Mineral and Vitamin Concentrations of Heat Processed Plukenetia conophora Seed Kernel Consumed in Nigeria

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____________________________________________________________________________________________
*Corresponding author: E-mail: anyalogbu@yahoo.com;
Journal of Scientific Research & Reports
3(20): 2694-2708, 2014; Article no. JSRR.2014.20.007
ISSN: 2320–0227
SCIENCEDOMAIN international
www.sciencedomain.org
Mineral and Vitamin Concentrations of Heat
Processed Plukenetia conophora Seed Kernel
Consumed in Nigeria
Ernest A. Anyalogbu
1*
, Eugene N. Onyeike
2
and Michael O. Monanu
2
1
Department of Biotechnology, Federal University of Technology, Owerri, Nigeria.
2
Department of Biochemistry, Faculty of Chemical Sciences, College of Natural and Applied
Sciences, University of Port Harcourt, Port Harcourt, Nigeria.
Authors’ contributions
This work was carried out in collaboration between all authors. All authors read and
approved the final manuscript.
Article Information
DOI: 10.9734/JSRR/2014/9450
Editor(s):
(1) Christian Scheckhuber, Goethe University, Frankfurt, Germany.
Reviewers:
(1) Anonymous, Federal Polytechnic Ilaro, Nigeria.
(2) Anonymous, University of Calabar, Nigeria.
Peer review History: http://www.sciencedomain.org/review-history.php?iid=629&id=22&aid=5812
Received 10
th
February 2014
Accepted 3
rd
April 2014
Published 21
st
August 2014
ABSTRACT
Mineral and vitamin concentrations of heat processed Plukenetia conophora seed kernel
consumed as snacks in Nigeria were investigated. The seeds which were obtained from
Ojoto in Anambra State, Nigeria were washed in several changes of distilled water,
divided into four lots - PC
raw
(raw sample), PC
45
, PC
90
and PC
135
(samples cooked for 45,
90 and 135min respectively), oven-dried and milled into flours. Concentrations of the
minerals (Ca, K, Mg, Na, Pb, Cu, Fe, I and Mn) in PC
raw
decreased as the time of cooking
increased from 45min (PC
45
) to 135min (PC
135
)
,
while for P, Zn and Se the concentrations
increased over time of heat processing. The most abundant mineral was sodium
(27.41mg/100g) followed by calcium (21.04mg/100g) and lowest in iodine (3.0µg/100g).
Original Research Article

Anyalogbu et al.; JSRR, Article no. JSRR.2014.20.007
2695
Iodine was the most heat-labile mineral followed by iron and then lead. Plukenetia
conophora seed kernel flours were found to be excellent sources of vitamins E, K, B
1
, B
6
and B
9
and good sources of vitamins D, B
2
, B
3
, B
5
and thus the plant food is
recommended for consumption sinceit could provide significant amount of the
recommended daily allowance of these micronutrients for adults.
Keywords: Micronutrient concentrations; heat processing; Plukenetia conophora seed flour.
1. INTRODUCTION
Nutrients (in food) are needed by the body for generation of energy and for growth and
maintenance. Vitamins and minerals are classes of nutrients required by the body in minute
amount and are therefore called micronutrients. Micronutrients are essential in the
maintenance of human health [1,2]. Minerals (inorganic substances) serve a variety of
functions including the formation of bones and teeth; as essential constituents of body fluids
and tissues, components of enzyme systems, nerve function. For microminerals the amount
needed by the human body per day is less than 100mg while for macrominerals it is greater
than 100mg. Vitamins are either fat- or water- soluble and are involved in the body’s
metabolism, cell production, tissue repair, and other vital processes.
Edible wild plants and fruits are exploited to provide supplementary nutrition in developing
nations [3,4,5].
Studies have shown that many plant foods contain high amount of minerals, vitamins, fiber
and phytochemicals that make them nutritionally important [6]. One of such plant foods is
Plukenetia conophora. P. conophora (African walnut) a climbing and twining plant (Liane)
over 30m long, is indigenous to Africa, especially West Africa. It is of the family
Euphorbiaceae and is commonly known in Nigeria as “Ukpa” (Igbo), “Asala” or “Awusa”
(Yoruba), “Okhue or Okwe” (Edo) [7,8]. The fruit is a capsule, 6-10cm long by 3-11cm wide
containing sub-globular seeds 2 - 2.5cm long with a thin brown shell resembling the template
walnut (Plate 1). The seed is eaten raw, roasted or cooked mainly as indigenous snacking
nut (masticatory).
Plate 1. Photograph of P. conophora seeds

Anyalogbu et al.; JSRR, Article no. JSRR.2014.20.007
2696
Heat processing has been reported to have the potential to alter the nutrient quality of foods
[9,10,11,12]. This, according to Ebirien et al. [13] depends on the degree of processing and
the nutrient in question.
Nutrients may be destroyed or lost when foods are processed because of their sensitivity to
heat, light, oxygen, pH of the solvent or combinations of these [14].
Processing may also made nutrients more available through the release from entrapment in
the plant’s matrix [15] or reduction in the concentration of antinutritional factors inherent in
the food [16,17,18]. Food processing method should therefore be such that does not
adversely affect the colour, texture, flavor, nutritional values especially the vitamins and
minerals [19]. This article is intended to evaluate the effect of heat processing on the mineral
and vitamin concentrations of P. conophora seed kernel consumed in Nigeria.
2. MATERIALS AND METHODS
All reagents were obtained from Merch (Darmstadt, Germany) and used as such. Fresh fruit
capsules of P. conophora were purchased from a farmer at Ojoto, Idemili South Local
Government Area of Anambra State, Nigeria. The capsules were cut open with a sharp knife
and the wholesome seeds collected.
2.1 Sample Processing
Wholesome samples were washed in several changes of distilled water and divided into four
(4) lots. The first lot was used raw and therefore labeled PC
raw
. Trial cooking using traditional
cooking method(which involved boiling at 98±0.03ºC in an aluminum cooking pot with
sufficient water) showed that accepted eaten tenderness was obtained 90min. The 2
nd
, 3
rd
and 4
th
lots were boiled in water (98±0.03
o
C) for 45, 90, and 135 min and labelled PC
45
,
PC
90
, and PC
135
respectively. The shell of PC
raw
, PC
45
, PC
90
and PC
135
were cracked with a
hammer and the kernels collected. The kernels were sliced thinly with a knife and dried for
48hr in an air-circulatory oven (50ºC) (Model OVE.100.130M.Gallenkamp, UK). The oven-
dried samples were groundin a mill (Model BL357. Kenwood, Birmingham UK), passed
through a 60-mess size screenand used in the analyses.
2.1.1 Mineral content analyses of the samples
The mineral content of the samples were determined by the use of Atomic absorption
spectrophotometry [20] as described by Onyeike and Acheru [21].
Three grams of the stock sample was incinerated in a muffle furnace (Model AAF 11/7,
Cabolite, Derbyshire, UK) at 550ºC until ash was obtained. The non-combustible inorganic
mineral contents of the ash were extracted with 20ml of 2.5%HCl. The extract was reduced
to 8.0ml by heating in a water-bath (98±0.03ºC) for 1hr, diluted to 50ml with deionized water
and stored in clean polyethylene sample bottle.
The mineral contents were determined using atomic absorption spectrophotometer (Model
2380, Perkin-Elmer, USA).
The instrument was calibrated with standard solution containing known amounts of the
minerals being estimated. The results were expressed in mg per 100g sample.

Anyalogbu et al.; JSRR, Article no. JSRR.2014.20.007
2697
2.2 Vitamin Analysis
The modified AOAC [22] method 992.03, 992.04 and 992.26(Codex-Adopted-AOAC
Method) for vitamin analysis was used. This involved the gas chromatographic analyses of
the vitamin contents of the sample extract using HP5890 powered with HP ChemStation
Rev.A09.01 (1206) software (Hewlett-Packard, California, USA).
The sample was pressed in a mortar carefully to avoid forming lumps. A 0.1g of the sample
and 0.05g ascorbic acid (as antioxidant, to reduce oxidation reactions that could affect
vitamins during saponification and extraction) were weighed into 16x126mm test tube and
5ml of alcohol (made by mixing 90.2% ethanol, 4.9% methanol, and 4.9% isopropanol) and
0.5ml of 80% KOH(w/v) were added and the tube vortexed for 30sec. The alcohol was
needed to stabilize the saponification solution and prevent the precipitation of soap material
[23]. Then, the test tube was flushed with nitrogen gas(N
2
) and capped (to reduce vitamin
loss to oxidation), and incubated for 30min in a water-bath (70
o
C) with periodic vortexing.
The tube was then placed in an ice bath for 5min to reduce the solubility of interfering
substances [24].
Deionized water (3ml) and 5ml of hexane were added to the test tube, vortexed for 30sec,
and then centrifuged at 1000xg for 10min. The upper hexane layer was transferred to
another test tube and the residue re-extracted two more times, each with 5ml hexane. The
pooled extract was concentrated to 1ml by evapouration under N
2
flow.
The concentrated extract was analyzed for vitamin contents in a HP Gas chromatograph
(Model 5890, Hewlett-Packard, USA) powered with HP ChemStation Rev.A09.01 (1206)
Software. The GC was calibrated with selected standards.
The gas chromatography conditions for the analysis of vitamins were as stated below.
The injection temperature was split while split ratio was 2:1. Carrier gas was nitrogen with
inlet temperature of 250ºC in a HP5 column type of dimension 30x0.25mmx0.25µm. The
oven was programmed to give initial temperature of 50ºC, first ramping at 10ºC/min for
20min maintained for 4min and second ramping at 15ºC/min for 4min maintained for
2min.The detector used was pulsed flame-photometric detector (PFPD) at 320ºC with
hydrogen and compressed air pressures of 20psi and 30psi respectively.
From the chromatogram of the sample extract and that of the mixture of standards produced
by the GC, the vitamin contents of the sample were identified and quantified by an enhanced
integrator which gave the result as mg/100g sample.
3. RESULTS AND DISCUSSION
The mineral contents of raw and cooked samples of P. conophora seed flours are presented
in Table 1.
Concentrations of Ca, K, Mg, Na, Pb, Cu, Fe, I and Mn decreased with increasing
processing time. Ebuehi [25] reported that boiling brings about losses of some minerals.
However, P, Zn and Se increased as time of heat processing increased. Adeniyan et al. [18]
reported that while the concentrations of some minerals were reduced others were increased
by boiling. Earlier, Severi et al. [9] reported that cooking resulted in losses of vitamins and
minerals.

Anyalogbu et al.; JSRR, Article no. JSRR.2014.20.007
2698
Table 1. Mineral concentrations
a
of raw and cooked P. conophora seed flour
Mineral
Samples
PC
raw
PC
45
PC
90
PC
135
Ca(mg/100g)
21.04
20.20
18.83
10.77
K(mg/100g)
8.97
6.52
4.75
3.63
Mg(mg/100g)
7.03
5.07
5.06
5.02
Na(mg/100g)
27.41
20.63
17.08
5.0
P(µg/100g)
17.0
22.0
24.0
22.0
Pb(µg/100g)
10.0
10.0
6.0
NDL
Cu(µg/100g)
560.0
450.0
450.0
440.0
Fe(mg/100g)
2.26
0.77
NDL
NDL
I(µg/100g)
3.0
NDL
NDL
NDL
Mn(mg/100g)
2.40
1.99
1.97
1.68
Zn(mg/100g)
2.47
2.56
2.76
2.62
Se(µg/100g)
4.89
7.61
8.0
10.35
a
Values are means of duplicate determinations on dry matter basis. NDL = non -detectable level
While the value for Se increased from PC
raw
to PC
135
, those of P and Zn were maximum at
PC
90
. The percentage differences between the mineral contents of raw and cooked samples
areshown in Table 2.
Table 2. Differences in mineral concentrations between raw and cooked
P. conophora seed flour
Mineral
a
Differences (percentage difference)
PC
raw
- PC
45
PC
raw
- PC
90
PC
raw
-PC
135
Ca
0.84(3.99)
2.21(10.50)
10.27(48.80)
K
2.45(27.31)
4.22(47.10)
5.34(59.53)
Mg
1.96(27.88)
1.97(28.02)
2.01(28.59)
Na
6.78(24.74)
10.33(37.69)
22.41(81.76)
P
-5.0(29.41)
-7.0(41.18)
-5.0(29.41)
Pb
0.0
4(40.0)
10.0(100)
Cu
110.0(19.64)
110.0(19.64)
120.0(21.43)
Fe
1.49(65.93)
2.26(100)
2.26(100)
I
3.0(100)
3.0(100)
3.0(100)
Mn
0.41(17.08)
0.43(17.92)
0.72(30.0)
Zn
-0.09(3.64)
-0.29(11.74)
-0.15(6.07)
Se
-2.72(55.62)
-3.11(63.6)
-5.46(111.7)
a
Negative sign indicates increase in value
Na was the most abundant mineral in the raw and sample cooked for 45min followed by Ca
and then K. The abundance of Ca, P and K in plants has been reported by Canellas and
Saura-Calixto [26]. The mineral with the lowest concentration was iodine in the raw sample
(PCraw), Se in PC
45
and PC
135
and, Pb in PC
90
.
Iodine was reduced beyond detectable level at PC
45
, Fe at PC
90
, and Pb at PC
135
.The level
of the effect of cooking depends on the processing time and the mineral in question as
earlier reported by Ebirien et al. [13]. At 45 min of heat processing, iodine was the most
susceptible being reduced by almost 100% followed by Fe (65.93%) and then Se (55.62%),
and Zn (3.64%).

Anyalogbu et al.; JSRR, Article no. JSRR.2014.20.007
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At 90 min, iron was the most affected (100%) followed by Se (63.60%) and then K (47.1%)
while selenium (111.66%) became the most susceptible at 135min followed by Pb (100%)
and then Na (81.76%).Osum et al. [27] and Adeniyan et al. [18] also reported reduction in
the Na content of Vitex doniana (black plum) leaf by blanching and Sesamum indicum
(beniseed) by boiling respectively. The observed range for the sample was comparable with
the value 10.4mg/100g obtained for the fruit pulp of black plum by Vunchi et al. [28]. The
recommended daily allowance (RDA) of Na for adult is 1000-13000mg [29]. It follows that
1kg of the sample could supply 27.44-17.0% of the RDA of Na for adult if not cooked for
more than 90min. Na is an essential element which in conjunction with K works for
extracellular fluid balances and normal osmotic pressure in the body, and in nerve
transmission [30,28,31,32].
Na/K ratio is of significance especially to a hypertensive patient [2]. A ratio of less than one
has been recommended for the prevention of high blood pressure [33]. The ratio obtained in
this work at all levels of processing is above 3. The consumption of the plant food is
therefore not recommendable for hypertensive patients.
K has been shown to play protective role against hypertension, stroke, cardiac dysfunctions,
renal damage, hypercalciuria, kidney stones and osteoporosis [34]. The RDA for K is
4700mg for adult. The K content of the P. conophora sample was reduced from 8.97-
3.63mg/100g by cooking. Adeniyan et al. [18] also reported that cooking progressively
reduced the K content of Sesamum inducum. The sample investigated is a poor source of
dietary K as 1kg could not supply up to 2% of the RDA for adult.
On the other hand the plant could be adjudged a good source of Mg as 1kg could supply at
least 15.69-21.97% of the 320-420mg RDA of Mg for adults[29]. Mg content of the sample
was reduced at all levels of processing given the range 5.02-7.03mg/100g. This value was
higher than the values 1.80-2.00mg/100g reported for African bread fruit by Ijeh et al. [35].
Mg is an important mineral element and is implicated in circulatory diseases [2,36]. It is
involved in the maintenance of the electrical potential of nerves and cell membranes and,
activation of many enzyme systems [37,38]. It also functions as a co-factor for many
enzymes in energy metabolism and biosynthesis of macromolecules [35].
P in the raw sample (17.0μg/100g) was made more available by heat processing. Adeniyan
et al. [18] also showed that P content of beniseed increased progressively with boiling time.
These contradicted earlier reports that boiling reduced the phosphorous content of yellow
yam [11] and red kidney bean [33]. P helps to control the acid-alkaline state of the blood
[39]. In association with Ca, P is involved in blood formation and, bone, teeth and muscle
growth and maintenance [40,4]. P is also a component of nucleotide molecules that are
structural components of the nucleic acids, DNA and RNA and of the energy transfer
molecules such as ATP, NAD, and FAD. Based on the RDA of P of 500mg for adults [11],
P. conophora is not a good source of dietary P.
Ca level was decreased by cooking. Akin-Idowu et al. [11] and Adeniyan et al. [18] earlier
reported that Ca content of yam and beniseed increased with boiling time. When cooked to
tenderness (PC90), the concentration of Ca was highest (18.83mg/100g).
The observed range of concentration of calcium 10.77-21.04mg/100g compared favourably
with the range 10.2-23.1mg/100g obtained for cashew nut [41, 39]. P. conophora could be
adjudged a good source of Casince 1kg of the sample could supply 13.46-26.3% of the
800mg RDA of Ca for adults [11,42]. Over 99% of Ca in the body is used as structural

Anyalogbu et al.; JSRR, Article no. JSRR.2014.20.007
2700
components of bones and teeth [43,27]. Ca participates in many enzyme-mediated
processes [41,28] and is involved in nerve conduction, aids muscle growth and prevents
muscle clamps [38]. Intestinal Ca absorption is governed by Ca/P ratio of the diet. A ratio of
more than one indicates the diet as “good” as more Ca would be absorbed [44,28,33]. At 45
min cooking, 65.93% of the 2.26mg/100g iron in theraw sample was lost leaving 0.77g/100g
which is lost completely when cooked to eaten tenderness. The plant food is a good source
of Fe but must be eaten raw or undercooked to contribute 9.63-28.25% of the 8mg RDA [28]
per 100g sample. Fe is an essential trace element required for haemoglobin formation,
normal function of central nervous system and energy metabolism [45, 46].
P. conophora is an excellent source of dietary copper as 100g could supply 48.89-62.22% of
the 900μg RDA [28]. Cooking decreased the Cu content of the sample giving the range
440.0-560.0μg/100g. Reduction was also reported by Musa and Ogbadoyi [32] for Hibiscus
sabdariffa. Earlier Ijeh et al. [35] reported that processing made copper more available in
cashew nut giving the range as 350-400μg/100g. Like Fe, copper is a component of
haemoglobin and participate in blood function [39].
Mn was progressively decreased (17.08-30%) by cooking giving the range 1.68-
2.40mg/100g. Adeniji and Tenkuano [47] and Audu and Aremu [33] also reported reduction
on Mn contents of plantain-banana hybrid and red kidney beans respectively. The observed
values for P. conophora compared favourably with the values 1.6-1.7mg/100g obtained for
red kidney beans. The Mn content of the raw sample (2.40mg/100g) compared very well with
the value (2.20mg/100g) obtained by Ayoola et al. [48] for air-dried fresh C. conophora
sample obtained from Oyo State, Nigeria. The concentrations of other minerals in this study
were tremendously lower than the corresponding values obtained by the researchers.The
sample investigated is an excellent source of Mn as 100g could supply the 1.2-3.2mg RDA
for adult [29] at all levels of processing. Mn is an activator of many enzymes [49] and a
component of the bone which functions in reproduction and actions of the CNS [50].
Processing increased the zinc content of the sample by 3.64-11.74%. The sample is a good
source for dietary Zn as 100g could supply 30.9-34.5% of the 8-11mg RDA for Zn [29]. Zn is
important in the absorption and action of B-complex vitamins and inhibits 5-alpha reductase
from converting testosterone into dihydrotestosterone (DHT), a form of testosterone that
promotes prostate growth. Zinc increases testosterone, and sperm count. In zinc deficiency,
sex drive is reduced in order to conserve the zinc (zinc is concentrated in semen) [51]. Zn is
also involved in gene expression, regulation of cellular growth and acts as cofactor for
enzymes responsible for carbohydrate, protein and nucleic acid metabolism [52]. It plays
important role in the metabolism of cholesterol, heart disease and diabetes [53,54].
Iodine was the most heat-labile element in the sample. The 3.0μg/100g concentration in the
raw sample reduced to non-detectable level at 45min cooking. The trace element is required
by the developing foetus due to its effect on brain development and is required for the
synthesis of thyroid hormones [55,35]. The sample is not a source of dietary iodine. On the
other hand, the Se content of 4.89-10.35μg/100g could supply 23.76-51.24% of the 20.2-
26.2μg RDA for Se [56,35] and was increased by cooking.
Higgs et al. [57] reported that Se content of oat and wheat were increased by boiling but
reduced to non-detectable level when the boiling time was beyond 45min. Most of the
selenium in the body is found in proteins as seleno-analogues of sulphur amino acids. Se is
an antioxidant that protects vitamin E from degradation and is involved in the maintenance of
defense against infections and modulation of growth and development [58,59]. Two

Anyalogbu et al.; JSRR, Article no. JSRR.2014.20.007
2701
selenium-containing enzymes (selenoenzymes) glutathione peroxidases and thioredoxin
reductases (Endogenous antioxidants) are involved in the protection of the body tissues
against oxidative damage by the highly reactive oxygen-containing metabolites (hydrogen
peroxide or lipid hydroperoxide) [60].
The lead content of the raw sample (10.0μg/100g) was not affected by cooking for 45min,
but decreased to non-detectable level at 135min. Audu and Aremu [33] reported 10μg/100g
for red kidney bean and that the value dropped to non-detectable level with boiling. Lead is
ubiquitous in the environment and thus present (at very low levels) in all foods. The
observed value may be site-specific relating to the extent of lead pollution of the sample area
[61]. Lead is very toxic when accumulated in the body and can lead to death [62,31]. The
daily permissible amount of lead for adult is about 232.14μg [63]. With 1kg of the sample
supplying at most 100μg of lead, the plant food is safe for consumption at all levels of
processing.
Tables 3 and 4 respectively represent the fat-soluble and water-soluble vitamin levels for raw
and cooked samples of P. conophora. The data showed that the most abundant fat-soluble
vitamin in the plant food at all levels of processing was vitamin E while the lowest
concentration was obtained in vitamin D
3
.
Table 3. Concentrations
a
of Fat-soluble Vitamins in raw and cooked P. conophora
seed flours
Vitamin
Samples
PC
raw
PC
45
PC
90
PC
135
A(µg/100g)
6.76
6.87
7.76
6.87
D
1
(IU/100g)
0.46
0.55
0.52
0.47
D
3
(IU/100g)
0.13
0.14
0.15
0.13
E(mg/100g)
0.74
0.75
0.75
0.75
K (µg/100g)
29.87
30.23
32.52
32.57
a
Values are means of duplicate determinations on dry matter basis
The water-soluble vitamin with the highest concentration was niacin (Vit. B
3
) and Choline
(Vit.B
4
) the lowest.
Heat processing (cooking) generally increased values of the fat-soluble and water-soluble
vitamins.Similar results have been reported for vitamins A and D
3
in raw English walnut and
soybean [64,65].
The concentration of vitamin K (Table 5) increased with increase in cooking time from PC
raw
– PC
135
giving a range of 29.87 - 32.57µg/100g (i.e. 1.21 – 9.04%). This is higher than the
values of 0.3μg/100g and 2.7µg/100g obtained for egg and English walnut respectively [64].
One kg of the sample when processed to acceptable cooking tenderness (PC
90
) could
supply 15.5-7.76% of 500-100µg RDA for vit. A 15-30% of 5-10µg RDA for vit.D, 75-
107.14% of 7-10mg RDA for vit.E and, 50.03-162.6% of the RDA for Vit.K for children and
adult [42,11]. Vitamins E, K and A are essential nutrients [66]. Vitamin E, through its
antioxidant property mops up excess free radicals produced in the tissues and thus controls
the development of oxidative stress - induced diseases [67]. Vit. K functions as cofactor in
the enzyme system that forms native prothrombin involved in the haemostatic (styptic)
coagulation [68]. Vitamin A on the other hand, is required in small amount by humans for

Anyalogbu et al.; JSRR, Article no. JSRR.2014.20.007
2702
normal functioning of the visual system and its deficiency leads to xerophthalmia, anaemia,
and weakened resistance to infection [27]. As reported by WHO [69], Vit. A deficiency affect
about 2.5million pre-school children in Africa. Consequently, the consumption of the kernel is
highly recommendable. Vit. A is also involved in the maintenance of growth, development
and soundness of cells, epithelial cellular integrity, immune function and reproduction [70].
Vitamin D through its regulatory effect on the transcription of a number of genes is involved
in Ca and P metabolism and, in the modulation of cell proliferation and differentiation [70].
From the comparison with the RDA, a properly processed sample of P. conophora seed
could be adjudged a moderate source for vitamins A and an excellent source for vitamins E
and K. The consumption of the seed kernel is therefore recommended for the prevention and
management of cellular diseases, haemophilia, and visual system dysfunction and, general
wellbeing.
Table 4. Concentrations
a
of water-soluble vitamins in raw and cooked P. conophora
seed flours
Vitamin
Samples
PC
raw
PC
45
PC
90
PC
135
Thiamine,B
1
(mg/100g)
0.35
0.37
0.35
0.32
Riboflavin,B
2
(mg/100g)
0.14
0.15
0.15
0.14
Niacin,B
3
(mg/100g)
1.13
1.23
1.24
1.27
Choline,B
4
(µg/100g)
0.87
0.85
0.83
0.82
Pantothenate,B
5
(mg/100g)
0.52
0.53
0.53
0.51
Pyridoxine,B
6
(mg/100g)
0.45
0.48
0.45
0.43
Folate,B
9
(µg/100g)
94.76
82.45
76.37
74.22
Ascobate, C (mg/100g)
0.15
0.15
0.15
0.14
a
Values are means of duplicate determinations on dry matter basis
Table 5. Difference in fat-soluble vitamins contents between raw and cooked
P. conophora seed flours
Vitamin
a
Differences (percentage differences)
PCraw – PC
45
PC
raw
– PC
90
PC
raw
– PC
135
A
-0.11(1.63)
-1.0(14.79)
-0.11(1.63)
D
1
-0.09(19.57)
-0.06(13.04)
-0.01(2.17)
D
3
-0.01(7.69)
-0.02(15.39)
0.00
E
-0.01(1.35)
-0.01(1.35)
-0.01(1.35)
K
-0.36(1.21)
-2.65(8.87)
-2.70(9.04)
a
Negative sign indicates increase in value
The most abundant water-soluble vitamin, niacinas shown in Table 6 was progressively
increased (8.85-12.39%) by cooking given the value 1.13-1.27mg/100g. The lowest
concentrated, choline, together with folate was steadily reduced by cooking giving the values
0.82-0.87µg/100g and 74.22-94.76µg/100g respectively from PC
raw
to PC
135
. Choline, though
not a vitamin by FDA definition, is a vital nutrient of B-complex vitamins needed for proper
functioning of the nervous system, muscle movement, brain function and maintenance of cell
membrane integrity [65]. It also regulates liver function and is necessary for normal fat
metabolism. Folate recorded 12.99-21.68% reduction (Table 6) to be the most sensitive
water-soluble vitamin in the sample. The observed value for folate compared closely with
77µg/100g obtained for egg [64].

Anyalogbu et al.; JSRR, Article no. JSRR.2014.20.007
2703
Table 6.
a
Differences in water-soluble vitamins contents between rawand cooked
P. conophora seed flour
Vitamin
Difference (percentage difference)
PC
raw
– PC
45
PC
raw
– PC
90
PC
raw
– PC
135
Thiamine,B
1
-0.02(5.71)
0.00
0.03(8.57)
Riboflavin,B
2
-0.01(7.14)
-0.01(7.14)
0.00
Niacin,B
3
-0.10(8.85)
-0.11(9.74)
-0.14(12.39)
Choline,B
4
0.02(2.30)
0.04(4.60)
0.04(5.75)
Pantothenate,B
5
-0.01(1.92)
-0.1(1.92)
0.01(1.92)
Pyridoxine,B
6
-0.03(6.67)
0.00
0.02(4.44)
Folate,B
9
12.31(12.99)
18.39(19.41)
20.54(21.68)
Ascobate,C
0.00
0.00
0.01(6.67)
a
Negativesign indicates increase in value
The concentrations of thiamine, riboflavin, pantothenate and pyridoxine increased when
cooked for 45min. Ayoola et al. [48] could not detect pantothenate, pyridoxine and folate in
their sample. Apart from ascorbate (4.15mg/100g) the values for vitE (0.12mg/100g),
thiamine (0.06µg/100g), riboflavin (0.02µg/100g) and niacin (0.05µg/100g) obtained by
Ayoola et al. [48] for air-dried C. conophora sample were far lower than the corresponding
values obtained in this study. The observed levels of thiamine and pyridoxine are
comparable to the values 0.341 and 0.537mg/100g obtained for English walnut [64].
Thiamine, riboflavin and pyridoxine principally function in macronutrient metabolism [27].
Ascobic acid content of the sample was reduced (6.67%) only when cooked for 135min
(Table 4). Ascobate is a dietary antioxidant acting as an electron donor for eight enzymes in
humans [71]. It prevents the formation of the potential mutagen N-nitroso compounds in the
stomach and thus reduces the risk of gastric cancer [72,73]. It is involved in protein
metabolism and collagen synthesis [28].
B-vitamins generally help the body to use energy-yielding nutrients such as carbohydrate, fat
and protein for fuel [74]. They are also involved in red blood cell formation and, cell
multiplication through their role in DNA replication.
Most nutrients in plant food are entrapped in the plant matrix and therefore not easily
accessible [15]. Some nutrients are also made unavailable to the consumer through the
formation of insoluble complex with antinutrients [75]. The observed increase in nutrient
content of the food sample due to cooking could be attributable to the fact that cooking, a
hydrothermal process may have disrupted the cell structure and membrane partitions of the
seeds and caused the release of minerals and vitamins, and also antinutrients from
entrapment in the plant matrix. The heat involved in cooking may also have caused the
destruction/inactivation of antinutrients making available the nutrients that are trapped in
complex formation [76,17,18]. The level of the antinutrients could also be reduced
(increasing nutrient availability) through leaching of soluble ones into the processing water
when the epidermal layers of the seeds are ruptured by heat processing [16]. The decreased
effect of cooking on minerals and vitamins could be attributed to leaching (extraction) of the
micronutrients into the processing water [77]. The leaching may be enhanced by the heat of
processing which increases the solubility of most of the nutrients [74]. Decreasing effect may
also be due to oxidation and thermal destruction of the micronutrients especially vitamins
[78,79,80,27].

Anyalogbu et al.; JSRR, Article no. JSRR.2014.20.007
2704
4. CONCLUSION
It can be concluded that cooking influenced the concentrations of all the minerals and
vitamins in the food samples investigated. The effect depended on the micronutrient and
duration of cooking. The plant food (sample) is an excellent source of vitamins E, K, B
1
,B
6
,
and B
9
but good source of vitamins D, B
2
, B
3
, and B
5
.
COMPETING INTERESTS
Authors have declared that no competing interests exist.
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