems while the
hydraulic press is commonly used in batch or semi-batch
extraction systems (Poku, 2002). During pressing, the crude
palm oil drains from the brous mesocarp leaving behind
ber materials that still retains about 56% of oil. In order to
avoid cracking the palm kernels, the pressure is normally
reduced and oil retention increases to 1012% (Corley &
Tinker, 2003;Obibuzor et al., 2012). The resulting press liquor
is a mixture of water, oil, dirt, and fruit debris in varying
concentrations. The liquor is processed further to maximize
oil yield and reduce the moisture content in the CPO to r10%
(Poku, 2002). This process, besides being critical to the quality
of the CPO, leads to oil loss and environmental pollution.
After most of the oil has been recovered, palm oil mill efuent
(POME) is left behind. More oil can be recovered from POME when
food grade solvents such as hexane and petroleum ether are
used for the oil extraction (Obibuzor et al., 2012). The CPO stock is
further puried by centrifugation and drying. Vacuum drying has
been suggested to avoid further degradation of the oil quality,
especially the FFA content. The dried oil is then cooled and
pumped to storage tanks or other suitable containers (Bassim,
Abdul, & Ng, 2003;Obibuzor et al., 2012). Norhuda and Mohd
Omar (2009) reported the feasibility of using supercritical carbon
dioxide extraction method for the extraction of CPO. This is more
applicable for the extraction of PKO from the crushed kernels.
Similarly, solvent extraction process is used in high capacity
mills for PKO extraction. It involves three main unit operations:
kernel pre-treatment, oil extraction, and solvent recovery from
the oil and meal. Poku (2002) reported that the yields and quality
oftheextractedoildependontheinitialoilandmoisture
contents, operating temperature, heating time and the applied
pressure.
The crude oil is usually washed with a solution of sodium
hydroxide or sodium carbonate to reduce the FFAs content,
remove the PLs and other polar lipids. This operation is
generally referred to as alkali rening. Alkali rening alone
cannot remove all objectionable compounds that may be
present (Čmolík & Pokorný, 2000). Other rening procedures
and targeted impurities are shown in Table 1.Dunford (2012)
reported a rening process involving heating the crude oil
with water or an aqueous solution of phosphoric acid. The
gums are subsequently removed by centrifugation. Pigments
are removed by bleaching with activated clay or charcoal,
while volatile oxidation products are removed through steam
distillation at high temperatures and reduced pressure. The
resulting oil is usually colorless, bland, and has good storage
stability (Čmolík & Pokorný, 2000;Dunford, 2012). Čmolík and
Pokorný (2000) reported that the disadvantages of alkali
rening include: losses of neutral triacylglycerols, high
0
10
20
30
40
50
60
2007 2008 2009 2010 2011
Million Metric tons
Yea r
Coconut Oil Cottonseed Oil Olive Oil
Palm Oil Palm Kernel Oil Peanut Oil
Rapeseed Oil Soybean Oil Sunflower Oil
Fig. 1 World supply of vegetable oils.
Food Bioscience 10 (2015) 26–4128
energy requirement, high cost of equipment, time consum-
ing, and generates large amounts of efuents that pollutes
the environment. For these reasons, physical methods of
rening are recommended. Physical rening is based on the
higher volatility of FFAs and TAGs at high temperatures and
low pressures. During physical rening, volatile compounds
including FFAs are volatilized and neutral oil droplets are
carried in the current of the stripping steam. These methods
include: steam rening, inert gas stripping, molecular dis-
tillation, membrane rening, hermetic system, supercritical
carbon dioxide, etc. (Dunford, 2012;Gunstone, 2011).
The quality of extracted palm oil determines the grades
and the premium payable. Generally, palm oil with low FFA
and moisture content, very low levels of impurities and good
bleachability index is considered to be of high quality. The
quality of palm oil dictates and directs its use. Broadly
speaking, high quality palm oils are used in the edible oil
industry while lower quality oils are used in the non-edible
industry for biofuels, candles, cosmetics and soap (Henson,
2012). Good quality oil contains more than 95% neutral TAGs
and 0.5% or less FFA. As an industry rule, the FFA content of
rened oils must be r0.1%. Most crude oils usually contain
13% of FFA. Where the oil has high FFA, physical rening is
recommended (Dunford, 2012;Gunstone, 2011). CPO contain-
ing 12% FFA has been reduced to 1.3% FFA at 220 1C and 0.5%
FFA at 230 1C by physical rening at a pressure of 0.8 kPa
(Čmolík & Pokorný, 2000). However, care must be taken since
high temperatures lead to destruction of carotenes. The
consequence is oil with reduced nutritional quality and color.
Lower deodorization temperatures are recommended
(Aparicio & Harwood, 2013). A two-step process for rening
CPO has also been reported. This involved acidifying to
remove PLs and other gums and steam stripping at lower
temperatures (180 1C and 200 1C). This procedure yielded oils
with satisfactory avor. Steam stripping at higher tempera-
tures 240270 1C at 0.251.32 kPa has been reported (Derksen
& Cuperus, 1998). The effectiveness of two modern deodor-
ization devices, Mellapak
s
and Optiow
s
, which guarantee
satisfactory mass transfer and a substantially improved
steam distribution have been reported (Čmolík & Pokorný,
2000;Faessler, 1998). The red color of palm oil is generally
accepted by the consumers. High carotene content is desir-
able because of its pro vitamin A and antioxidant activities.
Ooi, Choo, Yap, and Ma (1996) proposed the use of a mole-
cular distillation unit which reduces the FFA content of CPO
to r0.1%, while retaining more than 80% of the carotenes
and tocopherols.
Sometimes, the food service and manufacturing industries
require CPO with bland and light color. CPO can be rened by
the chemical or physical process to meet that requirement.
The major unit operations in CPO rening are shown in Fig. 2.
The difference between the two processes is that the acid
neutralization step is omitted in the physical rening process
where the FFAs are removed at the deodorization step.
Chemical rening is carried out at a lower temperature and
shorter time. Losses of tocopherols, tocotrienols and oxida-
tive damage are higher in the physical rening process
especially if air leakage occurs during the process. Physically
rened oils have lower storage stability. In physical rening,
it is important to eliminate phosphorus as much as possible
during the degumming step and to prevent phosphoric acid
slip-through, as this would affect the efciency of heat
bleaching later on in the process (Chong, 2012;Dunford,
2012).
The utilization of most natural vegetable oils can be
diversied through physical and chemical modication pro-
cedures. One such modication process is fractionation.
Fractionation is a selective physical and/or thermo-
mechanical process that separates a mixture into two or
more fractions with distinct physical and chemical proper-
ties. It is a fully reversible modication process. Oils are
fractionated to change the physicochemical properties of the
oil such as reducing the degree of unsaturation of the acyl
groups. This is done by redistributing the fatty acids chains
using different selective crystallization and ltration meth-
ods (Kellens et al., 2007). The separation is based on differ-
ences in solidication, solubility, or volatility of the
constituents. CPO is fractionated based on the differences in
the crystallization behavior of the TAGs. CPO easily separates
into a low melting liquid fraction (6570% palm olein) and a
high melting solid fraction (3035% palm stearin). The pro-
ducts mainly have different iodine values (IV). There are
three different types of fractionation: dry fractionation,
detergent fractionation, and solvent fractionation (Kellens
et al., 2007;Pande, Akoh, & Lai, 2012). Fractionation adds
value to the oil and creates no undesirable byproducts.
Table 2 gives a summary of the advantages and disadvan-
tages of the rening and fractionation methods.
The importance and uses of palm oil, palm olein, and
palm stearin are well discussed by Kellens et al. (2007) and
their health effects by Sambanthamurthi et al. (2000). These
major fractions, like CPO can also be rened, bleached and
deodorized (RBD). RBD palm olein is used in frying, cooking,
shortenings and margarines. RBD palm stearin is used mainly
in food applications that require higher solid fats content
such as shortenings, margarines and vanaspati (hydroge-
nated vegetable oils used as substitute for butter in South
Asia especially India). Other fractions such as PMF are used as
Table 1 Rening operation and target impurities.
Source:Aparicio and Harwood (2013),Čmolík and Pokorný (2000)
Rening operation Targeted impurity
Hydration/degumming Phospholipids; other polar lipids (gums)
Neutralization Free fatty acids; residual phospholipids; metals
Bleaching Pigments; residual soaps; phospholipids
Deodorization Volatile oxidation products; other contaminants
Food Bioscience 10 (2015) 26–41 29
cocoa butter equivalents in confectioneries while super olein
(double fractionated palm olein) is used in mayonnaise and
salad dressings (Sarmidi, El Enshasy, & Hamid, 2009). While
olive, rapeseed and canola oils contain Z60% of cis-oleic acid,
palm olein has E48% of oleic acid. It has been reported that
in healthy normocholesterolaemic humans, palm olein could
be substituted for olive oil without adversely affecting serum
lipids and lipoprotein levels since it is rich in oleic acid
(Sambanthamurthi et al., 2000).
3. Characterization
The most commonly used method for the determination of
total fats in dried food samples is Soxhlet extraction. There are
also instrumental techniques and procedures adapted from
pharmaceutical and chemical engineering analyses protocols.
The extraction technique is simpler, more accurate and more
generally applied in lipid analyses than the instrumental
methods. However, extraction techniques are timeconsuming,
destructive and generate large volumes of laboratory efuents
that lead to disposal challenges. On the other hand, instru-
mental techniques are non-destructive, give rapid useful
results for online quality measurements in laboratories and
food factories. Due to the chemical nature of vegetable oils,
most standard methods recommend that they be character-
ized using Soxhlet methods. Recent analytical procedures such
as chromatography and spectroscopy [Gas Chromatography
Flame Ionization Detector (GCFID); Gas Chromatography
Mass Spectroscopy (GCMS) and High Performance Liquid
Chromatography (HPLC)], which are based on physics rather
than chemistry (Gunstone, 2011) are increasingly being used
for vegetable oils' characterization. The use of procedures such
as thermogravimetric analysis (TGA) (Debnath, Raghavarao, &
Lokesh, 2011), differential scanning calorimetry (DSC)
(Marquez & Maza, 2003;Tan & Man, 2000), Fourier transform
infrared (FTIR) and Fourier transform near-infra red (FTNIR)
spectroscopy have been reported as well (Azizian, Kramer, &
Winsborough, 2007;Casale, Casolino, Ferrari, & Forina, 2008;
Mba, Adewale, Dumont, & Ngadi, 2014).
International organizations such as those listed below
provide similar but not identical techniques, methods, pro-
cedures and protocols for the analysis of lipid samples. The
guidelines differ as efforts continue to be made to ensure
accuracy and precision of outcomes; and more sensitive test
tools continue to evolve. The procedures require that the test
sample must be a true representative of the target oil sample
(s). Guidelines also exist for transport and storage of the lipid
samples before analysis. In order to ensure the reliability of
the analytical results, care must be given to details such as
the storage temperature, the type of container and the
possible addition of antioxidants (Gunstone, 2011;Stier,
2004). The organizations providing guidelines include
The Association of Ofcial Analytical Chemists (AOAC),
The American Oil Chemists' Society (AOCS),
The British Standards Institution (BSI),
The International Organization for Standardization (ISO),
The International Union of Pure and Applied Chemists
(IUPAC),
German Society for Fat Research (DGF),
Palm Oil Research Institute of Malaysia (PORIM),
American Society for Testing of Materials (ASTM), and
Codex Alimentarius Commission for Oils and Fats.
Crude Palm Oil
Physical Refining
Chemical Refining
Degumming
Bleaching
Alkali Neutralization
Deodorizing
RBD Palm Stearin
Palm Fatty Acid
Distillates
Refined Bleached
Deodorized (RBD)
Palm Oil
Fractionation
RBD Palm Olein
RBD Palm Stearin
RBD Palm Olein
Bleaching
Deodorizing
Fractionation
Fig. 2 Palm oil rening process.
Food Bioscience 10 (2015) 26–4130
3.1. Physicochemical characterization of palm oil
The Mongana report of 1955 was one of the earliest compre-
hensive research works on palm oil characterization. It dealt
with palm oil milling and CPO quality in Africa. Then, CPO
quality was mainly dened in terms of total percentage of
FFA, moisture and impurities. After the Second World War, a
more complex quality grading system was introduced to
regulate oil production by cottage industries. A ve point
grading system was introduced. Grade 1oils must have
FFAo1% while grade 5oils have FFA436%. Grades 2, 3 and
4oils have FFA ranges of 918%, 1827%, and 2736%,
respectively. This grading system stimulated the small scale
producers to improve their oil quality. Later, the specication
Special Gradepalm oil with maximum FFA level of 4.5% at
the point of sale was introduced. Further adjustment put the
maximum FFA at 3.5%. Trade reports showed that by 1965
more than 80% of CPO export from Africa was of the Special
Gradequality (Berger & Martin, 2000;Iwuchukwu, 1965).
Since the 1990s, some countries such as Malaysia have the
set limits of FFA to r5% and a maximum of 0.25% for
moisture and impurities for locally produced CPO (Chong,
2012).
The physicochemical properties of palm oil and its frac-
tions were extensively studied during the 1980s and 1990s.
Brilliant works on the physicochemical properties of palm oil
and its fractions have been published (Tan & Oh, 1981;Tan &
Man, 2000;Tan & Nehdi, 2012). CPO is classied as saturated
oil with iodine value (IV) range of 5158 g/100 g oil. Palm oils
with a wider IV range of 4663 g/100 g oil have been reported.
These types of palm oil may be mixtures of oils from different
species of oil palm tree or oil mixed with various proportions
of palm stearin (Edem, 2002;Elias & Pantzaris, 1997;OBrien,
2010;Tavares & Barberion, 1995). The major physicochemical
characteristics of palm oil are presented in Table 3.
3.2. Fatty acid characterization
When compared to other vegetable oils, CPO has a unique
fatty acid composition (FAC). FAC analysis is the most widely
practiced analytical technique in lipid science. The FAC of
palm oil has been widely reported by many researchers
(Almeida et al., 2013;Che Man, Setiowaty, & Van de Voort,
1999;OBrien, 2010;Tan & Nehdi, 2012). The mixed triacylgly-
cerols are derivatised to methyl or silyl esters and subse-
quently separated and identied using appropriate gas
chromatography column and protocol (Christie, 1993;
Durant, Dumont, & Narine, 2006;Gunstone, 2011).
Table 2 Advantages and disadvantages of different rening and fractionation methods.
Source:Čmolík and Pokorný (2000),Dumont and Narine (2007),Kellens et al. (2007)
Operation Advantages Disadvantages
Rening
Chemical (1) Functional process
(2) Great reduction of FFA
(1) Losses of neutral TAGs
(2) High energy requirement
(3) Very expensive
(4) Time consuming
(5) Generates polluting efuents
Physical (1) Less energy requirement
(2) Less by products generated
(3) Reduced cost
(1) Destruction of carotenes
(2) Loss of deep red color
(3) High oxidative damage
(4) Likely loss of Vitamins E
(5) Reduced storage stability
Fractionation
Dry (1) Simple
(2) Cheap
(3) No chemicals
(4) No efuent
(5) No losses
(6) No additional substance
(7) Multi-step operation possible
(1) Viscosity problems
(2) Limited degree of crystallization
Detergent (1) Crystals easily suspended in the aqueous phase (1) Very expensive
(2) Risk of product contamination
(3) Requires additional accessories
Solvent (1) Reduced viscosity
(2) Short process time
(3) High separation efciency
(4) Improved yield
(5) Higher purity of products
(1) High capital investments
(2) High production costs
(3) Possible re hazards
(4) Hazardous chemicals and efuents
Food Bioscience 10 (2015) 26–41 31
The near equal composition of saturated fatty acids (SFA)
and unsaturated fatty acids (UFA) in CPO makes it naturally
semi solid at room temperature. CPO has a high level of
palmitic acid (C16:0) which accounts for approximately 44% of
the FAC. The other major fatty acids are oleic acid (C18:1),
linoleic acid (C18:2) and stearic acid (C18:0) accounting for
40%, 10% and 5%, respectively (Tan & Man, 2000). Similar to
other vegetable oils, CPO and its fractions, namely palm olein;
palm stearin; and superolein are comprised of mixed triacyl-
glycerols (TAGs) and partial acylglycerols, such as diacylgly-
cerols (DAGs) and monoacylglycerols (MAGs). DAGs and
MAGs are hydrolysis products of TAGs that can affect the
melting point and crystallization behavior of the oil (Foster,
Williamson, & Lunn, 2009). Partial acylglycerols can cause
cloudiness at concentrations above 10% especially when
temperatures drop below 20 1C(Berger, 2007). The fatty acid
and glyceride composition of palm oil is shown in Table 4.
Choe and Min (2007) reported that the range of TGAs in CPO
and fractions are 9498%; DAGs 58%; MAGs 0.210.34%; and FFA
25%. Poor storage and handling conditions can lead to increased
values due to hydrolytic breakdown. The remaining 1% consists
of the minor components, namely, carotenes, tocopherols and
tocotrienols, sterols and squalene (Berger, 2007). The type of TAG
is determined by its FA composition, the distribution of the FAs
in the TAG molecule, the proportions of the individual FAs, the
source of the oil, and the processing history (Foster et al., 2009;
Ghotra,Dyal,&Narine,2002). The TAGs can be further grouped
into four categories: trisaturated (SSS); disaturatedmonounsatu-
rated (SSU); monosaturateddiunsaturated (SUU); and triunsatu-
rated (UUU). Tan and Man (2000) reported that these four TAG
groupsandmorethan33TAGmolecularspeciescanbefoundin
palm oil. The structurally symmetrical POP, POO, PPO, PLO, and
PLP are the major ones (P¼palmitic; O ¼oleic; and L ¼linoleic).
Scores of research and review articles published within
the last decade agree that the principal triacylglycerol species
in palm oil is palmitic acid. The majority of the palmitic are
located at the outer sn-1 and sn-3 positions of the glycerol
molecule. However an estimated 1323% palmitic acid of CPO
is found at the sn-2 position (Andreu-Sevilla, Hartmann,
Burlo, Poquet, & Carbonell-Barrachina, 2009;Atinmo &
Bakre, 2003;Berger, 2005;Curvelo, Almedia, Nunes, &
Feitosa, 2011;Gebauer, Harris, Kris-Etherton, & Etherton,
2005;Hayes & Khosla, 2007;Ismail, 2005;Pande et al., 2012;
Stier, 2013;Sundram, Sambanthamurthi, & Tan, 2003;Tan &
Nehdi, 2012). In infant feeding and formulae preparation,
there is better absorption and energy release in having
palmitic acid at the sn-2 position (Innis, 2011;Ramirez,
Amate, & Gil, 2001). Filippou, Berry, Baumgartner, Mensink,
and Sanders (2014), reported that dietary TAGs with an
increased proportion of palmitic acid in the sn-2 position do
not have acute adverse effects on the insulin and glucose
response to meals in healthy adults. The FAC prole of CPO is
signicantly different from that of PKO, which is made up of
85% SFA, mainly lauric acid (Sambanthamurthi et al., 2000).
Largely, there is no signicant difference in the FAC of palm
oil obtained from different geographical zones (Tan, Ghazali,
Kuntom, Tan, & Arifn 2009). However, Lin (2011) reported
that the composition of Nigerian palm oil shows considerably
larger variation. Palmitic acid range is 2755%; oleic acid
2856% and linoleic acid 6.518%. These variations serve as
Table 3 Physicochemical properties of palm oil.
Characteristics Typical Range Reference/source
Apparent density at 50 1C (g/ml) 0.8920.899 OBrien (2010),Codex Alimentarius (1999)
AOM stability (h) 54.0 53.060.0 OBrien (2010)
Melting point (1C) 37.5 33.045.0 OBrien (2010),Firestone (2006)
Oxidative stability index at 110 1C (h) 16.9 16.619.0 OBrien (2010)
Refractive index at 50 1C1.4491.456 OBrien (2010),Firestone (2006)
Smoke point (1C) 230.0235.0 Gunstone (2011)
Solidication point (1C) 35.042.0 OBrien (2010)
Solid fat content
10 1C 34.5 30.039.0 OBrien (2010)
21.1 1C 14.0 11.517.0 OBrien (2010)
26.7 1C 11.0 8.014.0 OBrien (2010)
33.3 1C 7.4 4.011.0 OBrien (2010)
37.8 1C 5.6 2.59.0 OBrien (2010)
40.0 1C 4.7 2.07.0 OBrien (2010)
Specic gravity at 50 1C0.8880.889 OBrien (2010)
Viscosity (cP) 45.0 45.049.0 Berger (2005)
Iodine value (g/100 g) 53.0 46.056.0 OBrien (2010),Edem (2002)
Free fatty acid (% FFA as palmitic) 3.175.0 Chong (2012)
Peroxide value (meqO
2
/kg) 0.110.0 OBrien (2010)
Anisidine value (mg KOH/g) 0.64.65 Chong (2012)
Saponication value (mg KOH/g) 196.0 190.0209.0 OBrien (2010),Chong (2012)
Unsaponiable matter (%) 0.5 0.150.99 OBrien (2010)
Total polar compounds (%) 13.5 9.4719.50 Almeida et al. (2013),Berger (2005)
Total polymer materials (%) 0.5 0.415.0 Berger (2005)
Saturated fatty acids SFA (%) 49.954.7 Tan and Nehdi (2012)
Mono-unsaturated fatty acids MUFA (%) 37.139.2 Gunstone (2011),Tan and Nehdi (2012)
Poly-unsaturated fatty acids PUFA (%) 8.110.5 Gunstone (2011),Tan and Nehdi (2012)
Crystal habit β0OBrien (2010)
Food Bioscience 10 (2015) 26–4132
a genetic pool for plant breeders to develop new palms with
the desired specications such as high oleic acid palms.
Nutrition studies have not only demonstrated the ade-
quacy of palm oil and its products, but have also led to
transitions in the understanding of the nutritional and
physiological effects of palm oil, its fatty acids and minor
components. There is evidence that a balance between
linoleic and palmitic acids may be required to maximize
HDL levels. Substitution of palmitic acid from CPO or palm
olein for the lauric acid and myristic acid combination from
PKO or coconut oil resulted in a decrease in plasma and LDL
cholesterol (Ng, Low, Kong, & Cho, 2012;OKeeffe & St-Onge,
2013;Sambanthamurthi et al., 2000;Sundram et al., 2003). In
contrast, the study conducted by Tholstrup, Hjerpsted, and
Raff (2011) did not support the previous ndings by Mensink,
Zock, Kester, and Katan (2003) and Sundram et al. (2003), that
palm olein is neutral to total plasma cholesterol and LDL
cholesterol in healthy individuals with normal plasma cho-
lesterol concentrations. Tholstrup et al. (2011) reported that
compared to olive oil, palm olein and lard increased the total
cholesterol (Po0.0001). However, palm olein resulted in a
lower plasma TAG concentration than olive oil (Po0.01). The
study concluded that there was no difference in the effects
observed in plasma HDL-cholesterol, high-sensitivity C-reac-
tive protein, plasminogen activator-1 (plasma proteins that
respond to tissue inammation and breakdown of blood
clots), insulin, and glucose concentrations.
3.3. Micronutrients characterization
Palm oil contains minor components that demonstrate major
nutritional and health benets. The micronutrients are listed
in Table 5. These micronutrients include carotenoids, toco-
pherols, tocotrienols, sterols, phospholipids, glycerolipids
and squalene (OBrien, 2010). The carotenoids, tocopherols
and tocotrienols maintain the stability and quality of palm oil
and also act as biological antioxidants (Wu & Ng, 2007). The
tocopherols and tocotrienols act as anti-cancer, anti-
inammatory agents (Wu, Liu, & Ng, 2008), control athero-
sclerosis, and decrease cholesterol (Das, Nesaretnam, & Das,
2007). The growing interest in the bioactivities of these
micronutrients has led to the development of functional
foods or nutraceuticals incorporated with phytosterols, toco-
pherols, and tocotrienols (Zou, Jiang, Yang, Hu, & Xu, 2012).
Carotenoids are responsible for the diversity of color in
nature. Alpha-carotene, β-carotene, and cryptoxanthin have
demonstrated provitamin A activity. Beta-carotene is the
most potent provitamin A carotenoid. Vitamin A is necessary
for vision, growth, cellular differentiation and other physio-
logic functions (Hendler & Rorvik, 2008). CPO contains 500
700 ppm of carotenoids and is thus the natural richest source
of carotenoids. CPO contains 33% α-carotene, 65% β-carotene
and 2% other carotenoids such as γ-carotene and lycopene
(Ng et al., 2012). The carotenes are responsible for the rich
orange-red color of CPO. They act as antioxidants by trapping
free radicals, neutralize thiyl radicals, chelate peroxy radicals
and quench singlet oxygen in lipids. Stated simply, carote-
noids protect the oil against oxidation by themselves being
rst oxidized before the oxidative attack on the triacylglycer-
ols (Edem, 2002;Gunstone, 2011;Hendler & Rorvik, 2008). In
1992, the Joint FAO/WHO Expert Committee on Food Addi-
tives (JECFA) accepted and included palm oil carotenoids
as a permissible food colorant (Zou et al., 2012). CPO has
been proposed as an alternative treatment for vitamin A
Table 5 Micronutrients and other minor components of
palm oil.
Micronutrient/component Range (ppm)
Carotenoids
α-Carotene 30.035.16
b
β-Carotene 50.056.02
b
Lycopene 1.01.30
b
Total carotenoids 500700
b
Tocopherol
α-Tocopherol 129215
a
β-Tocopherol 2237
a
γ-Tocopherol 1932
a
δ-Tocopherol 1016
a
Total tocopherol 500600
a
Tocotrienols
α-Tocotrienol 4473
a
β-Tocotrienol 4473
a
γ-Tocotrienol 262437
a
δ-Tocotrienol 70117
a
Total tocotrienols 10001200
a
Phytosterols 326527
b
Phospholipids 5130
b
Squalene 200500
b
Ubiquinones 1080
b
Aliphatic alcohols 100200
b
Triterpene alcohols 4080
b
Methyl sterols 4080
b
Aliphatic hydrocarbons 50
b
a
OBrien (2010).
b
Zou et al. (2012).
Table 4 Fatty acid and glyceride composition of palm oil.
Compound Typical Range
a
Range
b
Fatty acid composition (%)
Lauric acid (C12:0) 0.0
a
0.11.0 0.00.4
Myristic acid (C14:0) 1.1
a
0.91.5 0.52.0
Palmitic acid (C16:0) 44.0
a
41.846.8 40.048.0
Palmitoleic acid (C16:1) 0.1
a
0.10.3 0.00.6
Stearic acid (C18:0) 4.5
a
4.55.1 3.56.5
Oleic acid (C18:1) 39.2
a
37.340.8 36.044.0
Linoleic acid (C18:2) 10.1
a
9.111.0 6.512.0
Linolenic acid (C18:3) 0.4
a
0.40.6 0.00.5
Arachidic acid (C20:0) 0.4
a
0.20.7 0.01.0
Triglyceride composition (%)
Trisaturated (SSS) 9.8
c
0.89.0
Disaturated (SUS) 48.8
c
38.550.3
Monosaturated (SUU) 36.5
c
31.844.4
Triunsaturated (UUU) 4.8
c
4.89.8
Diglycerides (%) 4.9
a
3.07.6
a
OBrien (2010).
b
Firestone (2006).
c
Tan and Nehdi (2012).
Food Bioscience 10 (2015) 26–41 33
deciency. The digestibility of α- and β-carotene found in CPO
is high and this enhances their bioavailability (Benadé, 2003;
Edem, Eka, & Umoh, 2002). Rice and Burns (2010) reviewed a
series of key intervention studies designed to investigate the
impact of using red palm oil to improve the status of vitamin
A. The review's focus was related to the use of palm oil in
dietary supplementation and food fortication studies. The
conclusion stated that red palm oil increased dietary intake
of provitamin A carotenoids especially β-carotenes which are
more abundant and better converted than α-carotenes. Palm
oil is highly effective in improving vitamin A status amongst
populations at risk of vitamin A deciency.
Tocopherols and tocotrienols (termed tocochromanols) are
usually called vitamin E. They are fat soluble. They have a
chromanol head, formed by phenolic and heterocyclic rings,
and a phytyl tail. The number and position of methyl
substitutions on the chromanol nucleus give rise to the
subfamily of α-, β-, γ-, and δ-tocopherols/tocotrienols. Alpha
tocopherol is the most abundant. The difference in the
structure of tocopherols and tocotrienols is only in the phytyl
tail. The tocopherols have a saturated tail, while the toco-
trienols have an unsaturated chain with three isolated double
bonds (Rossi, Alamprese, & Ratti, 2007;Zou et al., 2012). The
tocopherols and tocotrienols are present at different concen-
trations depending on the type of vegetable oil and its origin
(Gunstone, 2011). Palm oil is one of the richest sources of
vitamin E in nature. The vitamin E in palm oil is unique since
it is composed of both tocopherols and tocotrienols. CPO
contains 6001200 ppm vitamin E. Tocopherols account for
1822% while tocotrienols account for 7882%. Amongst the
tocotrienols, the major ones are γ-tocotrienol, α-tocotrienol
and δ-tocotrienol (OBrien, 2010;Ping & May, 2000;Zou et al.,
2012). Some vitamins E in CPO are lost during processing and
rening. During fractionation, vitamin E tends to partition
preferentially into the olein fraction (Obahiagbon, 2012;
Sambanthamurthi et al., 2000;Sundram et al., 2003). Recent
ndings showed that palm oil's tocotrienols signicantly
diminish the synthesis of pro-collagen 1 and 3; and inhibit
the transforming growth factor-β1. These are responsible for
the type of inammatory bowel disease known as Crohn
syndrome (Luna, Masamunt, Llach, Delgado, & Sans, 2011).
The stability of the different tocopherols and tocotrienols
present in the rened vegetable oils basically depend on the
fatty acid composition of the oil, and the type of tocopherol
and tocotrienol homologs present. The homolog, γ-tocotrie-
nol in palm super olein proved to be the least stable during
the deep-fat frying, thus preserving the other homologs
(Rossi et al., 2007). As antioxidants, tocopherols and tocotrie-
nols act as free radical quenchers which contribute to the
stability of palm oil. Tocopherols can interrupt lipid oxidation
by inhibiting peroxide formation in the chain propagation
step, or the decomposition process by inhibiting aldehyde
formation. Alpha tocopherol is reported to be highly reactive
towards singlet oxygen and protects the oil against photo-
oxidation (Sundram et al., 2003). The tocotrienols and the
isometric position of its fatty acids are credited as being
responsible for palm oil's nutritional benets (OBrien, 2010).
Carotenoids, along with vitamin E, protect the oil from
thermal oxidation. During thermal oxidation carotene radi-
cals are formed which are converted back to active carotene
in the presence of tocotrienols. Schroeder et al. (2006)
reported that this synergistic relationship decreased the
oxidation of oil during frying of potato slices at 163 1C.
Other minor components of palm oil such as the sterols,
higher aliphatic alcohols and hydrocarbons are found in the
unsaponiable fraction. Similar to all other edible oils of
vegetable origin, the cholesterol content of palm oil is negli-
gible. Rening decreases the phytosterols, ketones, wax and
methyl esters present (Edem, 2002;Sambanthamurthi et al.,
2000). Ping and May (2000) reported that, generally the minor
components act as antioxidants, boost energy, enhance the
immune system and provide benets in the prevention and
treatment of coronary heart diseases (CHD). Palm oil also
contains low levels (o100 mg/L) of phenolic compounds. The
phenolic compounds are responsible for the initial darkening
of palm oil during frying (Berger, 2005;Sundram et al., 2003).
Like all vegetable oils, a mixture of sterols is found in CPO,
palm olein and their rened products. The sterols found in
palm oil include β-sitosterol, campesterol, stigmasterol and
avenesterols. Amongst them, avenesterols exhibit antioxidant
activity (Berger, 2005;Gunstone, 2011). The sterols of plant
origin are referred to as phytosterols. Phytosterols are suscep-
tible to oxidative degradation during food processing opera-
tions such as frying. During frying, phytosterols degradation
occurs due to auto-oxidation. The products of this degradation
are termed phytosterols oxidation products (POP). The POP can
be found in both frying oil and the fried products (Dutta,
Przybylski, Eskin, & Appelqvist, 2007). Tabee, Jagerstad, and
Dutta (2009) reported that the POP found in palm olein used in
frying French fries at 180 1C for 5 h increased from 1.9 mg/g to
5.3 mg/g in the nal batch. The degradation of phytosterols
depends on the type of oil and polyunsaturated fatty acids
present. Phytosterols appear to degrade faster in oils with high
content of linoleic and linolenic acids. The rate of POP forma-
tion is also inuenced by the type of sterol and the tocopherols
content of the oil (Przybylski, Zambiazi, & Li, 1999).
Generally there is no clear evidence of a negative effect of
palmitic acid on health (Fattore & Fanelli, 2013). CPO is a
complex alimentary medium, in which palmitic acid is just
one of its many components. The presence of oleic acid and
many antioxidant compounds in palm oil provide some form
of nutritional balance. While POP are absorbed and found in
human serum, they do not directly affect the absorption of
cholesterol (OCallaghan, McCarthy, & OBrien, 2014).
4. Use in frying
Frying is cooking food in fat or oil. It includes deep-frying,
stir-frying, pan-frying and sautéing. In the 1980s, there were
campaigns to convince the public that food products contain-
ing saturated tropical oils contributed to increased risk of
coronary heart disease (McNamara, 2010). These tropical oils
include coconut oil (CNO), palm kernel oil (PKO) and crude
palm oil (CPO). Saturated fatty acids such as lauric acid and
myristic acid (from CNO and PKO) have demonstrated
cholesterol-raising effect (Wattanapenpaiboon & Wahlqvist,
2003). This has amplied uneasiness over the health con-
sequences of the consumption of palm oil since it contains
large amount of palmitic acid. Decker (1996),Innis (2011), and
Food Bioscience 10 (2015) 26–4134
Karupaiah and Sundram (2007) strongly reasoned that fatty
acid stereospecic locations must be given important con-
sideration in the design and interpretation of lipid nutrition
studies.
Since then research into the utilization of palm oil and its
fractions have intensied. The use of palm oil and its
fractions in food processes is illustrated on the chart shown
in Fig. 3. It ranges from use in domestic cooking and frying to
large scale production. Certain characteristics of palm oil
such as a high solid fat content (requiring no hydrogenation),
high oxidative stability (long shelf life), high and low melting
TAGs (wide plastic range), constant supply, competitive price,
slow crystallization properties, structural hardness, and a
tendency for recrystallization permit the use of palm oil in
these food applications (Barriuso et al., 2013;Edem, 2002).
Deep-fat frying is one of the most popular methods for the
preparation of food. It is an easy, fast, and a relatively cheap
cooking method that results in palatable foods with wonder-
ful avors and aromas. Frying temperatures range between
150 1C and 190 1C. Most deep-fat frying operations are done at
180 1C. During frying, heat and mass transfer processes occur
between the oil and the food. The outcome is a cooked, dried
and crispy product (Blumenthal & Stier, 1991;Choe & Min,
2007;Krokida et al., 2000). Fried food quality is a function of
the oil quality. Frying enhances color, avor and texture of
the fried food. Lesser nutrients losses occur during frying
than during cooking in water and stewing. Water soluble
vitamins, proteins and carbohydrates are also better retained.
Frying, like cooking in water, improves digestibility and
bioavailability of some nutrients in the digestive tract
(Bognar, 1998;Zhang, Wang, Wang, & Zhang, 2014). Frying
increases the amount of fat in the fried product and can lead
to loss of heat labile and oxidation susceptible vitamins
(Boskou, 2011;Pokorny, Panek, & Trojakova, 2001).
During frying a number of chemical reactions such as
oxidation, polymerization, and hydrolysis of the fatty acids
occur. These reactions change the oil from a medium that is
almost pure triacylglycerol when fresh to one that contains
literally thousands of different degradation compounds. This
could compromise the texture, taste, avor and the overall
perception of the product. In addition, potential risk to
human health and nutrition may arise (Naghshineh &
Mirhosseini, 2010;Stier, 2013). Therefore, in choosing frying
oil, the oxidative and thermal stability are very important
indices, since the frying oil becomes a signicant part of the
food. The fatty acid composition of the oil naturally present
in the food is changed towards the fatty acid composition of
the oil used for frying (Matthaus, 2007). For instance, frying
with olive oil resulted in a high amount of oleic acid in the
fried product, whereas saturated and monounsaturated fatty
acids predominated in products fried in palm olein. Oils with
higher amounts of PUFAs are not stable to oxidation and the
products fried using such oils have shorter shelf stability.
PUFA oils quickly break down at frying temperatures to form
gums (Boskou, 2011;Matthaus, 2007).
Frying medium can be all-vegetable oil, all-animal fat, a
blend of animal fats and vegetable oils or a blend of different
vegetable oils. The important characteristics of frying lipids
are high oxidative stability, high smoke point, low foaming,
low melting point, bland avor and good nutritional value.
FFA o0.1% indicates that the oil is properly rened. The
peroxide value (PV) is a measure of initial oxidation products;
if PV o1.0 meq O
2
/kg, the oil is fresh. A smoke point 4200 1C
is recommended so that the oil does not smoke when rst
used. Moisture content o0.1% indicates the frying oil is pure
fat, and no spattering will occur when rst used. Another test
commonly quoted in the technical trade is the Rancimat
stability, which gives an indication of the stability of a fat. To
avoid quick polymerization, regulations in most developed
countries limit the amount of linolenic acid (C18:2) to r2%
(Boskou, 2011;Kochhar, 2001;Stier, 2013). CPO and palm olein
contain no trans fatty acids. They contain moderate amount
of linoleic acid, and little or no linolenic acid. They have high
levels of antioxidants (tocotrienols, tocopherols and β-caro-
tene). These excellent properties make CPO and palm olein
ideal for domestic and industrial frying (Edem, 2002;Lin, 2011;
Sue, 2009).
Palm oil has largely replaced beef tallow and lard in large
scale industrial frying. Palm oil and palm olein are mostly
used to fry foods like French fries, fried chicken, instant
noodles, snack foods (Fan & Eskin, 2012) and chicken llets
(Chen et al., 2014). A large amount of palm oil is also used for
frying in fast food restaurants (Berger, 2005). Matthaus (2007)
reported that palm olein was comparable with high oleic
vegetable oils and hydrogenated sunower and cottonseed
oils in terms of oxidative stability during frying. Palm oil is
resistant to oxidation, polymerization and foaming. Palm oil
does not produce any gummy or sticky residues in the fryer.
Kochhar (2001) reported that palm oil's good performance
and high oxidative stability is making it the oil of choice for
the major snack food manufacturers in many European
Union (EU) countries. The most popular commercial frying
oil is palm olein which has a lower melting point (2224 1C)
than CPO (3236 1C), resulting in no waxy or greasy mouth-
feel of the fried products (Lin, 2011). Xu, Tran, Palmer, White,
and Salisbury (1999) reported that palm olein had comparable
frying performance as high-oleic, low linolenic canola oil. The
useful life of palm oil as a frying medium is reported to be 12
days of continuous frying. The frying oil management may
0
20
40
60
80
100
120
Estimated Use (%)
Palm Oil Palm Olein Palm Stearin Super Olein Palm Mid-Fraction
Fig. 3 Specic food applications of palm oil and its
fractions.
Food Bioscience 10 (2015) 26–41 35
involve ltration and replenishment of oil with fresh oil
samples (Ismail, 2005).
Oil and nutrient diffusion in the fried product depends on
the shape, nature, texture and microstructure of the food. It
also depends on the viscosity of the oil, the frying tempera-
ture and time (Boskou, 2011). The use of palm oil in frying is
based not only on the frying stability, but also on the
assumption that the tocopherols, tocotrienols, the carote-
noids and phenolic components will migrate into the fried
products. The major mechanisms of the diffusion of these
micronutrients together with the frying oil are molecular
mechanism (Aguilera, 2005); capillary forces (Moreira &
Barrufet, 1998;Yamsaengsung & Moreira, 2002) and over
pressure across the food matrix also referred to as vacuum
effect after removing food from the fryer (Vitrac, Dufour,
Trystram, & Raoult-Wack, 2002;Ziaiifar, Achir, Courtois,
Trezzani, & Trystram, 2008). The amounts of micronutrients
in fried products can be estimated from their respective
concentrations in the frying oil. The type of oil, the quality,
and the frying procedure appear to have an impact on the
diffusion and distribution of these nutrients in the fried
product. The amounts of the minor constituents tend to
decrease during frying thus affecting their concentration in
food products (Chiou, Kalogeropoulos, Boskou, & Salta, 2012).
Not much has been published to detail the presence of these
micronutrients in fried foods. Table 6 shows that while many
types of foods have been fried and studied only French fries
have been studied to a limited extent concerning its enrich-
ment with micronutrients from the oil. The evaluation and
characterization of the constituents of the oil absorbed by
different food products still require closer attention in order
to promote the manufacture of micronutrients enriched fried
products.
5. Blending
In the frying industry, the trend is to modify the vegetable oil
in order to improve the nutritional quality, functional proper-
ties, oxidation stability and technical performance of the
frying oil. Blending two or more oils with different character-
istics, such as fatty acid chain length and/or patterns of
unsaturation, is another option to making new specic frying
oils (De Leonardis & Macciola, 2012;OBrien, 2010;Tiwari,
Tiwari & Toliwal, 2014).
In blending, the composite oils share advantages and dis-
advantages depending on the blend ratio. It is important that the
blend complies with all the food laws and guidelines as well as
meet consumers' expectations. The objective of blending can be
commercial, technical, functional, nutritional or their interac-
tions depending on the intended application. Blending is widely
accepted because it does not increase processing cost (Chu &
Kung, 1998;Waghray & Gulla, 2011). Blending of polyunsaturated
oils with highly saturated oils reduces the content of linoleic and
linolenic acids to the desirable level where the effect is similar to
partial hydrogenation without worrying about the formation of
trans fatty acid isomers (Hoffmann, Swiderski, Zalewski, &
Berger, 2002;Naghshineh & Mirhosseini, 2010;Tiwari et al.,
2014). It may be necessary to interesterify oil blends. Interester-
ication is a procedure for rearranging the fatty acids in oil or in
Table 6 The distribution of micronutrients in products fried in palm oil or palm olein.
Food Frying conditions Micronutrients References
Temperature
(1C)
Time
(min)
Total polyphenol
(CAE mg/100 g
Phytosterol
(mg/100 g)
Total carotene
(mg/100 g)
Total
tocopherol
(mg/100 g)
Total
tocotrienol
(mg/100 g)
Frozen par
fried potato
180 5 ––1388 ––Andreu-Sevilla et al. (2009)
French fries 17575 6 8.2 –– Chiou et al. (2007)
French fries 175756––1200 Chiou, Kalogeropoulos, Salta, Efstathiou, and
Andrikopoulos (2009)
French fries 175756820020,800 ––Salta, Kalogeropoulos, Karavanou, and
Andrikopoulos (2008)
CAE¼caffeic acid equivalents.
Food Bioscience 10 (2015) 26–4136
a blend of oils so that triacylglycerol composition is changed. The
fatty acid composition of the single oil or the blend remains
unchanged and do not interact with triacylglycerols as they are
of similar chemical composition (Benjumea, Agudelo, & Agudelo,
2008;Christie & Han, 2010).
The oxidation stability of a blend highly depends on those
of the individual oils in the mix (Isbell, Abbott, & Carlson,
1999;Tiwari et al., 2014). The oxidative stability of palm oil in
a blend is principally due to its high saturation and heavy
presence of natural antioxidants, especially γ-tocotrienol
(Bansal, Zhou, Barlow, Lo, & Neo, 2010;De Leonardis &
Macciola, 2012;De Marco et al., 2007). Different researchers
have evaluated the frying characteristics of blends of other
vegetable oils and palm oil/palm olein (Del Carmen Flores-
Álvarez, Molina-Hernández, Hernández-Raya, & Sosa-Morales
2012;Kupongsak & Kansuwan, 2012;Naghshineh &
Mirhosseini, 2010;Tiwari et al., 2014). Blending palm oil with
rice bran oil signicantly lowered serum lipids in rats after 8
weeks of feeding trial (Reena & Lokesh, 2012). De Leonardis
and Macciola (2012) reported that the fatty acid composition
of oils and blends appeared to be the most decisive factor
inuencing oxidation stability. The saturated/unsaturated
fatty acid ratio near to 1 offers optimally stable condition.
The American Heart Association/WHO guideline for smart
blend ratio is 1:1:1 for SFA, MUFA and PUFA vegetable oils.
Some important ndings in literature concerning blends of
palm oil or palm olein are summarized in Table 7.Hayes and
Khosla (2007) reported that palm oil (or palm olein) is the oil
of choice for blending with unsaturated oils to provide
specic functional characteristics without compromising
health. This is because partially hydrogenated fats contain
trans fatty acids which have demonstrated adverse health
effects (Chen et al., 2014;Mozaffarian, Aro, & Willet, 2009).
Blending tailors and improves frying properties of oil by ne
tuning the fatty acid composition and antioxidant balancing.
It improves the fried product quality, improves appearance
and enhances the shelf life of the product. Blending also
helps moderate the retail prices of oil for the consumers
benet.
6. Conclusion
Palm oil has nearly equal amounts of saturated and unsatu-
rated fatty acids. Palmitic acid is the major saturated fatty
acid while oleic acid is the monounsaturated fatty acid. The
oil is semi-solid at room temperature; it does not require
hydrogenation. With about 500700 ppm of carotenoids, palm
oil is nature's richest source of β-carotene and lycopene.
It is also very rich in vitamin E, especially tocotrienols
and tocopherols. The carotenoids and the vitamins E act
synergistically as powerful natural antioxidants. They confer
Table 7 Summary of effects of blending palm oil/palm olein and other vegetable oils.
Oil blends Blend ratio, %
(palm oil:
other oil)
Effect Reference
Palm oil:sunower
oil
80:20 Palm olein with much higher IV Nor Aini, Hasmadi, Mamot, and
Radzuan (2005)60:40 40% Blends reduced olein's cloud point
Palm olein:olive oil 75:25 Oil remained liquid at ambient temperature.
Increased
oxidative stability
Naghshineh et al. (2009)
50:50
Palm olein:canola oil 50:50 Better PV after repeated frying at 180 1C; French
fries had
reduced fat content than olein alone
Enriquez-Fernandez, Yanez, and Sosa-
Morales (2011)
Palm olein: canola oil 50:50 Stable against oxidation; depressed melting point Mobin Siddique et al. (2010)
Palm oil:extra virgin
Olive oil
88:20 Induction time and oxidative stability similar to
pure palm
oil at 120, 130 and 140 1C
De Leonardis and Macciola (2012)
Palm olein:sunower
oil
50:50 Exhibited very high radical scavenging activity Ramadan, Amer, and Sulieman (2006)
Palm olein:peanut oil 90:10
to 60:40
Increasing peanut imparted a pleasant nutty
avor; signicant
changes in percentage of C16:0 and C18:2
Myat, Abdulkarim, Mohd Ghazali, and
Karim (2009)
Palm oil:sunower
oil
65:35 Decreased rate of evolution of FFA and polar
compounds during
8 h of discontinuous frying; reduced degradation
rate
of tocopherols and tocotrienols
De Marco et al. (2007)
Palm olein:canola oil 75:25 Frying stability of canola oil signicantly improved
by
the blending
Farhoosh, Kenari, and Poorazrang
(2009)
Palm olein:olive oil:
corn oil
75:15:10 Frying performance of ternary blend better than
binary blends
Farhoosh et al. (2009)
Palm oil:sesame oil 52:48 Resulted in ideal fatty acid composition of 1:1:1
(SUFA:MUFA:PUFA)
stable to oxidative deterioration enhanced
nutritional qualities
Tiwari et al. (2014)
Food Bioscience 10 (2015) 26–41 37
oxidative stability to palm oil in most food applications
especially during frying. CPO can be fractionated to a liquid
palm olein and a solid palm stearin. This further diversies
the oil's usefulness. Worldwide, 90% of palm oil is used for
edible purposes while 10% is used in the soap and oleo-
chemical industries. Palm oil is widely used as frying oil
because of its high smoke point (230 1C) and a stronger
resistance to thermoxidation than most other vegetable oils.
Blending palm oil with more unsaturated or monounsatu-
rated oils is an option adopted to improve and enhance the
commercial, functional, nutritional and technical attributes
of the oil. Blending minimizes the changes caused by hydro-
lysis, oxidation, and polymerization during high thermal
stress. Blending is a desirable alternative to the negative
effects associated with hydrogenation and high cost asso-
ciated with interesterication.
It is recommended that more attention be given to study-
ing the retention and migration of the micronutrients into
the fried products with a view to optimizing production of
healthier fried products. The distribution of the absorbed oil
within the food matrix as well as interaction between the
native food nutrients and the frying oil should be investi-
gated. The health implications of using composite oils should
be studied further. The kinetics of degradation of CPO and
blends as frying medium also needs to be evaluated.
Acknowledgments
The authors wish to thank Tertiary Education Trust Fund
(TETfund) Abuja Nigeria and the Natural Science and Engi-
neering Research Council (NSERC) of Canada for their nan-
cial support (grant no. RGPIN 217012).
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