The fatty acid and tocopherol constituents of the seed oil extracted from 21 grape varieties (Vitis spp.)

Abstract

Fatty acids and tocopherols in appropriate quantities are invaluable attributes that are desirable in seeds of agricultural products. Studies have generally focused on the evaluation of the oil and tocopherol components of oil crops. Recently, investigations revealed that the grape seed has robust potential in the production of healthy fatty acids as well as tocopherols. This study was thus conducted to determine the oil and tocopherol components of grape seeds, obtained from various grape cultivars of different species, including two rootstock varieties.
The grape seed oil concentration of the studied varieties ranged from 7.3 to 22.4%. The determined fatty acid profiles of the genotypes conformed to the pattern described in the literature for grapes. Linoleic acid is the major component comprising 53.6-69.6% of the total, followed by oleic (16.2-31.2%), palmitic (6.9-12.9%) and stearic (1.44-4.69%). The oils of all the seeds analysed showed a preponderance of α-tocopherol (ranging from 260.5 to 153.1 mg kg⁻¹ oil extract). β-Tocopherol, γ-tocopherol and δ-tocopherol were also detected with the general means of 0.98, 22.2 and 0.92 mg kg⁻¹, respectively. Linoleic acid showed a significantly negative correlation with all the fatty acids analysed. The strongest negative correlation existed between linoleic and oleic acids (r = -0.834, P < 0.01).
Present investigations indicated that oil content, fatty acid composition and tocopherol constituents of grape seed show great variation among the genotypes. Markedly higher proportions of linoleic acid with considerable amounts of tocopherols found in the oil samples suggest that grape seed is a good source for culinary, pharmaceutical and cosmetic uses.

Full text

1982
Research Article
Received: 26 May 2011 Revised: 1 December 2011 Accepted: 1 December 2011 Published online in Wiley Online Library: 23 January 2012
(wileyonlinelibrary.com) DOI 10.1002/jsfa.5571
The fatty acid and tocopherol constituents of
the seed oil extracted from 21 grape varieties
(Vitis spp.)
Ali Sabira∗Ahmet Unverband Zeki Karaa
Abstract
BACKGROUND: Fatty acids and tocopherols in appropriate quantities are invaluable attributes that are desirable in seeds of
agricultural products. Studies have generally focused on the evaluation of the oil and tocopherol components of oil crops.
Recently, investigations revealed that the grape seed has robust potential in the production of healthy fatty acids as well as
tocopherols. This study was thus conducted to determine the oil and tocopherol components of grape seeds, obtained from
various grape cultivars of different species, including two rootstock varieties.
RESULTS: The grape seed oil concentration of the studied varieties ranged from 7.3 to 22.4%. The determined fatty acid
profiles of the genotypes conformed to the pattern described in the literature for grapes. Linoleic acid is the major component
comprising 53.6–69.6% of the total, followed by oleic (16.2 –31.2%), palmitic (6.9 –12.9%) and stearic (1.44 –4.69%). The oils of
all the seeds analysed showed a preponderance of α-tocopherol (ranging from 260.5 to 153.1 mg kg−1oil extract). β-Tocopherol,
γ-tocopherol and δ-tocopherol were also detected with the general means of 0.98, 22.2 and 0.92 mg kg−1, respectively. Linoleic
acid showed a significantly negative correlation with all the fatty acids analysed. The strongest negative correlation existed
between linoleic and oleic acids (r=−0.834, P<0.01).
CONCLUSION: Present investigations indicated that oil content, fatty acid composition and tocopherol constituents of grape
seed show great variation among the genotypes. Markedly higher proportions of linoleic acid with considerable amounts of
tocopherols found in the oil samples suggest that grape seed is a good source for culinary, pharmaceutical and cosmetic uses.
c
2012 Society of Chemical Industry
Keywords: grape seed oil; fatty acids; tocopherols; natural antioxidants
INTRODUCTION
Natural antioxidants such as vitamin C, vitamin E, polyphenols,
and flavonoids have been proven as functional compounds that
prevent free radical damage.1Therefore, recent epidemiological
research has focused on the influence of by-products such as
grape seed on chronic diseases including cancer, coronary heart
disease, atherosclerosis and diabetes.2Grape seeds, an agricultural
residue, are attractive sources of potential natural antioxidants,
constituting about 5% by weight of the grape berry and contain
10–20% oil with a high vitamin E content, which is important
for human health.3Vitamin E (a generic term for tocopherols
and tocotrienols) possesses hypocholesterolaemic, antitumour,
neuroprotective and antioxidant activities.4,5 Tocopherols have
long been known as the powerful natural fat-soluble antioxidants
whose mode of action is by two unique mechanisms, namely
a chain-breaking electron donor mechanism and an oxidation
preventive property.6
Grape seed oil is also rich in unsaturated fatty acids, such as
linoleic and oleic acid and thus offers many advantages for human
consumption. Accordingly, the food, pharmaceutical and cosmetic
industries have shown great interest in grape seed oil due to its
premium antioxidant activity properties. The oil content of grape
seeds in the usual range is 10–16% of dry weight, depending on
grape variety.7
In Turkey, various kinds of grapes are locally cultivated.
Approximately 37% of the fresh grapes produced are processed
for grape juice and other local consumption products such as
sausage, vinegar, kofter, pekmez (boiled concentrate juice); 3%
are used in wine production; 27% are marketed as table grapes;
and 33% are dried as raisins.8As a result of such an extensive
industry, large quantities of grape seed are available throughout
the country. As commonly known, by-products of the grape juice
and wine industry have economic potential and may be new
food sources for human consumption. Most of the publications
concerning grape seed have dealt with the determination of lipid
and protein constituents of the wine grapes,9–13 whereas, to
the best of our knowledge, few publications on the table and/or
rootstock varieties were concerned with the fatty acid composition
of the grape seed. This study was conducted to evaluate the fatty
∗Correspondence to: Ali Sabir, University of Selcuk, Faculty of Agriculture,
Department of Horticulture, 42075, Konya, Turkey. E -mail: asabir@selcuk.edu.tr
aUniversity of Selcuk, Faculty of Agriculture, Department of Horticulture, 42075,
Konya, Turkey
bUniversity of Selcuk, Faculty of Agriculture, Department of Food Engineering,
42075, Konya, Turkey
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Fatty acids and tocopherols from grade seed oil www.soci.org
acid and tocopherol contents of a wide range of grape genotypes,
consisting of 19 grape cultivars (table, juice and wine grapes) and
two American rootstocks.
MATERIALS AND METHODS
Materials
The materials consisted of 17 varieties of Vitis vinifera L. (table
grapes: Red Globe, M ¨
us¸k¨
ule, Antep Karası, Eks¸i Kara, Cardinal,
B¨
uzg ¨
ul ¨
u, Razakı, H ¨
on ¨
us ¨
u, Adana Beyazı, Royal, G ¨
ul ¨
uz ¨
um ¨
u, Perle
de Csaba, Italia, Alphonse Lavall´
ee, Siyah Dimrit; and wine grapes:
Narince and Kalecik Karası), a V. labrusca L. variety (Isabella), a
hybrid of V. vinifera ×V. labrusca (Kyoho) with two American
rootstocks, namely 41 B (V. vinifera ×V. berlandieri)and5BB(V.
berlandieri ×V. riparia).
The pomace, produced as by-product of grape processing for
juice or wine-making purposes, was obtained from Research and
Implementation Vineyard of Selcuk University Agriculture Faculty
Horticulture Department (Konya/Turkey) and the commercial
vineyards around the mountainous regions of Konya Province
where viticulture is widespread. The fresh pomace (containing
seeds) was immediately transferred to the laboratory and was
placed on trays and subsequently dried in air. The seeds were then
sieved out from dry pomace.
Crude oil content
The crude oil content of seeds was analysed according to AOAC.14
The seed oils were extracted with n-hexane (50 ◦C) in a Soxhlet
apparatus. The extracts were evaporated under vacuum in a
rotary evaporator. The lipid extracts were collected in a flask. The
extracted lipid was weighed to determine the oil content and
stored under nitrogen at 4 ◦C for further analyses.
Fatty acid analysis
For the determination of fatty acid composition of the oils, fatty
acid methyl esters were prepared from grape seed oils, using a cold
transmethylation15 by shaking a solution of 0.2 g oil and 3 mL of
hexane with 0.4 mL of 2 mol L−1methanolic potassium hydroxide.
A Shimadzu (Kyoto, Japan) gas chromatograph, equipped with
a flame ionisation detector and a split/splitless injector, was
employed. Separations were made on a Teknokroma TR-CN100
(Barcelona, Spain) fused-silica capillary column (60 m ×0.25 mm
i.d. ×0.20 µm film thickness). The carrier gas was nitrogen, with a
flow rate of 1 mL min−1. The temperatures of the injector and the
detector were held at 220 and 250 ◦C, respectively. The initial oven
temperature of 90 ◦C was maintained for 7 min, raised to 240◦C
at a r ate of 5 ◦Cmin
−1, where it was maintained for 15 min. The
injection volume was 1 µL. Peaks were identified by comparison of
their retention times with those of authentic reference compounds
(Sigma–Aldrich, St Louis, MO, USA).
Determination of tocopherols
Tocopherols were evaluated according to IUPAC 2432 method.16
Seed oils (1.5 g) were dissolved in 10 mL hexane and injected
into the high-performance liquid chromatography system with
a LiChroCART, Si 60 column (25 cm ×4mm ×5µm) (Merck,
Darmstadt, Germany). The chromatographic separation was
performed using a Shimadzu liquid chromatograph equipped
with an isocratic pump LC-20AT prominence, a CTO-10AS VP heater
(column temperature 22 ◦C), a SIL-20A prominence autosampler
and a SPD-M20A Prominence diode-array detector, fixed at a
wavelength of 295 nm (Shimadzu, Kyoto, Japan). The mobile phase
was 0.5% isopropanol in n-hexane. The total run time was 40 min
and the injection volume was 20 µL. Tocopherols were quantified
by an external standard method; α-, β-, γ-andδ-tocopherol
standards were obtained from Sigma-Aldrich (St Louis, MO, USA).
Statistical analysis
Data on fatty acid composition and tocopherols were reported
as mean ±standard deviation (SD) from triplicate determinations
for each grape seed oil sample. Analyses of significant group
differences were conducted (SPSS for Windows, Ver. 13.0, Chicago,
IL, USA) by using the Tukey test to identify differences among
means. Statistical significance was declared at P<0.05 or
P<0.01.In addition, the analysedfatty acids and tocopherolswere
separately subjected to correlation analysis for further exploring
and illustrating the relationship between them.
RESULTS AND DISCUSSION
Seed oil contents of the varieties
As illustrated in Fig. 1, statistically significant (P<0.01) variation
was determined in the quantity of seed oils across the grape
varieties consisting of various Vitis spp. genotypes including two
American rootstocks (41 B and 5 BB). Italia (V. vinifera L.) and Isabella
(V. labrusca) cultivars were outstanding with their markedly higher
oil yields with their values 223.7 and 214.4 g kg−1, respectively. In
contrast, the oil contents of Perle de Csaba (V. vinifera), Kyoho (V.
vinifera ×V. labrusca), Siyah Dimrit (V. vinifera) cultivars and 5 BB (V.
berlandieri ×V. riparia) rootstock (73.2, 88.1, 91.4 and 93.9 g kg−1,
respectively) were substantially lower than the others. Overall
range of the seed oil across the genotypes conforms to literature
investigations revealed by various researchers using different
cultivars.17 – 19 On the other hand, the oil content range obtained
in the present study is apparently higher than that suggested by
Beveridge et al.20 who studied the oil content of eight grapes by
supercritical carbon dioxide (in range of 5.9 –13.6%) and petroleum
ether (in range of 6.6– 11.2%). Such a partial discrepancy might
most probably have arisen from varietal distinction as well as
different cultivation conditions which, according to Noreen and
Ashraf21 affect the chemical composition of grape seeds. Besides,
Ohnishi et al.17 and Gokturk-Baydar and Akkurt18 sugested that
oil content differences among the cultivars might also be related
with the time of berry maturity.
Fatty acid composition of the varieties
The proportional composition of the analysed fatty acids of the
grape seed oil revealed that the grape seed oil is constituted mainly
by the unsaturated (such as linoleic, oleic and linolenic) and also by
the saturated (palmitic and stearic) fatty acids (Table 1). The studied
fatty acid compositions displayed significant (P<0.05) variation
across the genotypes. Among the varieties under the study, oleic
(C18 : 1) and linoleic acids (C18 : 2) were the most abundant fatty
acids as previously indicated by several researchers.10,12,13 The
highest linoleic acid content was found in 41 B rootstock (70.4%),
followed by G ¨
ul ¨
uz ¨
um ¨
u (70.1%), M ¨
us¸k¨
ule (69.6%) and Perle de
Csaba (69.4%). In contrast, the least linoleic acid content was
determined in Isabella (53.3%) and H ¨
on ¨
us ¨
u (56%) cultivars. Oleic
acid (C18 : 1) was the second fatty acid in abundance across the
samples. The highest oleic acid content was found in H ¨
on ¨
us ¨
u
(31.2%), followed by Isabella (30.5%), then 5 BB rootstock (26.2%),
and finally Razakı (24.1%). Comparing the oleic and linoleic acid
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www.soci.org A Sabir, A Unver, Z Kara
Figure 1. Seed oil contents of the analysed varieties (g kg−1). Each column represents the mean of triplicate determinations. Error bar stands for the
standard deviation of that mean.
Table 1. Proportional fatty acid composition of grape seeds (%, mean ±SD)
Cultivar Linoleic, C18 : 2 Oleic, C18 : 1 Palmitic, C16 : 0 Stearic, C18 : 0 Linolenic, C18 : 3 Arachidic, C20 : 0
Red Globe 68.8±0.30 18.1±0.12 10.7±0.04 1.89 ±0.01 0.61 ±0.008 0.09 ±0.003
M¨
us¸k¨
ule 69.6±0.38 22.3±0.04 6.9±0.09 1.81 ±0.01 0.40 ±0.005 0.10 ±0.005
Antep Karası 63.8±0.26 22.7±0.10 10.5±0.13 1.71 ±0.01 0.43 ±0.008 0.10 ±0.003
Eks¸i Kara 68.4±0.22 18.3±0.03 10.2±0.07 2.14 ±0.10 0.71 ±0.008 0.11 ±0.006
Narince 65.3±0.11 24.0±0.11 9.3±0.02 1.90 ±0.01 0.40 ±0.003 0.03 ±0.004
Cardinal 56.0±0.10 23.8±0.13 12.9±0.07 4.69 ±0.17 0.59 ±0.004 0.12 ±0.002
B¨
uzg ¨
ul ¨
u63.0±0.01 23.8±0.06 10.4±0.01 1.87 ±0.03 0.75 ±0.006 0.18 ±0.002
Razakı 66.2±0.17 24.1±0.11 8.3±0.06 1.89 ±0.02 0.47 ±0.006 0.03 ±0.004
H¨
on ¨
us ¨
u53.6±0.38 31.2±0.06 9.3±0.06 1.44 ±0.04 0.45 ±0.007 0.04 ±0.003
Kyoho 62.6±0.37 23.8±0.10 8.0±0.05 3.59 ±0.35 0.47 ±0.005 0.12 ±0.002
Adana Beyazı 67.7±0.23 21.8±0.08 9.5±0.10 1.79 ±0.02 0.20 ±0.005 0.11 ±0.003
Royal 67.4±0.08 21.3±0.03 8.6±0.06 2.35 ±0.06 0.29 ±0.007 0.08 ±0.005
G¨
ul ¨
uz ¨
um ¨
u70.1±0.20 19.8±0.06 8.8±0.09 1.70 ±0.05 0.21 ±0.007 0.08 ±0.002
Perle de Csaba 69.4±0.23 16.2±0.03 9.0±0.07 2.95 ±0.06 0.63 ±0.006 0.16 ±0.007
Isabella 53.3±0.28 30.5±0.06 10.0±0.11 4.40 ±0.16 0.91 ±0.010 0.06 ±0.004
Italia 65.6±0.21 24.6±0.28 7.0±0.10 1.37 ±0.02 0.61 ±0.008 0.09 ±0.002
41 B 70.4±0.37 19.3±0.21 7.5±0.07 1.79 ±0.11 0.42 ±0.008 0.07 ±0.003
5BB 62.8±0.23 26.2±0.11 8.7±0.05 1.44 ±0.13 0.52 ±0.009 0.10 ±0.005
Alphonse Lavall´
ee 66.6±0.47 21.8±0.27 7.8±0.13 2.03 ±0.06 0.41 ±0.011 0.10 ±0.007
Siyah Dimrit 66.5±0.40 18.5±0.36 11.7±0.06 1.89 ±0.11 0.50 ±0.009 0.16 ±0.008
Kalecik Karası 63.7±0.38 23.2±0.14 10.3±0.06 2.47 ±0.14 0.20 ±0.008 0.10 ±0.004
Mean 64.79 22.64 9.30 2.24 0.48 0.096
Values are means of triplicate determinations.
contents of Isabella and H ¨
on ¨
us ¨
u, the assertion of Pardo et al.12
regarding the reverse order between these two fatty acids might
be verified. The researchers found that the highest oleic acid
content was found in Garnacha Tintorera whose linoleic content
was the lowest, while, conversely, Petit Verdot had the highest
amount of linoleic acid and the least oleic acid.
Due to the high unsaturated fatty acid content (around
85%), grape seed oil is proven as a high-quality nutritional oil
which possesses unique properties in prevention of thrombosis,
reduction of cholesterol in blood serum, dilation of blood vessels,
alleviation of cardiovascular diseases and regulation of autonomic
nerves.22 Evidence from epidemiological and clinical secondary
prevention trials suggests that linoleic acid (configurational
isomers of C18 : 2) is an effective agent for inhibiting coronary
heart disease, colon, forestomach and skin carcinogenesis.23
Palmitic acid (C16 : 0) is known to be the predominant saturated
fatty acid. The porportion of palmitic acid (also known as
hexadecanoic acid) content in grape seed oil varied from 12.9%
(Cardinal) to 6.9% (M ¨
us¸k¨
ule). The highest stearic (C18 : 0) acid was
found in Cardinal (4.69%), followed by Isabella (4.40%), while the
least values were determined in Italia (1.37%) and H ¨
on ¨
us ¨
u (1.44%).
Results on the analysed fatty acid composition showed that
the grape seed oil was rather poor in linolenic (between 0.20 and
0.91%) and arachidic (between 0.03 and 0.18%) acids. The highest
linolenic acid (C18 :3) content was found in Isabella (0.91%) while
Kalecik Karası, a common Turkish red wine variety, had the least
linolenic acid (0.20%). Linolenic acid content of grape seed is
markedly lower than those of soybean, maize and olive,24 which
accordingly raises the oxidative stability. Assurance of a high
quality of seed lipids and prolonging their storage time is directly
associated with their optimum stabilisation. The high oxidation
stability of lipids is important for health protection and economic
reasons.25 Morover, according to Gokturk-Baydar et al.10 low levels
of linolenic acid are desired in edible oils, because high levels of
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1985
Fatty acids and tocopherols from grade seed oil www.soci.org
Table 2. Tocopherol composition of grape seeds (mg kg−1oil extract, mean ±SD)
Cultivar α-Tocopherol β-Tocopherol γ-Tocopherol δ-Tocopherol
Red Globe 142.2±1.74 1.29 ±0.022 25.5±0.66 0.87 ±0.013
M¨
us¸k¨
ule 159.1±1.61 0.94 ±0.031 21.6±0.47 0.65 ±0.024
Antep Karası 260.5±1.47 0.87 ±0.027 14.1±0.26 0.98 ±0.006
Eks¸i Kara 154.4±1.45 0.73 ±0.019 26.6±0.71 0.65 ±0.042
Narince 170.2±1.09 1.10 ±0.008 29.1±0.15 0.89 ±0.016
Cardinal 188.6±1.47 0.72 ±0.053 17.3±0.53 0.72 ±0.010
B¨
uzg ¨
ul ¨
u 156.8±0.60 1.05 ±0.049 17.9±0.28 1.26 ±0.005
Razakı 192.1±1.49 0.95 ±0.036 23.8±0.36 1.08 ±0.031
H¨
on ¨
us ¨
u 200.8±0.70 0.96 ±0.019 30.2±0.55 0.80 ±0.005
Kyoho 167.4±1.79 0.85 ±0.029 21.6±0.36 0.96 ±0.008
Adana Beyazı 196.1±1.53 0.98 ±0.007 13.7±0.65 0.66 ±0.008
Royal 161.0±1.84 0.79 ±0.014 18.0±0.18 0.84 ±0.010
G¨
ul ¨
uz ¨
um ¨
u 213.2±2.58 0.50 ±0.005 27.7±1.01 0.50 ±0.005
Perle de Csaba 235.5±1.60 1.75 ±0.017 17.0±0.69 0.91 ±0.009
Isabella 214.4±1.15 1.26 ±0.013 20.9±1.00 0.71 ±0.007
Italia 212.7±1.58 0.95 ±0.057 18.2±0.47 0.77 ±0.003
41 B 166.7±1.48 0.79 ±0.005 23.4±0.64 0.89 ±0.004
5 BB 195.8±1.49 0.89 ±0.014 16.1±0.24 1.46 ±0.004
Alphonse Lavall´
ee 135.1±1.02 0.46 ±0.004 20.0±0.11 1.40 ±0.007
Siyah Dimrit 139.4±1.15 0.79 ±0.003 27.4±0.42 0.88 ±0.010
Kalecik Karası 172.4±1.90 0.70 ±0.007 27.5±0.47 0.63 ±0.005
Mean 187.6±1.47 0.98 ±0.020 22.2±0.50 0.92 ±0.011
Values are means of triplicate determinations.
this fatty acid can produce an unfavourable odour and taste in
oil. Moreover, linolenic acid is oxidised readily because of the
three double bonds on its hydrocarbon chain26 and therefore the
stability or shelf life of linolenic acid-rich oil would be shorter.
Overall, the fatty acid composition of the studied cultivars fall
within the similar ranges in the literature10,12,18,19,27 although wide
variability among the varieties can be observed and explained by
genetic factors. Nonetheless, certain fatty acid contents in several
cultivars were found to be slightly beyond the general ranges. For
example, oleic acid contents of H ¨
on ¨
us ¨
u and Isabella were higher;
while, conversely, stearic acid levels of G ¨
ul ¨
uz ¨
um ¨
u (0.70%), Adana
Beyazı (0.79), M ¨
us¸k¨
ule (0.81%) and Narince (0.90%) were markedly
lower than those of literature reports. It is well accepted that
environmental conditions have considerable effects on the fatty
acid composition of plants.21 Therefore, the present differences
may most probably be the result of different cultivation conditions
as well as cultivar aptitude. The analysed fatty acid compositions
of V. labrusca grape Isabella and hybrid cultivar Kyoho (V. vinifera
×V. Labrusca) were found to be in the same range as the seed oil
content in Vitis vinifera grapes.
According to the overall results of the present study, the
proximate fatty acid composition of the analysed grapes could
be adjusted to the following values: 53 –70% linoleic acid (C18 : 2),
18 –31% oleic acid (C18 : 1), 7 – 13% palmitic acid (C16 : 0), 1.4 –4.7%
stearic acid (C18 :0), 0.2– 0.9% linolenic acid (C18: 3), 0.06–0.16%
arachidic acid (C20 : 0). These % compositions are consistent with
those that have been previously reported by several researchers7,20
for these grape seed oils, except for stearic acid which was slightly
lower in most of the varieties studied. Such deviation about the
proportion of stearic acid was also reported by Pardo et al.12 which
may probably indicate the sensitivity of stearic acid to distinct
cultivation conditions. The consistent findings of various studies
including the present work indicate the existence of a tight genetic
control of the basic oil composition of the seeds.
Tocopherol content of the varieties
The tocopherol contents of grape seeds are presented in
Table 2. There are four isoforms of tocopherol, α-, β-, γ-and
δ-tocopherols,28 with their relative vitamin E potencies of 100,
50, 10 and 3%, respectively.6The four isoforms were detected in
all samples in significantly varying degrees (P<0.05). Individual
tocopherol contents of 21 grape varieties exhibited great variation.
Mean values of individual tocopherol contents of the studied
samples were 187.6, 0.98, 22.2 and 0.92 mg kg−1oil extract for
α-, β-, γ-, and δ-tocopherols, respectively. These values are overly
similar to the previous reports by Wie et al.29 who analysed the
tocopherol contents of grape seeds from 14 different varieties
growninKorea.α-Tocopherol ranged from 135.1 to 260.5 mg kg−1
oil extract. It was the most abundant tocopherol among the
samples analysed as previously indicated by Gokturk-Baydar and
Ozkan9who determined the tocopherol contents of wine by-
products including grape seed, pomace (seed, skin and stem) and
bagasse (skin and stem) by using two different extraction methods.
The highest α-tocopherol content was found in Antep Karası
(260.5 mg kg−1oil), followed by Perle de Csaba (235.5 mg kg−1
oil), then Isabella (214.4 mg kg−1oil), and finally G ¨
ul ¨
uz ¨
um ¨
u
(213.2 mg kg−1oil). Among the studied varieties, Perle de Csaba
was also outstanding with its markedly higher linoleic acid and
α-tocopherol contents, pointing to an inheritable capacity that
makes this variety valuable in breeding programmes for high
linoleic and/or α-tocopherol line. γ-Tocopherol was the second
most abundant constituent, ranging from 13.7 mg kg−1(Adana
Beyazı) to 30.2 mg kg−1(H ¨
on ¨
us ¨
u). β-Tocopherol and δ-tocopherol
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1986
www.soci.org A Sabir, A Unver, Z Kara
Table 3. Correlations between the fatty acids analysed
Acid
Acid Stearic Palmitic Arachidic Oleic Linoleic Linolenic
Stearic 1 0.292∗0.775∗∗ 0.405∗∗ −0.717∗∗ 0.723∗∗
Palmitic – 1 0.357∗∗ 0.063 −0.450∗∗ 0.452∗∗
Arachidic – – 1 0.403∗∗ −0.735∗∗ 0.788∗∗
Oleic – – – 1 −0.834∗∗ 0.395∗∗
Linoleic – – – – 1 −0.771∗∗
Linolenic – – – – – 1
∗P<0.05 ∗∗ P<0.01.
were found in low concentrations compared with α-andγ-
tocopherols.
Tocopherols, fat-soluble vitamin complexes, are invaluable
antioxidant sources for human nutrition and healthy diets.30
Previously, seeds of higher plants were reported to contain
predominantly the γ-tocopherol (>70%) form.31 In contrast to this,
the results presented in this study, verifying several reports, show
that grape seeds contain primarily the alpha form of tocopherol.
α-Tocopherol possesses the highest vitamin E activity among the
tocopherols existing in functional foods. Therefore grape seed
appears to have unique potential for human health as a great
vitamin E source.
Correlation analysis between individual fatty acids and
tocopherols
The correlation coefficients among the fatty acids of the grape
seeds are presented in Table 3. Analysis using combined data from
all the studied grape genotypes revealed that linoleic acid, the
major oil component, showed significantly negative correlation
with oleic (r=−0.834, P<0.01), linolenic (r=−0.771,
P<0.01), arachidic (r=−0.735, P<0.01), stearic (r=−0.717,
P<0.01) and palmitic (r=−0.450, P<0.01) acids. The
strongest inverse association existed between linoleic and oleic
acids, the predominant fatty acids in grape seeds. Such a high
negative correlation was also reported before by Gokturk-Baydar
and Akkurt,18 analysing oil properties of 18 grape cultivars. A
similarly strong inverse association between the mentioned acids
was also revealed by Were et al.32 who analysed the fatty acid
composition of 30 sesame accessions in a 3-year study. Actually,
linoleic acid displays significantly negative correlation with all
the fatty acids analysed. The implication of the results is that
selection for high linoleic acid, an effective agent for inhibiting
coronary heart disease, in grape should lead to a concomitant
reduction in palmitic and stearic acids (dominant saturated acids
in proportional quantity). Accordingly, for a breeding study, aiming
to improve an accession with high and healthy oil content, linoleic
acid-rich genotypes would be strongly desired.
On the other hand, correlation coefficients between tocopherols
were not pronounced as with the fatty acids (Table 4). There were
statistically significant (P<0.01) positive correlations between
α-andβ-tocopherols (r=0.573) and also between β-and
δ-tocopherols (r=0.423).
The results of this study along with the previous reports suggest
that grape seeds have great nutritional potential with their high
oil and tocopherol contents. The expected growth of the grape
processing industry will increase the volume of grape seed as by-
Table 4. Correlations between the tocopherols analysed
α-
Tocopherol
β-
Tocopherol
γ-
Tocopherol
δ-
Tocopherol
α-Tocopherol 1 0.573∗∗ −0.047 0.236
β-Tocopherol – 1 0.158 0.423∗∗
γ-Tocopherol – – 1 −0.05
δ-Tocopherol – – – 1
∗∗ P<0.01.
product. Accordingly, this by-product is likely to become a great
source for the food, pharmaceutical and cosmetic industries.
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