Evaluation of Hexane Content in Edible Vegetable Oils Consumed in Iran

Abstract

Solvent residue such as hexane in foodstuff, especially edible oil could be considered as the undesirable substances when exceeds maximum residue limit (MRL). The aim of this study is to determine the hexane content in various brands of edible oils. Totally forty samples (23 brands) of different types of vegetable oils including frying oils (n=14), blended oils (n=13), sunflower oils (n=6), corn oils (n=5) and canola oils (n=2) from Iran´s market were analyzed for hexane content using solid phase microextraction gas chromatography equipped with a flame-ionization detector (SPME)-GC-(FID). The hexane residue was detected in thirty-six out of forty examined samples, ranged from lower than LOD to 42.6 µg/kg. However, in all of them hexane content were below the MRL of 1 mg/kg which set by the European Union.

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Evaluation of Hexane Content in Edible Vegetable Oils Consumed in Iran
Mojtaba Yousefi 1,2, Hedayat Hosseini2,*
1Food Safety Research Center (Salt), School of Nutrition and Food Sciences, Semnan University of Medical
Sciences, Semnan, Iran
2Department of Food Science and Technology, Faculty of Nutrition Sciences, Food Science and Technology/National
Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Abstract
Solvent residue such as hexane in foodstuff, especially edible oil could be considered as the undesirable
substances when exceeds maximum residue limit (MRL). The aim of this study is to determine the hexane
content in various brands of edible oils. Totally forty samples (23 brands) of different types of vegetable oils
including frying oils (n=14), blended oils (n=13), sunflower oils (n=6), corn oils (n=5) and canola oils (n=2)
from Iran´s market were analyzed for hexane content using solid phase microextraction gas chromatography
equipped with a flame-ionization detector (SPME)-GC-(FID). The hexane residue was detected in thirty-six out
of forty examined samples, ranged from lower than LOD to 42.6 µg/kg. However, in all of them hexane content
were below the MRL of 1 mg/kg which set by the European Union.
JOURNAL OF EXPERIMENTAL AND CLINICAL TOXICOLOGY
ISSN NO: 2641-7669
Research DOI: 10.14302/issn.2641-7669.ject-17-1790
Corresponding author: Hedayat Hosseini, Address: 46, West Arghavan St., Farahzadi Blvd., Shahrak Qods,
National Nutrition & Food Technology Research Institute, Zip Code: 1981619573, P.O. Box
19395-4741, Tehran, Tel: +9822376426; Fax: +982122360660, Email address: Hedayat@sbmu.ac.ir
Keywords: Edible oils, Hexane, GG, Solvent residue
Running title: Contamination of edible oils with hexane
Received: Sep 23, 2017 Accepted: Oct 20, 2017 Published: Nov 01, 2017

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Introduction
Edible oils and fats can be produced either by
solvent or mechanical extraction of oilseeds. Hexane is
one of the most commonly used solvents in the edible
oil industry (1). Commercial hexane consists of some
isomers of six-carbon paraffins, normally
n
-hexane and
it has toxic effects (2). Long or acute exposure to
haxane might cause several human health implications
such as polyneuropathy, muscular weakness, headache,
dizziness, giddiness, slight nausea (3, 4). It has been
reported by O’Quinn
et al.
(1997) that hexane may
cause some degeneration of the digestive system of
animals (5). Hexane residue has been found toxic to
humans and animals at relatively low concentrations as
mentioned by Sparks
et al
. (2006) (6). Since refining,
bleaching and deodorization are carried out as
complementary processes before using oil as food
products, it is likely that solvent residue approximately
eliminated (7). However, a trace amount of hexane may
be found in the final product. Therefore, maximum
residual limit (MRL) has been established for hexane
residue by various organizations. The European Union
(EU) Community has set 1 mg/kg of hexane residue in
vegetable oils (8). Several studies estimated hexane
residue in vegetable oil (9), beeswax (10), annatto
extracts (11) using headspace gas chromatography
(GC).
Michulec
et al.
(2004) evaluated the presence
of hexane, benzene and toluene in the vegetable oils,
cardamom and vitamin A using HS- GC-FID (12). Ligor
and Buszewski (2008) developed SHS-GC-FID and SPME
-GC-FID methods to investigate the presence of
solvents such as acetone, n-hexane, benzene, and
toluene in various edible oils and they found that these
methods could be successfully applied in the usual
analysis of residue solvents in vegetable oils (13).
Based on our knowledge, there is not a
comprehensive study in order to evaluate the
concentration of hexane residues in consumed edible
oils in Iran. Therefore, the aim of this study was to
assess the hexane residues in 40 collected edible oil
samples from of Iran market.
Materials and Method
Chemical Materials
Milli-Q apparatus was utilized to supply
deionized water (Billerica, MA, USA).The SPME
apparatus with Carboxen (CAR)/PDMS–thickness 75 lm)
coating fibers was supplied from Supelco(Bellefonte, PA,
USA). The precondition of SPME fibers was done at
200°C for 10 min.
Analytical grade of hexane and chemical
materials were supplied from Merck (Darmstadt,
Germany).
Samples Collection and Preparation
In total, 40 oil samples (consisting of sunflower
(n=6), corn (n=5), canola (n=2), frying (n=14) and
blended oils (n=13)) of 24 brands were collected from
Iranian market (Tehran, summer 2014). All the samples
were stored at the dark room (25°C), in their original
packages (Polyethylene terephthalate (PET)). The
analysis all were performed in triplicate.
Hexane Measurement
The solid phase microextraction Agilent
Technologies 7890A GC system (SPME)-GC-(FID) (Palo
Alto, CA, USA) which was coupled to a flame-ionization
detector (FID)were used to determine residual hexane
according to the Ligor and Buszewski (2008), Briefly, 50
mL of oil samples were placed in the HS vials (120 mL).
Isolation step was carried out at 40 ± 1°C for 30 min
without stirring. After that desorption was done for 5
min by the fiber in the injection port in where the
temperature was adjusted 200°C (injector position –
splitless). Then the oven temperature program was
started (position–split). Separation was performed using
The Stabilwax (Restek) column (30 m× 0.25 mm × 0.25
µm). The oven temperature program consisted of 3 min
isothermal period at 40°C, then raised at 4°C/min
increase to 100°C (held for 0 min), followed by
increasing the temperature by 15°C/min to 190°C/min
(held 4 min). Helium (99.999% purity) was utilized as a
carrier gas with a pressure of 100 kPa. The temperature
of split – splitless injector and the FID detector were
adjusted 200°C (13).
Result and Discussion
Hexane Concentration
Hexane is one of the most commonly used
solvents not only in the edible oil industry but also in
the process of herbal medicine and bioactive

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components production (14, 15). So, hexane may be
present in trace amounts in these kinds of products. A
study has previously shown that 2,5-hexanedione which
is derived from the metabolism of hexane is neurotoxic
(16). Therefore, various maximum residual limit (MRL)
has been determined for residual solvent in these
products in order to reduce or eliminate chronic toxic
effects of the solvents. So, in this study the hexane
residue in 40 collected edible oil samples from of Iran
market was evaluated. The limit of detection (LOD) and
the limit of quantification (LOQ) were 3 µg/kg and 5µg/
kg, respectively. The high correlation coefficients (0.981)
indicated that there is a good linear behavior in the
tested range (5-100 µg/kg). In this study, analysis of 40
oil samples described that 36 of them had hexane
residue and its concentration ranged from < LOD to
42.6 µ/kg (Table 1). The results showed that 35% of the
samples had hexane residue ranging from 5-42.6 µg/kg,
while 10% of the samples were free of hexane and any
hexane residue was detected in these 4 samples. The
55% of remaining samples had hexane residue, but it
value was lower that LOQ.and LOD. As can be seen in
Table 1 the highest hexane content as observed in
canola oil. Based on the maximum residue limit of 1 mg/
kg of hexane in the vegetable oils which is set by the
European Union, none of the analyzed samples exceed
the limit (8). There are only a few studies about the
hexane residue in vegetable oils. Commercial orujo oil
samples with various percentages of virgin olive oil
(5–10%) were analyzed by Peña
et al.
(2003) for the
presence of residual hexane and the results showed that
almost all the samples were negative in term of hexane
residue (lower than LOD) and just two samples had
hexane at concentration of 2 and 3 mg/kg (3). The
presence of solvent residue, including hexane, benzene,
and toluene has been investigated by Michulec
et al.
(2004) in the different brands of primrose oil using HS-
GC-FID. The value of 0.004, 0.009 and 0.017 mg/kg
were achieved as limits of detection (LOD) for hexane,
benzene, and toluene, respectively. They found that in
all the primrose oils, the content of benzene was lower
than LOD. Hexane residue in the most of the samples
was lower than LOD, and only three samples had the
value of 0.13, 0.16 and 0.70 mg/kg for hexane content
(12). Similarly, the content of toluene was lower than
LOD in the most oil samples. Oh
et al.
(2005) found that
hexane residue varied from trace amounts to 2.8 mg/kg
in 87 commercial vegetable oils (9). Additionally, Ito
et
al
. (2012) evaluated 23 annatto extract products for
hexane residue by applying HS-GC/FID, and nearly 91%
of the samples were free of hexane and only two
samples containing hexane in the value of 0.6 and 0.7
mg/kg (11). Ligor and Buszewski (2008) investigated the
presence of some solvents including acetone, n-hexane,
benzene, and toluene in various edible oils using SPME-
GC-FID and SHS-GC-FID methods. A value of 0.003 and
0.002 mg/kg were obtained for a limit of detection by
SPME-GC-FID and SHS-GC-FID methods, respectively.
Their results showed that the residual amount of hexane
in various vegetable oils was between 0.005 –0.460 mg/
kg, which was below the permitted value of Polish norm
(1000 mg/kg) (13). Jeong et al. (2017) developed HS-
GC/MS method to evaluate hexane residue in health
functional food products. They claimed that by applying
this approach, it is likely to determine hexane residue in
various kinds of these commodities. Their results
showed that the average content of hexane in γ-
Linolenic acid, omega-3 fatty acid, and conjugated
linoleic acid was 0.39, 0.45 and 0.74 mg/kg,
respectively. Furthermore, they achieved the value of
0.56 and 0.76 mg/kg as the mean content of hexane
residue in lecithin and phosphatidylserine, respectively
(14). Based on our study and similar research that
evaluated the presence of hexane in the vegetable oils,
bixin-based products, and some commercial functional
food products, it seems that there is no concern about
hexane residue in these commodities.
Conclusion
Hexane is the solvent that is widely utilized in
the process of herbal medicine and bioactive
components production and oil industry. However, it
may not be completely removed and hexane residue,
especially more that standard limit is undesirable. In this
study the content of hexane in forty samples (23
brands) of different type of vegetable oil including
frying, blended, sunflower, corn, and canola oils were
investigated. Although, hexane residue was determined
was detected in thirty-six out of forty examined samples,
hexane content was below the MRL of 1 mg/kg which
set by the EU in all of oil samples.
Conflict of Interest

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Table 1. Content of hexane residue in different brands of vegetable oil
Type of edible oil Hexane residue (µg/kg) Type of edible oil Hexane residue (µg/kg) Type of edible oil Hexane residue (µg/kg)
Frying oil
(Brand)
Blended oil
(Brand)
Sunflower oil (Brand)
1 (A) <LOD 1 (A) <LOD 1 (A) 5±0.2
2 (B) ND 2 (B) <LOD 2 (B) <LOD
3 (C) <LOQ 3 (C) 4.8±0.15 3 (C) ND
4 (D) 9±1.44 4 (D) <LOQ 4 (I) <LOD
5 (E) 5±0.45 5 (E) 10.4±0.32 5 (J) <LOD
6 (F) <LOQ 6 (F) <LOD Corn oil (Brand)
7 (G) <LOD 7 (G) <LOQ 1 (A) 5.5±0.15
8 (H) 5.5±0.2 8 (H) <LOQ 2 (B) <LOQ
9 (I) 4.6±0.15 9 (J) <LOD 3 (P) LOD
10 (K) 4.8±0.45 10 (N) <LOQ 4 (Q) 5.7±0.15
11 (L) ND 11 (O) ND 5 (R) 18.3±0.25
12 (M) <LOD 12 (T) <LOD 6 (S) 6.9±0.2
13 (U) 5.4±0.15 13 (W) <LOD Canola oil (Brand)
14 (V) <LOQ 1 (A) 42.6±0.2
2 (B) <LOD
The authors declare there are no conflicts of
interest.
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