INTERNATIONAL JOURNAL OF FOOD AND NUTRITION SCIENCE VOL1 NO2 MARCH 2012
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Extraction and Physicochemical Determination of Garlic
(Allium sativum L) Oil
Gafar M. K., A. U. Itodo, A. A. Warra and L. Abdullahi

Abstract—The oil was extracted from powder of garlic cloves
using soxhlet extraction method with n-hexane as the solvent. The
garlic cloves give 22.5% oil yield with specific gravity density of
0.90g/cm3. The oil is light yellow in colour with a pungent smell.
The chemical analyses revealed saponificacation value of 192 ±
1.00mgKOH/g, peroxide value of 2.5 ± 0.50mg/100g, acid value of
4.18 ± 0.01mgKOH/g, free fatty acid value of 2.10 ± 0.05% and
Iodine value of 12.69 ± 0.05g/100g. These results obtained shown
that the oil could be of benefit for soap production.
Index Terms — chemical analysis, Extraction, Garlic oil, oil
yield, Industrial uses.
I. INTRODUCTION
A
llium the Latin word given to garlic[1], a flowering plant
with hundreds of distinct species; which many have been
harvested through human history, but only about a dozen
are still economically important today as crops or garden
vegetables[2]. One of the species belong to this genus is the
Allium sativum L. also known as the cultivated garlic, which
belong to the onion family Alliaceae and closely related to the
onion, shallot, leek, chive, and rakkyo[3]. It has been used
throughout recorded history for both culinary and medicinal
propose[4]. Garlic plant is moderately tall (up to three feet) it
is an erect herb normally grown as an annual that is a plant that
only last for a year, it has adventitious roots and condensed,
flattened stem and narrow flat leaves. The bulb consists of 6 to
35 bulblets called cloves with glistering and transparent
covering, the plant grows as a vegetable rosette close to the
ground, the leaves is broad like kidney shaped. The plants also
produce an erect flowering stem with numerous quitter inch.
The majority of Allium species are native to the Northern
hemisphere, mainly in Asia. A few species are native to Africa
and South America. They grow in various conditions from dry,
well-drained mineral-based soil to moist organic soil, most
grow in sunny locations but a number also grow in forests, or
even in swap water areas[5].
Manuscript received January 23, 2012.
Lecturers; Gafar M. K., Dr .A. U. Itodo and Research student L. Abdullahi
are from the Department of Chemistry, Kebbi State University of Science and
Technology, Aliero, Nigeria.
Researcher A.A. Warra is a Senior Laboratory Technologist from the
Department of Biochemistry, Kebbi State University of Science and
Technology,Aliero Nigeria.
Dr. A.U. Itodo (e-mail: [email protected]).
Allium sativum L. consist of sulfur containing compounds such
as allicin, alliin, ajoene, dially disulfide, dithiin and Sallylcysteine.These large number of sulfur compounds
contributes to the smell and taste of garlic. Dially disulfide is
believed to be an important odour component in the garlic.
Allicin has been found to be the compound most responsible
for the spiciness of the raw garlic and being a powerful
antibiotic and antifungal compound, it believe to be the agent
responsible for the speed recovery from strep throat or other
mild ailments when garlic is used[6]. Garlic contain oil which
is an essential oil, the oil is extracted by process of steam
distillation of the garlic cloves using n-hexane as solvent.
Essential garlic oil contains variety of sulfide such as dially
disulfide and dilly trisulfide. During the process allicin is
completely eliminated from the oil[7]. Commercially available
garlic oil capsules generally contain vegetable oil and a small
amount of garlic essential oil because of the pungent odors.
Other garlic supplements fall into one of these categories,
dehydrated garlic powder, garlic oil macerate and aged garlic
extract[8]. Garlic oil has numerous uses in the world today, its
uses include the flavouring some cuisine like salads, and
sauces[9]. The regular consumption of garlic oil can reduce
blood pressure, prevent heart disease including atherosclerosis,
high cholesterol and cancer[10]. Garlic oil is an effective
antibiotic, anti-viral, anti-fungal agent, which could be
used to prevent nausea, diarrhea, ease coughs, even
treatment in conditions such as malaria and cholera
probably an immune system enhancement, some studies
have found lower rates of certain types of cancer in
people[11].
II.
MATERIALS AND METHODS
Sampling and sample treatment: The garlic cloves were
obtained from Kurya Madaro town Kaura Namada Local
government area of Zamfara State and identified by a
taxonomist at Botany department in Kebbi State University of
Science and Technology, Aliero as cultivated garlic Allium
sativum L. The transparent covering of garlic was removed
manually and sun-dried for two weeks. Mortar and pestle was
used to pound the dry garlic cloves into powder, then sieved
and stored in a covered plastic container for further uses. All
reagents were of analytical reagent grade unless otherwise
stated. Distilled water was used in the preparation of solutions
and dilution unless otherwise stated. The physiochemical
analyses were carried out in triplicates unless otherwise stated.
INTERNATIONAL JOURNAL OF FOOD AND NUTRITION SCIENCE VOL1 NO2 MARCH 2012
Oil extraction
The extraction of garlic oil was conducted with a soxhlet
extractor using n-hexane (boiling point of 40oC - 60oC) for six
hours. The oils were obtained after the solvent was removed
under reduced temperature and pressure and refluxing at 70 oC
so as to remove any excess solvent used for the oil extracted.
The extracted garlic oil was stored in refrigerator freezer at
2oC for subsequent physicochemical analyses[12].
Determination of percentage yield
The oil which was recovered by complete distilling of the
solvent on a heating mantle was then transferred into a
measuring cylinder. The measuring cylinder is then placed
over water bath for complete evaporation of solvent for about
2-3 hours in accordance with the method reported[12] and
volume of the oil was recorded and expressed as oil content
(%) as follow[12].
Oil content (%) = Volume of the oil x 100%
Weight of sample
Determination of specific gravity 10cm3 of the oil was
measured in a pre – weighed measuring cylinder. The weight
of the cylinder and oil were measured, the weight of the oil
was then obtained by subtracting the weight of the cylinder
from the weight of the oil and cylinder. The specific gravity of
oil was obtained using equations below[13].
Density of water = W1 – W0
V0
Where
W1 = weight of empty measuring cylinder + water
W0 = weight of measuring cylinder
V0 = volume of water used
Density of oil = W1 – W0
V0
Where
W1 = weight of empty measuring cylinder + oil
W0 = weight of measuring cylinder
V0 = volume of oil used
Therefore specific gravity = Density of water used
Density of oil used
5
Determination of peroxide value
2.0g of oil extracted was added to 22cm3 of a solution mixture
of 12cm3 chloroform and 10cm3 acetic acid. 0.5cm3 of
saturated potassium iodide was added to the flask. The flask
was corked and allowed to stay with occasional shaking for 1
minute. 30cm3 of distilled water was then added to the mixture
and titrated against 0.1M of Na2S2O3 until yellow colour is
almost gone. 0.5cm3 of starch indicator was quickly added and
titration continued until blue colour just disappeared. A blank
titration was also carried out at the same condition[15].
(S – B) X N
x 1000
W
Where
Peroxide value =Meq peroxide per 100g of sample
S = volume of titrant (cm3) for sample
B = volume of titrant (cm3) for blank
N = molarity of Na2S2O3 solution (mEq/cm3)
1000 = conversion of units (g/kg)
W = Weight of oil sample
Peroxide value =
Determination of iodine value
0.4 g of the garlic oil sample was weighed into a conical flask and
20 cm3 of carbon tetrachloride was added to dissolve the oil. Then 25
cm3 of wij’s reagent was added to the flask using a safety pipette in
fume chamber. Stopper was then inserted and the content of the flask
was vigorously swirled. The flask was then placed in the dark for 2
hours 30 minutes. At the end of this period, 20 cm3 of 10% aqueous
potassium iodide and 125ml of water were added using a measuring
cylinder. The content was titrated with 0.1M sodium-thiosulphate
solutions until the yellow colour almost disappeared. Few drops of
1% starch indicator was added and the titration continued by adding
thiosulphate drop wise until blue coloration disappeared after
vigorous shaking. The same procedure was used for blank test and
other samples[14].
The iodine value (I.V) is given by the expression
Iodine value = 12.69C (V1-V2)
M
Where C = Concentration of sodium
V1 = Volume of sodium thiosulphate used for blank
V2 = Volume of sodium thiosulphate used for determination
M = Weight of the sample.
Determination of saponification value
Determination of free fatty acid
About 2 g of the garlic oil was added to a flask with 30 ml 2.0g
of of oil was measured into 250cm3 Erlenmeyer flask,
ethanolic KOH and was then attached to a condenser for 30 minutes
100cm3 of ethanol was added and followed by 2cm3 of
to ensure the sample was fully dissolved. After sample the had
phenolphthalein indicator. The mixture was shake and titrated
cooled, 1 ml of phenolphthalein was added and titrated with 0.5M
against 0.1M NaOH with continuously shaking until the
HCl until a pink endpoint has reached[14].
endpoint is reached, which is indicated by a slight pink color
Saponification value was calculated from the equation[14]
that persists for 30seconds, the free fatty acid is expressed
as[16]
Saponification value = (S-B) x M x 56.1
%FFA = V X N X 282 X100
Sample weight (g)
W
Where S = sample titre value
Where %FFA = Percent free fatty acid (g/100g)
B = blank titre value
V = Volume of NaOH (cm3)
M = molarity of the HCl
N = Molarity of NaOH
56.1 = molecular weight of KOH
282 = Molecular weight of oleic acid
W = weight of oil sample
INTERNATIONAL JOURNAL OF FOOD AND NUTRITION SCIENCE VOL1 NO2 MARCH 2012
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3.58%[21], indicates that the oil can be kept for a very long
period of time[21].
Determination of acid value
25cm3 of 5% ethanol was boiled on a water bath the heating is to
ensure the removal of dissolved gases. 2.5g of garlic oil was addedAcid
to value: The acid value 4.18 ± 0.01mgKOH/g obtained
25cm3 of hot ethanol and the mixture was heated to boil. Then few
from the oil is low when compared to Sheanut butter oil
drops of 1% phenolphthalein indicator was added and titrated against
10.3mgKOH/g[22] and high when compared to 2.39 ±
0.1M KOH with constantly shaking until a permanent pink colour
0.065mgKOH/g, 1.20 ± 0.065mgKOH/g and 0.81 ±
was obtained, the acid value is expressed as[17].
0.01mgKOH/g for castor seed oil, jatropha oil and cotton seed
Acid value = 56.1X M X V
oil respectively[12]. Thus the higher the acid value of an oil,
W
the lower its storage quality and vice-versa[15], this shows that
Where M = Concentration of KOH
the garlic oil have an excellent storage quality when compared
V = Titre value
to that of Sheanut butter oil[22].
56.1 = Molecular weight of KOH
W = weight of oil sample
Free fatty acid: - Free fatty acid (oleic acid), determine the
suitability of the oil for edibility or industrial uses. The free
III. RESULTS AND DISCUSSION
fatty acid value is 2.10 ± 0.05% which is low when compared
The results of the physicochemical analyses conducted on the
to the Hyptus spicigera seed oil 3.50%. This shows that it is
garlic oil sample are presented in Tables 1and 2.
suitable for eating[23].
TABLE 1
Physical properties of the garlic oil
Parameters
Colour of oil
Specific gravity
Smell
Oil yield
Results
Light yellow
0.90
Pungent odour
22.5%
TABLE 2
Chemical properties of garlic oil
Parameters
Results
Saponification value
(mgKOH/g)
Peroxide value (mg/100g)
Acid value (mgKOH/g)
Free fatty acid (% oleic acid)
Iodine value (gI2/100)
192 ± 1.00
2.50 ± 0.50
4.18 ± 0.01
2.10 ± 0.05
12.69 ± 0.05
Saponification value: -The saponification value of the garlic
oil was found to be 192 ± 1.00mgKOH/g which is high when
compared to 183.1mgKOH/g of shea butter oil[22] and 123.3
± 3.428mgKOH/g, 122.49 ± 2.591mgKOH/g and 199.42 ±
0.53mgKOH/g for castor seed oil, jatropha oil and cotton seed
oil respectively, which they have potential for soap
production[12]. This indicates that the oil could be used in
soap making since its saponification value is higher than these
oils22.
Iodine value: - This is a measure of the proportion of
unsaturated acid or fat and oil present, but the test measures
the amount of iodine absorbed per gram of sample. The
determination of iodine value measures the reaction of the
double bonds with halogen[24]. The iodine value 12.69 ±
0.05g/100g which was obtained from the oil is low when
compared to 16.0g/100g Tiger nut oil[24]. The oil shows quite
degree of unsaturated fatty acid which indicates that the oil is
suitable for consumption and can also be used as a non drying
oil, which are useful in the manufacture of soap[24].
Values expressed as: Mean ± SD
Physical properties
The percentage yield was found to be 22.5% which is low
when compared to Bottle Gourd Lageneria siceraria seed oil
39.22%[18] and specific gravity is 0.90g/cm3 which is within
0.915g/cm3 and 0.923g/cm3 in Sesamum indicum L. seed
oil[19] and 0.89g/cm3 in African Oil Bean seeds Pentaclethra
marcrophylla[20], this indicate that the oil could be used on
commercial scale. The colour of the oil is light yellow with a
pungent odour. However the oil is liquid at room temperature
which could indicate the presence of oleic acid and linoleic
acid and other unsaturated fatty acids[18].
Chemical properties
Peroxide value: This measured deterioration of oil from
oxidation[16]. Therefore, the low peroxide value 2.50 ± 0.50%
obtained from oil when compared to palm kernel oil
IV. CONCLUSION
The results in this analysis indicated good quality for the garlic
oil. chemical analyses presented saponification value ,
peroxide value, acid value ,free fatty acid and Iodine values
that fell within the range of those acceptable as having good
potential for soap production and with an excellent storage
property.
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Correspondence to Main Author: * Gafar M.K
Department of Chemistry, Kebbi State University of Science
and Technology, Aliero, Nigeria
Email: [email protected]
Tel: +2348027415703