Irvingia gabonensis (Aubry Lecomte ex O’Rorke) Baill., commonly
known as “African mango”, “Dika nut”or “bush
mango” is a tree of 15-40m, with bole slightly buttressed. Irvingia
gabonensis occurs in the wild lowland forest; 2-3 trees occur together
and in some areas, it is reported to be gregarious. It is largely distributed
in Africa (Leakey, 1999; Burkill, 1994; Leakey and Tchoundjeu, 2001).
This plant with edible fruits is largely used in traditional and modern
medicine for the treatment of several illnesses, as well as in industry
(Lowe et al., 2000; Anegbeh et al., 2003).
Ethnocultural specificities on Irvingia gabonensis and Irvingia
spp. products (Irvingiaceae) in Congo-Brazzaville, this study showed
food properties of Irvingia gabonensis (Aubry-Lecomte ex O' Rorke) Baill.
and Irvingia sp. is centered on the contribution of almonds to the art
of cooking of the forest communities to Congo (Kimpouni et al., 2007).
Many studies were undertaken on the nutritional or medicinal value of
Irvingia gabonensis have been reported (Surville, 1955; Berhaut,
1975; Adamson et al., 1986; Adamson et al., 1990; Okolo
et al., 1995; Ngondi et al., 2005).
Methanolic extract of Irvingia gabonensis are use in the treatment
of bacterial and fungal infections (Kuete et al., 2007).
Margarine is a butter-like product obtained from mixtures of various
edible fats and oils. Usually margarine contains appropriate ratios of
hard vegetable fats from coconut, palm kernel, interesterified vegetable
oils and/or hydrogenated vegetable oils. Mostly in the industrial catalytic
hydrogenation process some natural fatty acids are destroyed and new artificial
trans isomers are produced that behave similar to saturated fats. These
isomers lack the essential metabolic activity of the parent compounds
and inhibit the enzymatic desaturation of essential fatty acids (Kandhro
et al., 2008).
The production of margarines, fat content to paste and shortenings appeals,
to satisfy the necessary functionalities (consistency), with processes
of transformation of the refined greasy substances: fractionation, inter
esterification and hydrogenation (total or partial), among which only
partial hydrogenation generates the Trans fatty acids (TFA) (Morin, 2007).
The aim of this work is a contribution of the Irvingia gabonensis
seed kernels valorization by an oil extraction and one of the technological
applications of this one by margarine manufacturing. All this in the objective
to diversify the sources lipids that have good food qualities for the
Congolese populations and certainly those of under area.
Materiels and Methods
Vegetable material: Vegetable material used is Irvingia gabonensis
seed kernels coming from two Congo Brazzaville localities: Sibiti
(3.69oS; 13.35oE) and Ouesso (1.61oN;
16.05oE); IGS and IGO.
Chemical composition of powdered seeds:
Protein content: Proteins are polymers of amino acids. Total protein
was determined by the Kjeldahl method. Protein was calculated using a
nitrogen conversion factor of 6.25 (Al-Gaby, 1998). Data were expressed
as percent of dry weight.
Carbohydrate and energy content: Total carbohydrate was obtained
by difference; the energy content was calculated by multiplying the mean
values of crude protein, crude fat and total carbohydrate by At water
factors of 4, 9 and 4, respectively, taking the sum of the products and
expressing the result in kilocalories per 100g sample
Carbohydrate content = 100 - [%Lipids + %Proteins + %Ash + %Moisture]
Ash content: To remove carbon, about 0.5g of powdered seed samples
were ignited and incinerated in the muffle furnace at 550oC
for about 12h. The ashes were dissolved in H2SO4 and
the mineral constituents (Ca, Na, K and Mg) were determined using an atomic
absorption spectrophotometer (Perkin-Elmer, model HGA 700).
Dry matter: The dry matter was determined according to the Association
of Official Analytical Chemists (AOAC, 1990).
Press method: For Irvingia gabonensis oil extraction by
press, 100mg of seed powder are placed in autoclave and to heat with 110oC
during 20 minutes under a pressure of 1bar and to press hot.
Soxhlet method: The weight of fat extracted from 40g of Irvingia
gabonensis seed kernels powder was determined to calculate the lipid
content. Seed kernels oils were extracted using the continuous Soxhlet
extraction technique with petroleum ether (40-60oC) for 5h.
After removing solvent, using a Rotavapor apparatus, the seed oil obtained
was drained under a stream of nitrogen and stored in freezer (-30oC)
for subsequent chemical analysis. Result was expressed as the percentage
of lipids in the dry matter of seed powder.
Bligh and dyer method: According to Bligh and Dyer (1959), 100mg
of seed powder are homogenized with a chloroform mixture: methanol (1:1)
and water. We obtain two phases, aqueous layer (methanol-water) and organic
Folch method: Oils from the seeds were extracted mainly according
to Folch (1957), this chemical method makes it possible to obtain the
cold lipids in anhydrous mixture chloroform: methanol (2:1; v/v).
The oils were recovered by distilling the solvent in a rotary evaporator
at 45oC, then dried to constant weight in a vacuum oven at
90oC for 1h and weighed.
Seed oil physicochemical analysis:
Chemicals analysis: The various indexes were obtained according
to the Association of Official Analytical Chemists.
Acid value (AOAC, standard 969.17, 1997); Iodine value (AOAC, standard
993.20, 1997); Peroxide value (AOAC, standard 965.33, 1997); Saponification
value (AOAC, standard 920.160, 1997) (Nzikou et al., 2007).
Acid value, %FFA: Acid value of Irvingia gabonensis oil
and margarines was determined according to AOAC Official Method Cd 3a-63.
Percentage free fatty acids (FFAs) were calculated using lauric acid as
Iodine value: Iodine value of seed oil was determined according
to AOAC Official Method 993.20,1997.
Saponification value: Saponification value was determined according
to AOAC Official Method 920.160,1997.
Peroxide value: Peroxide value was determined according to AOAC
Official Method 965.33,1997.
Differential scanning calorimetry (DSC): Calorimetric evaluations
of sample melting behavior were performed in a Perkin-Elmer (Model Pyris
1, Perkin Elmer Corp., and Norwalk CT). All samples were tempered in the
DSC cell according to the following conditions: samples were tempered
at -60oC during 10 min. DSC analysis were performed from -60oC
to 60oC at a scan rate of 5oC/min. The onset, major
peak maximum temperatures and enthalpy of melting (J/g) were analyzed
from thermograms using the Pyris software (version 2.04, 1997).
Fatty acids composition by Gas chromatography (GC): Fatty acid
composition of each lipid classes was determined after transmethylation
using potassium hydroxide in methanol (2N) by gas chromatography. A PerichromTM
2000 system gas chromatographs (Perichrom, Saulx les Chartreux, France),
equipped with a flame-ionization detector and was used for analyzing FAME.
Chromatographic parameters were set as fellows: fused silica capillary
column (30m x 0.22mm id. x 0.25μm film thickness, BPX 70 SGE Australia
Pty. Ltd., analytical products); injector and detector temperatures 260oC;
oven temperature programming: held 5 min at 145oC then ramped
to 210oC at 2oC/min followed by a hold period of
10 min. Fatty acid were identified by comparison of their retention times
with standard mixtures (PUFA1 from marine source and PUFA2
from animal source; Supelco, Bellfonte, P.A.).
Statistical analysis: Each reported value is the mean of determinations
for triplicate samples. The statistical processing was carried out with
Microsoft Excel 8.0 software.
Results and Discussion
Physicochemical characterization of powdered seed kernel:
Oil content: Irvingia gabonensis oil content varies between
34.28 and 62.67% for IGO var (Table 1) and between 34.55
and 73.82% for IGS var (Table 2). These seed kernels
are richer in lipids than other unconventional oilseeds such as Canarium
schwenfurthii fruits (36.1%), Balanites aegyptiaca almonds
(48.3%) (Nzikou et al., 2006) and Dacryodes edulis pulp
(29-67.5%) (Silou et al., 2006; Dzondo et al., 2005) (Table
3). Their oil content is also higher than that of some conventional
oilseeds: cotton seed, soybean, sunflower and rapeseed and palm fruit
(Table 3). The quantity of oil extracted by solvent
(51.04-73.82%) is higher than that obtained by press (34.55%).
The preceding work carried out by Womeni et al. (2006a,b) made
it possible to extract a significant quantity of fat (70.11%) however
Ekpe et al. (2007) obtained 66.6%.
With the aqueous extraction without enzyme, they could obtain 27.36%
fat content of almonds. When one adds separately of Alcalase, Pectinex
and Viscozyme one respectively obtains 34.86%, 42.24% and 67.97%.
Protein, ash and dry matter content: The ash content is 3.8%,
the almond used are thus relatively pure. They must contain biogenic salts.
With a proteins content of 8.71%, Irvingia gabonensis almonds are
less rich than Dacryodes edulis pulp (34%) and certain current
oilseeds: groundnut (48%), sunflower (34%) soya (40%) (Nzikou et al.,
But it is high compared to that of the majority of the cereals which
return in our daily food (corn, sorghum, corn, rice etc), which generally
does not exceed 13%. The content of rather high matter (99.98%) indicates
that the samples are dry.
Carbohydrate and energy content: Total carbohydrate ranged from
24.80±0.10% to 30.03±0.08% in IGO and from 15.77±0.21%
to 38.54± 0.78% but was generally low, due to the high levels of
crude fat and crude protein. The calorific value (kcal/g sample) was highest
in IGS (693.83) followed by IGO (685.29).
These energy values would meet the Food and Agriculture Organization’s
(FAO, 1973) recommended value of 800 to 1200 kcal if the samples were
consumed at 173g per day. Individuals requiring oil-free or low oil diets
should be mindful of diets prepared using the seeds investigated in this
study. However, the speculation that the high lipid levels in all the
samples studied may give rise to hyperlipidaemia and the associated coronary
heart diseases may not be of concern due to the fact that the amount consumed
per day is not high, but adequate to supply the daily energy need of the
Physicochemical characterizations of oils and margarines: Oils
obtained have a acidity ranging between 1.98 and 4.61% lauric acid for
IGO var (Table 1) and to 1.52 and 8.97% lauric acid
for IGS var (Table 2).
Each oil has a rate in free fatty acid below the limit of which the maximum
is 5.0% according to NIFOR (NIFOR, 1989). The food value of a greasy substance
depends on the quantity of free fatty acids (for example, butyric acid
out of butter, lauric acid for lauric oils).
According to, Bassir (1971); Onyeike and Acheru (2002), an oil of kitchen
must have an acid content fatty free below 3%. Oils extracted by the Soxhlet
method are not specific to consumption.
The bottom grades of the % FFA indicate that these oils would be good
salad oils and who can be stored for a long time without fearing deterioration
due to oxidizing rancidity.
Saponification value varies between 189.92± 4.6 and 237.69±
7.2mg KOH/g for IGO var (Table 1), of 196.32±6.2
and 277.69±2.5mg KOH/g for IGS var (Table 2).
The oil extracted by the method of Folch has the highest of saponification
value (204.17-277.4mg KOH/g). For each var SV average value is 207.82mg
KOH/g for IGO var and is 230.96mg KOH/g for IGS var. Irvingia gabonensis
saponification value is higher than that Dacryodes edulis pulp
oil (201) (Nzikou et al., 2007) and those of oils extracted of
conventional oilseeds as soya (189-195), the groundnut (187-196) and cotton
(189-198) (Alimentarius Codex, 1993). The high saponification values of
Irvingia gabonensis oil (207.82-230.96mg KOH/g) suggest that the
oils could be good for soap making and in the manufacture for lather shaving
cream (Eka, 1980; Nzikou et al., 2007)
The iodine value lies between 4.3±0.10 and 4.8±0.09 for
IGO var (Table 1) and it varies to 4.1±0. 01
and 4.9±0.05 for IGS var (Table 2). It is noted
that there is no considerable difference. With an average value of 4.5,
this oil is saturated in comparison with that of the pulp of Dacryodes
edulis (60-85) (Dzondo et al., 2005), Coula edulis (90-95),
Canarium schwenfurthii (71-95) (Abayeh et al., 1999), Abelmoschus
esculentus (124.7) (Nzikou et al., 2006), Solanum nigrum
L (111.89) (Nzikou et al., 2007).
|| Physicochemical properties
of Irvingia gabonensis almond and its oil (IGS)
|Proteins = NT x 6.25; R1= % lipids/%
proteins, % Carbohydrate = 100 - [% Lipids + % Proteins + % Ash +
Minerals (mg/100g); Calorific value (kcalg-1)
|| Typical oil extraction from 100kg
|*(Silou et al., 2006). The others from Nzikou
et al., 2007
The oils peroxide contents are Soxhlet (1.2±0.05-1.9±0.07meqO2/kg),
Bligh and Dyer (0.95±0.07meqO2/kg) and Folch (0.85±0.06-1.45±0.04meqO2/kg).
These oils are fresh because the content peroxide lower than 10 méqO2/kg
and bus oils grow rancid when the content peroxide lies between 20.0 and
40.0méqO2/kg (Pearson, 1976; Ojeh, 1981). In the contrary
case, oils having high percentages of peroxide are unstable and grow rancid
easily (an unpleasant odor). These oils are saturated; therefore there
is no risk of formation of peroxides.
Fatty acids composition of oils and margarine: Fatty acid composition
of the two studied seed oils is shown in Table 4.
In oil seven fatty acids were present, five of which were saturated.
The most abundant fatty acids of Irvingia gabonensis seed kernels
oil were myristic (C14:0), lauric (C12:0) and palmitic (C16:0) which together
composed about 95% of the total fatty acids. The major fatty acids found
in those cultivars were myristic acid (C14:0) (50.92-53.71%) and lauric
acid (C12:0) (36.60-39.37%). This is in agreement with previous reports
(Womeni et al., 2006a; Womeni et al., 2006b) who found myristic
acid (C14:0) (52% ) and lauric acid (C12:0) (38%) in Irvingia gabonensis
seed kernels oil extracted by several method (aqueous with and without
enzyme and solvent) from Cameroon var.
Those differences may be attributed to the variability of the studied
Several authors reported that Irvingia gabonensis seed kernels
oil may be regarded as myristic-lauric oil because myristic acid was most
abundant, followed by lauric acid.
|| Irvingia gabonensis oil and margarines
In margarine six fatty acids were present, four of which were saturated
and the others are unsaturated.
The most abundant fatty acids of were margarine containing Irvingia
gabonensis seed kernels oil were oleic (C18:1n-9), palmitic (C16:0),
myristic (C14:0) and lauric (C12:0). The major fatty acids found in those
margarines (with and without lecithin) were oleic acid (35.51-37%) followed
by palmitic acid (18.47-19.56%) and myristic acid (18.45-19.3%) and lauric
acid (13.17-15.13%). Margarine is more unsaturated than the oil which
was used as raw material; it can be regarded as oleic acid source. The
average contents of linoleic acid and linolenic acid are respectively
of 7.07% and 0.63%, these margarines can be used for food frying (%C18:3n-3
lower than 2%).
In comparison with other oils and fat (Table 6), we
note that; Irvingia gabonensis seed kernels oil is oil which more
saturated than conventional oils saturated such as coconut oil and palm
oil, it is an oil of major food frying.
Many studies showed that the Congolese mother's milk is rich in poly
unsaturated fatty acids and presents also a good ratio 18:2n-6/18: 3n-3
whereas it’s better between 1 and 12 (Dhellot et al., 2006),
in margarine the ratio is an around 11.
With UFA/SFA = 0.81, margarine (IGO-IGS) is more saturated than Butter
(0.52), Ghee clarified butter (0.54) and hard margarine (0.38), however
it’s less unsaturated than soft margarine.
Thermal profile of oils and margarine: Differential Scanning Calorimetry
(DSC) is a fast and direct way to assess the quality of oil (Gloria and
Aguilera, 1998). Using this method, various physical properties of Irvingia
gabonensis seed kernels oil can be studied.
The thermal analysis makes it possible to determine the variations of
bound energy on a change of state. The temperatures of the peaks and the
fusion or crystallization enthalpy are obtained by analyzing the thermo
grams using the software Pyris I (Perkin Elmer Corp, Norwalk, the USA).
||Fatty acids classes content of usual
edibles oils and fats (from CIQUAL Databases, AFSSA report, 2003).
The differential thermal analysis enabled us to determine the thermo
grams of fusion and crystallization of Irvingia gabonensis oil
and margarine manufactured containing these oils. Thermogramm shows that
oils and margarines have a simple polymorphism.
IGO oil exhibited a melting peak (2.53oC), a melting enthalpy
(-12.29J/g) for crystallization process and second fusion peak (39.66oC)
enthalpy is 9.93J/g slightly different from those of IGS oil (2.07oC,
-12.1J/g and 36.08oC, 10.91J/g, respectively) (Table
Margarine manufactured containing these oils exhibited a first peak at
low temperature at -4oC and a second fusion peak at (30-36oC).
Margarine contains two fatty acids classes (UFA and SFA).
Conclusion: Proximate analysis of Irvingia gabonensis seed
kernels showed that they are lipids sources (34.5-73.82%). Oil extracted
of Irvingia gabonensis seed kernels is saturated, a source of lauric
and myristic acids. The thermograms analysis showed the presence of a
simple polymorphism, with a fusion peak with (2.07-2.53oC)
and a crystallization peak with (36.08 - 39.66oC)
It is a technical fat (major frying oil) because it resists thermo oxidative,
hydrolytic and enzymatic adulterations. It is a natural shortening.
The margarine manufactured with Irvingia gabonensis seed kernels
oil has a nutritional value because it is rich in oleic acid (35.51-37%),
it is an alternative solution with the trans fatty acids which have bad
effects on health.