Nigerian Journal of Tropical Engineering
Vol. 18 No. 1 |ISSN: 1595-5397| Apr. 2024
DOI: 10.59081/njte.18.1.005
EFFECT OF MOISTURE CONTENT ON SOME SELECTED
MECHANICAL PROPERTIES OF FARO 44 AND 57 VARIETY OF
RICE (PADDY AND DEHUSKED)
Moses Mazza1,2*, Lawan Garba Abubakar2, M. Hamisu Muhammad3,
OlaosebikanLayi Akangbe2, Bala Gambo Jahun2, Mohammed Aminu2,
Abubakar Abdulkarim Jilima4, Danlad Drambi Usman2, Suleiman Haruna5
1
Department of Agricultural Engineering, National Cereals Research Institute, Badegi, P.M.B. 8 Bida,
912101, Nigeria
2
Department of Agricultural and BioresourceEngineering, 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
5
Department of Agricultural and Bioenvironmental Engineering, Federal Polytechnic P.M.B.0231,
Bauchi
*Corresponding author email: mosesmazza@gmail.com Telephone: +2348032913213
Abstract
The mechanical properties of rice are among the most important parameters for designing and development
of a rice milling machine, destoning machine as well as materials handling. The objective of the study was
to determine the mechanical (angle of sliding and internal frictions) properties of (FARO 44 and FARO
57) paddy and dehusked at three different moisture content (5, 10 and 15%) moisture content dry basis.
These properties were determined using Funnel and Baker technique and shear box apparatus respectively.
The results showed that, angles of internal friction were at least 15.2°, on the average within the moisture
ranges tested however, 35° angles were also obtained. Angles of sliding friction ranged between 40° - 50°.
This study concludes that moisture content and variety affect the engineering property; angle of internal
friction is useful in the determination of lateral and horizontal stress in the silo for grain storage.
Keywords: rice varieties, form, mechanical properties, and moisture content
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].
It is highly valued and competitive commodity in
the world trade over a decade’s [2 and 1]. Oryza
sativa is the dominant species followed by Oriza
glaberrima and is regarded as the third most
popular crop after wheat and maize in world crop
production [3 and 4]. More than four (4) billions
of world population depends on rice as their
major source of calories [3]. 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 and
storage therefore, static coefficient of friction of
seeds (rice) against different materials, angle of
repose, hardness, true and bulk densities are
among the properties that are considered 49
“physical” by researchers as per seed [5]. These
variables are central in classification of seeds and
in the design of machines for processing or
analyzing the behavior of the products in
handling or grading [6]. They are central because
they give technical information to the designer on
what are the basic “inputs” for their design.
All mechanical properties of seeds are dependent
on the moisture content. They respond either in
increasing or decreasing angle of sliding friction
and angle of internal friction as the moisture
content varies. The initial moisture content is
determined by subjecting seeds to oven drying
(either air or vacuum) at temperatures between
80oC to 130oC for 8hrs to 24hrs by [7]. [8] stated
that in order to design a harvesting, conveying
and processing equipment, it is necessary for the
determination of physical and mechanical
properties of grains [9] studied the effect of
moisture content on the physical properties for
Nigerian Journal of Tropical Engineering
Vol. 18 No. 1 |ISSN: 1595-5397| Apr. 2024
three Egyptian paddy rice varieties, they recorded
the increase occurring in seed sphericity (S) due
to the increase of moisture content .Cereal-grain
kernel densities have been of interest in breakage
susceptibility and hardness. [10 and 11] reported
that various physical properties of green beans
(Phaseulus aureus L.) were evaluated as a
function of moisture content in the range of 8.39
to 33.40% db. 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.
Mechanical properties of rice is very important in
the design of rice processing machine, milling
machine, and destoning machine Frictional
coefficient and angle of repose influence the flow
of rice materials in machine and outlets. Flow
ability of materials which is characterized by the
angle of repose and the coefficient of friction on
a particular surface determined the type of
handling system and its components [12].
According to [13] have reported an increase in
moisture content was found to increase the linear
dimensions, mass of 100 seeds, surface area,
apparent volume, true volume, arithmetic mean
diameter,
effective
geometric
diameter,
sphericity, angle of repose, porosity and static
coefficient of friction while bulk density and true
density decreased with increase in moisture
content. The purpose of this study was to
determine the effect of moisture content on the
mechanical properties of FARO44 and FARO57
rice which is the most common rice variety
grown in Nigeria. Therefore, machine designers
and engineers can utilize this information for
future design of equipment related to rice seed,
specifically FARO44 and FARO57variety.
2.
MATERIALS AND METHODS
The materials used in this research includes Hot
air oven, angle of repose apparatus galvanized
steel and mild steel, Shear box apparatus, FARO
44 and FARO 57 both paddy and dehusked.
Experimental Design: A random sampling
technique was carried out, two variety, two form,
three. For angle of sliding friction; 2x2x3x3=36
experiment and angle of internal friction;
2x2x3x3=36, total 36+36 =72 experiment.
2.1 Moisture content determination
The moisture contents of the samples were
determined using the procedure reported by [14]. 50
DOI: 10.59081/njte.18.1.005
The sample were oven dried at 130±3oC for 2
hours, the weight loss of the samples was
recorded and the moisture contents in percentage
were determined in dry basis using Equation (1)
[15]
𝑊 −𝑊
𝑀𝐶𝑑𝑏 = 100 × [ 𝑎𝑊 𝑏]
… (1)
𝑏
Where:
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
2.2
Determination of Angle of sliding
friction.
The coefficient of friction of the seeds is equal to
the tangent of the angle of internal friction for the
material [6], this was determined on plywood,
glass and galvanized steel surfaces using a tilting
table. The angle of inclination of the table to the
horizontal at which samples started sliding was
measured with the protractor attached beside the
inclined plane apparatus and used in Equation
(13) to calculate the static coefficient of friction]
and reported by [14]
𝜇 = tan 𝛼
... (2)
Where:
𝜇 𝑖𝑠 𝑠𝑡𝑎𝑡𝑖𝑐 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑒𝑛𝑡 𝑜𝑓 𝑓𝑟𝑖𝑐𝑡𝑖𝑜𝑛
𝛼 𝑖𝑠 𝑎𝑛𝑔𝑙𝑒 𝑜𝑓 𝑡𝑖𝑙𝑡 𝑖𝑛 𝑑𝑒𝑔𝑟𝑒𝑒𝑠
(Angle
internal friction)
of
2.3 Determination of Angle of Internal
friction.
While there's no single ISO standard specifically for
the angle of internal friction of grains, ISO 178924:2017 provides a framework for determining shear
strength parameters, including the angle of internal
friction grains, direct shear test Shear box apparatus
was used to determine the shear stress of the rice
at different moisture content. The normal stress
(𝜎), Apparent cohesion (C) and the shear stress at
failure (𝜏) were determined and used Coulomb’s
equation (3) to determine the angle of internal
friction.
𝜏 = 𝐶 + 𝜎 tan ∅
... (3)
Where:
𝜏 = shear strength of the rice (KN/m2)
𝐶 = Apparent cohesion of the rice (KN/m2)
𝜎 = normal stress on the plane of rupture
(KN/m2)
∅ = angle of internal friction (degree)
Nigerian Journal of Tropical Engineering
Vol. 18 No. 1 |ISSN: 1595-5397| Apr. 2024
DOI: 10.59081/njte.18.1.005
3. Results and discussion
Results of the analysis of variance carried out on
the data generated in the laboratory on
mechanical properties of paddy and dehusked
forms of Faro 44 and Faro 57 rice varieties at 5,
10 and 15% product moisture contents in dry
basis are provided in Table 1. Only form,
moisture content and the interaction between
variety and form had significant influence on the
angle of sliding friction of rice grains on
galvanized steel surface and it is in-line with the
findings by [16] to have reported the sliding
friction increases with increase in moisture
content on galvanized steel when the same
property was determined on mild steel surface,
only form and moisture were observed to be the
important influence parameters responsible for
observed variations in angle of sliding friction of
the grown rice varieties on mild steel surface.
Table 1: ANOVA on effects of Rice variety, Rice form and moisture content on mechanical properties
Source of variation
Property
Angle of sliding friction (on galvanized steel),
θsfg (°)
Angle of sliding friction (on mild steel), θsfm (°)
Variety
0.34
Form
<0.001
Moistur
e
0.012
Variety
X
Form
<0.001
0.019
<0.001
0.012
0.067
Variety
X
Moistur
e
0.924
Form
X
Moistur
e
0.583
Variety
X
Form
X
Moistur
e
0.374
0.552
0.917
0.71
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% level; where p values are greater than 0.05, observed effects are not significant statistically.
Table 2: Main effects of influence factors on some properties of rice
Property
Angle of internal friction,  (°)
Moisture content
(%, dry basis)
Variety
Faro
44
Form
Faro
57
Dehusked
Paddy
5
10
15
24.00
17.30
26.08
15.17
24.25
20.25
17.38
Angle of sliding friction (on galvanized
43.67a 44a
41.5b
46.17a
43.25b 43.67b
44.58a
steel), 𝜃𝑠𝑓𝑔 (°)
Angle of sliding friction (on mild steel),
47.44a 46.5b
45.78b
48.17a
46.25b 46.92ab 47.75a
𝜃𝑠𝑓𝑚 (°)
Means comparison is restricted within factor subsets and is property-wise. Values with the same alphabets are not significantly
different, statistically.
increased to 20.25° as moisture content was
lowered to 10%. When moisture content was
further lowered to 5%, mean value of the angle of
internal friction increased to 24.25°, this
concurred with [17] that with decrease in
moisture content, the angle of internal friction
increases. In Figure 1, a comparison of angles of
internal friction of the two varieties and forms of
rice. Useful empirical relationships for estimating
angles of internal friction of the two varieties of
rice in paddy and dehusked forms, as a function
of moisture content of the produce determined
using the method of least squares are presented in
table 3
3.1 Effects of Influence Factors on Angles of
Internal Friction
The angles of internal friction of the two varieties
of rice used in this study were determined for
paddy and dehusked grains at the indicated
product moisture contents. Angle of internal
friction of the Faro 57 variety (17.3°) was
significantly lower than that of Faro 44 which
was 24°. Mean angle of internal friction of paddy
forms of the two rice varieties was 15.17° while
that of dehusked rice was 26.08°. Evidently, as
the moisture contents of the varieties of rice used
decreased, mean values of the angles of internal
friction increased; angle of internal friction was
17.38° at 15% product moisture content but
51
Nigerian Journal of Tropical Engineering
Vol. 18 No. 1 |ISSN: 1595-5397| Apr. 2024
Angle of internal friction (°)
Faro 44 Paddy
Faro 57 Paddy
DOI: 10.59081/njte.18.1.005
Faro 44 Dehusked
Faro 57 Dehusked
Figure 1: Effect of moisture content on angle of
internal friction
40
35
30
25
20
15
10
5
0
4
9
14
Moisture content (%)
19
Table 3: Dependence of angle of internal friction on moisture content
Variety
Faro 44 Paddy
M2
-0.1360
M
2.0600
C
27.40
R2
1.0000
Faro 44 Dehusked
-0.2840
4.4000
5.00
1.0000
Faro 57 Paddy
0.4520
-10.8800
76.10
1.0000
Faro 57 Dehusked
0.0580
-0.1300
9.00
1.0000
of angles of sliding friction may be had using the
empirical forms fitted to the dataset using the
method of least squares. These relationships are
presented in Table 4.
3.2 Effects of Influence Factors on Angles of
Sliding Friction
As to the angle of sliding friction, on galvanized
steel these angles were the least for dehusked
forms of Faro 44 as they ranged between 40° 41°. This was followed by angle of sliding
friction of dehusked Faro 57 rice on galvanized
steel which ranged between 42° - 43°. The angle
of sliding friction of paddy forms of Faro 57
ranged in values between 45° - 46.3° while those
of paddy forms of Faro 44 ranged in values
between 46° - 48° degrees on galvanized steel
surface. These angles approximate the angles of
repose of these varieties of rice in the indicated
forms and at the stated moisture conditions.
Graphical comparison of these was done in
Figure 2. It may be seen that the dehusked forms
presented with smaller angles of sliding friction
than paddy forms of both varieties. Within the
limits of moisture levels investigated, estimates
Angle of sliding friction (°)
60
50
40
30
Faro 44 Paddy
Faro 44 Dehusked
Faro 57 Paddy
Faro 57 Dehusked
20
10
0
4
9
14
Moisture content (%)
Figure 2: Effect of moisture content on angle of
sliding friction on galvanized steel
52
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Nigerian Journal of Tropical Engineering
Vol. 18 No. 1 |ISSN: 1595-5397| Apr. 2024
DOI: 10.59081/njte.18.1.005
Table 4: Dependence of angle of sliding friction (on galvanized steel) on moisture content
M
0.2000
C
44.667
R2
0.7500
Faro 44 Dehusked
0.1000
39.667
0.7500
Faro 57 Paddy
0.1333
44.333
1.0000
Faro 57 Dehusked
0.1000
41.333
0.7500
Variety
Faro 44 Paddy
M2
Angles of sliding friction were much larger for
the stated forms of the two varieties of rice on
mild steel than they were on galvanized steel, and
they ranged in values between 45° - 47° for
dehusked forms of Faro 44 and 45° - 46° for
dehusked forms of Faro 57 on mild steel. Angles
of sliding friction of paddy forms of Faro 44
ranged between 48° - 50° while those for paddy
forms of Faro 57 ranged from 47° - 48° on mild
steel, this agreed with the range given by [18]
they found the range to be 46° - 49° for paddy,
and 45° - 48° for dehusked rice. Comparing these
results (Figure 3), it may be seen that angles of
sliding friction were smaller for dehusked forms
but larger for paddy forms. Regression equations
by which these angles may be estimated within
the limits of the test moisture contents are
presented in table 5. These angles not only
approximate the angles of repose for these
products at the indicated conditions on the test
surfaces but also are directly proportional to the
coefficients of sliding friction of the grains of rice
on these surfaces.
Faro 44 Paddy
Faro 57 Paddy
Faro 44 Dehusked
Faro 57 Dehusked
Angle of sliding friction (°)
51
50
49
48
47
46
45
44
4
9
14
Moisture content (%)
Figure 3: Effect of moisture content on angle of
internal friction on mild steel
Table 5: Dependence of angle of sliding friction (on mild steel) on moisture content
M
0.2
C
47.000
R2
1.0000
Faro 44 Dehusked
0.2
43.667
0.7500
Faro 57 Paddy
0.1
46.333
0.7500
Faro 57 Dehusked
0.1
44.687
0.7500
Variety
Faro 44 Paddy
M2
53
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Nigerian Journal of Tropical Engineering
Vol. 18 No. 1 |ISSN: 1595-5397| Apr. 2024
DOI: 10.59081/njte.18.1.005
4.
Conclusion
Angles of internal friction were at least 15.2°,
on the average. Within the moisture ranges
tested however, 35° angles were also
obtained. Angles of sliding friction ranged
between 40° - 50° with change in moisture
contents. According to the [19 and 6] agreed
that the moisture content of rice has an effect
on mechanical properties, angle of internal
friction increases significantly from 10% to
20% moisture content. Increase in moisture
content led to an increase in cohesion which
agreed with [19]. In this study, some designrelated mechanical properties of two varieties
of rice commonly grown in Nigeria were
determined using standard laboratory
techniques
and
following
standards
recommended in literature. The friction
properties determined were as follows:
[3] Food and Agriculture Organization of the
United Nations (FAO). (2003). World
rice trade dynamics and rice price
volatility. https://www.fao.org/marketsand-trade/commodities/rice/rmm/en/
[4]Food and Agricultural Organization
(FAO), (2012). World Rice Production.
Www.wikipadia
[5]Bande YM, Adam NM, Azmi Y, Jamarei
O (2012) Determination of selected
physical properties of Egusi melon
(Citrullus colocynthis lantus) seed. J
Basic Appl Sci. 8: 257 – 265.
[6]Awad M., Osama F., Wael F., Wael E. B.,
Mohsen E., Walied E. F. and Mahmoud
O. (2022). A combined machine for
collecting and chopping rice straw.
1. Angles of sliding friction fall within the
range of 40°- 50°.
2. Angles of internal friction occur within
the range of 15.2° - 35°.
[7] American Society of Agricultural and
Biological Engineers (ASABE) S352.2
(2018).
Moisture
Measurement—
Unground Grain and Seeds. American
Society of Agricultural and Biological
Engineers, St. Joseph.
These results may only be employed for
operations to be carried out within the range
of moisture contents employed for their
determination.
[8] Zareiforoush1 H, Hosseinzadeh1 B,
Adabi1 M.E, Motavali1 A (2011).
Moisture-dependent physical properties
of paddy grains Journal of American
Science, 2011;7(7) page 175-182.
REFERENCES
[1] International Rice Research Institute
(IRRI). (2023). Rice: Production, trade,
and
consumption
trends.
http://books.irri.org/RT12_1_content.pd
f
[9]Zareiforoush, M., Komarizadeh, M. H., &
Khoshtaghaza, M. H. (2021). Effect of
moisture content on some physical
properties of paddy grains. Journal of
Agricultural Science and Technology,
23(3), 349-359.
[10]Mujumdar, A. S. (2014). Physical
properties of grains. In Handbook of
post-harvest operations and processing
(pp. 75-120). CRC Press.
[2]Mohidem, N. A., Hashim, N., Shamsudin,
R., & Che Man, H. (2022). Rice for Food
Security: Revisiting Its Production,
Diversity, Rice Milling Process and
Nutrient Content. Agriculture, 12(6),
741.
https://www.mdpi.com/20770472/12/6/741:
https://www.mdpi.com/20770472/12/6/741
54
Nigerian Journal of Tropical Engineering
Vol. 18 No. 1 |ISSN: 1595-5397| Apr. 2024
DOI: 10.59081/njte.18.1.005
[11]Nimkar P.M. and Chattopadhyay
P.K. PH—Postharvest Technology:
Some physical properties of green gram.
Journal of Agricultural Engineering
Research, (2001), vol. 80, no. 1, pp.
183–189.
DOI:
https://doi.org/10.1006/jaer.2000.0664
[17] Petal N. S., Jagan, K. S., Sinha, J. P. &
Kumar A. (2013). Physical Properties of
Basmati Varieties of Paddy Rice.
Journal of Agricultural Engineering.
50(4).
[18]
[12] Solaf A. E., Mahmoud A., Fatma A. E.,
Mokhtar C. and Mahmoud O. (2022).
Influence of operating parameters on the
milling quality of long-grain white rice.
INMATEH - Agricultural Engineering,
68(3), 669–680.
Jafar M. & Javad K. (2022).
Simultaneous Measurement of Rice
Grain Friction Coefficient and Angle of
Repose using Rotary Cylinder
[19] Kajuna S.T.A.R and . Rugenga E.
(1998). Relationship between the Angle
of Repose and Angle of Internal Friction
for Agricultural Granular Materials:
Agricultural Engineering and Land
Planning Department : Tanzania Journal
of Agricultural Sciences 1(2): 187
[13]Abdul-Rasaq A. Adebowale & Lateef O.
Sanni &Hameed O. Owo & Olayinka R.
Karim (2010). Effect of variety and
moisture content on some engineering
properties of paddy rice. Journal of Food
Sci Technology (September–October
2011)
48(5):551–559DOI
10.1007/s13197-010-0173
[14] Gheorghe V., Gabriel, A. C. P., Elena,
M. S., Bianca, S. Z. (2010). Aspects
Regarding the Determination of the
Moisture Content of Cereal and
Granular Materials with Apparatus with
Infrared Radiations. Faculty of
Biotechnical Systems Engineering,
Biotechnical Systems Department
[15]Kabutey, A., Herak, D., Choteborsky,
R., Mizera, Č., Sigalingging, R., &
Akangbe, O. L. A. (2017). Oil point and
mechanical behaviour of oil palm
kernels
in
linear
compression.
International Agrophysics, 31(4), 427434. doi:10.1515/intag-2016-0055
[16] Abdulrasaq, A. A., Lateef O. S.,
Hameed O. O., & Karim O. R. (2011).
Effect of Variety and Moisture Content
on Some Engineering Properties of
Paddy Rice. Journal of Science and
Technology.
55