American Journal of Food Science and Nutrition Research
2017; 4(1): 1-8
http://www.openscienceonline.com/journal/fsnr
ISSN: 2381-621X (Print); ISSN: 2381-6228 (Online)
Effect of Process Parameters on Oil Yield
Mechanically Expressed from Almond Seed (Using
Response Surface Methodology)
Vivian C. Akubude1, Jehoshaphat N. Maduako1, Celestine C. Egwuonwu1, Adesoji M. Olaniyan2,
Isaac C. Ozumba3, Caesar Nwosu3, Olawale E. Ajala4
1
Department Agricultural and Bioresource Engineering, Federal University of Technology, Owerri, Imo State Nigeria
2
Department of Agricultural and Bioresources Engineering, Federal University Oye-Ekitti, Ekiti State, Nigeria
3
National Centre for Agricultural Mechanization, Ilorin, Kwara State, Nigeria
4
Department of Chemical Engineering, University of Ilorin, Ilorin, Kwara State, Nigeria
Email address
[email protected] (V. C. Akubude)
To cite this article
Vivian C. Akubude, Jehoshaphat N. Maduako, Celestine C. Egwuonwu, Adesoji M. Olaniyan, Isaac C. Ozumba, Caesar Nwosu, Olawale E.
Ajala. Effect of Process Parameters on Oil Yield Mechanically Expressed from Almond Seed (Using Response Surface Methodology).
American Journal of Food Science and Nutrition Research. Vol. 4, No. 1, 2017, pp. 1-8.
Received: March 20, 2016; Accepted: April 9, 2016; Published: October 21, 2016
Abstract
Investigation was carried out on the effect of process parameters on oil yield from sweet almond seed (Terminalia catappia)
expressed using a mechanical oil rig. A four factor, five levels central composite design (CCD) under response surface
methodology was applied to determine the effect of four independent variables (moisture content (6, 7, 8, 9, 10%w.b),
temperature (80, 85, 90, 95, 100°C), heating time (10, 14, 18, 22, 26min.) and applied pressure (20, 21, 22, 23, 24KN)) on oil
yield. Results showed that all the variables significantly affected the oil yield at 95% confidence level. The maximum oil yield
of 37.138%, was obtained at temperature, pressure, heating time and moisture content of 90°C, 24KN, 18minutes and 8%w.b
respectively.
Keywords
Almond Seed, Oil Extraction/Expression, Oil Yield, Response Surface Methodology
1. Introduction
Oil is found in large amounts usually in the seeds of the
plants and occasionally in the fleshy part of the fruits, as in
the olive and the oil palm [1]. Oil-bearing seeds and nuts are
found in the roots, stems, fruits and leaves of some tropical
and subtropical plants. They are mostly grown as annual
crops and constitute the major source of vegetable oil for
domestic and industrial uses. Some of the most common oil
seeds and nuts cultivated in the tropics, subtropics and
temperate regions include; groundnut, coconut, shea nut,
castor, sunflower, sesame, oil palm etc. [2]. Oilseeds are
important components of tropical agriculture as they provide
readily available and highly nutritious human and animal
foods [3]. Oilseeds provide highly nutritious human food and
oil crops and their products represent one of the most
important commerce commodity.
Almond seed is one of the versatile tree nut [4], perennial
in nature, usually grown within the cold and temperate
regions [5] mainly as shade during hot weather [6] or as
orchard crop [7] or for ornamental purposes [8]. The fruit is
made of a kernel (seed) enclosed by a hard shell (endocarp)
which also have fleshy covering (mesocarp) [9, 8]. There are
basically two varieties of almond: sweet and bitter almond
[10, 11, 12]. Sun-dried kernels yield 38-54% of edible, bland,
yellow, semi-drying oil known as Indian almond oil [13].
Oil expression/extraction is an energy intensive process
[14] which involves recovering of oil from oil-bearing
agricultural products through manual, mechanical, or
chemical extraction [2]. Mechanical extraction method
involves the direct application of force to oil bearing seeds to
2
Vivian C. Akubude et al.: Effect of Process Parameters on Oil Yield Mechanically Expressed from Almond Seed
(Using Response Surface Methodology)
release its oil from the cell under rupture [15, 16]. It is the
most common method of oil extraction [17, 18] and
equipment such as screw press, hydraulic press, mechanical
oil rig, expellers [19], rolling press etc can be used for this
method.
The oil yield from Mechanical oil extraction method is
affected by factors such as applied pressure, moisture content,
pressing time, heating duration, particle size, and temperature,
[20, 21, 22]. Research on roselle seed showed that Oil yield
increases by 5%–6% with an increase in the processing
parameters of pressure up to 30 MPa, temperature of 100°C
and decreased beyond these points where as it increased by
7% –8% with an increase in moisture content. Finely ground
samples were found to have higher yield than coarsely
ground samples at the different processing parameters [22].
Reports from work carried out on sesame seed showed that
the oil yield increased with decrease in moisture content of
sample after heating. The highest oil yield (based on total
mass expressed) of 33.5% corresponding to an expression
efficiency (based on seed oil content) of 65.7% was obtained
when sesame seeds were conditioned to moisture content of
6.1%, heated at 85°C for 20 min, and expressed at a pressure
of 20 MPa [23].
Response surface methodology (RSM) was adopted in the
design of experimental combinations. It is a useful
mathematical approach that is widely used to investigate and
optimize the combinational effects of several process
variables influencing response(s) with a reduced number of
experimental runs while varying the variables simultaneously
[24]. Works done using this method recorded that it is
capable of determining the effect of given parameter(s) on a
given factor(s) and can be used in predicting the optimum
value(s) of such given parameter(s) [24, 25].
There are limited research on the process parameters
necessary for the optimum extraction of almond seed oil.
Hence the knowledge of the appropriate set of parameters for
the extraction of almond seed oil will enhance the production
almond oil. The main objectives of this work is to evaluate
the effect of temperature, heating duration, applied pressure,
and moisture content on the oil yield of almond seed
2. Materials and Methods
2.1. Materials
The sweet species of almond fruits (Terminalia catappia)
were harvested manually from Benue, Anambra and Imo
state of Nigeria by hand picking those that fell by wind
action and by shaking the trees to release the ripe ones. The
harvested fruits were then washed with water to remove sand.
The pulp/mesocarp was manually peeled using knife to
expose the endocarp (shell). The peeled fruits were sun dried
for 5-7 days to avoid seed breakage during cracking and
kernel rancidity. The dried almond fruits were dehulled
manually using hammer. Each fruit was cracked along the
margin to release the brown spindle-shaped kernel from the
endocarp and then cleaned by separating the nut from the
husk through winnowing. Then the kernel was further dried
for three days under the sun (at average temperature of 51°C)
to safe moisture content for storage in air tight bucket till the
date of the experimentation. Therefore, 300kg of dried peeled
almond fruit was used for the experiment.
Fig. 1. Almond seed obtained from the dried fruit after cracking.
2.2. Seed Conditioning
The initial moisture content of the sun dried almond seeds
was determined using oven drying method based on
Association of Analytical Chemists [26] standard. Based on
this standard, at temperature 130°C for 6hour, 100g of seed
sample was oven dried to a constant weight. After 6 hours
the sample was allowed to cool in a desiccator for over 30
minutes and then reweighed to determine the final weight
(M2). The moisture content was determined using the
equation below;
%
∗ 100
(1)
The method used by [27] was adopted for the seed
conditioning. The dried almond seeds were reduced in size
using motorized attrition mill. The reduced seed samples
were graded into the coarse particle size of Ф ≥ 2 mm using
manual sieve. The sample was then subdivided into five parts
and the moisture content of each was properly adjusted to 7,
8, 9 and 10% (wet basis) by adding calculated quantity of
water to the sample. Sample with 6% moisture content was
not tempered with as it is within the moisture content level to
be used. The specific quantity of water required to be added
to each portion was determined using the equation below as
given by [28];
American Journal of Food Science and Nutrition Research 2017; 4(1): 1-8
∆
1
(2)
Where Wm is water to be added (g), W1 is initial weight of
the seed at M1 (g), ∆M = M2 – M1 (for M2 > M1) and ∆M =
M1-M2 (for M1 >M2), M1 is initial moisture content (%w.b)
and M2 is final moisture content (%w.b). The coarse seed
samples conditioned with water were sealed in polyethylene
bags and stored in the freezer for not less than 48 hours for
the moisture to be evenly distributed within the sample.
Before any experimental run, the samples were removed
from the freezer and allowed to thaw completely until
equilibrium is attained.
3
24KN, four other heating duration levels of 14, 18, 22 and
26minutes and four other moisture content levels of 7,8, 9,
and 10%(w.b).
2.3. Experimental Design
A four variable (five levels of each variable) central
composite experimental design was employed. The
parameters (temperature, pressure, heating time and moisture
content with the coding X1, X2, X3, and X4 respectively) and
their levels were chosen based on the literature [29] and
preliminary experiment and is given as shown in table 1
Table 1. Parameters and their levels in central composite design.
Parameters
Temperature
Pressure
Heating time
Moisture
content
Coded
Symbol
Unit
Working
range
Min Max
80
100
20
24
10
26
X1
X2
X3
°C
KN
Min.
X4
%w.b 6
10
Coded levels
80
20
10
85 90 95 100
21 2 2 23 24
14 18 22 26
6
7
8
9
10
2.4. Oil Expression Procedure
Oil expression from almond seed was carried out using
mechanical oil rig as shown in figure 3. This rig was
designed and fabricated at National centre for Agricultural
mechanization (NCAM) [30]. A sample of 80 g of crushed
almond sample at 6% (w.b) moisture content (particle size ≤
2mm) was weighed and transferred into the press cage
cylinder. The sample was heated inside the press cage
cylinder with the aid of the temperature controlled band
heater at 80°C for 10 minutes. Pressure was gradually
applied manually through the hydraulic press handle moving
the compression piston downward. The compression piston
serves as the pressing ram and distributes pressure from the
hydraulic press evenly on the oilseed sample in the press
cage cylinder and compresses the heated almond seed
thereby releasing the oil which flows through the mesh into
the oil collector. The applied pressure was measured by
digital force measuring unit through the load cell data cable
connected to it. The pressure was measured in terms of the
compressive force as 20KN. After expression, the
compression piston was lifted well above the press cage
cylinder. The press cage cylinder (with the residual cake
inside) was unscrewed and the residual cake was extruded
into the cake extruding die. The experiment was repeated for
the four other heating temperature levels of 85, 90, 95 and
100°C; four other applied pressure levels of 21, 22, 23 and
Fig. 2. Process flowchart for mechanical expression of oil from almond
seeds.
4
Vivian C. Akubude et al.: Effect of Process Parameters on Oil Yield Mechanically Expressed from Almond Seed
(Using Response Surface Methodology)
LEGEND
A
B
C
D
E
F
G
H
I
J
K
% oil yield =
Plunger
Frame
Compression piston
Digital force measuring device
Press cage cylinder
Heating band
Support platform
Load cell
Discharge channel
Hydraulic press handle
Temperature controller
!
(3)
∗ 100
"#
Wcs = weight of crushed almond seed sample (g)
Woe = weight of oil expressed (g).
The oil content of almond seed was determined through
proximate analysis using standard solvent extraction method
[26]
3. Results and Discussion
Fig. 3. Pictorial view of the mechanical oil rig mounted on hydraulic press.
The oil yield was determined using the equations given by
[16, 19] as stated below:
The result of the experiment is shown in table 2. The
individual, interactive and quadratic effects of such process
parameters such as pressure, temperature, heating time and
moisture content on the oil yield were evaluated using design
expert 8.0. The oil content of the seed from the proximate
analysis is 49.38%.
Table 2. Experimental design matrix and results for Oil yield.
S/N
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
RUN
16
18
3
12
17
7
13
2
30
22
10
23
11
15
19
27
6
14
8
25
5
21
1
28
26
4
20
9
24
29
X1 (°C)
85
95
85
95
85
95
85
95
85
95
85
95
85
95
85
95
80
100
90
90
90
90
90
90
90
90
90
90
90
90
X2 (KN)
21
21
23
23
21
21
23
23
21
21
23
23
21
21
23
23
22
22
20
24
22
22
22
22
22
22
22
22
22
22
X3 (mins.)
14
14
14
14
22
22
22
22
14
14
14
14
22
22
22
22
18
18
18
18
10
26
18
18
18
18
18
18
18
18
X4 (%w.b)
7
7
7
7
7
7
7
7
9
9
9
9
9
9
9
9
8
8
8
8
8
8
6
10
8
8
8
8
8
8
Oil yield (%)
30.375
31.875
31.938
34.815
32.163
31.138
33.875
34.125
35.025
36.938
33.875
37.000
35.125
34.575
34.000
34.613
32.750
36.125
35.388
37.138
32.063
31.625
30.938
36.188
37.125
36.250
37.000
37.125
36.875
36.938
Table 3. ANOVA table for oil yield from almond seed.
SOURCE
SOURCE
Temperature (X1)
Pressure (X2)
Heating time (X3)
Moisture content (X4)
X1 X2
X1X3
X1X4
X2X3
X2X4
X3X4
X12
SUM OF SQUARES
138.04
9.95
4.62
0.40
40.94
1.58
6.41
0.14
2.43E-003
8.09
2.91
11.34
DF
14
1
1
1
1
1
1
1
1
1
1
1
MEAN SQUARE
9.88
9.95
4.62
0.40
40.94
1.58
6.41
0.14
2.43E-003
8.09
2.91
11.34
F-VALUE
121.80
122.92
57.03
4.95
505.79
19.51
79.19
1.73
0.030
99.92
35.95
140.08
P-VALUE PROB>F
<0.0001*
<0.0001*
<0.0001*
0.0418*
<0.0001*
0.0005*
<0.0001*
0.2077**
0.8645**
<0.0001*
<0.0001*
<0.0001*
American Journal of Food Science and Nutrition Research 2017; 4(1): 1-8
SOURCE
2
2
X32
X42
PURE ERROR
COR TOTAL
SUM OF SQUARES
0.96
45.74
20.36
0.53
139.28
DF
1
1
1
5
29
MEAN SQUARE
0.96
45.74
20.36
0.11
F-VALUE
11.80
565.04
251.54
5
P-VALUE PROB>F
0.0037*
<0.0001*
<0.0001*
(Where * denotes those factors significant at 5% confidence level while ** denotes insignificants terms)
The analysis of variance result is shown in table 3. This
table shows that the individual, interactive and quadratic
effects were significant (*) at p≤0.05 except for interaction
between temperature and moisture content (X1X4) and the
interaction between pressure and heating time (X2X3). The Fvalues also indicated the order of significance of the process
parameters giving moisture content as the most important
variable that affected the oil yield followed by temperature,
applied pressure and heating time. This trend of significance
is in agreement with findings on sesame seed by [23] and on
dika nut by [20] which revealed moisture content as the
process factor with the most significant effect on oil yield.
Figure 4 shows the interaction effect of pressure and
temperature on oil yield. Oil yield increases with pressure at
constant temperature, heating time and moisture content. It
can also be observed that the oil yield tend to decrease or
level off as the pressure increases from 23 to 24KN. This
observation may be due to the blocking of oil path between
some inter-kernel voids because of compaction of particles or
may suggests boundary were optimum pressure for oil yield
could be obtained for range of values used. The plot also
reveals that oil yield increases with increase in temperature
and pressure. High oil yield of 37.138% and 36.125% were
obtained at high pressure of 24KN and temperature of 100°C
respectively while low oil yield of 35.388% and 32.75%
were obtained at low pressure of 20KN and temperature of
80°C respectively. This temperature trend is in agreement
with previous works which attribute this behaviour of oilseed
to the fact that heat coagulates the protein and reduces the
viscosity of the oil thereby facilitating oil expression process
as moisture reduction takes place simultaneously. At higher
temperature, prolonged heat treatment causes a substantial
moisture loss leading to hardening of oil seed sample which
best explains the reason behind the reduction in yield at
higher temperature [31, 22, 23]. This observation conforms
to findings on previous works carried out on dika nut,
groundnut, and shea kernel [20, 24, 19].
Figure 5 shows the interaction effect of heating time and
temperature on oil yield. Increase in temperature and heating
time favours oil yield as pressure and moisture content are
held constant. High oil yield of 36.125% and 31.625% were
obtained at high temperature of 100°C and heating time of 26
minutes respectively while low oil yield 32.75% and 32.063%
were obtained at low temperature of 80°C and heating time of
10 minutes respectively at constant pressure of 22KN and
moisture content of 8 % w.b. The oil yield increases towards
the centre of the response surface plot and moves away from
the centre as temperature and heating time is further increased
resulting to reduction in oil yield. This suggest the centre area
as boundary were optimization of oil yield could be obtained.
Figure 6 indicates the response plot for interaction effect
of temperature and moisture content on oil yield. As heat
treatment increases (temperature) from 80-100°C with
moisture content from 6-9%w.b, moisture is lost, this loss
creates a void that serves as a migratory for the release of the
oil from its cells as viscosity is also lowered thereby
enhancing oil flow through the oil cells, hence increasing oil
yield. The gradual decrease in oil yield as moisture migrates
beyond 9%w.b suggests that optimum oil yield could be
within the area below 10%w.b.
From figure 7, it was observed that there was a slight
decrease in oil yield as heating time increased from 10-26
minutes and oil yield increased with increase in pressure
from 20–24KN. This suggests that high oil yield will be
favoured at lower heating time and higher pressure and this
finding is in agreement with the work on groundnut which
revealed that lower heating time and higher applied pressure
would favor oil yield more than higher heating time and
lower applied pressure [24].
The interaction between moisture content and pressure is
shown in figure 8. At constant temperature and heating time,
oil yield increases with increase in moisture content from 6.0
– 8% w.b but decreases as the moisture content migrates
from 8 – 10% w.b. And as pressure increases from 20 – 24
KN oil yield is favoured.
The response surface plot for moisture content and heating
time is shown in figure 9. At constant temperature and
applied pressure, oil yield increased slightly as moisture
content increased from 6 – 8%w.b and decreased as the
moisture content increased from 7 – 10% w.b. And as the
heating time increases from 10 – 18minutes oil yield is
favoured but decreases as it moves from 18 – 26 minutes.
Fig. 4. Response surface plot showing the combined effect of interaction of
pressure and temperature on oil yield.
6
Vivian C. Akubude et al.: Effect of Process Parameters on Oil Yield Mechanically Expressed from Almond Seed
(Using Response Surface Methodology)
Fig. 5. Response surface plot showing the combined effect of interaction of
heating time and temperature on oil yield.
Fig. 8. Response surface plot showing the combined effect of interaction of
moisture content and pressure on oil yield.
Fig. 6. Response surface plot showing the combined effect of interaction of
moisture content and temperature on oil yield.
Fig. 9. Response surface plot showing the combined effect of interaction of
moisture content and heating time on oil yield.
4. Conclusion
This study on effect of process parameters on oil yield from
almond seed using RSM revealed that the most important
variables are moisture content and heating temperature.
Moisture content had the most significant effect while heating
time had the least effect on oil yield. The maximum oil yield
of 37.138%, was obtained at temperature, pressure, heating
time and moisture content of 90°C, 24KN, and 18minutes and
8%w.b respectively. This implies that these process parameters
must be controlled to effectively extract oil from almond seed.
Hence, this knowledge is a great guide to researchers and
designers for future work on almond oil production.
Acknowledgement
Fig. 7. Response surface plot showing the combined effect of interaction of
heating time and pressure on oil yield.
We are grateful to the Department of Agricultural and
Bioresource Engineering in Federal University of Technology,
Owerri, Imo state, Nigeria, Daniel Jemirin of Chemistry
American Journal of Food Science and Nutrition Research 2017; 4(1): 1-8
7
Department University of Illorin, Kwara state and National
Centre for Agricultural Mechanization, Ilorin, Kwara state.
[14] Kalia, V. C., Sadhana, L. and Rashmi (2002). Modified cold
percolation method for extracting oil from oil seeds. Journal
of Scientific and Industrial Research, 61: 630-634.
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