Nigerian Journal of Tropical Engineering
Vol. 17 No. 1 |ISSN: 1595-5397| Dec. 2023
DOI: 10.59081/njte.17.1.008
EFFECTS OF MOISTURE CONTENT ON
PHYSICAL PROPERTIES OF PADDY AND
DEHUSKED RICE
1Moses Mazza, 2Lawan Garba Abubakar, 3M. Hamisu
Muhammad, 2OlaosebikanLayi Akangbe, 2Bala Gambo Jahun, 2Mohammed Aminu,
4Abubakar Abdulkarim Jilima
1
Department of Agricultural Engineering, National Cereals Research Institute, Badegi, P.M.B. 8
Bida, Niger State, Nigeria,
2.
Department of Agricultural and Bioresource Engineering, Abubakar Tafawa Balewa
University, P.M.B. 0248, Bauchi, Nigeria,
3.
Department of Mechanical and Production Engineering, Abubakar Tafawa Balewa University,
P.M.B. 0248, Bauchi, Nigeria,
4.
Department of Agricultural and Environmental Engineering, Modibbo Adama University,
Yola, P.M.B 2076, Yola, Adamawa State, Nigeria
Corresponding author’s email: mosesmazza@gmail.com Telephone: +2348032913213
Abstract
The physical properties of rice are among the most important parameters for design of
agricultural machine and other equipment for handling, planting, harvesting, processing,
packaging and storing. This work is aimed at the determination of some of the physical properties
of two varieties of rice at varying moisture content that are important in designing rice handling
machine. The physical properties of two most popular produced rice varieties in Nigeria (FARO
44 and FARO 57) both paddy and dehusked at three different moisture content (5, 10 and 15%)
were determined. Laboratory studies were carried out to determined physical properties of the
two varieties of rice ((FARO 44 and FARO 57) important properties for the laboratory work
includes: bulk density, unit density, roundness, axial dimensions, sphericity, projected areas, unit
volume, unit weight, apparent density, were determined based on different moisture content and
random sampling techniques. The results showed that minimum lengths of dehusked rice ranged
from 4.57 - 5.29 mm while maximum lengths were between 8.21 - 8.25 mm. For paddy these
lengths were minimally 7.65 - 8.78 mm and maximum lengths were 11.39 mm. The least range of
minor diameters of dehusked rice was 4.57 - 5.29 mm and maximally these were 8.21 - 8.25 mm.
Intermediate diameters were minimally 1.43 mm and maximally in the range of 2.71 - 2.78 mm
for dehusked rice; for paddy these were 1.65 - 1.76 mm and 2.46 - 2.78 mm, respectively.
Geometric mean diameters ranged between 3.31 - 4.05 mm. For paddy, projected area obtained
within the range of 11.71 - 29.75 mm2. For dehusked rice, projected area obtained in the range
of 8.79 - 21.19 mm2. Estimates of roundness were not higher than 33.6% for paddy or 54% for
some grains of dehusked rice. The grains appeared more spherical than they were round since
paddy were 35.3 - 48.3% spherical while dehusked grains were 39.8 - 59.4% spherical. Bulk
densities ranged between 531.0 - 553.8 kg/m3 and 839.6 - 852.7 kg/m3 for dehusked forms of Faro
44 and Faro 57, respectively. True density was in the range of 1071.6 - 1566.2 kg/m3.This study
concludes that moisture content and variety affect the engineering property and is useful in the
design, development of machine for processing and handling of rice products.
Keywords: physical properties; rice varieties, form and moisture content of paddy and dehusked
Mazza M. et al.
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Nigerian Journal of Tropical Engineering
Vol. 17 No. 1 |ISSN: 1595-5397| Dec. 2023
DOI: 10.59081/njte.17.1.008
subjecting seeds to oven drying (either air or
vacuum) at temperatures between 80 to 130
0
C for 8hrs to 24hrs by American Society of
Agricultural and Biological Engineers
(ASABE) S352.2 standard [9].
Abdul-Rasaq [10] reported that increase in
moisture content was found to increase the
linear dimensions, mass of 100 seeds,
surface area, apparent volume, true volume
and arithmetic mean diameter. Zareiforoush
[11] Stated that in order to design
harvesting, conveying and processing
equipments, it is necessary to determine
physical properties of grains. Zareiforoush
[12] investigated the impact of moisture
content on two Iranian paddy rice varieties
(Alikazemi and Hashemi) at five moisture
levels ranging from 8% to 21% (dry basis)
and reported that increased moisture content
led to: Increased grain dimensions (length,
width, thickness), Higher equivalent
diameter, Larger surface area and volume,
Higher sphericity (roundness), Increased
angle of repose (flowability), Decreased
bulk density and true density.
Arije [13] reported that the principal axial
dimensions of rye seeds are useful in
selecting sieve separators and in calculating
power during the rye milling process.
Mujumdar [14] reported that Knowing the
grain’s bulk density, true density and
porosity can be useful in sizing grain
hoppers and storage facilities: they can
affect the rate of heat and mass transfer of
moisture during the aeration and drying
processes. Cereal-grain kernel densities
have been of interest in breakage
susceptibility and hardness studies [15].
Researchers Nimkar [16] evaluated the
physical properties of green gram
(Phaseulus aureus L.) as a function of
moisture content in the range of 8.39 to
33.40% d.b and reported that the average
length, width, thickness and the mass of
thousand seeds were 4.21 mm, 3.17 mm,
3.08 mm, and 28.19 g, respectively at
1. Introduction
Rice (Oryza sativa) belongs to the grass
family of Gramineae, it is among the major
sources of carbohydrate, more than half of
the human race regard and consume rice as
their staple food [1 and 2]. It is highly valued
and competitive commodity in the world
trade over a decade’s [3 and 4]. Oryza-sativa
is the dominant specie followed by Orizaglaberrima and is regarded third most
popular crop after wheat and maize in world
crop production [3]. More than four (4)
billions of world population depends on rice
as their major source of calories [5].
Information on the physical and mechanical
properties of the agricultural products is an
important tool for designing equipment for
the purpose of planting, harvesting,
dehulling, drying, handling as well as
storing. Therefore, seed dimensions (width,
thickness and length), 1000 seed mass
(M1000), surface area, porosity, sphericity,
static coefficient of friction against different
materials, repose angle, hardness, true and
bulk densities are among the properties that
are considered “physical” by researchers as
per seed [6]. These variables are central in
classification of seeds and in the design of
machines for processing or analyzing the
behavior of the product in handling or
grading [7 and 8]. They are central because
they give technical information to the
designer on what are the basic “inputs” for
their design.
All physical properties of seeds are
dependent on the moisture content. They
respond either in increasing or decreasing
trend as the moisture content varies. The
initial moisture content is determined by
Mazza M. et al.
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Nigerian Journal of Tropical Engineering
Vol. 17 No. 1 |ISSN: 1595-5397| Dec. 2023
DOI: 10.59081/njte.17.1.008
moisture content of 8.39% (d.b.). Also, the
geometric mean diameter increased from
3.45 to 3.77 mm, whereas sphericity
decreased from 0.840 to 0.815. They
observed that with the increase of moisture
content the bulk and true densities decreased
from 807 to 708 kg/m³ and from 1,363 to
1,292
kg
/m³,
respectively.
The
corresponding bulk porosity increased from
40.77 to 45.16%. The static coefficient of
friction is used to determine the angle at
which chutes must be positioned to achieve
consistent flow of materials through the
chute.
The aim of this research is to determine the
physical properties of FARO 44 and FARO
57 rice varieties both paddy and de-husked
as influence by 5,10 and 15% moisture
contents.
𝑊 −𝑊𝑏
𝑀𝐶𝑤𝑏 = 100 × [ 𝑎𝑊
2. MATERIALS AND METHODS
The materials used in this research includes:
Hot air oven,
Weighing balance,
Photographic enlarger, Planimeter, Drawing
set, Toluene, density bottle, FARO 44 and
FARO 57 both paddy and dehusked.
Pycnometer, cold bath, ice block, dry bulb
thermometer, distilled water and sensitive
weighing balance.
𝑎
𝑊 −𝑊𝑏
𝑀𝐶𝑑𝑏 = 100 × [ 𝑎𝑊
𝑏
]
… (1)
]
… (2)
Where:
𝑀𝐶𝑤𝑏 is Moisture content, wet basis, %
𝑀𝐶𝑑𝑏 is Moisture content, dry basis, %
𝑊𝑎 is Weight of water in the sample, g
𝑊𝑏 is Weight of dry matter in the sample, g
2.1
Preparation of sample for the
determination of the properties
The two samples of rice (FARO 44 and
FARO 57) were used for the laboratory
analysis to determine the physical properties.
The samples both paddy and dehusked of
FARO 44 and FARO 57 were selected,
cleaned and sorted by removing broken, split,
spoiled and deformed seeds before the
commencement of laboratory work.
2.3
Determination of the size of paddy
and dehusked rice
Major, minor and intermediate diameters of
paddy and dehusked rice were measured as
𝐴, 𝐵, 𝐶 using photographic enlarger and
graduated transparent ruler at the three
different levels of moisture contents of 5, 10
and 15%. The tri-axial dimensions were used
in Equation (3) to calculate the mean
geometric diameter as reported by [18]
2.2
Moisture content determination;
The moisture contents of the samples were
determined using the procedure specified by
ASABE S352.2 standard [9]. The sample
were oven dried at 105oC for 72 hours, the
weight loss of the samples were recorded and
the moisture contents in percentage were
determined on wet basis and dry basis using
Equations (1 and 2) as reported by [17].
1
𝐺𝑚 = ⌈𝐴 × 𝐵 × 𝐶⌉ ⁄3
... (3)
Where;
𝐺𝑚 𝑖𝑠 𝑔𝑒𝑜𝑚𝑒𝑡𝑟𝑖𝑐𝑎𝑙 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟, mm
𝐴 𝑖𝑠 𝑡ℎ𝑒 𝑚𝑎𝑗𝑜𝑟 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟, 𝑚𝑚
𝐵 𝑖𝑠 𝑚𝑖𝑛𝑜𝑟 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟, 𝑚𝑚
𝐶 𝑖𝑠 𝑡ℎ𝑒 𝑖𝑛𝑡𝑒𝑟𝑚𝑒𝑑𝑖𝑎𝑡𝑒 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟, 𝑚𝑚
Mazza M. et al.
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Nigerian Journal of Tropical Engineering
Vol. 17 No. 1 |ISSN: 1595-5397| Dec. 2023
DOI: 10.59081/njte.17.1.008
𝑉𝐶 𝑖𝑠 𝑡ℎ𝑒 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑜𝑛𝑡𝑎𝑖𝑛𝑒𝑟, 𝑐𝑚3
2.4 Determination of the roundness and
sphericity of paddy and dehusked rice.
A photographic enlarger was used to project
the area of the rice on the vertical wall and
trace the seeds shadow at their natural rest
position and when the seeds were turn by 90o
and twist vertically to 180o. Millimetre scales
were also projected with the seeds and the
area (𝐴𝑐 ) of circumscribed circle were then
calculated using Equation (4).
𝐴𝑐 =
𝜋𝑑𝑐 2
2.7 Determination of true density
Ratio of mass of sample of seeds to its true
volume is called true density. It was
determined by using toluene displacement
method reported by [18]. The true density
was then be calculated using Equation (8)
available in [18].
𝑇𝑟𝑢𝑒 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 (𝜌𝑡 ) =
… (4)
4
… (5)
𝑐
1
𝑆𝑝ℎ𝑒𝑟𝑖𝑐𝑖𝑡𝑦 = 100 × [
(𝐴×𝐵×𝐶) ⁄3
𝐴
]
… (6)
2.5 Determination of Seed weights
Single seed weights and one thousand seed
weights were determined for FARO 44 and
FARO 57 (Paddy and dehusked) seeds
following the method described by [18].
2.6 Determination of bulk density
The bulk density 𝜌𝑏 is the ratio of the sample
mass of seeds to its total volume , The bulk
density of the seeds was then calculated using
Equation (7) as reported by [19.
𝑀
𝐵𝑢𝑙𝑘 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 (𝜌𝑏 ) = 𝑉 𝑆
𝐶
...8
2.8 Experimental Design
A random sampling technique was carried
out, Two varieties (FARO 44 and FARO 57),
two form (paddy and de-husked) and
moisture content at three levels (5, 10 and
15%) where used giving a total of 2x2x3=12
treatments at single replication. It was
replicated 3 times making a total of 36
treatments for bulk density, true density. And
50 sample were randomly selected making a
total of 50x2x2x3=600 experiment for size
and
shape.
Total
600+36+36=672
experiment
The Projected (𝐴𝑝 ) and circumscribed areas
were used in Equations (5) and (6) to
compute the roundness and sphericity of the
grains respectively as reported by [18].
𝐴𝑝
𝑉𝑤
Where:
𝑀𝑆 𝑖𝑠 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 𝑠𝑢𝑠𝑝𝑒𝑛𝑑𝑒𝑑 𝑖𝑛 𝑎𝑖𝑟, 𝑔
𝑉𝑤 𝑖𝑠 𝑡ℎ𝑒 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑑, 𝑐𝑚3
Where:
𝐴𝑐 is area of circumscribed circle, mm2
𝑑𝑐 is diameter of circumscribed circle, mm
𝑅𝑜𝑢𝑛𝑑𝑛𝑒𝑠𝑠 = 100 × ( 𝐴 )
𝑀𝑆
... (7)
Where:
𝑀𝑆 𝑖𝑠 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 𝑓𝑖𝑙𝑙𝑒𝑑 𝑡ℎ𝑒 𝑐𝑜𝑛𝑡𝑎𝑖𝑛𝑒𝑟, 𝑔
Mazza M. et al.
75
3.
Results and discussion
Results of the analysis of variance (ANOVA)
carried out on the data generated in the
laboratory on physical properties of paddy
and dehusked forms of Faro 44 and Faro 57
rice varieties at 5, 10 and 15% product
moisture contents in wet basis are provided in
Table 1. The main effects on rice form and
moisture content each had highly significant
effect on major diameter of rice grains and so
did the interaction of rice form with moisture
content and the interaction of rice variety,
Nigerian Journal of Tropical Engineering
Vol. 17 No. 1 |ISSN: 1595-5397| Dec. 2023
DOI: 10.59081/njte.17.1.008
rice form and moisture content with each
other. Variety and its separate interactions
with each of product form and moisture had
no significant effect on observed variations in
major diameters of rice grains. As for minor
diameter, only the interaction of rice variety
with rice form had no significant effect. All
the main factors (that is, variety, form and
moisture) and the other interactions had
significant effects on variations observed in
minor diameters of rice grains. All the factors
considered, as well as their interactions, had
highly significant effects on intermediate
diameter, except for the effects of the
interaction of rice variety with rice form and
that of the interactions of the three main
influence factors together, both of which had
no significant effects on this property of rice
grains. This last trend was observed to be true
for the geometric mean diameter on which
the interaction of rice variety and rice form
and of rice variety, rice form and moisture
content had no significant effect (Table 1).
Again, all the factors considered in this study
and their interactions had effect of the
projected areas of rice grains. Only the level
of moisture and the interaction of rice variety
with rice form did not have significant effect
on the roundness of rice grains. All main
factors and the remaining interactions had
highly significant effects on roundness of rice
grains. Only rice variety, rice form, the
interaction between rice form and moisture
content and the interaction of rice variety
with both of rice form and moisture content,
together, had highly significant effect on the
sphericity of rice grains. Rice form and
moisture content did not have significant
effect on bulk density, as also the interaction
of the three factors (Table 1)
Table 1: ANOVA on the effects of rice variety, rice form and moisture content on physical
properties
Source of variation
Property
Major diameter, a (mm)
Minor diameter, b (mm)
Intermediate diameter, c (mm)
Geometric mean diameter, d
(mm)
Projected Area, Ap (mm2)
Roundness, R (%)
Sphericity, S (%)
Bulk density, b (kg/m3)
Variety
0.071
<0.001
<0.001
<0.001
Form
<0.001
<0.001
<0.001
<0.001
Variety
X
Moisture Form
<0.001
0.089
<0.001
0.321
<0.001
0.088
<0.001
0.291
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
0.166
<0.001
0.175
0.101
0.242
Probability (p) values less than 0.05 indicate
significance, at the 5% level and p values less
than 0.01 indicate significance at the 1%
<0.001
0.038
0.076
<0.001
Variety
X
Moisture
0.115
0.001
<0.001
<0.001
Form
X
Moisture
<0.001
<0.001
<0.001
0.001
Variety
X
Form
X Moisture
<0.001
0.025
0.34
0.978
<0.001
<0.001
0.147
<0.001
0.019
0.001
<0.001
0.006
0.04
0.035
<0.001
0.098
level; where p values are greater than 0.05,
observed effects are not significant
statistically.
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Nigerian Journal of Tropical Engineering
Vol. 17 No. 1 |ISSN: 1595-5397| Dec. 2023
DOI: 10.59081/njte.17.1.008
Table 2: Main effects of variety, form and moisture content on some properties of rice
Property
Major diameter, a (mm)
Minor diameter, b (mm)
Intermediate diameter, c
(mm)
Geometric mean diameter, d
(mm)
Projected Area, 𝐴𝑝 (mm2)
Roundness, R (%)
Sphericity, S (%)
Bulk density, 𝜌𝑏 (kg/m3)
True density, 𝜌𝑡 (kg/m3)
Faro 57
8.379a
3.0183a
Form
Dehusked
6.793b
2.696b
Paddy
9.884a
3.0233a
Moisture content
(%, dry basis)
5
10
8.054b
8.459a
2.7686c 2.8688b
2.0791b
2.1432a
1.9902b
2.2321a
2.0479c
2.1052b
2.1804a
3.5837b
3.7715a
3.3067b
4.0485a
3.557b
3.6972a
3.7786a
16.04b
27.73b
44.15b
552.6b
1191.89
18.578a
30.29a
45.77a
830.82a
1268.50
13.315b
34.75a
48.89a
693.13a
1357.27
21.303a
23.27b
41.03b
690.28a
1085.13
16.053b
29.24a
45.19a
691.3a
1175.58
17.869a
29.36a
44.62a
694a
1251.76
18.004a
28.43a
45.07a
689.82a
1263.24
Variety
Faro 44
8.298a
2.7009b
15
8.502a
2.9414a
Means comparison is restricted within factor subsets and is property-wise. Values with the same
alphabets are not significantly different, statistically
Major diameter of Faro 57 paddy ranged
from 8.78 - 11.39 mm. Major diameter of
3.1 Effects of Variety, Form and Moisture
dehusked Faro 57 rice ranged from 5.29 Content of Rice on Major Diameter
8.25 mm. Also, major diameter tended to
The main effects of variety, form and
increase as product moisture content
moisture content on physical properties of the
increased (Table 2). Empirical relating the
varieties of rice used are presented in Table
influence of moisture content on changes in
2. Mean major diameter of Faro 44 was 8.29
major diameter of rice grains tended to be
mm while that of Faro 57 was 8.38 mm.
either linear or parabolic in nature, depending
Dehusked rice was 6.79 mm long while a
on the form and variety (Figure 1). These
grain of rice paddy was 9.88 mm, on the
relationships are presented in Table 3. Based
average. Apparently, paddy grains were
on the coefficients of determination (R2)
longer than grains of dehusked rice. Major
values obtained, it may be seen (Table 3) that
diameter of Faro 44 paddy ranged from 7.65
up to 85.36 - 100% of the changes in this
- 11.39 mm while those of dehusked forms of
property as a function of moisture content are
this variety ranged from 4.57 - 8.21 mm.
explained by these relationships
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DOI: 10.59081/njte.17.1.008
12
Major diameter (mm)
10
8
6
4
Faro 44 Paddy
Faro 44 Dehusked
2
Faro 57 Paddy
Faro 57 Dehusked
0
4
6
8
10
12
Moisture content (%)
14
16
Figure 1: Effect of moisture content on major diameter
Table 3: Dependence of major diameter (mm) on moisture content
Variety
M2
M
C
R2
Faro 44 Paddy
-0.0027
0.0473
9.7235
1.0000
0.0738
5.9765
0.8536
0.5160
7.5232
1.0000
0.0763
6.1096
0.9110
Faro 44 Dehusked
Faro 57 Paddy
-0.0240
Faro 57 Dehusked
M = moisture content (%, dry basis
3.2 Effects of Variety, Form and Moisture
Content of Rice on Minor Diameter
As for minor diameters of rice grains, they
ranged from 3.1-3.5 mm for paddy forms of
Faro 57 and 2.5 – 2.6 mm of dehusked forms
of the same variety. Paddy forms of Faro 44
variety of rice had minor diameters ranging
between 2.7 – 2.8 mm and dehusked forms
had minor diameters ranging between 2.5 –
2.6 mm. Faro 57 had significantly higher
minor diameter than Faro 44 and minor
diameters of paddy forms of the rice grains
were significantly higher than those of the
dehusked forms (Table 2). Minor diameter
tended to increase as moisture content
increased. When empirical relationships were
fitted to these trends, it was observed that
these trends differed by rice variety and form
(Figure 2 and Table 4)
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DOI: 10.59081/njte.17.1.008
Table 4: Dependence of minor diameter (mm) on moisture content
Variety
Faro 44 Paddy
M2
M
0.0250
C
2.6044
R2
0.8443
Faro 44 Dehusked
Faro 57 Paddy
-0.0020
0.0300
0.0360
2.4030
2.8321
1.0000
0.8413
0.0102
2.7429
M = moisture content (%, dry basis)
0.7732
Faro 57 Dehusked
4
3.5
Minor diameter (mm)
3
2.5
2
Faro 44 Paddy
1.5
Faro 44 Dehusked
Faro 57 Paddy
1
0.5
0
4
6
8
10
12
Moisture content (%)
14
16
Figure 2: Effect of moisture content on minor diameter
grains of rice while Faro 57 had significantly
larger intermediate diameters than Faro 44.
As moisture level increased, intermediate
diameter Increased. Relationships fitted to
intermediate diameters of these rice varieties
in relation to the indicated moisture levels
using the method of least squares are
presented in Figure 3. The relationships fitted
were purely linear in nature and appeared to
explain between 78.8 - 100% of the changes
3.3 Effects of Variety, Form and Moisture
Content of Rice on Intermediate Diameter
Intermediate diameters of grains of Faro 44
ranged between 1.65 - 2.46 mm and 1.43 2.71 mm for paddy and dehusked forms,
respectively. For Faro 57 however,
intermediate diameters of grains of paddy
and dehusked rice ranged between 1.76 - 2.78
mm and 1.43 - 2.68 mm, respectively.
Intermediate diameters were significantly
higher for paddy forms than for dehusked
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in intermediate diameter as a function of
changes in moisture content (Table5)
Intermediate diameter (mm)
2.5
2
1.5
1
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
0.5
0
4
6
8
10
12
Moisture content (%)
14
16
Figure 3: Effect of moisture content on intermediate diameter
Table 5: Dependence of intermediate diameter (mm) on moisture content
Variety
Faro 44 Paddy
Faro 44 Dehusked
M2
M
-0.0061
0.0182
Faro 57 Paddy
Faro 57 Dehusked
C
2.2491
1.7888
R2
0.8933
0.8022
0.0053
2.2234
0.7880
0.0357
1.6530
1.0000
M = moisture content (%, dry basis)
mean diameter was 3.58 mm. Grains of
paddy were significantly larger at 4.05 mm
3.4 Effects of Variety, Form and Moisture
than grains of dehusked rice which had mean
Content of Rice on Geometric Mean
geometric diameter of 3.31 mm. Moisture
Diameter
increase tended to influence change in
Geometric mean diameters of the grains of
geometric mean diameter positively (Figure
rice sampled are presented in Table 2. These
4). Moisture dependence relations of
diameters differed significantly along
geometric mean diameter are presented in
varietal lines and with the form of rice. Faro
Table 6. It was observed that although mean
57 had grains with significantly larger
geometric diameter was least at the lowest
representative geometric mean diameters
moisture content
(3.78 mm) than Faro 44 whose geometric
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Geometric mean diameter (mm)
4.5
4
3.5
3
2.5
2
1.5
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
1
0.5
0
4
6
8
10
12
Moisture content (%)
14
16
Figure 4: Effect of moisture content on geometric mean diameter
Table 6: Dependence of geometric mean diameter (mm) on moisture content
Variety
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
M2
-0.0026
-0.0010
C
3.6576
2.9316
R2
1.0000
1.0000
0.0238
3.9133
0.0370
3.0220
M = moisture content (%, dry basis)
0.9617
0.9983
M
0.0595
0.0403
(Table 2), gains in geometric mean diameter
as a result of increase in moisture content
were similar at 10 and 15% moisture
contents. Only curvilinear trends were found
to fit the data for Faro 44 were Faro equations
describing the dependence of geometric
mean diameter in Faro 57 on moisture
content were observed to be satisfactorily
linear (Table 6).
3.5 Effects of Variety, Form and Moisture
Content of Rice on Projected Area
As for projected area (Table 2), it was
significantly larger for Faro 57 being
18.58mm2 than for Faro 44 (which was 16.04
mm2). Mean projected area of paddy grain
was larger at 21.3 mm than that of dehusked
rice which was 13.32 mm. This property
tended to be influenced significantly by
moisture content (Figure 5). The
relationships obtained are presented in Table
7 and all were only satisfactorily parabolic in
nature.
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30
Projected area (mm2)
25
20
15
10
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
5
0
4
6
8
10
12
Moisture content (%)
14
16
Figure 5: Effect of moisture content on projected area
Table 7: Dependence of projected area (mm2) on moisture content
Variety
Faro 44 Paddy
M2
-0.0575
M
1.2621
C
13.6660
R2
1.0000
Faro 44 Dehusked
Faro 57 Paddy
-0.0557
-0.0452
1.2420
1.1284
6.5825
17.0180
1.0000
1.0000
0.0239
-0.1627
12.9610
M = moisture content (%, dry basis)
1.0000
Faro 57 Dehusked
As to the bounds of the parameter
determined, projected area ranged between
11.71 - 26.51 mm2 and 14.44 - 29.75 mm2 for
paddy forms of Faro 44 and Faro 57,
respectively. As for dehusked forms of Faro
44 and Faro 57, projected areas ranged
between 9.00 - 18.24 mm2 and 8.79 - 21.19
mm2, respectively.
roundness, it was observed that the seeds
were hardly round since they possessed low
roundness of values in the range of 10.19 37.67% and 11.07 - 33.60% for paddy forms
of Faro 44 and Faro 57 varieties of rice.
Dehusked grains of Faro 44 and Faro 57 had
roundness values in the range of 18.22 46.15% and 17.10 - 54.11%, respectively.
The values were however larger for Faro 57
than for Faro 44 and for paddy than for
dehusked grains (Table 2). Moisture level
within the range studies did not seem to
modify the shape of rice grains much in terms
3.6 Effects of Variety, Form and Moisture
Content of Rice on Shape
When it was sought to describe the grains of
the two varieties of rice in terms of
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of their roundness as noticeable changes
resulting from moisture variation were not
statistically significant (Table 2). The relative
differences in these proportions by factor
subsets are indicated in Figure 6. However,
relationships for changes that may be
obtained in roundness proportions in terms of
moisture content are presented in Table 8.
40
35
Roundness (%)
30
25
20
15
10
Faro 44 Paddy
5
Faro 44
Dehusked
0
4
6
8
10
12
Moisture content (%)
14
16
Figure 6: Effect of moisture content on roundness
Table 8: Dependence of roundness (%) on moisture content
Variety
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
M2
0.0182
C
25.6960
R2
1.0000
0.1183
-2.4757
44.8800
-0.0997
1.7246
19.3950
-0.1207
2.7367
22.2910
M = moisture content (%, dry basis)
1.0000
1.0000
1.0000
M
-0.6292
When it again it was sought to describe the
shape of the grains in terms of their
sphericities, not much improvement was
recorded. Sphericity of rice grain of Faro 44
and Faro 57 varieties ranged respectively
between 35.33 - 49.70% and 35.61 - 48.25%
for paddy and 39.79 - 59.36% and 42.11 58.17%, also respectively, for dehusked
grains.From the mean values, however, these
varieties of Nigerian grown rice may be
better defined in terms of their sphericities
than in terms of their roundness since they
possess larger values of sphericity than they
do of roundness (Table 2). The comparative
differences in these proportions are indicated
in Figure 7. Changes that may be had in
sphericity as moisture level increases, though
not significant on the average (Table 2) may
be determined using the empirical equations
generated using the method of least squares
and presented in Table 9.
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60
Sphericity (%)
50
40
30
20
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
10
0
4
6
8
10
12
Moisture content (%)
14
16
Figure 7: Effect of moisture content on sphericity
Table 9: Dependence of sphericity (%) on moisture content
Variety
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
M2
-0.0148
C
37.7590
R2
1.0000
0.0656
1.5444
56.0670
0.0833
1.5798
48.1290
-0.0527
1.0495
45.1480
M = moisture content (%, dry basis)
1.0000
1.0000
1.0000
M
0.3990
the grains within the limits studied did not
significantly alter the bulk density of any of
the two varieties of rice investigated (Table
2). Bulk density ranged between 551.0 580.1 kg/m3 and 800.8 - 829.3 kg/m3 for
paddy forms of Faro 44 and Faro 57,
respectively and between 531.0 - 553.8 kg/m3
and 839.6 - 852.7 kg/m3 for dehusked forms
of Faro 44 and Faro 57, respectively. The
relative differences in bulk density for the
different forms of rice are indicated in Figure
8. Within the range of moisture contents
studied, empirical equations describing the
3.7
Volume, Mass and Density
Relations
For volume and mass relationships, bulk and
true densities of grains of the two varieties of
rice were determined in paddy and dehusked
forms at the stated moisture levels. Bulk
density of grains of Faro 57 was found to be
significantly higher than that of Faro 44, both
being 830.82 kg/m3 and 552.6 kg/m3,
respectively. This property did not differ
significantly for paddy and dehusked forms,
on the average. Increasing moisture level in
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relationship between bulk densities of the
two rice varieties and changes in moisture
content are given in table 10.
10 and 15% product moisture contents were
1175.58 kg/m3, 1251.76 kg/m3 and 1263.24
kg/m3, respectively. True density of Faro 44
variety of rice was found to occur within the
range of 1071.63 - 1234.0 kg/m3 for paddy
and 1272.56 - 1357.4 kg/m3 for dehusked
grains. True density of grains of Faro 57
ranged between 1057.71 -1071.64 kg/m3 for
paddy and 1428.85 - 1566.23 kg/m3 for
dehusked
grains.
The
comparative
differences in true density for the forms of the
grains and the relationships describing these
are presented in Figure 9 and Table 11,
respectively.
Mean true density for Faro 44 was
determined to be 1191.89kg/m3 while that for
Faro 57 was found to be 1268.50 kg/m3.
Paddy forms had mean true density of
1085.13 kg/m3 while dehusked grains had
mean true density of 1357.27 kg/m3. Within
the range of moisture contents evaluated, it
was observed that true density tended to
increase with increasing moisture content, on
the average. Mean values of true density at 5,
900
800
Bulk density (kg/m3)
700
600
500
400
300
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
200
100
0
4
6
8
10
12
Moisture content (%)
14
16
Figure 8: Effect of moisture content on bulk density
Table 10: Dependence of bulk density (kg/m3) on moisture content
Variety
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
M2
-0.4145
M
8.6127
C
526.65
R2
1.0000
-0.2396
1.5780
-2.0534
4.3539
525.00
836.68
829.90
0.7681
0.9298
1.0000
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M = moisture content (%, dry basis)
1800
1600
True density (kg/m3)
1400
1200
1000
800
600
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
400
200
0
4
6
8
10
Moisture content (%)
12
14
16
Figure 9: Effect of moisture content on true density
Table 11: Dependence of true density (kg/m3) on moisture content
Variety
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
M2
-7.5664
M
156.6900
C
423.78
R2
1.0000
-0.5567
15.9690
11.1340
1116.20
1016.00
0.9987
1.0000
13.7390
1337.30
M = moisture content (%, dry basis)
0.7500
surge from 5 to 15%. Geometric mean diameters
and projected area also increase as the moisture
content increase while roundness, sphericity and
bulk density were not significantly affected by
increase in moisture content but true was found to
be positively correlated to moisture content and
increases from 1175.58 to 1263.24 kg/m3). This
results will assist researchers and in designing
machines for handling and processing of rice.
4.
Conclusion
In this study, some design-related
physical properties of two varieties of rice
commonly grown in Nigeria were determined
using standard laboratory techniques and
following standards recommended in
literature. Major, minor and intermediate
diameter of Faro 44 and 57 Dehusked and paddy
increased from 8.05 to 8.51, 2.77 to 2.94 and 2.04
to 2.18 mm respectively as the moisture content
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Recommendations
1. These results may only be employed
for operations to be carried out within
the range of moisture contents
employed for their determination.
2. Caution should be exercised with the
use of the geometric mean diameter.
It is recommended that this property
be limited in its use for the
determination
of
aerodynamic
parameters. Where size consideration
is the object, it is appropriate to make
direct employment of the major,
minor and intermediate diameters and
not a pooled average of the nature of
the geometric mean diameter.
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Shamsudin, R., & Che Man, H. (2022).
Rice for Food Security: Revisiting Its
Production, Diversity, Rice Milling
Process
and
Nutrient
Content.
Agriculture,
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