Physical properties of Irvingia gabonensis, Detarium microcapum, Mucuna pruriens and Brachystegia eurycoma seeds

Abstract

A culinary enhancer is a substance that enhances the flavor and other properties of soups, stews and foods. Normally in flour form, culinary enhancers are used to enhance the proximate composition, viscosity, flavor and some other rheological and functional properties of soups and convenience foods. Physical properties of culinary seeds are utilized in the development of their handling, storage and processing facilities. The unit operations in the process of converting culinary seeds into flour include handling or conveying, cleaning, drying, storage, cracking, and separation of chaffs and shells before milling of the kernels or endosperm into flour. The aim of this study was to determine some postharvest physical properties of four African culinary enhancers, namely Irvingia gabonensis (Ogbono), Detarium microcapum (Ofor), Mucuna pruriens (Ukpo) and Brachystegia eurycoma (Achi) seeds. Ogbono seed had the highest dimensions (Length, L = 3.91, Width, W = 3.13, Thickness, T = 2.34 cm, Geometric mean diameter, Dg = 3.06, Arithmetic mean diameter, Da = 3.13 cm, Equivalent mean diameter, De = 2.87 cm and Square mean diameter, Ds = 1.02 cm), followed by Ukpo, Ofor and Achi seeds. The average sphericity, surface area and 1000-unit mass were 0.6, 25.61 cm2 and 11130 g; 0.95, 13.24 cm2 and 4019 g; 0.94, 17.79 cm2 and 7720 g and 0.48, 3.11 cm2 and 8960 g for Ogbono, Ofor, Ukpo and Achi seeds respectively. These properties are useful baseline data required for further research studies on rational development of handling and processing systems for the products. The seeds' dimensions, size, and shape will be useful in the design and development of their cleaning, sorting, and grading machines and in the analyses of their drying behavior. The seeds' densities and porosity values will be used to develop their conveying and storage facilities. The angles of repose and coefficient of friction will be used to design their conveying chutes and hoppers of their cracking machines and storage facility outlets.

Full text

Research article
Physical properties of Irvingia gabonensis,Detarium microcapum,Mucuna
pruriens and Brachystegia eurycoma seeds
Felix Uzochukwu Asoiro, Sunday Louis Ezeoha
*
, Cosmas Ngozichukwu Anyanwu,
Nneoma Nkem Aneke
Department of Agricultural and Bioresources Engineering, University of Nigeria, Nsukka, Nigeria
ARTICLE INFO
Keywords:
Agriculture
Food science
Mechanical engineering
Physical properties
Irvingia gabonensis
Detarium microcapum
Soup thickener
Arithmetic mean diameter
ABSTRACT
A culinary enhancer is a substance that enhances the flavor and other properties of soups, stews and foods.
Normally in flour form, culinary enhancers are used to enhance the proximate composition, viscosity, flavor and
some other rheological and functional properties of soups and convenience foods. Physical properties of culinary
seeds are utilized in the development of their handling, storage and processing facilities. The unit operations in
the process of converting culinary seeds into flour include handling or conveying, cleaning, drying, storage,
cracking, and separation of chaffs and shells before milling of the kernels or endosperm into flour. The aim of this
study was to determine some postharvest physical properties of four African culinary enhancers, namely Irvingia
gabonensis (Ogbono), Detarium microcapum (Ofor), Mucuna pruriens (Ukpo) and Brachystegia eurycoma (Achi) seeds.
Ogbono seed had the highest dimensions (Length, L ¼3.91, Width, W ¼3.13, Thickness, T ¼2.34 cm, Geometric
mean diameter, D
g
¼3.06, Arithmetic mean diameter, D
a
¼3.13 cm, Equivalent mean diameter, D
e
¼2.87 cm
and Square mean diameter, D
s
¼1.02 cm), followed by Ukpo, Ofor and Achi seeds. The average sphericity, surface
area and 1000-unit mass were 0.6, 25.61 cm
2
and 11130 g; 0.95, 13.24 cm
2
and 4019 g; 0.94, 17.79 cm
2
and
7720 g and 0.48, 3.11 cm
2
and 8960 g for Ogbono, Ofor, Ukpo and Achi seeds respectively. These properties are
useful baseline data required for further research studies on rational development of handling and processing
systems for the products. The seeds' dimensions, size, and shape will be useful in the design and development of
their cleaning, sorting, and grading machines and in the analyses of their drying behavior. The seeds’densities
and porosity values will be used to develop their conveying and storage facilities. The angles of repose and co-
efficient of friction will be used to design their conveying chutes and hoppers of their cracking machines and
storage facility outlets.
1. Introduction
Irvingia gabonensis (Ogbonoin Ibo language of Nigeria), Detarium
microcapum (Oforin Ibo language), Mucuna pruriens (Ukpo in Ibo lan-
guage) and Brachystegia eurycoma (Achi in Ibo language) are economic
trees and leguminous plants that are traditionally found in the savannah
and forest zones of Africa. Among the various crops used in Africa as
culinary enhancing agents during soup making, Irvingia gabonensis
(Ogbono), Detarium microcapum (Ofor), Mucuna pruriens (Ukpo) and Bra-
chystegia eurycoma (Achi) are most profound due mainly to their thick-
ening, emulsification, stabilization, drawability and spicing function in
soups and stews (for eating fufu made from garri, cocoyam and pounded
yam). The seeds when pulverized to flour can cause changes in viscosity
of other foods by swelling in water. They also serve as food additives to
create required changes in the texture and functional properties of con-
venience foods, due to their absorption capacity (Ajayi et al., 2006).
These seeds have excellent economic and nutritional advantages.
They are good sources of bioactive compound especially saponins, al-
kaloids, tannins, and flavonoids. They also contain protein, minerals,
vitamins, carbohydrate, fats and soluble fiber. The component vitamins
are soluble in water, which also possess high nutritional importance
(Uhegbu et al., 2009). The proteins of these crops are rich in lysine but
deficient in sulfur containing amino acids particularly cysteine and
methionine. Precisely, Mucuna sloanei (Ukpo) contains between 6-19%
crude protein, 39.8–61.49% carbohydrate, 1.84–5.9% fat and
11.24–17.10% vitamins. Brachystegia eurycoma seed (Achi) contains 56%
carbohydrate, 15% crude fat, 9% protein, 4.5% ash and 2.9% crude fibre
(Uhegbu et al., 2009;Ene-Obong, 1992). Detarium microcapum (Ofor)
* Corresponding author.
E-mail address: sunday.ezeoha@unn.edu.ng (S.L. Ezeoha).
Contents lists available at ScienceDirect
Heliyon
journal homepage: www.cell.com/heliyon
https://doi.org/10.1016/j.heliyon.2020.e04885
Received 19 May 2020; Received in revised form 19 August 2020; Accepted 7 September 2020
2405-8440/©2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-
nc-nd/4.0/).
Heliyon 6 (2020) e04885

contains 12.0–15.6% protein, 0.79% vitamins, 6.0% fat and 35.4–68.2%
carbohydrate (Ajayi et al., 2006;Ene-Obong, 1992). Irvingia gabonensis
(Ogbono) seed consists of approximately 62.8% of fats and 19.7% of
carbohydrates. Protein is about 8.9%, dietary fibre, 5.3% and ash, 3.2%
(Ejiofor, 1994).Brachystegia eurycomaand Detarium microcarpum are re-
ported to be very effective in the lowering of blood glucose level and
blood cholesterol content and help in stabilizing the body temperature
(Onimawo and Egbekun, 1998). The seed gum from Brachystegia eur-
ycoma can be used as a binding agent in tablet formulation and compares
favourably with the industrial type (Olayemi and Jacob, 2011). The seed,
stem bark and exudates have been reported to possess antioxidant,
anti-inflammatory, antibacterial, antifungal activities as well as facili-
tating wound healing (Igwe and Echeme, 2013;Igwe and Okwu, 2013;
Adekunle, 2000). Irvingia gabonensisseed has very huge amount of soluble
fibre and therefore commonly used in Western countries as a supplement
for weight loss. It is also widely used in West Africa as a binder in
pharmaceutical industries and a very important ingredient in the pro-
duction of confectionary, edible fats, soap and cosmetics (Ogunsina et al.,
2008;Agbor, 1994). Each species of the seed differs from the others and
so have their individual engineering and thermal properties, different
flavours, taste, odour, texture and nutritional composition which they
impart on foods. Often, choice depends on individuals, but Brachystegia
eurycoma and Detarium microcarpum are the most favourite culinary en-
hancers in South Eastern, Nigeria.
A lot of researchers have investigated the postharvest physico-
mechanical and thermal properties of some seeds and crops. Soy-
bean (Azadbakht et al., 2013), Jatropha (Shkelqim and Joachim,
2010), Soyabean (Deshpande et al., 1993),oilbeanseed(Oje and
Ugbor, 1991), karingda seed (Suthar and Das, 1996), cumin seed
(Singh and Goswami, 1996), lentil seeds (Carman, 1996), sunflower
seeds (Gupta and Das, 1997), green (Nimkar and Chattopadhyaya,
2001), chick pea seeds (Konak et al., 2002), neem nuts (Visvanathan
et al., 1996), quinoa seeds (Vilche et al., 2003), hemp seed (Sacilik
et al., 2003), faba bean (Haciseferogullaria et al., 2003), rapeseed
(Calisir et al., 2005), African yam beans (Asoiro and Ani, 2011)and
coffee (Chandrasekar and Viswanathan, 1999) have all been investi-
gated. The following researchers have also studied some
physico-mechanical properties of other seeds and crops (Aydin, 2003;
Baryeh and Mangope, 2002;Gezer et al., 2002;Guner et al., 2003;
Olajide et al., 2000;Olaoye, 2000).
However, there is scarcity of information in literature on physical
properties of Irvingia gabonensis (Ogbono), Detarium microcapum (Ofor),
Mucuna pruriens (Ukpo) and Brachystegia eurycoma (Achi). Seed di-
mensions are very necessary in their electrostatic separation from con-
taminants and in the design and fabrication of sizing, sorting, conveying
and grading systems (Mohsenin, 1986). Shapes of seeds are vital in the
analysis and prediction of their drying behavior (Esref and Halil, 2007).
True density, bulk density, density ratio and porosity are needed in the
development and sizing of grain hoppers and storage facilities. They also
affect the rate of heat and mass transfer of moisture during drying,
cooling and aeration processes. Low porosity seed bed will require a high
powered fan during drying or aeration as occasioned by the resistance to
water vapor escape. Seed densities are needed during hardness studies
and breakage susceptibility tests. When designing the angles at which
chutes or hoppers must be positioned in other to achieve smooth flow,
data on the static coefficient of friction are always necessary. Such in-
formation is also vital in determining the size of motor needed during
seed handling and transportation (Ghasemi et al., 2007). The develop-
ment of handling and storage machineries requires data on bulk den-
sities, coefficients of friction on some commonly used material surfaces
(galvanized steel, plywood and concrete) and angles of repose of crops
(Parde et al., 2003). The knowledge of these properties are also needed
for predicting the load and pressure on storage structures as well as for
design of grain hoppers for processing machinery. The maximum angle of
a pile of grains with the horizontal axis is normally used in the mea-
surement of angle of repose (Mohsenin, 1986).
The processing of Irvingia gabonensis (Ogbono), Detarium microcapum
(Ofor), Mucuna pruriens (Ukpo) and Brachystegia eurycoma (Achi) for value
addition involves parboiling, soaking or roasting, frying, dehulling and
size reduction. These processes are laborious and time consuming, and
are still done manually across West Africa with low output. In order to
take advantage of the huge economic, nutritional and culinary potentials
of these African seeds, there is the need to develop machines, systems and
equipment for carrying out the dehulling, processing, cooking and
handling operations which require knowledge of the physical and me-
chanical properties. The aim of this study therefore, was to investigate
Figure 1. Brachystegia eurycoma (Achi), Detarium microcapum (Ofor), Irvingia gabonensis (Ogbono) and Mucuna pruriens (Ukpo).
F.U. Asoiro et al. Heliyon 6 (2020) e04885
2

the postharvest physical properties of Irvingia gabonensis (Ogbono),
Detarium microcapum (Ofor), Mucuna pruriens (Ukpo) and Brachystegia
eurycoma (Achi) which will serve as baseline data for the development of
their handling and processing facilities.
2. Materials and methods
2.1. Collection and preparation of sample
Matured, harvested and dried samples of Irvingia gabonensis (Ogbono),
Detarium microcapum (Ofor), Mucuna pruriens (Ukpo) and Brachystegia
eurycoma (Achi) were sourced from Afikpo market, Ebonyi State, Nigeria.
Manual cleaning was used to separate foreign materials and damaged
seeds. Manual cracking was done, and the seeds were grouped and the
physical properties measured. The physical properties were determined
in the Food and Bioprocess Laboratory, University of Nigeria, Nsukka,
Nigeria. Figure 1 shows the seeds of Irvingia gabonensis (Ogbono), Deta-
rium microcapum (Ofor), Mucuna pruriens (Ukpo) and Brachystegia eur-
ycoma (Achi).
2.2. Determination of physical properties
The dimensions of 100 randomly picked seeds –Length, L; width, W
and thickness, Twere measured using Electronic Digital Caliper Vernier -
Table 1. Physical properties of Irvingia gabonensis (Ogbono) seeds.
Property No. of Samples Range Mean Value Standard Deviation Coeft. of Variability (%)
Length, L (cm) 100 2.85–4.58 3.91 0.38 9.72
Width, W (cm) 100 2.34–4.10 3.13 0.33 10.54
Thickness, T (cm) 100 1.76–2.86 2.34 0.23 9.83
Geometric mean diameter, D
g
(cm) 100 2.32–3.50 3.06 0.25 8.17
Arithmetic mean diameter, D
a
(cm) 100 2.37–3.61 3.13 0.26 8.31
Equivalent mean diameter, D
e
(cm) 100 2.21–3.37 2.87 0.24 8.36
Square mean diameter, D
s
(cm) 100 0.77–1.17 1.02 0.08 7.84
Sphericity, S
p
100 0.58–0.76 0.64 0..05 8.09
Aspect ratio, R
a
100 0.64–0.96 0.80 0.08 10.00
Surface area, S (cm
2
) 100 14.81–33.49 25.61 4.13 16.13
Specific surface area, S
s
(cm
2
cm
3
) 100 1.47–2.26 1.71 0.15 8.77
Solid volume, V
s
(cm
3
) 100 6.56–22.44 15.25 3.58 23.48
Bulk volume, V
b
(cm
3
) 100 398.8–400.3 399.95 0.5 3.28
Solid mass, M
s
(g) 100 6.4–16.7 11.08 2.78 25.09
Bulk mass, M
b
(g) 100 118–136 129.5 5.55 4.29
1000-unit-mass, M
u
(g) 100 8720–13200 11130 80.67 7.79
Solid density,
ℓ
s(g cm
3
) 100 0.33–1.73 0.78 0.30 38.46
Bulk density,
ℓ
b(g cm
3
) 100 0.3–0.34 0.33 0.01 3.03
Density ratio (%) 100 101.74–535.85 241.66 89.95 37.51
Porosity,
ε
(%) 100 1.71–81.34 52.81 17.63 34.14
Angle of repose, ϕ(
o
) 100 28.81–55.30 37.88 6.88 18.16
Table 2. Physical properties of Detarium microcapum (Ofor).
Property No. of Samples Range Mean Value Standard Deviation Coeft. of Variability (%)
Length, L (cm) 100 2.76–3.76 3.41 0.24 7.04
Width, W (cm) 100 2.22–2.88 2.61 0.16 6.13
Thickness, T (cm) 100 1.04–1.87 1.26 0.14 11.11
Geometric mean diameter, D
g
(cm) 100 1.98–2.43 2.23 0.11 4.93
Arithmetic mean diameter, D
a
(cm) 100 2.08–2.65 2.43 0.13 5.35
Equivalent mean diameter, D
e
(cm) 100 1.86–2.27 2.10 0.10 4.76
Square mean diameter, D
s
(cm) 100 0.66–0.81 0.74 0.04 5.41
Sphericity, S
p
100 0.88–0.98 0.96 0.05 5.05
Aspect ratio, R
a
100 0.71–0.83 0.77 0.03 3.90
Surface area, S (cm
2
) 100 10.46–15.65 13.24 1.29 9.74
Specific surface area, S
s
cm
2
cm
3
) 100 2.07–2.57 2.27 0.12 5.29
Solid volume, V
s
(cm
3
) 100 4.07–7.56 5.89 0.85 14.43
Bulk volume, V
b
(cm
3
) 100 300–300.6 300.31 0.17 2.89
Solid mass, M
s
(g) 100 2.10–5.40 4.11 0.89 21.65
Bulk mass, M
b
(g) 100 160–192 177.3 9.34 5.27
1000-unit-mass, M
u
(g) 100 3900–4780 4019 32.1 0.99
Solid density,
ℓ
s(g cm
3
) 100 0.38–1.20 0.72 0.20 27.78
Bulk density,
ℓ
b(g cm
3
) 100 0.53–0.64 0.59 0.03 5.09
Density ratio (%) 100 101.29–216.37 140.15 27.91 29.25
Porosity,
ε
(%) 100 1.28–53.78 26.03 13.72 36.84
Angle of repose, ϕ(
o
) 100 19.98–34.18 27.49 3.87 14.08
F.U. Asoiro et al. Heliyon 6 (2020) e04885
3

150MM LCD: Konga Product code: 3003530 (0–150, 0.01 mm). Geo-
metric mean diameter (D
e
) Arithmetic mean diameter (D
a
), Equivalent
mean diameter (D
e
) and Square mean diameter (D
s
) were calculated from
length, L; width, Wand thickness, Taccording to Eqs. (1),(2),(3), and (4)
Dg¼ðLWTÞ1=3(1)
Da¼ðLþWþTÞ
3(2)
De¼DgþDaþDs
3(3)
Ds¼LW þWT þTL
31=2
(4)
where, L, W, T, D
g
,D
a
,D
e
and D
s
are all in cm.
Sphericity (S
p
) and aspect ratio (R
a
) of the seeds were also calculated
from the L, W and T using the expressions by Mohsenin (1986) and
Asoiro et al. (2017) in Eqs. (5) and (6).
Sp¼ðLWTÞ1=3
L(5)
Ra¼W
L(6)
Specific surface area (S
s
) and Surface area (S) were evaluated using
the expression by (Haciseferogullariari et al. (2007) and Subukola and
Onwuka (2011), given in Eqs. (7) and (8) respectively.
Ss¼S
ℓ
b
Ms
(7)
S¼
π
BL2
2LB(8)
where, B is (LT)
1/2
(cm), M
s
and
ℓ
bare solid mass (g) and bulk density (g
cm
3
) of seed respectively.
Solid volume (V
s
) and bulk volume (V
b
) (cm
3
) were determined by
water displacement method (Asoiro et al., 2017).The Solid density, Bulk
density, Density ratio and Porosity of Irvingia gabonensis (Ogbono), Deta-
rium microcapum (Ofor), Mucuna pruriens (Ukpo) and Brachystegia eur-
ycoma (Achi) seeds were calculated using Eqs. (9),(10),(11), and (12)
respectively, according to Asoiro et al. (2017):
ℓ
s¼Ms
Vs
(9)
ℓ
b¼Mb
Vb
(10)
ℓ
r¼
ℓ
s
ℓ
b
100 (11)
ε
¼
ℓ
s
ℓ
b
ℓ
s
100 (12)
where, M
s
and M
b
are solid mass (g) and bulk mass (g) of seeds
respectively.
A digital weight balance (Metler Digital Electric Weighing Balance
(Range: 0–30,000 g) 0.01 g; Model: ME-702718) was used to measure
and record 1,000-unit-mass, bulk mass for randomly selected samples
from a mass of 50 kg. The method by Heidarbeigi et al. (2008) was used
in the determination of angle of repose by employing a trigonometry
rules and hollow cylinder. The seeds were placed into a hollow cylinder
of known diameter (D) and known height (H) above a table top. The
cylinder was gradually pulled off to allow the seeds flow out to form a
conic shape. Angle of repose of a seed is the angle with the horizontal at
which the seed will stand when piled (Paksoy and Aydin, 2004). This was
calculated using the expression in Eq. (13).
ϕ¼Tan12H
D(13)
where, ϕis angle of repose (), His height of the pile (cm) and Dis
diameter of the pile (cm).
Table 3. Physical properties of Mucunapruriens (Ukpo) Seed.
Property No. of Samples Range Mean Standard Deviation Coeft. of Variability(%)
Length, L (cm) 100 2.23–3.22 2.84 0.16 5.63
Width, W (cm) 100 2.06–3.09 2.81 0.18 6.41
Thickness, T (cm) 100 1.23–2.22 1.94 0.18 9.28
Geometric mean diameter, D
g
(cm) 100 1.89–2.70 2.49 0.15 6.02
Arithmetic mean diameter, D
a
(cm) 100 1.94–2.73 2.53 0.15 5.93
Equivalent mean diameter, D
e
(cm) 100 1.84–2.64 2.43 0.15 6.17
Square mean diameter, D
s
(cm) 100 0.63–0.90 0.83 0.05 6.02
Sphericity, S
p
100 0.84–0.98 0.94 0.06 6.31
Aspect ratio, R
a
100 0.83–1.08 0.99 0.05 5.05
Surface area, S (cm
2
) 100 9.95–21.16 17.79 2.13 11.97
Specific surface area, S
s
(cm
2
cm
3
) 100 1.98–2.83 2.19 0.14 6.39
Solid volume, V
s
(cm
3
) 100 3.52–10.31 8.19 1.30 15.87
Bulk volume, V
b
(cm
3
) 100 699.1–700.4 700.11 0.36 4.39
Solid mass, M
s
(g) 100 4.0–9.3 7.62 1.03 13.52
Bulk mass, M
b
(g) 100 300–381 344.4 22.03 6.40
1000-unit-mass, M
u
(g) 100 7050–8440 7720 33.0 4.27
Solid density,
ℓ
s(g cm
3
) 100 0.39–2.45 0.97 0.30 30.93
Bulk density,
ℓ
b(g cm
3
) 100 0.42–0.54 0.49 0.03 6.12
Density ratio,
ℓ
r(%) 100 125.42–489.42 197.96 56.89 29.68
Porosity,
ε
(%) 100 20.27–79.57 46.64 11.24 34.42
Angle of repose, ϕ(
o
) 100 17.06–30.86 24.61 2.94 11.95
F.U. Asoiro et al. Heliyon 6 (2020) e04885
4

The moisture content MC
db
, % and (MC
wb
) of the seeds was evaluated
according to ASAE (1983) recommended methods. The sample seeds
were weighed (M
initial
) and then oven-dried at 105 C to a constant
weight (M
final
).The moisture content of the seeds (%) dry basis (wb) and
wet basis (db) were calculated using the expressions in Eqs. (14) and (15)
respectively.
MCdb ¼Minitial Mfinal
Mfinal
(14)
MCwb ¼Minitial Mfinal
Minitial
(15)
where, M
initial
and M
final
are initial and final mass of seeds (g)
respectively.
The method used by Asoiro et al. (2017) and Pliestic et al. (2006) was
employed to determine the coefficient of static friction of the seeds on
surfaces of plywood, corrugated metal sheet, aluminum, asbestos, glass
and plastic. An open-ended hollow metal cube was filled with the seeds
and put on adjustable tilting surface. The surface was gradually tilted to
angle
Ɵ
at which the cube began to slide down the surface. The expres-
sion in Eq. (16) was used to determine the coefficient of static friction,
μ
.
μ
¼Tanθ(16)
3. Results and discussion
Table 1 presents some physical properties of Irvingia gabonensis
(Ogbono) seeds. At a MC. of 8.27 1.05 % db, Ogbono seed had a mean
length, L of 39.1 3.8 mm; a width, W of 31.3 3.3 mm; and a thickness,
T of 23.4 2.3 mm Ohaeri and Ohaeri (2015) had earlier reported a
slightly higher dimension of 44.00–47.73 mm, 33.50–34.89 mm,
20.60–21.79 mm and 32.20–33.73 mm for major, intermediate, minor
and equivalent diameters respectively as moisture content (MC) rose
from 7.02% to 15.04% db. Aviara et al. (2012) had earlier reported a
slight increase in the average, L, W, T, D
a
,D
e
, and geometric mean
diameter by 2.7, 1.0, 0.4, 1.6, 1.4 and 1.3% for Irvingia gabonensis and
4.1, 0.1, 0.6, 2.2, 1.6 and 1.6% for Irvingia wombolu with increasing
moisture content, respectively. At moisture content values of 10.6, 21,
32.54 and 43.14% db, Nwigbo et al. (2013) reported slightly related
values for surface area (2598 36, 2650 62, 2662 68 and 2664 69
mm
2
), aspect ratio (78.47 1.64, 77.56 2.09, 77.23 2.26 and 77.23
2.23%), porosity (61.62 1.81, 64.15 3.05, 65.7 3.5 and 66.1 
4.05%) and bulk density (124500 500, 117000 400, 114000 550
and 112000 650 kgm
3
). The linear dimensions and shape of Irvingia
gabonensis seeds are necessary in their effective separation from un-
wanted materials and in design and construction of grading and sorting
gadgets. Knowledge of the porosity, true density, bulk density and den-
sity ratio are useful data in development sizing of hoppers and other
storage facilities as well as influencing the heat and mass transfer rates
during freezing, drying and aeration operations. Density is also used to
separate materials with different densities.
Some measured physical properties of Detarium microcapum (Ofor)
seed at a MC. of 10.96 0.30% db are presented in Table 2. The mean
length, width, and thickness were 34.1 2.4 mm, 26.6 1.6 mm, and
12.6 1.4 mm, respectively. Adedeji et al. (2012) determined and re-
ported slightly different values of solid density, bulk density and porosity
of dry ground powder of Ofor sample as 1.79 g cm
3
, 0.44 g cm
3
and
Table 4. Physical properties of Brachystegia eurycoma (Achi) seed.
Property No. of Samples Range Mean Value Standard Deviation Coeft. of Variability (%)
Length, L (cm) 100 1.46–2.66 2.11 0.23 10.90
Width, W (cm) 100 1.04–2.0 1.62 0.23 14.20
Thickness, T (cm) 100 0.24–0.45 0.36 0.05 13.89
Geometric mean diameter, D
g
(cm) 100 0.72–1.29 1.07 0.12 11.22
Arithmetic mean diameter, D
a
(cm) 100 0.92–1.62 1.36 0.15 11.03
Equivalent mean diameter, D
e
(cm) 100 0.74–1.33 1.11 0.13 11.71
Square mean diameter, D
s
(cm) 100 0.24–0.43 0.36 0.04 11.11
Sphericity, S
p
100 0.32–0.57 0.48 0.05 10.42
Aspect ratio, R
a
100 0.62–0.91 0.77 0.07 9.09
Surface area, S (cm
2
) 100 1.39–4.45 3.11 0.63 20.26
Specific surface area, S
s
(cm
2
cm
3
) 100 3.99–7.22 4.88 0.64 13.12
Solid volume, V
s
(cm
3
) 100 0.19–1.11 0.66 0.19 28.79
Bulk volume, V
b
(cm
3
) 100 297.5–300.6 299.78 0.97 19.89
Solid mass, M
s
(g) 100 0.5–1.4 0.86 0.20 23.26
Bulk mass, M
b
(g) 100 197–217 207.4 6.71 3.23
1000-unit-mass, M
u
(g) 100 7400–9900 8960 5.4 6.03
Solid density,
ℓ
s(g cm
3
) 100 0.66–4.67 1.47 0.77 52.38
Bulk density,
ℓ
b(gcm
3
) 100 0.66–0.72 0.69 0.02 2.90
Density ratio,
ℓ
r(%) 100 102.31–699.52 216.57 113.96 52.89
Porosity,
ε
(%) 100 2.26–85.70 44.47 21.68 50.79
Angle of repose, ϕ(
o
) 100 14.83–27.46 20.63 3.35 16.24
Table 5. Comparative average value of some physical properties of the four African culinary enhancers at a glance.
Seed L (cm) W (cm) T (cm) D
a
(cm) S
p
ℓ
s(gcm
3
)
ℓ
b(gcm
3
)R
a
ϕ(
o
)M
u
(kg) S (cm
2
)
Ogbono 3.91 3.13 2.34 3.13 0.64 0.78 0.33 0.8 37.88 11.1 25.61
Ofor 3.41 2.61 1.26 2.43 0.96 0.72 0.59 0.77 27.49 4.0 13.24
Ukpo 2.84 2.81 1.94 2.53 0.94 0.97 0.49 0.99 24.61 7.7 17.79
Achi 2.11 1.62 0.36 1.36 0.48 1.47 0.69 0.77 20.63 9.0 3.11
F.U. Asoiro et al. Heliyon 6 (2020) e04885
5

75.51% respectively. The variation in values may be as a result of the
grinding of the sample. Aviara et al. (2015), however, reported average
values of 17.3 mm, 1316 kg m
3
, 653 kg m
3
, 3.184 kg,35%, and 58% for
arithmetic mean diameter, particle density, bulk density, 1000-unit mass,
porosity, and sphericity at a MC of 8.2% db. The differences are likely
because of different moisture contents and different size composition of
the experimental samples.
Table 3 shows the measured physical properties of Mucuna pruriens
(Ukpo) seed at average moisture content of 11.39 0.82% db. Ukpo seed
has a mean length, width, and thickness of 28.4 1.6 mm, 28.1 1.8
mm, and 19.4 1.8 respectively. Other average physical properties of
Ukpo seed include sphericity (1.11 0.05), aspect ratio (0.99 0.03),
surface area (1779 213 mm
2
), and specific surface area (21.9 1.4
mm
2
/mm
3
). The solid volume, solid mass, and 1000-unit mass of Ukpo
seed is 819 13.0 mm
3
, 7.62 1.03 g, and 7720 33 g respectively. Its
solid density, bulk density, density ratio, porosity, and angle of repose are
0.97 0.30 g cm
3
, 0.49 0.03 g cm
3
, 19.83 5.89%, 45.82 
15.77%, and 24.61 2.94
o
respectively.
Physical properties of Brachystegia eurycoma (Achi) seeds at an
average MC. of 12.64 0.27% db are shown in Table 4. The average
length, width, and thickness of Achi seed is 21.10 0.23 mm, 16.2 
0.23 mm, and 3.6 0.5 mm respectively. Its average solid volume, solid
mass, and 1000-unit mass are 660 190 mm
3
, 0.86 0.20 g, and 8960 
5.4 g respectively. However, Aviara et al. (2014) had reported that the
axial dimensional length, width and thickness increased from 2.29 mm to
2.45 mm, 1.65 mm–1.91 mm and 0.34 mm–0.52 mm respectively, as
moisture content, MC increased from 2.79% to 27.13% d.b. In the same
MC range, one thousand seed weight, particle density, porosity, round-
ness, angle of repose, surface area and sphericity also increased linearly
from 0.901 kg to 1.252 kg, 2270 kg m
3
to 2520 kg m
3
, 11.23%–
15.46%, 35%–47%, 16.8–29.2, 7.67 cm
2
–8.48 cm
2
and67% to 82%
respectively, while bulk density decreased from 745.4 kg m
3
to 613.6 kg
m
3
.
Table 5 shows comparative average values of some physical proper-
ties of the four African culinary enhancers at a glance. Obviously, based
on the arithmetic mean diameter (D
a
), Ogbono seed is larger than Ukpo,
Figure 2. (A) Comparative porosity, density ratio (B) coefficient of static friction and moisture content (db) of four African culinary enhancers.
F.U. Asoiro et al. Heliyon 6 (2020) e04885
6

Ofor, and Achi seeds in that order; but less spherical (S
p
) than Ofor and
Ukpo. The average solid density was higher than the average bulk density
for all the seeds. Similar findings had earlier been documented for Jamin
Syzgium cuminii) seeds (Bajpai et al., 2019). The average solid and bulk
densities (
ℓ
sand
ℓ
b) of Achi seeds were higher than that of Ukpo, Ofor, and
Ogbono seeds. The solid density values showed that Ogbono (0.78 g
cm
3
), Ukpo (0.97 g cm
3
) and Ofor (0.72 g cm
-
3) seeds are lighter and
will most likely float in water except for Achi (1.47 g cm
3
), which make
them easily separated from the mixture with one another or other bio-
materials in water. The aspect ratio (R
a
)ofUkpo is more than that of
Ogbono, Ofor, and Achi seeds. The angle of repose (ϕ)ofOgbono seed is
greater than that of Ofor, Ukpo, and Achi seeds. This indicates that
Ogbono (37.88
o
) seeds aggregate and stick more closely together, fol-
lowed by Ofor (27.49
o
), Ukpo (24.61
o
) and Achi (20.63
o
). The angle of
repose values for Ofor, Ukpo and Achi were clearly within the range of
values (27.37–33.53
o
) for Jamun Syzgium cuminii) seeds as MC
increased from 11.54 to 26% (db) (Bajpai et al., 2019). Equally, Ogbono
seed has the highest 1000-unit mass (M
u
), followed by Achi, Ukpo, and
then Ofor. Again, Ogbono seed had a larger surface area (S), followed by
Ukpo, Ofor, and then Achi seeds.
Based on the size and shape differences, Ukpo and Ofor seeds would
flow or roll down chutes and hoppers more readily than Achi and Ogbono
seeds. On the average, it will be more economical to package and
transport Achi seeds than Ogbono and Ukpo seeds because of its higher
bulk density. Based on the Aspect ratio value, Ukpo seeds would sort
better than Ogbono, Ofor, and Achi seeds in that order. The porosity
values indicate that it would cost more to aerate or dry Achi seeds in
storage than Ukpo, Ofor, and Ogbono seeds in that order due to higher
pressure requirement.
Figure 2 presents the comparative porosity, density ratio, coefficient
of static friction and moisture content (% db). The porosity (
ε
) of Ogbono
seed (52.81%) is greater than that of Ukpo (46.64%), Achi (44.47%) and
Ofor (26.03%) seeds, with similar trend also observed for density ratio.
The increase in porosity is dependent upon the cellular arrangement of
the seeds, bulk and solid densities (Bajpai et al., 2019).
The coefficient of static friction values for Ogbono seeds on surfaces
of aluminum, plastic and corrugated metal falls within the range of
values of 0.37–0.7, 0.3–0.64 and 0.5–0.82 respectively, reported by
Ohaeri and Ohaeri (2015) over a moisture content range (7.02–15.04%
db.). However, the coefficient of static friction for plywood fell slightly
below the range of values (0.6–0.92) reported by Ohaeri and Ohaeri
(2015) over the same moisture content range.
From Figure 2, the nature of material surface used for design of the
conveying material significantly affected the coefficient of static friction.
Similar findings had earlier been reported by Bajpai et al. (2019) for
Jamun Syzgium cuminii) seeds. The trend may be as a result of differ-
ences in surface roughness and the force of cohesion between the seeds
and the material surfaces. Coefficient of static friction gives information
about the friction which the food material has with respect to the ma-
terial surfaces in contact with the material. It is an important property in
the design of conveyors. The entire seeds offered maximum static friction
on corrugated metal sheet and minimum on glass surface, except for Achi
where plastic surface was the minimum. This is likely due to the force of
adhesion and roughness between the contacting surfaces (Singh and
Meghwal, 2019). Ogbono seed with MC of 8.27% db suggests better
storage stability than Ofor (10.96% db), Ukpo (11.39% db) and Achi
(12.64% db).
4. Conclusions
Based on arithmetic mean diameter, Irvingia gabonensis (Ogbono) seed
was larger (31 mm) than Ofor seed (24 mm), Ukpo seed (25 mm), and
Achi seed (14 mm). Ofor seed (0.96) is more spherical than Achi seed
(0.48);Ofor seed therefore has more tendency to roll down a surface than
Achi seed. The mean surface area of Ogbono seed was larger (2561 413
mm
2
) than Ofor seed (1324 129 mm
2
), Ukpo seed (1779 213 mm
2
),
and Achi seed (311 63 mm
2
). Achi seed (0.69 0.02 gcm
3
) has more
bulk weight than Ogbono seed (0.33 0.01 gcm
3
), Ofor seed (0.59 
0.03 gcm
3
), and Ukpo seed (0.49 0.03 gcm
3
). Based on surface of
plywood, the static coefficient of friction of Ogbono seed (0.52 0.04) is
higher than that of Ofor seed (0.33 0.01), Ukpo seed (0.30 0.02) and
Achi seed (0.41 0.02). Ukpo seed with the smallest static coefficient of
friction would therefore flow more easily down a plywood surface than
the other seeds. The high coefficient of variability for properties of
Ogbono seed (3.03–34.42), Ofor seed (2.53–27.78), Ukpo seed
(2.97–34.42), and Achi seed (1.87–52.87) indicates the need to classify
the seeds into large, medium, and small before carrying out any process
operations based on their size. This study has generated baseline data for
the development of processing, handling, storage, packaging and trans-
portation facilities for the seeds studied.
Declarations
Author contribution statement
Felix Uzochukwu Asoiro: Conceived and designed the experiments;
Performed the experiments; Contributed reagents, materials, analysis
tools or data; Wrote the paper.
Sunday Louis Ezeoha: Performed the experiments; Analyzed and
interpreted the data; Contributed reagents, materials, analysis tools or
data; Wrote the paper.
Cosmas Ngozichukwu Anyanwu: Analyzed and interpreted the data;
Contributed reagents, materials, analysis tools or data.
Nneoma Nkem Aneke: Contributed reagents, materials, analysis tools
or data.
Funding statement
This work was supported by the Postharvest Technology Research
Group (PTeRG), University of Nigeria, Nsukka (to pay for transportation
and procurement of experimental materials).
Competing interest statement
The authors declare no conflict of interest.
Additional information
No additional information is available for this paper.
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