Aug 2014 – Oct. 2014, Vol. 4, No. 4; 3261-3273.
E- ISSN: 2249 –1929
Journal of Chemical, Biological and Physical Sciences
An International Peer Review E-3 Journal of Sciences
Available online atwww.jcbsc.org
Section B: Biological Sciences
CODEN (USA): JCBPAT
Research Article
Evaluation of the cooking process of neem (Azadirachta
indica) nuts as a pretreatment prior to oil extraction
Nde Bup Divine1,5, Siriyabe Marth2, Mohagir M. Ahmed3, Fon Abi Charles4, Zourmba
Paul2, Nkeng Elambo George5, Kapseu Cesar6
1
Higher Institute of the Sahel, University of Maroua, P.O. Box 46, Maroua, Cameroon
Department of Chemistry, Higher Teachers’ Training College, University of Maroua,
Cameroon
2
3
Faculty of Science and Technologies, University of Sarh, P.O. Box 105, Chad
Department of Chemistry, Higher Teachers’ Training College, University of Yaounde1,
Cameroon
4
5
Department of Chemistry, Faculty of Science, University of Buea, Cameroon and Ecole
Nationale Supérieure des Travaux Publiques (ENSTP) B.P 510, Yaounde, Cameroon
6
Department of Process Engineering, ENSAI, University of Ngaoundere, P.O. Box 455
Ngaoundere, Cameroon
Received: 22 May 2014; Revised: 14 August 2014; Accepted: 22 August 2014
Abstract: Traditional methods are usually used locally to produce ‘bio-neem oil’ which is
void of residual solvents. The major disadvantages of the method are low oil yields and
high acid values. To ameliorate this process, cooking of neem nuts was evaluated by
response surface methodology. Independent variables studied were cooking time and
temperature while the responses were moisture content of the cooked kernels, quantity of
oil extracted, acid value and the refractive index of the oil. Cooking time and temperature
significantly influenced the cooking process but their interaction effect was negligible.
Optimum ranges obtained for the cooking process were cooking time (5-20 min) and
cooking temperature (40-50oC). At the mid-point of these ranges (12.5 min and 45 oC) the
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optimum responses obtained were: moisture content 46.37 % w.b., oil content 21.43 %,
acid value 3.53 mg KOH/g oil and refractive index 1.460. Experiments conducted under
these optimal conditions showed no significant difference with the calculated results.
Results for the raw kernels were: moisture content 43.00±1.41 % w. b., quantity of
extracted oil 15.88±0.26 %, Acid value 8.13±0.78 %, and refractive index 1.461±0.01,
indicating that, there was a 35 % increase in quantity of oil extracted and a 57 % reduction
in acid value.
Key words: Neem, cooking, traditional extraction, optimization.
INTRODUCTION
Vegetable oils have played and continue to play a very vital role in human nutrition, traditional medicines,
cosmetics and other diverse uses in industry. Market demands and the development of new uses have
generated interest on scientific and technical research on under exploited oilseeds and oil bearing materials15
. Research in this area has been centered on improved extraction and characterization methods that give
oil of high quality in good quantity. There exists today a plethora of oilseeds which are still under-exploited
and have not been given proper research attention in order to fully derive the potential benefits that they
present. One of such oilseed is Azadirachta indica commonly called the neem tree. Neem is a tree of Indian
origin with almost each part of the tree having potential curative effects in traditional medicines. Tinghui
et al.6 reported that, the neem tree is present in Asia (Bangladesh, Burma, Cambodia, India, Indonesia, Iran,
Malaysia, Nepal, Pakistan, Sri-Lanka,Thailand and Vietnam); in Africa (Benin, Burkina Faso, Cameroon,
Chad, Ethiopia, Gambia, Ghana, Guinea, Ivory Coast, Kenya, Mali, Mauritania, Mozambique, Niger,
Nigeria, Senegal, Somalia, Sudan, Tanzania and Togo,) and the Americas (Antigua, Barbados, Belize,
Bolivia, Brazil, Dominican Republic, Ecuador, Guatemala, Guyana, Honduras, Jamaica, Mexico,
Nicaragua, Suriname, St. Lucia and Trinidad and Tobago).The tree is therefore widely distributed and
given the potentials of neem oil for use in pharmaceutics, cosmetics and as a potential source of raw material
in the biodiesel industry it is expected that the demand for this oil should expand in the near future7-9. Some
of the applications of neem oil require the use of an extraction method that retains as much as possible the
natural properties of the oil that confer curative and/or insecticidal properties. One of such methods is the
cold extraction method. In Cameroon and in most African countries extraction is done mostly in a traditional
manner to produce the so called ‘bio-neem oil’ (that is, neem oil extracted without the use of solvents). This
method consists of depulping the fruit, and decorticating the nut to have the kernel, sun drying of the kernel,
grinding and extraction. In the extraction process the ground kernels are boiled in water and the oil layer
on the surface of the water is ladled off and further heated to remove the residual water. This is called the
water extraction method. In the second traditional extraction method, the ground kernels are mixed in a
mortar with a pestle with very little quantities of warm water added at intervals to decrease oil viscosity
and aid oil flow. This is referred to as water assisted traditional extraction method. The major disadvantages
of these methods are low yields and high acid values of the oil. Meanwhile it has been demonstrated that
cooking oilseeds prior to processing improved oil yields and reduced FFA values of shea butter10-11.
Cooking of neem nuts prior to oil extraction may also offer these advantages. The precise cooking
conditions vary as a function of type and size of oilseed, temperature, cooking time etc. It is necessary to
define these optimum conditions for each type of oilseed as such data is very valuable in engineering
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calculations for process scale-up. The Doehlert experimental design has been reported as a useful surface
response method to optimize various processes12. The various advantages of this design over others are well
elaborated by Mathieu and Phan-Tan-Luu13 and Imandi et al.12 and are summarized in Bup Nde et al.10.
Studies evaluating the influence of cooking of neem nuts on oil yields and quality to the best of our
knowledge are scarce in the literature. It is worth noting that the traditional processing and sale of neem oil
is done mostly by local women and this represents substantial income earning opportunities for them.
Studies that can improve yields and quality of neem oil will therefore be beneficial to them as they may sell
at higher prices and earn more money. The aim of this work was therefore to evaluate the effect of cooking
on the traditional oil extracted yields and some quality parameters of neem oil.
Table 1: Experimental matrix and values of the responses obtained
Coded Values
Exp't N0
x1
x2
1
0
0
1
0
1
Real values
Responses
X2
Y1
Y2
Y3
Y4
62.5
70
51.02
14.60
7.39
1.463
0
62.5
70
46.94
18.67
7.70
1.461
0
0
62.5
70
45.10
18.51
7.08
1.463
2
1
0
120
70
53.06
16.61
8.71
1.465
2
1
0
120
70
48.98
16.42
8.09
1.463
2
1
0
120
70
52.20
16.45
8.80
1.463
3
0.5
0.866
91.25
100
58.00
16.97
6.41
1.463
3
0.5
0.866
91.25
100
56.00
18.09
5.29
1.461
3
0.5
0.866
91.25
100
59.31
18.20
5.85
1.463
4
-1
0
5
70
48.08
20.71
5.05
1.463
4
-1
0
5
70
49.02
18.57
6.35
1.461
4
-1
0
5
70
48.65
18.91
5.66
1.461
5
-0.5
-0.866
33.75
40
48.98
19.59
4.95
1.461
5
-0.5
-0.866
33.75
40
44.90
19.33
5.04
1.461
5
6
-0.5
-0.866
33.75
40
47.08
19.31
3.92
1.461
0.5
-0.866
91.25
40
50.00
15.46
7.40
1.461
6
0.5
-0.866
91.25
40
46.00
16.81
8.46
1.461
6
0.5
-0.866
91.25
40
48.34
15.55
7.72
1.461
7
-0.5
0.866
33.75
100
59.18
13.53
7.79
1.463
7
-0.5
0.866
33.75
100
60.78
14.66
7.40
1.463
7
-0.5
0.866
33.75
100
58.90
14.50
8.01
1.461
X1
x1, and x2 are the coded values while X1, and X2 are real values of cooking time and cooking temperature
respectively. Y1, Y2, Y3 and Y4 are moisture content, amount of oil extracted, acid value and refractive index
respectively
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MATERIALS AND METHODS
Mature neem fruits used in this work were collected from the town of Maroua, Cameroon in April 2013.
They were stored in a freezer at -18oC to limit oil hydrolysis. Before the cooking experiments, the fruits
were withdrawn from the freezer and stored on a laboratory bench overnight to thaw at ambient temperature.
The samples were then depulped manually and washed in a large quantity of distilled water to remove the
residual pulp. The nuts were cooked following the Doehlert experimental design chosen in this work (Table
1).In the cooking process, the experimental variables were cooking time (5-120mins) and cooking
temperature 40-100oC. 350mL of distilled water were placed in a 600 mL beaker and heated to the desired
experimental temperature. 300g of neem nuts were then placed in the beaker and the beaker covered with
Aluminium foil and cooked for the required length of time (Table1). After cooking the water was drained
and the nuts were manually cracked to give the kernels. A portion of the kernels was withdrawn for the
determination of moisture content while the other portion was dried at 50oC in an electric oven for 24 h to
a constant mass. This latter portion was used for oil extraction and subsequent oil analysis.
Determination of moisture content of cooked kernels: Moisture content was determined by drying a
known quantity of the cooked kernels in a ventilated electric oven at 105oC for 24 hours. The dried kernels
were cooled in a dessicator and reweighed14. Moisture content (Y1 % w.b.) was calculated from the relation
𝑌1=
𝑀0 −𝑀1
𝑀0
× 100
[1]
M0 is wet mass of sample and M1 is the dry weight of the sample. All experiments were carried out in
triplicates.
Oil extraction process: The dried kernels were ground using a kitchen type manual grinder. The adjusting
knob of the grinder was set to maximum for each run, to ensure that grinding for the different runs was
done under uniform conditions. In the extraction process, the traditional water assisted extraction method
which is normally used in the production of organic neem oil was used. This consisted of mixing and
pressing the ground paste in a laboratory porcelain mortar using a pestle with occasional addition of 1520ml of warm water (40oC) at 3 different intervals. The oil was then drained from the mortar and filtered
through a Whartman No. 42 filter paper. The oil was placed in an oven at 60oC to remove residual water for
2 hours. A control experiment was carried in a similar manner but for the fact that the samples were not
cooked prior to drying and oil extraction. The average extraction time for each run was 15-20 minutes. All
extraction experiments were carried out in triplicates. The quantity of oil extracted was calculated from the
equation
Mass of oil
𝑌2= Sample mass × 100
[2]
Determination of Acid value: Acid value was determined by back titration. 2 g of the oil sample was
weighed into a conical flask and 0.2N ethanolic KOH solution was added to the flask and shaken vigorously
for about 1 minute. Excess KOH remaining in the flask was then titrated against 0.1N HCl, using
phenolphthalein as indicator. A blank titration was carried out in a similar manner without the oil sample.
This was done in triplicates. Acid value was calculated from the equation.
𝑌2 =
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N(𝑉1− 𝑉2 )×56.01
Sample mass
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[3]
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Nde Bup et al.
N is the normality of KOH, V1 is the titre volume for the blank and V2 the titre volume for the test sample.
Modeling of the cooking process: A second order model with interaction was proposed to describe the
cooking process of neem kernels. This model was represented as follows:
𝑌 = 𝑏0 + 𝑏1 𝑥1 + 𝑏2 𝑥2 + 𝑏11 𝑥12 + 𝑏22 𝑥22 + 𝑏12 𝑥1 𝑥2
[4]
The coefficients of the model b0, b1, b2, b11, b22 andb12 were determined through multiple linear regressions
on SigmaPlot 11.0 (SystatInc, USA).
Validation of Models: The criteria for validating models were the regression coefficient (R2) and/or
absolute error (AE) observed between the experimental and theoretical results. R2 was obtained from
regression analysis while AE was determined from the equation,
𝑌 −𝑌
100 𝑛
∑𝑛=1 | 𝑒𝑥𝑝 𝑐𝑎𝑙 |
𝑛
𝑌𝑒𝑥𝑝
[5]
Where Yexp and Ycal are the measured and calculated responses respectively. n is the number of points at
which measurements were carried out. A model was considered valid if at least one of the two criteria was
satisfied. That is R2>0.7 and/or EA<10%
Optimization of the cooking process: To optimize the cooking process, the optimum point for each
response (minimum or maximum point) of Eq. 1 was defined as the point where the first partial derivative
of the function equals zero10:
𝜕𝑌⁄𝜕𝑥1 = 𝑏1 + 2𝑏11 𝑥1 + 𝑏12 𝑥2
[6]
𝜕𝑌⁄𝜕𝑥2 = 𝑏2 + 𝑏12 𝑥1 + 2𝑏22 𝑥2
The system of equations for each response was solved to give the values of x1 and x2 in coded values which
were then transformed to real values. Experiments were then conducted at these points to verify the
mathematically determined optimal conditions.
RESULTS AND DISCUSION
Modeling of the cooking process : Values of the responses studied Y1 (Moisture content % w.b), Y2
(Quantity of oil extracted %) and Y3 (acid value mg KOH/g oil) are presented in Table 1 while the model
constants, P values, value of model constants (VMC), R2 and AE values for the second order models are
presented in table 2. A model was considered valid if R2 > 0.700 and/or AE < 10. Table 2 shows that all of
the responses satisfied either one or all of the conditions. These models were therefore judged satisfactory
to describe the influence of the variables (cooking temperature and cooking time separately or in
combination) on the measured responses.
To better appreciate the influence of the variables on the responses, the validated model was used in four
different ways: First the probability (p) values given by multiple linear regression analysis for each model
coefficient for a particular response were considered. A factor associated to a model constant with p < 0.05
was considered to have a significant effect on the response of interest. Secondly, the percentage value of
each model constant (CMC) calculated as its ratio to the sum of all the models constants (absolute values)
for the response in question was considered. The higher the value, the higher its contribution to the
magnitude of the response. A positive sign associated with the model coefficient will tend to increase the
value of the response, all other factors being constant and vice versa. Thirdly, the effect of each independent
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factor on the responses was considered by Maintainingone of the factors constant at the central point
(cooking time 62.5 min or cooking temperature 70oC) and plotting the other as a function of the response.
Lastly the combined effect of the two factors was evaluated using surface response plots. The following
sections describe the effect of Cooking time and temperature on the responses using these four approaches.
Table 2: Model constants (MC), P values, contribution of model constants (CMC), R2 and AE
values for the second order models
Moisture content (%)
Constant MC
VMC P-value
b0
47.687 72.86
0.001
b1
0.823
1.26
0.230
b2
6.435
9.83
0.001
b11
2.312
3.53
0.118
b22
6.478
9.90
0.001
b12
-1.719
2.63
0.211
2
R
0.890
AE (%)
2.73
Quantity of oil extracted
Acid value
Refractive index
PPPMC
VMC value
MC
VMC value
MC
VMC value
17.26 69.85
0.001
7.39 56.11
0.001
1.462 99.81
0.001
-0.959
3.88
0.027
1.172
8.90
0.001 0.0007
0.05
0.067
-0.972
3.93
0.025
0.314
2.38
0.112 0.0008
0.05
0.037
0.685
2.77
0.421 -0.280
2.13
0.488 0.0003
0.02
0.648
-0.797
3.23
0.350 -1.067
8.10
0.016
0.001
0.07
0.182
4.038 16.34
0.001 -2.948 22.38
0.001
0.000 0.000
1.00
0.740
0.884
0.470
4.32
6.75
0.05
Effect of Cooking time and Cooking Temperature on Moisture content: The evaluation of the moisture
content of neem nuts after cooking is important because it plays a vital role to determine drying time of the
kernels and in the hydrolysis of the oil. From table 2 it can be observed that the p-values of the model
constants b2 and b22 which are associated with the linear and quadratic effect of temperature are both less
than 0.05 indicating that they had significant effect on the moisture content. Again table 2 shows that apart
from the constant term which had the highest contribution (77.05 %) to the value of the moisture content
(as expected), b2 and b22 had positive contributions of 9.83 and 9.90% to the magnitude of the moisture
content. That is, there is the tendency of moisture content increasing with cooking temperature. This can be
confirmed by the significant variation of moisture content with temperature at constant cooking time
(Figure 1a). As cooking temperature increases there is the possibility that heat denatures the membranes
of the neem nut making it more porous and permeable to the cooking water which leads to the observed
increase in water absorption as temperature increases. Neem nuts are small in size measuring about 14 x 6
mm; a factor that can favor water absorption15. Several studies have shown that water absorption increases
with temperature and this has been linked to the increased porosity of the substrate brought about by
cooking16-20. The contribution of cooking time to water absorption by the kernels was small compared to
temperature and was insignificant at the 95% level of confidence. Figure 1a shows very slight variation of
moisture content with cooking time. Figure 1b shows the combined effect of cooking time and temperature
on the moisture content which confirms the previous discussions. Moisture content varied significantly with
temperature but does not change much as a result of increased or prolonged heating. Therefore cooking
should be done at lower temperatures and shorter times to limit water absorption.
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Temperature (oC)
40
50
60
70
80
90
100
60
80
100
120
60
58
Moisture content (%)
56
Time
Temperature
54
52
50
48
46
44
0
20
40
Time (min)
Figure 1a: Influence of cooking time (temperature constant at 70oC) and cooking temperature (Time
constant at 62.5 min) on the moisture content of the cooked kernels
44
46
48
50
52
54
56
58
60
62
62
58
56
54
52
50
120
100
48
46
80
90
40
80
Temp
70
60
erature o
( C)
Ti
me
(
60
44
mi
n)
Moisture conten
t (%)
60
20
50
40
Figure 1b: Combined influence of cooking time and temperature on moisture content of the cooked
kernels
Quantity of oil extracted: The quantity of oil extracted was significantly influenced by the linear effects
of cooking time and temperature as well as the interaction effect of the factors (b12) which had a 16.34 %
tendency of increasing the quantity of oil extracted (Table 1). Cooking time and temperature had the
tendency of reducing the quantity of oil extracted as exemplified by their negative coefficients. The quantity
of oil extracted was highest within the first few minutes of cooking and then reduced to significantly lower
values as cooking time and temperature increased. Cooking coagulates proteins thereby allowing free space
for the diffusion of oil. The gelatinization temperatures for starches vary generally from 52 to 83.5 °C,
while proteins are equally coagulated within this temperature range21. It can be observed from figure 2b
that, high quantities of oil were extracted within the temperature of protein coagulation and starch
gelatinization. Bup Nde et al.22 demonstrated the denaturation of proteins of another oilseed sheanut kernel
by cooking at 85 ± 5oC. The decrease in oil yield with time and temperature observed in this work was
therefore contrary to our expectation. A possible explanation to this could be due to the fact that neem nuts
are small in size (14 x 6mm) and can absorbed water easily as reaction progresses (Figures 1a and b).
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Therefore the presence of absorbed water in the kernels blocks available pores for oil flow which could
hinder the release of oil. The variation of quantity of oil extracted with temperature observed in this work
was different from that reported by Bup Nde et al.10 in which the amount of oil extracted increased
continuously with cooking time up to a steady value. This difference could be attributed to the small size
of neem nut (14x6 mm) compared to that of shea nut (45 x 25mm) which permitted water absorption in
neem nuts right from the onset of the cooking process. Overall the quantity of oil extracted from the cooked
kernels was significantly higher than that extracted from the raw ones.
Temperature (oC)
40
50
60
70
80
90
100
19.5
Quantity of oil extracted (%)
19.0
Time
Temperature
18.5
18.0
17.5
17.0
16.5
16.0
15.5
0
20
40
60
80
100
120
Time (min)
Figure 2a: Influence of cooking time (temperature constant at 70oC) and cooking temperature (Time
constant at 62.5 min) on the quantity of oil extracted
12
14
16
18
20
22
24
22
20
18
16
120
100
14
80
90
80
40
70
60
Temp
eratur
e (%)
Ti
me
(
60
12
mi
n)
tra
Quantity of oil ex
cted (%)
24
20
50
40
Figure 2b: Combined influence of cooking time and temperature on the quantity of oil extracted
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Acid value: Acid value was significantly influenced by the linear term of cooking time (b 1) and the
quadratic term of time (b11) and interaction effect (b12) of the two factors (Table 1). Their respective
contributions to the magnitude of the acid value were 8.90, 8.10 and 22.38 %. The linear terms had the
tendency to increase while the quadratic and interaction terms had the tendency to decrease acid value.
Figure 3a shows the magnitude of the variation of acid value with cooking time which at constant
temperature was more pronounced compared to the variation with temperature at constant reaction time.
One of the main aims of cooking is to denature the lipase enzymes which usually promote lipid hydrolysis.
In this work it was observed (Figure 3a) that acid value increased continuously with cooking time and was
highest at 120 min when the reaction temperature was kept constant at 70oC. This was contrary to our
expectation. It has earlier been explained that due to its small size, the nuts absorbed water throughout the
cooking process. It is therefore possible that, in the presence of water the hydrolysis reaction took
precedence over enzyme denaturation leading to increase oil acidity. Increase in acid number can also be
linked to primary oxidation of triglycerides to FFAs. However at higher temperatures with prolonged
cooking (Figure 3b), some of the FFA acids produced from the hydrolysis and primary oxidation reactions
may have undergone a secondary oxidation reaction to produce aldehydes and ketones and this led to the
observed reduction in acid values. Oxidation can be promoted by heat, light, metals, and several initiators
and can be inhibited by antioxidants acting in different ways23. Primary oxidation of unsaturated fatty acid
moieties in triglycerides is thought to be initiated/occur at the double bonds which are electrophilic and
therefore susceptible to attack by oxygen. If this happens the triglycerides are oxidized first to free fatty
acids which are further oxidized in secondary oxidation to aldehydes and/or ketones.
Temperature (oC)
40
50
60
70
Acid value (mg KOH/ g oil)
8.5
80
90
100
Time
Temperature
8.0
7.5
7.0
6.5
6.0
5.5
10
20
30
40
50
60
70
80
90
100
110
120
Time (min)
Figure 3a: Influence of cooking time (temperature constant at 70oC) and cooking temperature
(Time constant at 62.5 min) on acid value of neem oil
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0
2
4
6
8
10
12
10
8
6
4
120
100
2
90
80
40
70
Temp
e
rature
60
( oC)
Ti
me
(
80
60
0
mi
n)
Acid value (mg
KOH/ g oil)
12
20
50
40
Figure 3b: Combined influence of cooking time and temperature on the acid value of the oil
OPTIMISATION OF THE COOKING PROCESS
Mathematical optimization of the cooking process as described in the material and methods section did not
give unique optimum points for the various responses studied (Table 3). Cooking time and cooking
temperature ranged from about 40 -50 min and from 51-85oC respectively. To obtain a unique optimum for
all the responses, their contour plots were superimposed (Figure 5). Optimum ranges (shaded area on
Figure 5) were located based on the common intersection area of the plots which corresponded to regions
of low moisture content, high amount of oil extracted, and low acid value at shorter times and lower
temperatures to minimize energy consumption. These optimum ranges were cooking time 5-20 min, and
temperature 40 -50 oC. Optimum responses calculated using the mid points of these ranges (12.5 min and
45 oC) were: moisture content 46.37 % w.b., oil content 21.43 %, acid value 3.53 mg KOH/g oil. Moisture
content, quantity of oil extracted and acid value obtained from verification experiments conducted at the
optimum conditions (12.5 min and 45oC) were 45.34±0.23, 22.05 ± 0.46 and 3.89 ± 0.31 which showed no
significant difference with the calculated responses. Results of the raw (control) nuts were: moisture content
43.00±1.41, quantity of extracted oil 15.88±0.26, acid value 8.13±0.78, and refractive index
1.461±0.001. Comparison with results obtained under optimum conditions showed that there was no
significant difference in moisture content (2.20%) with that of the raw kernels, oil content was significantly
higher (34.89%) in the cooked kernels while acid value was significantly lowered (56.70%) by the cooking
process. These results point to the fact that cooking under the established optimum conditions will lead to
a gain in the quantity of oil extracted and a significant reduction in acid value.
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Nde Bup et al.
60
15
58
56
90
58
58
56
56 17
16
6 58
7
54
54
52
52
Moisture content (%)
56
18
Quantity of oil extracted (%)
16
54
7
Acid value (mg KOH/ g oil)
54
Optimum region
7 52
17
Temperature (oC)
80
17
17
50
52
50
50
18
70
6
7
48
817
48
50
48
19
17
18
8
60
7
20
5
6
50
17
4618
46
20
16
9
19
21
4
48
46
5
7
6
223
15
16
848
50
14
40
20
40
60
80
100
120
Time (min)
Figure 4: Superimposed contour plots showing the optimum region
CONCLUSION
In this work the effect of cooking time and cooking temperature on moisture content of cooked neem nuts,
quantity of oil extracted, acid value and refractive index of neem oil was investigated using the Doehlert
experimental design. All the independent variables had a significant effect on the responses studied.
Optimum values determined for the cooking process were cooking time (5-20 min) and cooking
temperature (40-50oC). Results of the verification experiments at the mid-point of the optimum ranges
compared very well with those calculated. The major advantage of the cooking process is the significant
increase in the quantity of oil extracted (35 %) and a significant reduction in acid value (57 %) at the
optimum point. These results point to the fact that cooking under the established optimum conditions will
lead to a gain in the quantity of oil extracted and a significant reduction in acid value.
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* Corresponding author: Nde Bup Divine
Higher Institute of the Sahel, University of Maroua, P.O. Box 46, Maroua, Cameroon
Email: bupdiv@yahoo.fr
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