Comparison of oil quality extracted from selected conventional and non conventional sources of vegetable oil from Malawi

1 Department of Basic Sciences, Faculty of Agriculture, Lilongwe University of Agriculture and Natural Resources, P. O. Box 219, Lilongwe, Malawi. 2 Department of Engineering, Malawi Institute of Technology, Malawi University of Science and Technology, P. O. Box 5196, Limbe, Malawi. 3 Department of Food Science and Technology, Faculty of Food and Human Sciences, Lilongwe University of Agriculture and Natural Resources, P. O. Box 219, Lilongwe, Malawi.


INTRODUCTION
The world demand for fixed oils (vegetable oils and fats) is increasing with a consequential increase in prices (Mielke, 2017).Universally, vegetable oil consumption is mainly based on soybean, palm, rapeseed and sunflower oil with 31.6, 30.5, 15.5 and 8.6 million tons consumed annually respectively (Stevenson et al., 2007).These conventional sources of fixed oil fall short in meeting up the spiking demand of oil from both domestic and industrial sectors (Idouraine et al., 1996;Kojima et al., 2006).
Over the years, studies have been extensively carried out on the chemical composition of oil seeds of leguminous plants (Rusníková et al., 2013) and indigenous fruits (Abiodun et al., 2012;Edogbanya, 2016).Legume seeds play important role in human (Nwosu and Ojimelukwe, 1993;Mbagwu et al., 2011) as well as animal nutrition contributing almost one-third of dietary protein (Graham and Vance, 2003;Rusníková et al., 2013).Legume seeds have been reported to have low fixed oil production with the exception of soybean (Rusníková et al., 2013) which has 22.7±0.5 % oil content (Siulapwa and Mwambungu, 2014).On the other hand, pigeon pea (Cajanus Cajan) has been reported to contain 2.74% oil (Adebowale and Maliki, 2011) whereas groundnut (Arachis hypogaea) is reported to contain 39.10% oil (Kumar et al., 2013).
P. curatellifolia, locally known as Maula in Malawi, belongs to the Chrysobalanceae family (Oladimeji and Bello, 2011).It is a tropical evergreen tree that grows in sandy loam soil (FAO, 1982) and produces 47% oil from the nuts (Kernels) (Ndabikunze et al., 2006).Oilseeds have paramount importance in economics, nutrition and technology aspects.Oil produced from oilseeds is used in cooking, making soaps, cosmetics, lubricants, greases and agrochemicals (Idouraine et al., 1996;Nadeem and Imran, 2016).Fixed oils constitute part of our diet in supplying nutrients and energy to our bodies as well as flavor to our food (Atasie et al., 2009).Oils are sources of fat soluble vitamins like anti-oxidant vitamin E and protect sensitive or damaged cells from infections (Atasie et al., 2009).It is recommended that 40% of human energy requirements should come from fats and oils besides nutrients provision (Sarwar et al., 2013).
Despite the main uses that oils possess, there is no single oil source that is suitable for all uses because of differences in their oil composition (Joshi et al., 2012).The quality of these oils for dietary purposes is based on parameters like acid value/free fatty acids, saponification values, peroxide value, and iodine value (Mousavi et al., 2012) besides the fractions of saturated and unsaturated fatty acid present in the oil (Rusníková et al., 2013).Based on this background, it is of paramount importance to intensify research on various aspects of oils such as in developing cooking oil supplies from non-conventional sources like Moringa seeds, P. curatellifolia, A. digitata and pigeon peas (Cajanus cajan).The objective of this current study was therefore to compare the oil quality parameters with respect to physicochemical and phytochemical characteristics in oils extracted from nonconventional and conventional sources of oil grown in Malawi.

Sample collection and preparation
Moringa oleifera and P. curatellifolia seeds were obtained from communities surrounding Lilongwe University of Agriculture and Natural Resources, Bunda College Campus and Bunda forest respectively whereas A. digitata fruit seeds were bought from Mtchesi market in Lilongwe district.A. digitata seeds were washed in distilled water to separate the seeds from the pulp.Sundried woody P. curatellifolia seed stones, whose pulp were eaten by birds were collected from the ground below/underneath the trees.The seed kernels were removed from the woody seed stone by crushing the stones with a hard stone (Figure 1).
Soybean (Glycine max) seeds, pigeon pea (C.cajan) seeds and groundnuts (Arachis hypogaea) locally known as Nambwindi were bought from Mitundu local market, in Lilongwe district.M. oleifera, Glycine max, C. cajan and A. hypogaea (Nambwindi) seeds were manually sorted to remove dust, stones and those seeds infected by diseases (Olawumi et al., 2012).Dried samples were ground through a 1 mm sieve using a Thomas-WILEY model 4 Laboratory Mill before analyzing the physicochemical properties.The ground samples were used to analyze the qualities of crude fat using Association of Official Analytical Chemists (AOAC), 1996 methods with minor modifications.

Oil extraction procedure
Oil from the different samples was extracted by using petroleum ether in a soxhlet extractor / apparatus for 16 h.20 g of finely ground sample was put into a porous thimble in a soxhlet apparatus connected to a weighed 250 ml flat bottomed quick fit flask containing 200 ml petroleum ether.The solvent was continuously boiled at 40 to 60°C extracting the fat from the sample.After 16 h of extraction the petroleum ether was evaporated by using a rotary *Corresponding author.E-mail: lecchatepa@yahoo.com.
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License evaporator.The flask containing the crude oil was then dried to constant weight at 105°C in the laboratory oven for 2 h.The crude oil was then refrigerated at 10°C in tight closed plastic bottles with no any further treatment waiting for some analysis (Adegbe et al., 2016).

Physicochemical analysis of oils
The determination of the physico-chemical properties of the oil followed the AOAC, 1996 methods with minor modifications.

Oil percentage
Following oil extraction method as described above, the oil percentage was calculated as in Equation 1. (1) Where: A= Weight of flask and oil after extraction (g) B= Weight of flask only (g) W = Weight of sample (g)

Determination of saponification value (SV)
1.0 g of the oil was weighed in a conical flask and 50 ml of 1.0 M ethanolic potassium hydroxide (KOH) was added.The flask was connected to a reflux condenser and was refluxed for 1 h until the solution became clear.A blank sample containing only 50 ml ethanolic Potassium hydroxide was similarly treated as the sample.The solution was then titrated to a faint pink colour end point against 1.0 M Hydrochloric acid (HCl) using phenolphthalein indicator (Ogungbenle and Sanusi, 2015).Saponification value (SV) was calculated as shown in Equation 2 below: (2) Where: A= Blank ethanolic HCl volume in ml B= Sample ethanolic HCl volume in ml N= Normality of HCl, W=Weight of sample / oil in grams.

Determination of acid value (AV)
1.0 g of oil was weighed in a 250 ml conical flask containing 25 ml of absolute ethanol and diethyl ether (1:1) solution.The mixture was heated in a warm water bath (40°C) for 5 min and 3 drops of phenolphthalein indicator was added.The mixture was titrated against 0.1 M potassium hydroxide (KOH) to a faint pink color that persisted for 30 s. Acid value was then calculated as in Equation 3: (3) Where N = Normality of KOH, W = Weight of oil sample in grams

Determination of free fatty acids (FFA)
Free fatty acids are the resultant of glycerin decomposition in oils and is measured as the number of milligrams of KOH required to neutralize a unit mass of oil.Therefore FFA value was analyzed by titrating 1.0 g of oil dissolved in 25 ml of absolute ethanol: diethyl ether (1:1 V/V) against 0.1 M ethanolic KOH to a faint pink color using phenolphthalein indicator.FFA is expressed as oleic acid equivalent and 0.1 M KOH = 28.2g oleic acid as presented in Equation 4 (Okene and Evbuomwan 2014): (4) Where N = Normality of ethanolic KOH, W = Weight of sample of oil in grams

Determination of peroxide value (PV)
1.0 g of oil sample was weighed into a 250 ml conical flask containing 20 ml of glacial acetic acid: chloroform solvent (3:2 v/v).1.0 ml of saturated potassium hydroxide was then added to the mixture in the conical flask and was kept in the dark for 1 min.30 ml of distilled water was added and the solution was titrated against 0.1 M Sodium thiosulphate (Na2S2O3) solutions using 5 ml of starch as an indicator.A blank sample was treated as the samples.Equation 5 was used to obtain results which were expressed as meq per kilogram (Ogbunugafor et al., 2011).
Where V1= Titre volume in ml of 0.1 M Na2S2O3 for blank, V2 = Titre volume in ml for sample, W = Weight of oil sample in grams.

Determination of iodine value (IV)
In determination of the iodine value (IV) of the oil, the methods described by the Association of Official Analytical Chemists (AOAC), 1996 and Choudhary and Pande (2000) methods were used with minor modifications in replacing carbon tetrachloride with cyclohexane.0.5 g of oil was weighed in a 250 ml conical flask and 20 ml of cyclohexane: glacial acetic acid (1:1 V/V) solution was added into the flask.10 ml of Wijs reagent was added to the flask, thoroughly mixed and kept in the dark for an hour.15 ml and 100 ml of 15% Potassium iodide (KI) and distilled water were added to the flask and the solution was titrated against 0.1 M Sodium thiosulphate (Na2S2O3) solution to colorless end point using starch as an indicator.The IV was calculated as shown in Equation 6:

Ester value (EV)
This is the milligrams of KOH that react with glycerin after saponification of a unit gram of oil.Therefore the EV was calculated as the different between the saponification value (SV) and acid value (AV) as shown in Equation 6.

Determination of oil refractive index
Refractive index was measured using Bellingham and Stanley No.A83304 refractometer.A drop of oil was placed on the lower prism and the prism box was closed.The water flowed through the equipment jacket at 25°C, the light was adjusted then the compensator knob was moved to get a dark borderline on the cross wires which was viewed through the refraction view piece.The reading was recorded from the scale view through eyepiece (Ogungbenle, 2014).

Calculation of specific gravity
The specific gravity of the extracted oils was determined by calculation using the Lund equation as described by Halvorsen et al. (1993).

Phytic acid determination
2 g of the sample was dissolved in 2% hydrochloric acid for 3 h and was filtered through Schleicher and Schuell 270 mm filter paper.25 ml of the filtrate was mixed with 5 ml of ammonium thiocyanate and the mixture was titrated against 1.04% iron / Ferric chloride to brownish yellow color that persisted for 5 minutes (Reddy et al., 1992).

Alkaloids determination
5 g of the sample was dissolved in 20% Acetic acid in ethanol and the solution was left to stand for 4 h.The solution was filtered and was evaporated to one fourth of the solution.Concentrated ammonium hydroxide was added to the solution drop wise till precipitation was complete.The precipitate was filtered and dried in the drying oven to constant weight (Obadoni and Ochuko, 2001).

Oxalate determination
1 g of the sample was dissolved in 75 ml of 1.5 M Sulphuric acid and was stirred for 1 h and filtered.25 ml of the filtrate was titrated while hot against 0.05 M potassium permanganate to a faint pink color that persisted for 30 s. Oxalate content was calculated as follows: 1 ml of 0.05 M KMno4 = 2.2 mg Oxalate (Chinma and Igyor, 2007).

Flavonoids determination
10 g of the sample was extracted with 300 ml of methanol: water (80:20 v/v) at room temperature for 1 h.The solution was filtered through a 125 mm whatman filter paper.The filtrate was transferred into a weighed crucible and evaporated to constant weight (Boham and Kocipai-Abyazan, 1974;Obadoni and Ochuko, 2001).

Statistical analysis
Data were analyzed using Statistical Package for Social Sciences (SPSS) version 16.Analysis were done in triplicates and presented as means ±SE.Analysis of Variance (ANOVA) with post-hoc was used to analyse and evaluate mean difference with a probability value of less than 0.05 being regarded as statically significant.

RESULTS AND DISCUSSION
Results on the physicochemical properties of the extracted oils are presented in Table 1.

Oil yield composition
Results The saponification value for P. curatellifolia oil of 90.09±0.30was lower than 135.1 reported in a study conducted in Zimbabwe (Ndaba, 2014).
Similarly, A. digitata seed oil saponification value of 122.54±0.11was lower than 158.62±0.07(Abubakar et al., 2015) as reported in Nigeria but higher than that of G. max and C. cajan oils obtained from this study.On the other hand, the saponification value of 55.93±0.02for G. max was higher than 13.47±0.06mg KOH/g (Essien et al., 2014).Interestingly, it was observed that the saponification values of crude oils were within the recommended values of 180-199 mg KOH/g oil (FAO/WHO, 2009) for edible oil, 187-196 (FAO, 1995) and 189-195 mg KOH/g (FAO, 1995) for A. hypogaea and G. max oils.As reported by various authors, saponification value measures the oxidation state of the oil (Nkafamiya et al., 2010), type of fatty acids in oils (Adejumo et al., 2013) and average molecular weight of the oils (Preeti et al., 2007).The different oil quality characteristics that saponification value measures as well as the differences in the way the oils were processed and handled in the different countries probably might have explained the reasons for the differences in the values obtained in this study.The high saponification values of the oils indicate oxidative state of the oils and the low values indicate the onset of oxidation (Nkafamiya et al., 2010).

Acid value composition
Results showed that C. cajan and M. oleifera had the highest acid values of 9.53±0.17and 9.46±0.02mg KOH/g oil followed by G. max oil (5.36±0.09), A. hypogaea oil (2.68±0., 1999).Acid value measures the degree of oil spoilage, in terms of free fatty acids (FFAs), from enzymatic activity (Amadi et al., 2013).This observation of high acid values in M. oleifera, C. cajan and G. max oil suggest that these oils contain higher levels of fatty acids, as oleic acids, than P. curatellifolia, A. digitata and A. hypogaea.

Peroxide value composition
Results on peroxide value similarly showed that there are differences in values for the two sources of oil.Peroxide values of crude oils ranged from 2.79±0.00 to 10.47±0.12meq O 2 /kg oil for M. oleifera and P. curatellifolia oils.The A. hypogaea peroxide value of 2.85±0.06meq O 2 /kg was closely similar to that of A. digitata, P. curatellifolia and M. oleifera oil registering 2.81±0.02,2.79±0.00 and 2.79±0.00meq O 2 /kg oil respectively.When compared with values previously reported by other authors, it was observed that peroxide value in M. oleifera was similar to 2.60 meq O 2 /kg (Adegbe et al., 2016) but higher than the value of 0.83±0.13meq O 2 /kg (Basuny and Al-Marzouq, 2016) and interestingly lower than the value of 15.96±0.13meq O 2 /kg (Abiodun et al., 2012) reported in studies conducted in Nigeria and Saudi Arabia.However, A. digitata, P. curatellifolia and A. hypogaea oils peroxide values were higher than the value of 1.5 (Atasie et al., 2009) for A. hypogaea oil reported in related studies.G. max had higher acid value of 5.18±0.21than the value of 2.42±0.06meq O 2 /kg (Okorie and Nwachukwu, 2016) for G. max oil studies conducted in Nigeria.
The values obtained in M. oleifera, A. digitata, G. max and P. curatellifolia oils were found to be within the recommended value of 5.0 meq O 2 /kg oil (FAO/WHO, 1999) for edible fat and oils whereas C. cajan peroxide value was within the recommended value of 10.0 meq O 2 /kg oil (FAO/WHO, 1999) for edible virgin and cold pressed fat and oils.Peroxide value measures the degree of either the occurrence of peroxidation or adulteration (Okene and Evbuomwan, 2014) and could be used to evaluate the quality and stability of oils during storage (Adejumo et al., 2013;Okene and Evbuomwan, 2014).Therefore the low peroxide values in M. oleifera, P. curatellifolia, A. digitata and A. hypogaea oils indicate that these oils are more saturated than C. cajan and G. max oils and therefore the low peroxide value reflects high quality in the oils.

Iodine value composition
Results showed that there were differences in iodine value composition for the two sources of vegetable oils.The iodine value for the extracted oils ranged from 35.53±4.59 to 69.64±5.19g I 2 /100 g for P. curatellifolia and C. cajan respectively.The iodine values for M. oleifera and A. digitata were very close as reflected by the recorded values of 43.11±6.81and 40.87±3.14respectively.On the other hand, A. hypogaea and G. max oils had similar iodine values of 53.30±6.54 and 52.23±3.95which were lower than the value of 69.64±5.19 for C. cajan obtained in this study.When compared with findings from other authors, it was observed that the M. oleifera iodine value of 43.11±6.81was lower than of 55. 02±0.15 (Abiodun et al., 2012) and 68.41 (Siyanbola et al., 2015).On the other hand, G. max and A. hypogaea oil had low iodine values as compared to the values of 123.42 (Eze, 2012) and38.71 (Atasie et al., 2009) for G. max and A. hypogaea reported in studies conducted in Nigeria.Similarly, values obtained in A. digitata reveled low iodine value of 40.87±3.14 as compared to the value of 54.41±0.94(Abubakar et al., 2015) reported in studies conducted in Nigeria.The iodine values of the extracted crude oils were lower than the recommended iodine values of 90-115 g I 2 /100 g oil for crude vegetable oil (FAO/ WHO, 2009).
Iodine value measures the degree of unsaturation (number of double bonds) of the oils.The high iodine value reflects high degree of unsaturation (more double bonds) of the oils meaning that the oils easily undergo oxidation and rancidification reaction (Egbuonu et al., 2015).The low iodine values for the extracted oils observed in this study suggest that the oils are saturated and therefore have low susceptibility to oxidation and rancid reaction during storage.

Ester value composition
Results on ester value ranged from 46.35±0.15 to 217.86±1.750mg KOH/g oil for A. hypogaea and C. cajan oils.Interestingly, M. oleifera and P. curatellifolia had similar ester values of 127.18±0.13mg KOH/g oil which were higher than that of A. digitata, C. cajan and G. max but lower than 217.86±1.75 for A. hypogaea oil.

Free fatty acid composition
Results on free fatty acid composition showed that the values ranged from 1.11±0.0 to 4.80±0.09mg KOH/g oil with P. curatellifolia and A. digitata registering the lowest values and Moringa and C. cajan the highest values.A. hypogeae free fatty acid value of 1.35±0.01was lower than the value of 3.01 mg KOH/g oil obtained by other researchers (Atasie et al., 2009) for work conducted in Nigeria.Contrastingly, the M. oleifera fatty acid value of 4.76±0.01was higher than the value of 2.8 and 3.3 (Anwar et al., 2006) for drought and irrigated M. oleifera and lower than the value of 11.2 for n-hexane extracted Moringa oil (Lalas and Tsaknis, 2002) obtained in related studies.The observed acid values for crude oils were higher than the recommended value of 0.6 mg KOH/g oil for refined edible oils (FAO/ WHO, 1999).

Physical and phytochemical composition
The physical and phytochemical compositions of the extracted crude oils in mg/g oil are presented in Table 2.

Physical composition
Results on the refractive indices of the extracted oils ranged from 1.4627±0.00 to 1.4695±0.00for A. hypogaea, C. cajan and Glycine max respectively.A. digitata had a refractive index of 1.4640±0.00which was slightly lower than the value of 1.4678±0.00for M. oleifera and P. curatellifolia oils respectively.The refractive index for M. oleifera oil was higher than the value of 1.4559 (Adegbe et al., 2016) but very close to the value of 1.4668 (Garba et al., 2015) as compared to studies previously done by other researchers.In addition, the A. digitata refractive index of 1.4640±0.00was similar to 1.498±0.002(Oyeleke et al., 2012) and 1.5±0.0(Osman, 2004) for A. digitata oil studies conducted in Nigeria and Saudi Arabia.Refractive indices of oils increase with either the increasing degree of unsaturation or increasing chain length of fatty acids in the triglycerides (Evans et al., 1974).The close values for the refractive indices of oils as presented in Table 2 probably suggest that the oils have either similar unsaturation or chain length.It was interesting to observe that the A. hypogeae and A. digitata refractive index values were within the recommended values of 1.460-1.465(FAO/WHO, 1999) for A. hypogaea whereas the refractive indices for P. curatellifolia (1.4678±0.0),C. cajan (1.4695±0.0)Glycine max (1.4695±0.0)and M. oleifera (1.4678±0.0)were closely similar to the recommended value for crude A. hypogaea (FAO/ WHO, 1999).
The calculated specific gravity for the crude oils ranged from 0.8650±0.00 to 0.9144±0.00for Glycine max and A. hypogaea respectively.G. max and C. cajan had similar specific gravity values of 0.8848±0.0 and 0.8650±0.00whereas P. curatellifolia, A. digitata and M. oleifera had specific gravity values of 0.8750±0.0,0.8848±0.0 and 0.8891±0.0respectively.When compared with findings obtained by other researchers, it was observed that M. oleifera had lower specific gravity value than the value of 0.9050 (Adegbe et al., 2012) but was within the range of 0.91±0.31(Abiodun et al., 2012).On the other hand, A. digitata specific gravity value of 0.8848±0.0 was close to the value of 0.9±0.00(Osman, 2004) but slightly lower than the value of 0.928±0.001(Oyeleke et al., 2012) for studies conducted in Saudi Arabia and Nigeria.The specific gravity values for the crude oils were within the recommended standard values of 0.9-1.16 for edible oils (FAO/WHO, 2009) and 0.919-0.925for soybean oils (FAO, 1995).

Phytochemical composition
Results showed that the phytate composition for the extracted crude oils, in mg/g, ranged from 44.52±0.40 to 240.47±5.24for A. hypogaea and C. cajan respectively.Phytate content in M. oleifera (87.78±0.22)was low compared to C. cajan (240.47±5.24)and G. max (104.32±0.12)but higher than 65.25±0.05for P. curatellifolia and closely similar to the value of 86.08±0.04 for A. digitata observed in this study.Phytic acid is an antinutritional factor that forms insoluble salts when mixed with food salts like phosphorus, calcium, iron magnesium and zinc making them unavailable for absorption into the blood system (Schlemmer et al., 2009).Phytate content in foodstuffs can be used in calculation of available phosphorus for absorption into the blood stream (Robert and Yudkin, 1999).Phytate content in A. hypogaea was high compared to the value of 4.18 mg/g oil obtained by other authors (Inuwa et al., 2011).
Oxalate content ranged from 75.41±0.40to 632.56±4.90mg/100 g for A. hypogaea and C. cajan respectively.Oxalate content for A. digitata was 210.08±17.80mg/100 g which was high compared to M. oleifera (149.916±3.42mg/100 g), G. max (116.04±6.34),P. curatellifolia 169.92(0.61)mg/100 g and A. hypogaea but lower than C. cajan obtained in this study.Oxalate content in A. hypogaea was higher than the value of 4.18 mg/g oil (Inuwa et al., 2011) when compared with findings from other researchers.M. oleifera oil registered a higher oxalate content compared to the value of 4.12±0.04mg/g oil (Abiodun et al., 2012) reported in related studies.
Alkaloids content, in mg/g oil, ranged from 58.28±4.88 to 1005±1.0 mg/g for M. oleifera and A. digitata oil respectively.P. curatellifolia oil had alkaloid content of 102.65±1.89mg/g which was lower than the values obtained in A. digitata (1005±1.0mg/g), G. max (163.50±3.80)and A. hypogaea (323.60±23.84mg/g) oil obtained in this study.Alkaloids contents in G. max and
On the other hand, flavonoids content in extracted crude oil was highest in P. curatellifolia (327.00±20.24mg/g) compared to 79.24±1.55mg/g for A. digitata observed in this study.M. oleifera oil has previously been reported to contain total flavonoids content of 18±0.01 mg/g oil (Ogbunugafor et al., 2011).

Conclusions
Results from this study have shown that there are differences in quality parameters in oils extracted from conventional and non-conventional sources.It has also been demonstrated that nonconventional sources of oil like M. oleifera, P. curatellifolia and A. digitata have the potential to become new sources of cheap vegetable oil which can be used by consumers.Results have further shown that oils from non-conventional sources have high oil yield values compared to conventional sources with exception of C. cajan.The low iodine and peroxide values of the conventional oils suggest that the oils have longer shelf life and are suitable for human consumption because of their saturation.It is therefore recommended that opportunities for extracting oils from non-conventional sources should be encouraged.

Figure 1 .
Figure 1.Removing kernels from the stones.
0.1 M Sodium thiosulphate used in titrating the blank S=Volume of 0.1 M Sodium thiosulphate used in titrating the sample 126.9=Molar mass of iodine M= Molarity of Sodium thiosulphate W=Sample weight in grams , means with same superscript were not significantly different (P>0.05).
on oil yield ranged from 46.05±0.19% to 4.71±0.12%forP.curatellifoliaandC. cajan respectively.Values obtained for M. oleifera of 34.91±0.93%wasslightlylowerthan the values of 38 and 45.8% reported by other researchers (Adegbe et al., 2016; Abiodun et al., e For each parameter, means with same superscript were not significantly different (P>0.05).2012).However, the value was in agreement with the work of other researchers in Sudan who reported a value of 34.8%(Anwar and Rashid,  2007).The oil content in P. curatellifolia kernelSaponification value compositionResults showed differences in the values of saponification value for the two sources of oil as well as values obtained by other researchers in previous studies.Groundnut (A.hypogaea) oil had the highest saponification value followed by M. oleifera, A. digitata, P. curatellifolia, G. max and C. cajan oils respectively.The saponification value of 220.54±1.76mgKOH/goilobtained in A. hypogaea was higher than 193.20 mg KOH/g(Atasie et al., 2009)for A. hypogaea oil obtained by other researchers in Nigeria.On the other hand, the saponification value in M. oleifera oil of 136.65±0.14mgKOH/gwas low compared to the value of 180.92 as reported previously by other researchers(Adegbe et al., 2016).

Table 2 .
Physical and phytochemical properties of extracted oil.