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The effect of consecutive steps of refining on squalene content of vegetable oils

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The aim of this study is to evaluate the effect of refining steps on the squalene content of some vegetable oils. A comparison has been made between the crude oils and consecutive steps of refining process (neutralization, bleaching, deodorization, winterization) in the amounts of squalene of the oil samples. Among the oils, virgin and refined olive oils contained higher amounts of squalene. A mean of 491.0 ± 15.55mg/100g squalene was found in virgin olive oil samples. While appreciable quantities of squalene has been reduced during refining, considerable level of squalene were still present in refined olive oils (290.0 ± 9.89mg/100g). The squalene content of crude seed oils varied from 13.8 ± 0.39mg/100g to 26.2 ± 0.08mg/100g as average. It has been determined that refining process reduced the level of squalene in examined oils. The highest reduction in squalene content of the oils was detected during deodorization. The effect of refining steps on the amount of squalene in vegetable oils was found to be significant (p < 0.05). Olive oil has been considered an important source of squalene, even after it has been refined, compared to seed oils. KeywordsVegetable oils–Refining–Squalene
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SHORT COMMUNICATION
The effect of consecutive steps of refining on squalene
content of vegetable oils
Cevdet Nergiz &Deniz Çelikkale
Revised: 13 November 2010 /Accepted: 22 November 2010 / Published online: 21 December 2010
#Association of Food Scientists & Technologists (India) 2010
Abstract The aim of this study is to evaluate the effect of
refining steps on the squalene content of some vegetable
oils. A comparison has been made between the crude oils
and consecutive steps of refining process (neutralization,
bleaching, deodorization, winterization) in the amounts of
squalene of the oil samples. Among the oils, virgin and
refined olive oils contained higher amounts of squalene. A
mean of 491.0±15.55 mg/100 g squalene was found in
virgin olive oil samples. While appreciable quantities of
squalene has been reduced during refining, considerable
level of squalene were still present in refined olive oils
(290.0±9.89 mg/100 g). The squalene content of crude seed
oils varied from 13.8±0.39 mg/100 g to 26.2±0.08 mg/
100 g as average. It has been determined that refining
process reduced the level of squalene in examined oils. The
highest reduction in squalene content of the oils was
detected during deodorization. The effect of refining steps
on the amount of squalene in vegetable oils was found to be
significant (p<0.05). Olive oil has been considered an
important source of squalene, even after it has been refined,
compared to seed oils.
Keywords Vegetable oils .Refining .Squalene
Introductıon
In recent years, understanding of the positive effect of some
minor components of foods on human health has encour-
aged the scientific research on this topic. A great interest has
been on the Mediterranean populations who have longer life
and more healthy living. This was due to the their diets as
extra virgin olive oil which is more consumed by this
populations as compared to other countries (Strandberg et al.
1990;Owenetal.2000a).
Squalene is one of the minor constituents of vegetable
oils and has a role on human health. Epidemiological
studies have shown that it can effectively inhibit chemically
induced colon, lung and skin tumourigenesis in rodents
(Smith et al. 2000). It has been also used in several
cosmetic applications as a solute component in fats because
it is absorbed easily by skin (Üstündağand Temelli 2004).
It was reported that the decreasing risk for various cancers
and reducing serum cholesterol levels has been ascribed to
the squalene in vegetable oils (He et al. 2003). Several
studies have been carried out to obtain squalene hydrocar-
bon from vegetable sources or marine animals by using
different methodologies (Vazquez et al. 2007). Squalene has
been sold in the markets as capsules for the beneficial effect
on human health recently.
Crude vegetable oils contain squalene in the minor
components which are generally constitute 13% of oil.
One of the most important differences between the olive oil
and other vegetable oils is the amount of squalene present
in the oil. Its concentration in olive oil varies between 0.2
and 0.7%, whereas in other edible vegetable oils it
constitutes only 0.0020.03% (Rao et al. 1998). On the
other hand, the techniques of olive growing (Psomiadou
and Tsimidou 1999), oil extraction methods (Nergiz and
Ünal 1990), Olive fruit variety (Draman and Hışıl2005),
C. Nergiz (*)
Department of Chemistry, Faculty of Arts and Sciences,
Fatih University,
34500 Büyükçekmece, Istanbul, Turkey
e-mail: cnergiz@fatih.edu.tr
D. Çelikkale
Department of Food Engineering, Engineering Faculty,
Celal Bayar University,
45140 Muradiye, Manisa, Turkey
J Food Sci Technol (MayJune 2011) 48(3):382385
DOI 10.1007/s13197-010-0190-2
refining process (Owen et al. 2000a) and adulteration of
virgin olive oil with seed oils affect squalene content of the
oils. The amount of squalene in virgin olive oil has also
been considered as an indicator for adulteration.
Despite variable the squalene content found in several
vegetable oils, there is no detailed investigation on the
factors affecting the amount of squalene in vegetable
oils. Among the factors, refining process is important,
since all the crude vegetable oils cannot be consumed
without refining, except good quality virgin olive oil.
The purpose of this study is to investigate the changes in
the amount of squalene in different vegetable oils during
refining process.
Materials and methods
Materials
Oil samples were collected from four different commercial
refineries representing for five different vegetable oils as
two replicates. For the analysis, about 150 mL of oil
samples were taken from each refining steps from selected
refineries. The collected oil samples of olive (10), sunflower
seed (10) and rapeseed (10) were refined by conventional
method. Soybean (8) and corn oil (8) samples were refined by
physical method. Their processing conditions were usually
the same as encountered in industry.
Reagents Squalene standard (purity97%) was purchased
from Fluka (Switzerland), Chloroform, diethylether and
hexane (A.C.S. grade) were obtained from Merck (Darmstadt,
Germany). TLC plates (20× 20 cm), pre coated (0.2 mm) with
silica gel 60 F
254
were obtained from Fluka (Switzerland),
The other reagents were analytical grade.
Equipment A gas chromatograph apparatus (Agilent 6890N
Series Network GC System) was used with a flame -
ionization detector and a capillary column (HP-5.30 m long ×
0.32 i.d.) coated with a 0.25 μm film thickness of liquid phase
(5% phenyl) methylpolysilioxane (Agilent Technology, USA).
Methods
Extraction of the unsaponifiable fraction of the oil samples
were conducted IUPAC Method 2.401 (1987). Five gram of
the oil sample was weighed into a flask and 50 mL 1 N
ethanolic potassium hydroxide solution was added. The
mixture was saponified for 1 h under reflux condenser.
After the saponification, 100 mL distilled water was added.
The solution was poured into the a 500 mL separating
funnel and extracted with 50 mL portions of diethyl ether.
The ethereal extracts were combined into the another
decanting funnel and were washed several times with
100 mL portions of distilled water until the wash-water
gave neutral pH. The ether solution was dried over
anhydrous sodium sulfate and evaporated in a rotary
evaporator under vacuum. The residue was dissolved in
1 mL chloroform and applied to the TLC plates, it was
developed with hexane -diethyl ether mixture (80:20, v/v)in
a developing tank. After drying bands were marked by
viewing under UV light at 254 nm. The spot of squalene
with same Rf value of the authentic squalene standard was
scraped off and dissolved with diethyl ether and filtered.
The ethereal solution was evaporated on a water bath by
passing through the nitrogen gas and dissolved in a certain
mL of hexane. The amount of squalene was determined gas
chromatographically and calculated using a calibration
curve of peak heights versus amount of injected squalene
standards. The chromatographic conditions were: initial
oven temperature 180 °C/min then programmed at 8 °C/min
to 270 °C. Injector temperature: 290 °C, detector temperature:
300 °C. Split ratio was 1:50 using hydrogen as carrier gas with
a flow of 1.0 mL/min. One μL sample was injected by
automatic injector (Agilent 7683 ALS series automatic liquid
sampler). Variance analysis (ANOVA) was used statistical
evaluation of the results by using a package programme SAS
Table 1 Changes in squalene content (mg/100 g) of vegetable oils during refining steps
a
Refining Steps Olive oil
(n=10)
Sunflowerseed oil
(n=10)
Rapeseed oil
(n=10)
Corn oil
(n=8)
Soybean oil
(n=8)
Crude oil 491.0a± 15.55 13.8a± 0.39 26.2a± 0.08 24.7a± 0.40 18.1a± 0.11
Neutralization/Physic. Refining 427.0a± 9.89 (13.0) 12.8b± 0.36 (6.9) 25.7b± 0.11 (1.7) 23.0b± 0.31 (7.3) 15.6b± 0.11 (13.5)
Bleaching 392.5b± 7.77 (7.0) 12.1b± 0.25 (5.3) 24.2c ± 0.10 (5.5) 20.4c±0.29 (11.9) 13.3c± 0.06 (13.0)
Deodorization 315.5c± 6.36 (15.6) 9.9c ± 0.32 (16.9) 22.0d± 0.08 (3.2) ––
Winterization 290.0d± 9.89 (5.2) 9.2d± 0.30 (4.0) 21.1e ± 0.06 (8.7) 25.9b± 0.27 (6.8) 12.5d±0.08 (4.4)
The values given in parenthesis are the % reduction of squalene during each of refining steps
ad Values with same letters within each column are not significantly different (p> 0.05)
a
Data are mean values of duplicate analysis ± standard deviation
J Food Sci Technol (MayJune 2011) 48(3):382385 383
(Statistical Analysis System) and Duncans multiple range test
(Anon 2001).
Results and discussion
The amounts of squalene in five different crude oil samples
and after each refining steps were given Table 1. Squalene
content of crude oil samples ranged from 13.8±0.39 mg/
100 g to 491.0±15.55 mg/100 g as average. These results
are in agreement with the values reported in the literature
related with squalene content of olive and seed oils
(Gutfinger and Letan 1974; Kiritsakis et al. 1998; Owen
et al. 2000b).
Table 1shows that the average squalene content of the
crude olive oil samples found to be 491.0±15.55 mg/100 g
and decreased for all the refining steps and the largest
reduction has occurred during the deodorization. This was
followed by the neutralization step. The least reduction in
squalene was determined during the vinterization. Squalene
reductions occurred during refining in olive oil samples
were very close. Total reductions during all the stages of
refining was found to be 40.94% as compared to crude
olive oil samples. A significant difference was found
among the refining steps in terms of squalene reductions
statistically (p0.05), which is in agreement with values
reported earlier by Vazquez et al. (2007). They also
reported that deodorization distillate is quite rich in
squalene content and can be used as source of vegetal
squalene. It was recovered from deodorization distillate in
the grade of 93% and 91% purity by supercritical fluid
extraction method (Vazquez et al. 2007).
The amount of squalene in sunflower seed oil was found
to be quite low level as compared to olive oil (Table 1).
Total average reduction for sunflower seed oil samples
during refining process was 32.9%. Table 1shows that the
most reduction has occurred during deodorization. Statisti-
cal evaluation has been made between the average values
pertaining to sunflower seed oil samples and a significant
difference was found among the refining steps in squalene
reductions (P<0.05).
Rapeseed oil samples showed similar results as shown
by olive and sunflower seed oil samples in squalene
reductions during refining process. Total decrease in the
amount of squalene belonging to rapeseed oil samples was
found to be 19.10% averagely (Table 1). The largest
reductionhasalsobeenfoundtooccurduringthe
deodorization step. A significant difference was found
among the refining steps in terms of squalene reductions
statistically (P<0.05). In the physical refining process the
amount of squalene content of corn oil was reduced
marginally (Table 1). Total lowering of squalene was
25.90% in corn oil during refining. In contrast to other
oils, the largest decrease was detected during bleaching step
in corn oil. Differences among the refining steps of corn oil
in terms of squalene content reduction were also found to
be significant (P<0.05).
Crude soybean oil contained 18.1±0.11 mg/100 g
squalene as average (Table 1). Similar values in soybean
oil has been reported by Kiritsakis et al. (1998). Squalene
reductions showed differences during physical refining of
soybean oil. In contrast to corn oil, the highest decrease in
amount of squalene has been found to occur during
deacidification process. This differences may be due to
both differences in nature of oils and refining conditions.
Whereas it was the deodorization step that gave largest drop
in squalene content for olive, sunflower seed and rapeseed
oils during chemical refining. Shahidi and Wanasundara
(1999), reported that the most losses of squalene (63%)
occurred during the deodorization step for sea blubber oil
refining. It was thought that high temperature applied
during deodorization caused evaporation and degradation
of squalene.
Conclusion
During the refining of five different types of vegetable oils
the decrease in the squalene level varied from 19,1 to
40,9%. In olive oil which had a higher level of squalene,
losses are relatively higher whereas in the seed oils that
contain lower level of squalene, it was found that the losses
are relatively lower. It has been determined that there is a
considerable difference between natural and refined olive
oil and seed oils in terms of squalene level; furthermore,
olive oil, even it is refined, contains 25 to 30 times more
squalene compared to seed oils. The oils, like olive,
sunflower and rapeseed, processed by chemical refining,
exhibited largest drop in squalene content during deodor-
ization step. In consideration of the fact that only 60% of
squalene that has been taken through a diet, could be
absorbed in human body, it is believed that other types of
vegetable oils could not be considered as a source of
squalene but olive oil.
Acknowledgement This study was supported financially by the
Scientific Research Fund of Celal Bayar University under project
number Müh.2007/037.
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The role of squalene in olive oil stability was studied for various concentrations and experimental conditions. No effect was found in induction periods of olive oil at elevated temperatures using the Rancimat apparatus. Samples were then stored at 40 and 62 degrees C in the dark, and the extent of oxidation was followed by periodic measurements of peroxide value and conjugated dienes. A concentration dependent moderate antioxidant activity was evidenced which was stronger in the case of olive oil compared to that found for sunflower oil and lard. In the presence of alpha-tocopherol (100 mg/kg) and caffeic acid (10 mg/kg) the contribution of squalene (7000 mg/kg) was not significant. No radical scavenging activity was observed using DPPH(*) in 2-propanol. The weak antioxidant activity of squalene in olive oil may be explained by competitive oxidation of the different lipids present which leads to a reduction of the oxidation rate. Squalene plays a rather confined role in olive oil stability even at low temperatures.
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The aim of this study was to evaluate the phenolic antioxidant and squalene content in a range of olive and seed oils. A mean of 290 +/- 38 (SEM) mg squalene/100 g was detected. However, while there was a weak significant difference between extra virgin (424 +/- 21 mg/kg) and refined virgin (340 +/- 31 mg/100 g; P<0.05) olive oils, highly significant differences were evident between extra virgin olive oils (P<0.0001) refined virgin olive oils (P<0.0001) and seed oils (24 +/- 5 mg/100 g). While seed oils were devoid, on average, the olive oils contained 196 +/- 19 mg/kg total phenolics as judged by HPLC analysis, but the value for extra virgin (232 +/- 15 mg/kg) was significantly higher than that of refined virgin olive oil (62 +/- 12 mg/kg; P<0.0001). Appreciable quantities of simple phenols (hydroxytyrosol and tyrosol) were detected in olive oils, with significant differences between extravirgin (41.87 +/- 6.17) and refined virgin olive oils (4.72 +/- 215; P<0.01). The major linked phenols were secoiridoids and lignans. Although extra virgin contained higher concentrations of secoiridoids (27.72 +/- 6.84) than refined olive oils (9.30 +/- 3.81) this difference was not significant. On the other hand, the concentration of lignans was significantly higher (P<0.001) in extra virgin (41.53 +/- 3.93) compared to refined virgin olive oils (7.29 +/- 2.56). All classes of phenolics were shown to be potent antioxidants. In future epidemiologic studies, both the nature and source of olive oil consumed should be differentiated in ascertaining cancer risk.
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