Extraction and
Characterization of Bio-oil from Phoenix
Dactylifera L. (Date Palm
Seed)
Saddiq Maryam1*
1Department of Chemistry,
Umaru Musa Yar’adua University, Katsina, Nigeria.
maryam.saddiq@umyu.edu.ng.
Abstract
The study was carried out to extract oil from phoenix dactylifera
L. (date palm seed) collected from Katsina town, Katsina State, Nigeria. Physicochemical
parameters such as oil
and moisture content, acid and saponification value were also determined. The sample was thoroughly cleaned and dried under shade for six (6)
weeks. It was then crushed into powder using crushing machine. The extraction
of oil from the ground seeds was done using n-hexane through soxhlet extraction
method. The results showed that the percentage of oil yield was 28 % and the
observed color of the oil was pale yellow with a mild nutty odor. The extracted
oil was found to have a pH of 6.1 and a refractive index of 1.463. Chemical
analysis revealed an acid value of 1.07 mg KOH/g and saponification value of
167.8 mg KOH/g indicating good oil quality and stability. FT-IR analysis
confirmed the presence of functional groups characteristic of vegetable oils,
including CH2, C=O, C=C, C-C & C-O while the GC-MS analysis
showed that the oil comprised
mainly of low molecular weight fatty acids such as oleic acid, linoleic acid, lauric
acid and palmitic acid and sterols such as β-sitosterol and stigmasterol. These findings
confirmed that, date palm seed oil possesses favourable physicochemical
properties which make it suitable for applications in food, cosmetics and
pharmaceutical industries, thereby promoting the valorization of agricultural
waste.
Keywords: Agricultural; Vegetable; Seed; Oil; Soxhlet.
1. Introduction
Date palm seeds, also known as date pits or stones are
the hard, oblong kernels found within the fruit of the date palm (Phoenix dactylifera L.). They constitute
approximately 10–15% of the total weight of the date fruit and are typically
considered a byproduct or waste in date processing industries. However, growing
interest in sustainable practices and valorization of agro-industrial waste has
led to increased research into their composition and potential applications (FAOSTAT, 2024). It is
widely cultivated in tropical and subtropical regions, notably in the Middle
East and North Africa (Qadir et al., 2018). Globally, the gross production value
of date fruits has been rising considerably since the 20th century, with the
highest value seen at more than US $14 billion in 2020 (FAOSTAT, 2024). Date
palm trees and fruits drive the economic and social aspects of date-producing
countries (Ghafoor et al., 2022; Mrabet et al., 2020). Date seeds, a by-product of date fruit production, are usually
treated as waste, utilized as animal feed or just disposed of (Qadir et al., 2018).
Oil extracted from date
seeds is gaining attention due to its favorable fatty acid profile, which
includes significant amounts of oleic, lauric and linoleic acids. Chemically,
date seeds are rich in carbohydrates, dietary fiber, proteins, fats, and
bioactive compounds, including phenolics and antioxidants (Habib et al., 2013). In addition to oil
extraction, date seeds have been studied for their potential in producing
activated carbon, animal feed, dietary supplements, and as raw materials in
cosmetics and pharmaceuticals industry (Niazi et al., 2017; Sadiq et al., 2013).
Owing to its health benefits, date seeds possess high potential as a
nutritional therapeutic agent for several chronic diseases (Hilary et al., 2021). Given the global production of dates, particularly in
Middle Eastern and North African countries, the sustainable utilization of date
seeds represents an opportunity for economic and environmental benefits (Qadir et al., 2018).
Consequently, research into their extraction methods, physicochemical
properties, and applications continues to expand (Al-Farsi & Lee, 2008).
2. Methodology
2.1
Sampling and Sample Pre-treatment
Date fruits were collected from a
date-producing area in Katsina city, Katsina, Nigeria in the month of October,
2025. After collection, seeds were separated
manually from the fruits where only healthy, undamaged, and fully matured seeds
were selected for the study in order to obtain the highest oil yield. The seeds
were washed thoroughly so as to remove the peels and dried under shade for six
(6) weeks. Thereafter, the seeds were crushed into a fine powder using crushing
machine. The ground palm date seed was stored in an air tight container for
further use.
2.2 Determination
of Moisture Content
The total moisture content in the
ground date palm seed was determined as described by Reddy et al. (2017).
2.3 Determination
of Oil Content
The total moisture content in the
ground date palm seed was also determined according to the procedure reported
by Reddy et al. (2017).
2.4 Extraction
of Oil
About
fifty (50 g) grams of the ground seed was measured and transferred to a cellulose
thimble and placed in a soxhlet extractor fitted with a condenser placed on a
distillation flask containing n-hexane as the extracting solvent. The ground
seed was then extracted under reflux for 5 h with 10 flushes and the sample was
removed. Thereafter, n-hexane was evaporated using rotary evaporator under
vacuum conditions. The extracted oil was allowed to cool down; the yield of the
oil was recorded using the expression below;
×100 %
2.5 Determination
of Acid value
Acid
value is the mass of potassium hydroxide (KOH) in milligrams that is required
to neutralize one gram of a chemical substance. It is a measure of the amount
of carboxylic acid groups in a chemical compound. The acid value was determined
by titrimetric analysis as described by Zhang et al. (2015). The
acid value (AV) of the date seed oil was calculated using the expression below;
Where:
V = Volume of KOH used (mL)
N
= Normality of KOH (0.1 N)
W
= Weight of oil sample (g)
56.1
= Molecular weight of KOH
2.6
Determination of Saponification Value
Saponification
value is a measure of the amount of potassium hydroxide (KOH) required in order
to hydrolyze one (1 g) gram of oil. The saponification value was determined by
titrimetric method as described by Akbari et
al. (2012). A blank experiment was carried out without the oil sample using
the same procedure and reagents. The volume of HCl required for the blank was
recorded. The saponification value (SV) expression is given by;
Where;
B = Volume of KOH without oil (blank sample)
S
= Volume of KOH with oil sample
N
= Normality of KOH (0.1 N)
W
= Weight of oil sample (g)
56.1
= Molecular weight of KOH
2.7 FT-IR Analysis
The
Fourier Transform Infrared Spectroscopy (FT-IR) is utilized to study functional
groups present in a liquid, solid and gaseous sample. The available functional
groups present in the oil were recorded on an Agilent Technology’s 630 FT-IR
spectrophotometer. The sample was fixed in potassium bromide (KBr) disc and the
sample was scanned in the range of 4000-650 cm-1 wavenumber.
2.8 GC-MS Analysis
The GC-MS analysis was
employed to determine the fatty acid composition of the extracted oil from phoenix dactylifera L. using Agilent Technologies GC system with
GC- 7890A/MS-5975C model (Agilent Technologies, Santa Clara, Ca, USA) equipped
with HP-5MS column (30 m in length × 250 mm in diameter ×
0.25 mm in thickness of film).
3.
RESULTS AND DISCUSSION
3.1
Moisture and Oil Content
The oil content of the
date palm seed was about 20 % and the moisture content was about 9.5 % which
were determined according to the procedure described by British Standards
Institution (BS EN ISO 665:
2000 & 2009). The low moisture content was due to the
fact that the seeds were fresh and had enough time dry off. This value is in
agreement with other studies were a value range between 3.1 -7.1 % moisture
content was obtained (Amani et al., 2013).
3.2
Oil yield and its Properties
Soxhlet extraction is the
most cited technique in the literature used for extracting oil from date seeds and
it is sometimes used as reference against other techniques because it gives the
best yield of oil (Alem et
al., 2017). Hexane on the other
hand, has been used for decades as solvents for fats and oils extraction from
plant materials (Abdalla et al., 2012). It has various qualities
for easy extraction of lipids such as easily removal by evaporation, stability
and convenient boiling point (Ali & El-Anany, 2025). The weight of the oil extracted was found to be 14 mL and
the percentage (%) yield was 28 % based on dry matter. This is attributed to
the extraction method, extracting solvent, solvent to sample ratio and extraction
time. The result agrees with previous studies and the parameters studied
contributed immensely in the yield of oil (Alem et al., 2017; Al-Juhaimi et
al., 2018).
However, the oil was
subjected to physicochemical analysis to determine its physical and chemical
properties as shown in Table 3.1. Oil’s appearance plays a crucial role in their potential applications.
The color of the oil was pale yellow which looks similar to that of vegetable
oil. Generally, vegetable oils color comes from the existence of coloring pigments
such as β-carotene, chlorophyll and tocopherols (The & Birch,
2013). The saponification value (167.8 mg
KOH/g) obtained was between that of palm kernel oil and coconut oil, which
suggests that the oil may be suitable for soap production. The pH value of the
oil was found to be 6.1, which shows that the oil is slightly acidic but
acceptable. This suggests that the oil is relatively stable and not highly
degraded. The refractive index is an indicative physicochemical
parameter easy to get for oils and it was found to be 1.463.
The low refractive index value indicated that their
fatty acids may be composed of low molecular weight hydrocarbon chains. The
acid value (1. 07 mg KOH/g)
of the oil indicates that the oil has low acidity. It is believed that, these
bio-solvents produced from agricultural sources are greater potential
candidates to replace petroleum
solvents (Sicaire et al., 2015;
Breil et al., 2016).
Table
3.1 Properties of the Extracted Oil
|
S/N |
Property |
Result |
|
1 |
Weight |
14 |
|
2 |
Percentage yield |
28 % |
|
3 |
Color |
Pale yellow |
|
4 |
Odor |
Mild nutty |
|
5 |
Refractive Index |
1.463 |
|
6 |
pH |
6.1 |
|
7 |
Acid Value |
1.07 mg/g |
|
8 |
Saponification Value |
167.8 mg/g |
3.3 FT-IR Analysis
Table 3.2 shows the FT-IR spectrum of the oil extracted
by n-hexane. From the FTIR analysis, it
was observed that the result showed the following functional groups. Peak 1267
cm-1 region indicated the stretching vibration of C-O ester group
and wagging of methylene (CH₂). The peak at 1756 cm-1 is assigned to
the stretching vibration of carboxylic acid (C=O) group. Moreover, peak
observed at 3324 cm-1 are due to bending and stretching vibration of
O-H bonds. Peaks found at 2922 cm-1 is assigned to C-H stretching
vibration and 1610 cm-1 was due to C=C stretching of alkene respectively.
These functional groups confirm the presence of fatty acids and triglycerides
in the oil and agree with previous studies conducted by Alem et al. (2017). Furthermore, the type of extracting solvent decides the nature
of the extracted compounds from the sample (Thakur & Arya, 2014).
Table 3.2 Result of FT-IR Analysis of the Extracted Oil
|
Wave
number (cm-1) |
Functional
group |
Assignment |
|
3324 |
Alcohol |
O-H stretch |
|
2922 |
Aliphatic |
C-H stretch |
|
1610 |
Alkene |
C=C stretch |
|
1267 |
Alkoxy |
C-O stretch |
|
1756 |
Carboxyl |
C=O Stretch |
3.4 GC-MS Analysis
Gas Chromatography Mass Spectrometry was employed to
identify the fatty acid composition in the date palm seed oil. The result
identified sixteen (16) compounds in the oil (Table 3.3) which include long
chain fatty (saturated and unsaturated) acids and triglycerides. Oleic acid, β-sterol,
linolenic acid and palmitic acid were present in substantial amount. Generally,
oils with high oleic acid contents showed good flavor and frying
stability and linolenic acid was reported to be
crucial for the healthy growth of human skin. Previous
studies on date palm seed by Akbari et al. (2012) have shown similar result.
Table 3.3 GC-MS Analysis of the Extracted Oil
|
S/N |
Name
of compound |
RT |
% |
|
1 |
Capric acid |
2.023 |
0.65 |
|
2 |
Caprylic acid |
1.781 |
0.54 |
|
3 |
Lauric acid |
2.413 |
7.89 |
|
4 |
Stearic acid |
4.872 |
4.05 |
|
5 |
β-sitosterol |
3.916 |
10.12 |
|
6 |
Eicosenoic acid |
7.422 |
1.23 |
|
7 |
Linoleic acid |
5.852 |
5.65 |
|
8 |
Oleic acid |
4.791 |
40.38 |
|
9 |
Hexadecenoic acid |
3.833 |
1.32 |
|
10 |
Palmitic acid |
3.538 |
9.39 |
|
11 |
Tridecanoic acid |
2.509 |
0.59 |
|
12 |
Pentadecanoic acid |
2.792 |
0.82 |
|
13 |
Myristic acid |
2.566 |
4.13 |
|
14 |
Stigmasterol |
4.810 |
3.23 |
|
15 |
Linolenic acid |
11.829 |
9.58 |
|
16 |
Palmitoleic acid |
19.620 |
0.43 |
RT= retention time
and %= percentage quality
4. Conclusion
Undoubtedly, the demand
for plant-derived products has increased across the world. The study involves
the extraction of oil from date palm seeds. The bio-oil obtained from date palm
seed was very similar to other bio-oils in physicochemical properties. FTIR
analysis confirmed the presence of important functional groups such as CH, C=O, C=C, O-H and C–O,
which are characteristic of saturated and unsaturated fatty acids. This further
confirms that the extracted oil is a typical vegetable oil with desirable chemical
properties. GC-MS analysis of the oil identified sixteen compounds (16) with low molecular weight
fatty acids and sterols having the highest percentage quality. Based
on the results obtained, it can be concluded that, date palm seed which is
often regarded as waste, is a valuable source of oil with promising
physicochemical characteristics, and its utilization can contribute to waste
reduction and value addition.
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