Int. J. Chem. Sci. Vol. 7 No. 1, ISSN 2006-3550
PROXIMATE AND CHEMICAL PROPERTIES OF
WATER MELON SEED AND OIL FROM KALGO,
KEBBI STATE, NIGERIA
ijcs
*Y. Yahaya; N. M. Samuel
Department of Pure and Applied Chemistry, Kebbi State University of Science and
Technology Aliero
Email address: yakubuyy@ymail.com; Phone number: +2348060653966
(Date Received: 12/11/13; Date Accepted 24/12/13)
Abstract
The proximate and chemical properties of water melon (Citrulluslanatus) seed and oil from
Kalgo, Kebbi State were evaluated to know whether it could be exploited for consumption and
other domestic applications. Values of 38.33%,19.89g/100g, 23.18g/100g, were observed for the
oil yield, crude fibre and crude protein respectively. The mean values of 20.74 µg/g, 7135.45
µg/g, 2560 µg/g,1452 µg/g,570 µg/g,42.50µg/g,33.12 µg/g, and 15.72 µg/g, were obtained for
Na, K, Mg, Ca, P, Fe, Zn and Cu respectively, as the mineral element composition of the seed.
For the oil, the mean values of 0.816 Kg/dm3 for the Specific gravity and 1.31 for the refractive
index both at 25oCindicated that the oil can be stored for some time. The mean values of
61.75gI2/100g,180.01 mg KOH/g,61.75gI2/100g,180.01 mgKOH/g, 12.22 mg KOH/g, 4.57 mg/g
were observed for iodine, saponification, acid and free fatty acid respectively. Generally, the
values indicated that both the seed and oil could be suitable for consumption and domestic
applications. The high acidity observed in the oil makes it uneconomical for the traditional
process of trans-esterification.
Keywords: Proximate, chemical, properties, Citrulluslanatus seed oil.
health andcitrulline, an amino acid that is
commonly converted by kidneys and other
organs into arginine and phenolic
antioxidants(Finaet al., 2013). In some parts
of the world, the young fruits and leaves are
cooked and eaten as vegetables. The seeds
are bruised and rubbed up with water to
form an emulsion, which is used to cure
catarrhal infections, disorders of the bowel,
urinary passage and fever (Sabahelkhieret
al., 2011). The seeds are also used for oil
production at the subsistence level in many
African countries and Middle East. Also, the
seeds have been found to be good sources of
INTRODUCTION
Water melon (Citrulluslanatus) belongs to
the family cucurbitaceae a medium sized
plant family found in the warmer regions of
the world. The fruit possesses a smooth
exterior ring and a juicy red, yellow or
orange interior flesh that contains over 90%
water (Jeffrey, 2005). The plant is a valuable
and portable source of water for desert
situations and when natural water supplies
were contaminated (Taiwoet al., 2008;
Sabahelkhieret al., 2011). Water melon fruit
is a good source of vitamin C, carotenoids
(lycopene) which is important for bone
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Int. J. Chem. Sci. Vol. 7 No. 1, pp 10-16, 2015
protein, vitamins, mineral elements and fatty
acids (Mirjana and Ksenija, 2005).
The fatty acid profile of edible oils play very
important role in their stability and
nutritional values. Monounsaturated (18:1)
and polyunsaturated (18:2) fatty acids have
been found to be effective in replacing
saturated fatty acids as part of cholesterol –
lowering diets. Though, researches have
shown that oils with substantial amounts of
unsaturation particularly 18:2 fatty acids
(such as linoleic acid) are susceptible to
oxidation and may produce products that
contribute
to
arteriosclerosis
and
carcinogenesis (Mirjana and Ksenija, 2005).
The oil from water melon seeds is reported
to contain high amount of unsaturated fatty
acids, it is viscous and has an indefinite
shelf life when stored in a cool and dry
places. Reports have also shown that the oil
has high content of omega acids and linoleic
acid which assist in the removal of excess
sebum within the skin for ensuring that the
skin cleansing. These properties have made
the oil an all-purpose oil (Zahra and Ali,
2010).
information on the nutritive composition of
the leaves, seeds and seed oil of the plant
from the area. The objective of this study
was to determine the proximate and mineral
element composition of the seed as well as
the physico-chemical properties of water
melon seed oil from Kalgo Local
Government area of Kebbi State. This is
with the view to make appropriate
recommendation on the health and other
domesticimplicationsof water melon seed
and its oil.
The demand for vegetable oil is increasing
at a rapid pace due to increasing demand for
non-food uses of vegetable oils such as in
biodiesel,
oleo-chemicals,
lubricants,
pharmaceuticals and cosmetic industries.
Only few known plant species are currently
commercially exploited to produce oils in
order to meet up with the challenge (Zahra
and Ali, 2010). In Nigeria, particularly in the
North, water melon plant is mostly grown
for the fruits. There are little or no effort on
the extraction and utilization of its oil. This
could be associated to lack of adequate
Proximate Analysis
Moisture, ash and crude protein contents of
the dried powder samples of the seeds were
determined in accordance with the methods
described by (Nayak and Patel, 2010). The
Total dietary fibre was determined by nonenzymatic-gravimetric method which was
carried out by suspending 500 mg of each of
the samples in two separate beakers with
distilled water and incubated at 37oC for 90
minutes. This was followed by precipitating
with four volumes of 95% ethanol. One of
the washed, dried and weighed residues was
MATERIALS AND METHODS
Sample Collection and Preparation
The fresh ripe water melon fruits were
collected randomly from three selected
agricultural fields surrounding Kalgo town.
The seeds were removed, washed and dried
in the sun for 48 hours. The seeds were
crushed in to powdered form using plastic
mortar and pestle to obtain a sample size
that passed through 80- mesh sieve. The
resultant seed materials were stored in a
refrigerator at 5oC until required for analysis
(Zahra and Ali, 2010; Kalkarniet al., 2012).
11
Proximate and Chemical Properties of Water Melon Seed and Oil from Kalgo, Kebbi State, Nigeria
ashed at 525oC for 3 hours while the second
portion was analysed for crude protein using
Kjeldahl method. The weight of the residues
after correcting for crude protein and ash
corresponds
to
the
Total
dietary
fibre(AOAC,
1998).
The
available
carbohydrate was determined as the
difference between 100 g dry mass of
sample and the sum of the values for ash,
fibre, crude lipid and protein (Stewente et
al., 1974; Mcdonaldet al., AOAC, 1998).
using refractometer at 25oC and titrimetry
respectively as described by Nayak and
Patel (2010). The specific gravity at 25oC
and free fatty acid compositions of the oil
were determined according to the methods
described by AOAC (1998).
Mineral Element Composition
Wet ashing technique was used and the
digestion processes were carried out in
thrice by weighing 1.0g of each of the oven
dried and powder sample into separate
100cm3Kjeldahl flasks, 30cm3 of 69.5%
(w/w) HNO3 was added to each of the flasks
and heated until about 10cm3 of each of the
solution remained. This was followed with
the addition of 2cm3 of 60% HClO4 acid,
10cm3 of 69.5% (w/w) HNO3 and 1cm3 of
98% (w/w) H2SO4 into each of the flasks.
The mixtures were further heated in a fume
cupboard until the appearance of white
fumes. The resulting solutions after cooling
were each filtered into separate 50cm3
volumetric flasks and diluted to the mark
with distilled water (Miller-Ihli and Bakar,
2000; Daniel, 2003). A blank solution was
prepared in the same way but without any
sample. Na and K were determined by flame
emission spectroscopy (Corning 400 model),
P was determined by colorimetric
(phosphor-vanadomolybdate) method using
spectrophotometer (6100, Jenway, UK). Mg,
CaFe, Zn and Cu were determined by AAS
(S4 Atomic Absorption Spectrometer
Thermo Electron, Cambridge, 2002).
Extraction of Oil
The oil was extracted by heating 100g of
each of the ground samples with 200cm3 of
n-hexane using soxhlet apparatus for 6h on a
heating mantle. The excess of the solvent
was removed by reduced pressure using a
rotary vacuum evaporator. The recovered oil
was freed of any traces of moisture by
mixing it with small amount of anhydrous
sodium sulphate before filtering. The
resultant oil was capped in a brown bottle
and stored in the refrigerator at a
temperature of about 5oC for further analysis
(Archanaet al., 2011).
Oil Characterization
The peroxide and acid values were
determined by the methods described by
(Louset al., 2011). Iodine and saponification
values were determined in accordance with
the methods described by (Archana and
Bachheti, 2011). The refractive index and
unsaponifiable matter were determined
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Int. J. Chem. Sci. Vol. 7 No. 1, pp 10-16, 2015
RESULTS AND DISCUSSION
Table 1. Proximate and mineral element composition of water melon seed expressed in dry
weight basis
Parameter
Value
Moisture
6.47±0.53g/100g
Ash
4.38±0.25g/100g
Crude protein
23.18±2.48g/100g
Crude fibre
19.89±1.76g/100g
Crude lipid
38.33±2.25g/100g
Carbohydrate
14.22±2.18g/100g
Na
20.44±1.33µg/g
K
7135.45±88.41µg/g
P
570.92±05.37µg/g
Mg
2560.34±76µg/g
Ca
1452.22±90µg/g
Fe
42.50±1.59µg/g
Zn
33.12±87µg/g
Cu
15.82±66µg/g
Data are expressed as mean ± standard deviation of three replicates
Table 2. Physicochemical properties of water melon seed oil
Parameter
Value
Colour
Yellow
Smell
Spice like
Nature of oil
Liquid at room temperature
o
Specific gravity at 25 C (Kg/dm3)
0.816±1.00
o
Refractive index at 25 C
1.31±0.25
Saponification value (mg KOH/g)
180.01±1.46
Iodine value (gI2/100g oil)
61.75±1.55
Peroxide value (mmol O2/kg)
4.48±0.06
Unsaponifiable matter (g/100g)
1.50±0.75
Acid value (mg KOH/g)
12.22±0.09
Free fatty acid (mg/g)
4.57±0.03
Data are expressed as mean ± standard deviation of three replicates
13
Proximate and Chemical Properties of Water Melon Seed and Oil from Kalgo, Kebbi State, Nigeria
Table 1 presents the proximate and mineral
element composition of water melon seed.
The moisture content value (6.47g/100g)
indicated that the seeds can be kept for a
long time without getting spoiled. The mean
value of 23.18g/100g for crude proteinwas
observed to be slightly high and closely
relate with the values of 21.8g/100g for
water melon seeds by Mirjana and Ksenija
(2005) and was within the range of 19.36 –
26.21g/100g for winter melon seeds reported
by Farooq et al. (2011). The value of
19.89g/100g for crude fibre is slightly lower,
but can help in the supply of fibre
particularly to those who take less
vegetables. The values were lower than the
range of 28.18 – 42.03g/100g reported by
Farooq et al. (2011). The percentage oil
yield of 38.33% was higher than
22.10g/100g reported by Mirjana and
Ksenija (2005), but compared well with the
values of 35% and 40%for black and white
seeds of water melon respectively reported
by Sabahelkhieret al. (2011). Similarly, the
oil yield was lower than the values of
45.54% from water melon seed reportedby
Zahra and Ali (2010) and 46.31% from
Jatropha seeds by Nayak and Patel (2010).
The seeds are therefore considered as good
source oil. The mean values of 20.74
µg/100g, 7135.45µg/g, 7135.45 µg/g, 2560
µg/g, 1452 µg/g, 570 µg/g, 42.50 µg/g,
33.12 µg/gand 15.72 µg/g were observed for
Na, K, Mg, Ca, P, Fe, Zn and Cu
respectively. The values particularly for K,
Mg, Ca, P, Fe are high enough to help man
meet their body requirements. The low value
for Na makes the consumption of the seeds
safe for high blood pressure patients. The
values generallycompared well with those
reported by Mirjana and Ksenija (2005).
Table 2 presents the physicochemical
properties of the oil extracted from water
melon seed. The yellow colour and spicy
odour of the oil are important features that
can encourage consumers to accept it
(Farooq et al.,2011). The mean value for
specific gravity displayed by the water
melon seed oil fall within the range of 0.88 –
0.94g/cm3
recommended
for
consumption(Farooq et al.,2011). Valuesfor
the specific gravity and refractive index
compared well with those reported in oil
from black and white water melon seeds by
Sabahelkhier, et al. (2011) and Mirjana and
Ksenija (2005). The refractive index and
specific gravity are important physical
properties that provide information on the
purity of vegetable oils (Farooq et al., 2011;
Montes et al., 2011). The saponification,
iodine, acid and peroxide values were
180.01 mgKOH/g, 61.75 mgI2/100g,
12.22mg.KOH/gand
4.48mmol
O2/kg,
respectively.The
saponification
value
compared well with the value of
188mgKOH/g reported by Mirjana and
Ksenija (2005) and the range of 182.30 –
194.10mgKOH/g reported for oil from
winter melon seeds by Farooq et al. (2011).
Iodine value which is the measure of the
average amount of unsaturation of fats and
oils was lower than the values of 119
mgI2/100g and 80 -85mgI2/100g reported by
Mirjana
and
Ksenija
(2005)
and
Sabahelkhier, et al. (2011), respectively.
The high iodine value observed in the oil is
likely to be due to its high content of
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Int. J. Chem. Sci. Vol. 7 No. 1, pp 10-16, 2015
unsaturated fatty acids. Oils with high iodine
and saponification values are suitable for
soft soap and cosmetic production as well as
for edible applications. The acid value was
much lower than the values reported for oil
from black and white water melon seeds by
Sabahelkhier, et al. (2011), but higher than
the value of 1.00 mg KOH/g reported by
Mirjana and Ksenija (2005). It compared
well with 11.0 mg KOH/g reported
forjatropha seed oil by Singh and Siroj
(2009). The high level of acidity observed in
the oil makes it uneconomical for the
traditional process of trans-esterification.
The peroxide value was slightly lower than
the values of 12 mg KOH/g and 9 mg
KOH/g reported by Sabahelkhier, et al.
(2011) and 7.9 mg KOH/g by Mirjana and
Ksenija (2005). The value obtained for
unsaponifiable matter compared well with
the values of 1.02% in both water melon and
jatropha seed oils by Mirjana and Ksenija
(2005) and Archcana and Bachheti (2011),
respectively. The low value obtained for free
fatty acid in the oil indicated the low level of
hydrolysis either due to chemical or
lypolytic hydrolysis and thus indicated the
quality of the oil (Farooq et al., 2011).
for consumption if produced in commercial
quantities. The values obtained for
saponification and iodine indicated that the
oil apart from consumption can also be used
in other domestic activities.
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CONCLUSION
The results obtained on the analysis of water
melon seed and its oil suggested that both
the seed and its oil could be used
successfully for human consumption and
could be an acceptable substitute for highly
unsaturated oils. The seed samples had
appreciable amount of crude protein and
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of the seed oil indicated that it is stable, can
be store for some time and can be acceptable
15
Proximate and Chemical Properties of Water Melon Seed and Oil from Kalgo, Kebbi State, Nigeria
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