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Characteristics of raspberry (Rubus idaeus L.) seed oil

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Studies were conducted on properties of oil extracted from raspberry seeds. Oil yield from the seed was 10.7%. Physicochemical properties of the oil include: saponification number 191; diene value 0.837; p-anisidine value 14.3; peroxide value 8.25 meq/kg; carotenoid content 23 mg/100 g; and viscosity of 26 mPa.s at 25°C. Raspberry seed oil showed absorbance in the UV-B and UV-C ranges with potential for use as a broad spectrum UV protectant. The seed oil was rich in tocopherols with the following composition (mg/100 g): [alpha]-tocopherol 71; [gamma]-tocopherol 272; [delta]-tocopherol 17.4; and total vitamin E equivalent of 97. The oil had good oxidation resistance and storage stability. Lipid fractionation of crude raspberry seed oil yielded 93.7% neutral lipids, 3.5% phospholipids, and 2.7% free fatty acids. The main fatty acids of crude oil were C18:2 n-6 (54.5%), C18:3 n-3 (29.1%), C18:1 n-9 (12.0%), and C16:0 (2.7%). The ratio of fatty acids, polyunsaturates to monounsaturates to saturates varied depending on lipid fraction. Polymorphic changes were observed in thermal properties of raspberry seed oil.
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Characteristics of raspberry (Rubus idaeus L.) seed oil
$
B. Dave Oomah
a,
*, Stephanie Ladet
b
, David V. Godfrey
a
, Jun Liang
c
, Benoit Girard
a
a
Food Research Program, Agriculture and Agri-Food Canada, Paci®c Agri-Food Research Centre, Summerland, British Columbia V0H 1Z0, Canada
b
E.N.S.A.M., E
Âcole Nationale Superieure Agronomique de Montpellier, 2, Place Pierre Viala, 34060 Montpellier Cedex 1, France
c
Shaanxi Fruit Crops Research Centre, Xi'an, Shaanxi 710065, China
Abstract
Studies were conducted on properties of oil extracted from raspberry seeds. Oil yield from the seed was 10.7%. Physicochemical
properties of the oil include: saponi®cation number 191; diene value 0.837; p-anisidine value 14.3; peroxide value 8.25 meq/kg;
carotenoid content 23 mg/100 g; and viscosity of 26 mPa.s at 25C. Raspberry seed oil showed absorbance in the UV-B and UV-C
ranges with potential for use as a broad spectrum UV protectant. The seed oil was rich in tocopherols with the following compo-
sition (mg/100 g): a-tocopherol 71; g-tocopherol 272; d-tocopherol 17.4; and total vitamin E equivalent of 97. The oil had good oxi-
dation resistance and storage stability. Lipid fractionation of crude raspberry seed oil yielded 93.7% neutral lipids, 3.5% phospholipids,
and 2.7% free fatty acids. The main fatty acids of crude oil were C18:2 n-6 (54.5%), C18:3 n-3 (29.1%), C18:1 n-9 (12.0%), and C16:0
(2.7%). The ratio of fatty acids, polyunsaturates to monounsaturates to saturates varied depending on lipid fraction. Polymorphic
changes were observed in thermal properties of raspberry seed oil. #2000 Published by Elsevier Science Ltd. All rights reserved.
Keywords: Raspberry seed; Raspberry oil; Oil quality; Tocopherols; Storage; DSC; Chemical and physical parameters
1. Introduction
About 18,000 metric tonnes of raspberries are pro-
duced annually in Canada with the total global pro-
duction at 312 thousand metric tonnes. In the
processing of raspberry juice, the seed becomes a
byproduct which is currently under exploited. Oil from
raspberry seed could amount to over 400 metric tonnes,
assuming 10% of seed in fresh berries, 23% oil content
of seeds (Johansson, Laakso & Kallio, 1997) and that
all raspberry produced in Canada is processed as juice.
The composition of raspberry seeds compiled by Win-
ton and Winton (1935) reveals that as early as 1907 oil
expressed from the seed amounted to 14.6±18%. These
raspberry seed oils contained 0.73±1.10% phytosterol,
and had a saponi®cation value of 187±192. Recently,
Johansson et al. (1997) found that linoleic, a-linolenic,
oleic and palmitic acids were typically the most abun-
dant fatty acids from seed oil of 22 common edible wild
northern berries, including raspberry. The seed mass,
100 seed weight, and seed oil content for raspberry were
10.1% (fw), 180 mg, and 23.2%, respectively.
Storage studies by Carnat, Pourrat and Pourrat
(1979) showed that raspberry seed oil oxidized very
slowly even at 60C with an increase in peroxide value
from 3 to 39 mmol/kg over 7 days. At ambient tem-
perature (22±23C), oxidation was slower yet, with per-
oxide values varying from 3 to 18 mmol/kg after 5
weeks. This resistance to oxidation of raspberry seed oil
was purported to be due to the presence of a minor
component in the unsaponi®able fraction of the oil
(Carnat et al.). In the quest to understand the oxidative
stability of raspberry seed oil, Pourrat and Carnat
(1981) stabilized the moisture content of raspberry seed
to 5±6% by drying at 50C for 4±5 h, then extracted oil
with chloroform. The oil yield was 16±18% by that process
andthefattyacidcompositioninpercentageofthe
chloroform extracted oil was: C16:0, 2.7; C18:0, 0.2; C18:1,
18.7; C18:2, 55.5; and C18:3, 32.6 (Pourrat & Carnat,
1981). The de®nitive reason for the high stability of rasp-
berry seed oil has not been fully clari®ed.
The incorporation of raspberry seed oil in cosmetics
and pharmaceutical products based on its anti-in¯am-
matory activity notably for the prevention of gingivitis,
rash, eczema, and other skin lesions has been patented
(Pourrat & Pourrat). The anti-in¯ammatory activity of
raspberry seed oil was superior compared to those of
other well-known oils such as virgin avocado oil, grape-
seed oil, hazelnut oil, and wheat germ oil (Pourrat &
0308-8146/00/$ - see front matter #2000 Published by Elsevier Science Ltd. All rights reserved.
PII: S0308-8146(99)00260-5
Food Chemistry 69 (2000) 187±193
www.elsevier.com/locate/foodchem
$
Paci®c Agri-Food Research Centre contribution no. 2017.
* Corresponding author. Tel.: +1-250-494-6399; fax: +1-250-494-
0755.
E-mail address: oomahd@em.agr.ca (B.D. Oomah).
Pourrat). According to this patent, raspberry seed oil can
be used as a sun screen, in toothpaste, cremes for pre-
vention of skin irritations, bath oil, aftershave cream,
antiperspirants, shampoos, and lipsticks.
Red raspberry forms part of the Paci®c Agri-Food
Research Centre small fruit breeding program. In addi-
tion to the release of new cultivars with high yields of
large fruits with excellent quality, pleasant ¯avor, ®rm
fruit and low susceptibility to pre- and postharvest dis-
eases, there is interest in the complete utilization of the
fruit for food and non-food uses. Raspberry seed oil may
be regarded as a speciality oil and as such may attract
considerable attention because of its possible nutraceu-
tical eects. It is a rare commodity and currently retails
at $52 a litre as a fragrant oil. Our aim is to transform
raspberry seed into economically valuable ingredients
for the food and nonfood industries. In this context, the
chemical and physical properties of oil extracted from
raspberry seed has been investigated to provide guide-
lines for innovative uses of this byproduct. The proper-
ties of raspberry seed oil was also compared with those
of two commercial oils, grapeseed and saower oils used
in the food, cosmetic and pharmaceutical industries.
2. Materials and methods
Raspberry (Rubus idaeus L.) seeds from a mixture of
dierent cultivars grown for processing were obtained
from Valley Berry Inc., (Abbotsford, British Columbia).
Since the moisture content of the seed was about 41.5%,
the seed samples were air-dried in a ¯uid bed dryer
(Lab-Line Instruments Inc., Melrose Park, IL) for 2 h at
25C to reduce the moisture to 13.6%. Raspberry seeds
were ground (Thomas Wiley Mill, Philadelphia, PA) to
pass a 1mm screen. Oil from milled samples was
extracted using hexane as described by Oomah, Mazza
and Przybylski (1996). Brie¯y, the sample (100 g) was
stirred for 2 h at 4C with hexane (1 l). The solvent was
removed by vacuum ®ltration and the sample was fur-
ther extracted twice. After the last ®ltration, the extract
was pooled, hexane removed (vacuum rotary evapora-
tion, 35C), purged with nitrogen and stored at ÿ20C
until analysis. A sample of raspberry seed was hydrau-
lically pressed (Carver Press, 280 kg/cm
2
) to extract
cold-pressed oil. A commercial grapeseed oil produced
and packed in Spain (Aceitas Borges Pont, S.A., Cata-
lonia) and saower oil (P.C.
TM
Product, Sunfresh Ltd.,
Toronto, Canada) purchased from a local food store
were used as controls.
2.1. Analytical procedures
Ocial methods (American Oil Chemists' Society,
AOCS, 1993) were used for the determination of the
saponi®cation value (method Cd 3-25) and p-anisidine
value (method Cd 18-90) of oils. Conjugated dienoic
and trienoic acids were determined by the spectro-
photometric method outlined in the Standard Methods
for the Analysis of Oils, Fats and Derivatives (Interna-
tional Union of Pure and Applied Chemistry, IUPAC,
1985). The peroxide value of the oils was determined
using the PeroXOquant quantitative peroxide assay kit
(Pierce, Rochford, IL, USA). Absorptivity and trans-
mission of oil solutions (0.1± 10% v/v) in hexane were
measured with a spectrophotometer (DU-640B, Beckman
Instruments Inc., Fullerton, CA, USA).
The AOAC method (958.05, Association of Ocial
Analytical Chemists, AOAC, 1990) with a few mod-
i®cations was used to evaluate carotenoid content of
oils. Carotenoid content, expressed as micrograms of b-
carotene per gram of oil, was performed by applying a
calibration curve constructed by preparing solutions of
increasing concentration, from 0.5 to 2.5 mgofb-car-
otene/ml hexane. Absorbance was recorded at 440 nm
(DU-640B, Beckman Instruments Inc., Fullerton, CA,
USA) using hexane as blank. Oil was diluted with hexane
(10% v/v for grapeseed and saower, 1% v/v for rasp-
berry) to b-carotene standard range. Moisture content
was determined by the AOAC method (AOAC, 1984).
Viscosity of the oil was measured with a controlled stress
Bohlin rheometer CVO (Bohlin Instruments Ltd.,
Gloucestershire, UK). Measurements were performed at
25C with a steel cone-plate geometry (20 mm, 2) under
a ramping shear of 2.5±10 Pa.
Tocopherols were analyzed by an HPLC system
(Waters 840 system, Milford, MA, USA) consisting of a
pump (Model 510), an autosampler (Model 712) and a
¯uorescence detector (McPherson SF-749 spectro-
¯uorometer, Acton, MA, USA) interfaced with a per-
sonal computer. A normal phase column (4.6150 mm,
Primesphere 5 silica 5 mm) with guard column (4.630
mm) (Phenomenex, Torrance, CA, USA) was used with
hexane/2-propanol/dimethyl propane (1000/5/1, v/v/v)
as a mobile phase. The system was operated iso-
cratically at a ¯ow rate of 1 ml/min. Separations were
carried out at 25C (Waters TCM temperature con-
troller) with the ¯uorescence detector excitation and
emission wavelengths set at 297 and 325 nm, respec-
tively. Typically, a 10 min equilibration period was used
between samples, requiring about 40 min/sample.
Quantitation was based on an external standard
method; the calibration curves ranged from 3.97 to
15.87, 5.41 to 21.63 and 6.0 to 24.0 mg/ml of reference
compounds a-, d-, and b-, g-tocopherols, respectively
(Sigma Chemical Co., St Louis, MO, USA). Prior to
HPLC analysis, the oil was diluted with hexane to
obtain a concentration of about 160 g/l, ®ltered (0.45
mm, Gelman Science Inc., Ann Arbor, MI, USA) and 20
ml sample was injected.
Crystallization and melting points were measured
with a dierential scanning calorimeter (DSC-2910
188 B.D. Oomah et al. / Food Chemistry 69 (2000) 187±193
Modulated DSC-TA Instruments, New Castle, DE, USA).
Oil (20±25 mg) was weighed in DSC-pan (aluminium
open pan, TA Instruments T70529) and DSC runs were
performed within the temperature range of 10 to
ÿ70C. A programmed cycle was followed in which the
sample was cooled from 10 to ÿ70Cat1
C/min,
maintained at this low temperature for 5 min and
heated back to 10C. An empty DSC pan was used as
an inert reference to balance the heat capacity of the
sample pan. The DSC was calibrated for temperature
and heat ¯ow using mercury (mp ÿ38.83C, TA Instru-
ments standard), distilled water (mp 0.0C), gallium
(mp 29.76C, TA Instruments standard) and indium
(mp 156.6C, 28.71 J/g, Aldrich Chemical Co.).
Separation of individual lipid classes was performed
using solid-phase extraction cartridge, (Bakerbond
amino [NH2] disposable extraction column, 500 mg, J.
T. Baker Inc., Phillipsburg, NJ), with aminopropyl
packing, essentially as described by Carelli, Brevedan
and Crapiste (1997). The cartridge was preconditioned
with 2 ml methanol, 2 ml chloroform, and 4 ml hexane
before use. A micropipet was used to inject 50±150 mg
of oil dissolved in chloroform. Lipid classes were
recovered by sequential elution under vacuum (5±10
mm Hg) with 4 ml each of chloroform/isopropanol (2/1,
v/v), diethyl ether/acetic acid (95/5, v/v), and methanol
to separate neutral lipids, free fatty acids and phospho-
lipids, respectively. The eluates were collected, evapo-
rated under nitrogen, weighed, and stored at ÿ20C for
fatty acid analysis.
The lipids were esteri®ed by the one-step methylation
method of Ulberth and Henninger (1992) with some
modi®cations. These included the omission of toluene in
the reagent and centrifugation for phase separation. The
top layer was transferred into a small vial and dried
with anhydrous Na
2
SO
4
. Samples were analyzed for
their fatty acid methyl esters on a Hewlett±Packard
model 5890 gas chromatograph (Avondale, PA), equip-
ped with a split/splitless injector, a ¯ame-ionization
detector, an automatic sampling device, and a 100 M
SP-2560 fused-silica capillary column (Supelco, Oak-
ville, ON) with 0.25 mm i.d. The column temperature
was programmed from 140 to 240Cat4
C/min, and
the injector and detector temperatures were set at
260C. Helium was the carrier gas. Peak areas of dupli-
cate injections were measured with a Hewlett±Packard
3396 computing integrator. All assays except thermal
analysis were performed in triplicates.
3. Results and discussion
Raspberry seed at 13.6% moisture content had a yield
of about 10.7% (db) oil by solvent extraction. Our oil
yield was at the lower end of the seed oil content for
Rubus species (10±23% dw) reported by Johansson et al.
(1997), and lower than (14±18%) those reported earlier
for raspberry seed (Pourrat & Carnat, 1981; Winton &
Winton, 1935). The lower oil yield obtained in this
study could be partly due to dierent seed samples and
solvent used for oil extraction. Raspberry seed oil is
yellow with a slight ``®shy'' o-note. Crude raspberry
seed oil showed some absorbance in the UV-C (100±290
nm) and UV-B (290±320 nm) range (Fig. 1). In the UV-
B range, the wavelengths of ultraviolet light responsible
for most cellular damage, raspberry seed oil can shield
against UV-A induced damage by scattering (high
transmission), as well as by absorption. The shielding
power in the UV-A (320±400 nm) range depends mostly
on the scattering eect. Thus, raspberry seed oil may act
as a broad spectrum UV protectant and provide pro-
tection against both UV-A, an exogenous origin of oxi-
dative stress to the skin, and UV-B. The optical
transmission of raspberry seed oil, especially in the UV
range (290±400 nm) was comparable to that of titanium
dioxide preparations with sun protection factor for UV-
B (SPF) and protection factor for UV-A (PFA) values
between 28±50 and 6.75±7.5, respectively (Kobo Pro-
ducts Inc., South Plain®eld, NJ).
Absorptivity at 245 nm, a wavelength which is
approximately at the lower limit of detectability for the
Fig. 1. Ultra violet/visible spectra of raspberry seed oil. Figure derived
from scans (l=200±290) of oil diluted 1:100; from scans (l=290±400
and l=400±800) of oil diluted 1:10, all in hexane. Black line is absor-
bance and gray line is transmission.
B.D. Oomah et al. / Food Chemistry 69 (2000) 187±193 189
human eye, was low for raspberry seed oil, inferring low
levels or absence of yellow pigments in the oil. Green
pigments, particularly chlorophyll content, usually
measured at 630, 670 and 710 nm, was negligible as
indicated by very low absorbance (0.003±0.007) in the
600±750 nm range for raspberry seed oil (1% oil in
hexane). The negligible amount of green pigments does
not impart undesirable color to the oil and may be
unable to promote oil oxidation, especially in the pre-
sence of light. Raspberry seed oil contained yellow col-
oring as indicated by absorbance between 0.084 and
0.108 at 440±460 nm for 1% oil in hexane and was
equivalent to the Munsell 1.25 Y 8/16 rating. These
yellow colors which include carotenoids are bene®cial,
since they simulate the appearance of butter without the
use of primary colorants such as carotenes, annatos,
and apocarotenals commonly used in the oil and fat
industry. Actual carotenoid content of raspberry seed
oil was 23 mg/100 g of oil (Table 1).
Raspberry seed oil has a low viscosity (Table 1), a
characteristic which may render it less occlusive than
hydrocarbon oils. The viscosity of raspberry seed oil
was lower than most vegetable oils and similar to that of
oleic acid (Noureddini, Teoh & Clements, 1992). Con-
jugated diene value of the seed oil was 0.837, and sig-
ni®cantly higher than those of commercial grapeseed
and saower oils analyzed under the same conditions.
This dierence is likely due to raspberry seed oil's high
18:3 content compared to the two commercial oils.
Conjugated triene was not detected in raspberry seed oil
suggesting absence or very low levels of linolenate oxi-
dation in oil. p-Anisidine value of the oil was 14.3 and
signi®cantly higher than those of the commercial oils,
indicating the presence of aldehydic carbonyl com-
pounds or secondary oxidation of the raspberry seed
oil. The peroxide value was 8.25 meq/kg oil, and lower
than those generally recommended for commercial
vegetable oils (410). However, the oil hydroperoxides
can be substantially lowered or reduced during bleach-
ing with acid-activated bleaching earth. The total oxi-
dation value (totox) of raspberry seed oil, calculated
using the peroxide and anisidine values (2Px+Av), was
30.8, and comparable to that of encapsulated ®sh oil,
but higher than those of vegetable oils (Shukla & Per-
kins, 1998). Raspberry seed oil was twice as prone to
auto-oxidation as saower oil (totox value of 12.4)
under the same test conditions. The saponi®cation value
of raspberry seed oil was high and comparable to those
of common vegetable oils indicating very high content of
low molecular weight triacylglycerols. It was similar to
the saponi®cation value of canola oil (Eskin et al., 1996)
and within the values for raspberry seed oil (187±192)
reported previously (Winton & Winton, 1935). Rasp-
berry seed oil may be prone to peroxide formation
based on its peroxide value and may be suitable for soap
production judging from the high saponi®cation value.
The major tocopherol in raspberry seed oil was the g
isomer at 75% of the total tocopherol. a- and d-Toco-
pherol contents of the oil were 71 and 17.4 mg/100 g,
respectively (Table 2). The a- and d-tocopherol levels of
Table 1
Physicochemical characteristics of raspberry, saower and grape seed
oils
Characteristic
a
Raspberry Saower Grape
Oil yield Ð
dry matter (%)
10.70.3
cc
Seed moisture (%) 13.60.1
cc
Viscosity (mPas.s)
b
261.1 47.30.4 49.40.3
Saponi®cation
number
1910.1 191.60.6 192.90.4
Diene value 0.8370.0003 0.5140.006 0.4670.001
Triene value
d
0.1340.006 0.0890.001
p-Anisidine value 14.30.2 5.360.006 10.460.03
Peroxide value
(meq/kg)
8.250.1 3.520.04 0.960.01
Carotenoid content
(mg/100 g)
230.04
dd
a
Means of 3.
b
Means of 10 measurements over ramping stress range (2.5 to 10 Pa).
c
Not applicable.
d
Not detected.
Table 2
Tocopherol contents of raspberry, saower and grape seed oils (mg/100 g)
Tocopherol Tocotrienol
Oils
a
abg dagTotal Vitamin E
Raspberry
Hexane extracted 710.5
b
2722.6 17.40.5
cc
3603.6 970.8
Cold pressed 46.12.2
c
14411.7 7.10.7
cc
19813.2 613.3
Saower 56.00.09 2.00.2 1.10.1
ccc
59.01.0 570.9
Grape 5.60.0 2.30.0 3.30.3
c
15.70.2 28.50.5 55.40.9 11.80.1
a
Means of 2.
b
Trace.
c
Not detected.
190 B.D. Oomah et al. / Food Chemistry 69 (2000) 187±193
cold-pressed raspberry seed oil was about half that of
the hexane-extracted oil. The reason for this dierence
is unclear, but could probably be due to the presence of
non-lipid material in cold-pressed oil which may dilute
the concentration of tocopherols. The biologically
active vitamin E content relative to that of a-toco-
pherol, calculated by using the formula proposed by
McLaughlin and Weihrauch (1979), were 97.8 and 58.4
mg/100 g for the hexane-extracted and cold-pressed oils,
respectively. Raspberry seed oil is a very rich source of
gamma tocopherol since its level (137±272 mg/100 g) is
much higher than those reported for other vegetable oils
and foods (Eskin et al., 1996; McLaughlin & Weihrauch).
The ratio of the tocopherol isomers a:g:din raspberry
seed oil was 20:75:5, and resembled that in commercial
re®ned corn oil at 17:78:3 (McLaughlin & Weihrauch,
1979). The high g-tocopherol concentration of rasp-
berry seed oil may exert a signi®cant biological eect in
non-ruminant animals since g-tocopherol concentration
is easily detected in animals fed natural source of toco-
pherols at concentrations of 100 and 1000 ppm (Eng-
berg, Jakobsen & Hart®el, 1993). Raspberry seed oil with
high levels of g-tocopherol may be as important as a-
tocopherol in the prevention of degenerative diseases.
Storage studies carried out at 37C in the dark
showed similar trends of increase in peroxide value with
time for raspberry and saower oils (Fig. 2). However,
the rate of increase in peroxide value for raspberry seed
oil was lower than that of saower oil. The data
describing the rate of autoxidation ®tted the poly-
nominal model (y=ax
2
+bx+c). The coecients of
regressions (R
2
) between the peroxide value and storage
time were 0.808 and 0.864 (P<0.05) for raspberry and
saower oils, respectively. At the end of the storage
period (240 h) both oils were roughly equivalent in
terms of oxidative degradation that had occurred. A
clear induction period was not observed in this study,
even when the storage period was extended to 900 h
(data not shown). Similar observations have been
reported for raspberry seed oil stored at ambient (22±
23C) temperature for 5 weeks (Carnat et al., 1979).
Raspberry seed oil consisted primarily of neutral lipid
(93.8%) with minor amounts of free fatty acid and
phospholipids (3.5 and 2.7% of the total crude oil,
respectively) (Table 3). Similar high levels of neutral
lipids (95.7±95.9%) have been reported for raspberry
seed oil (Winton & Winton, 1935), and other berry fruit
Fig. 2. Stability of raspberry seed oil at 37C evaluated as peroxide value. *=raspberry seed oil, &=saower seed oil.
Table 3
Fatty acid composition of raspberry seed oil
Composition (mass%)
Fatty acid Crude oil
a
Neutral
lipid
Free fatty
acid
Phospholipid
Fractions (%)
b
93.72.0 3.51.13 2.73.1
C16:0 2.690.14 2.68 10.46 10.92
C18:0 0.970.01 1.02 1.26
c
C18:1 11.990.01 12.11 26.62 19.24
C18:2 54.520.10 55.12 47.28 63.55
C18:3 29.110.05 28.74 14.35 6.29
a
Means of 4.
b
Means of 2.
c
Not detected.
B.D. Oomah et al. / Food Chemistry 69 (2000) 187±193 191
oils such as sea buckthorn seed oil (92%) (Zadernowski,
Nowak-Polakowska, Lossow, Nesterowicz, 1997). The
phospholipid content of raspberry seed oil at 2.7% was
higher than that of fruit stone oils from the Rosaceae
species (0.4±1.1% for peach, apricot, and cherry seed
oils) at the expense of neutral lipids (97.2±98.7%) (Zla-
tanov & Janakieva, 1998). Raspberry seed oil had higher
free fatty acid content but comparable phospholipid
content than those of common edible oils (canola, soy-
bean, sun¯ower, corn) 0.3±1.8%, and 0.2±4.0%, respec-
tively. For edible purposes, these non-triglycerides
components are considered detrimental to oil quality
and should be removed through processing.
The phospholipids are useful as emulsi®ers in food
and pharmaceutical applications. In raspberry seed oil,
the phospholipids may act as a natural antioxidant
(Re
Âblova
Â& Pokorny, 1995) and consequently increase
oil stability and shelf life.
The most abundant fatty acids of raspberry seed oil
were linoleic, a-linolenic, and oleic acids, which together
comprised 96% of the total fatty acid. The fatty acid
composition of raspberry seed oil was similar to that
reported previously (Pourrat & Carnat, 1981) and to
that of Rosa dumalis (Johansson et al., 1997). The lino-
leic acid content of raspberry seed oil was similar to that
of walnut oil (56±59%) (Ruggeri, Capelloni et al., 1998).
Neutral lipids which constituted about 94% of the total
lipids, had fatty acid composition similar to that of
crude raspberry seed oil. The phospholipid fraction was
richer in saturated and monounsaturated fatty acids (11
and 19% of the total fatty acid, respectively), but much
lower in polyunsaturates compared to the neutral lipid
fraction. The polyunsaturates of the free fatty acid
fraction amounted to only 61% of the total fatty acids,
while the monounsaturated and saturated fatty acids
amounted to 27 and 12%, respectively. Hence, the ratio
of polyunsaturates to monounsaturates to saturates
varied from 84:12:4 to 61:27:12, depending on lipid
fractions. The crude raspberry seed oil and the neutral
lipid fraction were particularly low in palmitic acid.
They contained high amounts of linolenic acid, which
makes them especially prone to oxidation, but which
may have favorable nutritional implications and bene-
®cial physiological eect in the prevention of coronary
heart disease and cancer (Oomah & Mazza, 1998). The
free fatty acid and phospholipid fractions with lower
levels of linolenic acid than the neutral fraction renders
them less susceptible to oxidation. The neutral lipid
fraction was characterized by the highest poly-
unsaturated/saturated (P/S) ratio of 22.7, while those of
free fatty acids and phospholipid fractions were 15.3
and 6.4, respectively. A high ratio of P/S is regarded
favorably in the reduction of serum cholesterol and
atherosclerosis and prevention of heart diseases (Rudel,
Kelly, Sawyer, Shah & Wilson, 1998). Similarly, the
ratio of n-6 to n-3 fatty acids were 1.92, 3.29 and 10.10
for the neutral, free fatty acid and phospholipid frac-
tions, respectively.
Raspberry seed oil has unique thermal characteristics
(Fig. 3). The oil presented a crystallization peak
atÿ62C with enthalpy of 38.3 J/g. Polymorphism was
detected in raspberry seed oil: after melting of the low
temperature modi®cation at ÿ45C, an additional
modi®cation crystallized with an exothermic peak at
ÿ43C. At ÿ23C, peak temperature, this modi®cation
melted with an originally existing crystallite of the same
kind. Similar DSC tracings were observed for grapeseed
oil in this study and by Kaisersberger (1990) and saf-
¯ower oil (data not presented). These polymorphic
changes can be hindered by addition of emulsi®ers (Kai-
sersberger). According to Garti, Schlichter and Sarig
(1988), the ®rst small endothermic peak at ÿ45C repre-
sents the melting of the unstable acrystal form followed
by the crystallization of the more stable bform which is
characterized by an exothermic peak. The melting
enthalpy of raspberry seed oil was 75 J/g. The amount of
melting according to DSC determinations (ratio of enthal-
pies) was 50.9%, i.e. the solid±liquid ratio of approxi-
mately 1:1 at ÿ23C. This solid±liquid ratio and, melting
and recrystallization characteristics of raspberry seed oil
can impinge on its consistency, taste and texture.
The potential for production of oil as a byproduct of
raspberry seed appears to be excellent. The unique fatty
acid composition, high tocopherol content and quality
and hence high protection against oxidative stress, rela-
tively good shelf life, and other desirable physicochem-
ical characteristics indicate potential uses of raspberry
seed oil in food, pharmaceutics, cosmetics, and other
nonfood industries. The microconstituents of raspberry
seed oil with its rich array of phytochemicals, especially
the omega-3 fatty acids and tocopherols suggest that it
is a nutraceutical and may be marketed as a dietary
supplement with a structure/function claim about heal-
thy blood circulation. The production of oil from rasp-
berry seed provides the use of a renewable resource, and
at the same time adding value to agricultural products
and improving the environment.
Fig. 3. DSC pro®le of raspberry seed oil.
192 B.D. Oomah et al. / Food Chemistry 69 (2000) 187±193
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