Physical Properties And Milling Characteristics Of Different Paddy

IJSART - Volume 1
Issue 4 –APRIL 2015
ISSN [ONLINE]: 2395-1052
Physical Properties And Milling Characteristics Of
Different Paddy Varieties
Manpreet Singh 1, Preetinder Kaur 2, Jugraj Singh 3
Department of Processing & Food Engineering
1, 3
Krishi Vigyan Kendra, Punjab Agricultural University, Ludhiana, Punjab
2
Punjab Agricultural University, Ludhiana, Punjab
Abstract- Physical properties of rice are necessary for the
design of equipment to handle, transport, process and store
the crop. The paddy varieties viz. PR-121, PR-114, PR-118 &
PR-122 were tested for characteristic diameter, sphericity,
angle of repose, bulk density, true density, porosity at 12%
moisture content (% db). The basic objective of a rice milling
system is to remove the husk and the bran layers, and produce
an edible, white rice kernel that is sufficiently milled and free
of impurities. Depending on the requirements of the customer,
the rice should have a minimum of broken kernels. Total
milled rice contains whole grains or head rice, and brokens.
The milling characteristics investigated includes husk content
(%), bran content (%), total yield (%), head yield (%), brokens
(%), milling degree (%) and milling recovery (%). Maximum
characteristic diameter (0.456cm) and bulk density (0.608
g/cc) was observed for PR-121 while maximum angle of
repose (44.8o) and porosity (51.182) was observed for PR122. Husk content of PR-122 is minimum (19.58%) but
comparable to PR-121 (19.68%) with non significant
difference in means. Head yield is maximum for PR-121
(64.86%) & brokens (10.25%) are also less which are
comparable to PR-118 (10.18%, minimum). Milling degree
(94.38%) and milling recovery (75.50%) of PR-121 and
milling degree (95.03%) and milling recovery (76.31%) PR122 are comparable with non significant differences in means.
Keywords- Paddy,
characteristics
varieties,
physical
properties,
milling
I. INTRODUCTION
Rice (Oryza sativa L.) stands out, constituting the
basic food for large number of human beings, sustaining twothirds of the world population (Zhout et al. 2002). Rice is one
of the most important food crops of India in term of area,
production and consumer preference. India is the second
largest producer and consumer of rice in the world. Rice
production in India crossed the mark of 100 million MT in
2011-12 accounting for 22.81% of global production in that
year. The productivity of rice has increased from 19.8 q/ha in
2004-05 to 23.7 q/ha in 2011-12. Indian share in global rice
Page | 59
production has been hovering in the range of 19.50 to 24.52 %
during the last decade (www.agricoop.nic.in ).
In India, rice consumption is generally accomplished
in various forms like whole cooked grain, as dish meal, where
rice is served normally in two ways, white rice and parboiled
grains. It is the main base for preparation of many indigenous
fermented food products (like idli, dosa, uttapam), sweets
(anarasa, khir), khichadi, pulav, puffed and extruded products.
The marketing values of rice as an agricultural
product depend on its physical qualities after the harvesting.
The percentage of whole grain is the most important parameter
for the rice processing industry (Marchezan 1991). Broken
grain has half the market value of head rice (head rice=75100% of whole kernel) (Trop Rice International Rice Research
Institute 2004). The physical and mechanical properties of
rice, which are important in the design and selection of storage
structures and storage and processing equipment, depend on
grain moisture content. Therefore, the determination and
consideration of properties such as bulk density, true density,
porosity of grain has an important role (Mohsenin 1980;
Molenda et al. 2002; Kashaninejad et al. 2006). The principal
axial dimensions of seeds are useful in selecting sieve
separators and in calculating power during the milling process.
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. A grain bed with low
porosity will have greater resistance to water-vapor escape
during the drying process, which may lead to the need for
higher power to drive the aeration fans. Cereal-grain kernel
densities have been of interest in breakage susceptibility and
hardness studies (Chang 1988). Other researchers have
determined the properties of different types of grains and
seeds: canola and wheat (Bargale et al. 1995) lentils; (Çarman
1996); sunflower seeds (Gupta and Das 1997); black pepper
(Murthy and Bhattacharya 1998); pigeon peas (Baryeh and
Mangobe 2002); cotton (Ozarslan 2002); millet (Baryeh
2002); popcorn (Karababa 2006); caper seeds (Dursun and
Dursun 2005); pistachio nuts (Kashaninejad et al. 2006); and
barley (Özturk and Esen 2008). Many studies have reported on
the physical, chemical and surface properties of wheat husks,
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IJSART - Volume 1
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ISSN [ONLINE]: 2395-1052
rye husks and soft wood and their polypropylene composites
(Bledzki et al. 2010).
Milling is a crucial step in post-production of rice.
The basic objective of a rice milling system is to remove the
husk and the bran layers, and produce an edible, white rice
kernel that is sufficiently milled and free of impurities.
Depending on the requirements of the customer, the rice
should have a minimum of broken kernels. Total milled rice
contains whole grains or head rice, and brokens. The byproducts in rice milling are rice hull, rice germ and bran layers
and brokens. This study investigated some physical properties
and milling characteristics of four varieties of rice viz. PR114, PR-118, PR-121 & PR-122, respectively typically
cultivated in Punjab. The properties measured were
characteristic diameter (mm), sphericity, angle of repose, bulk
density (g/cc), true density (g/cc), porosity and the milling
characteristics include husk content(%), bran content(%),
total yield (%), head yield (%) and brokens (%), milling
degree (%) and milling recovery (%).
II. MATERIAL AND METHODS
The samples for four varieties of paddy viz. PR-121, PR-114,
PR-118 & PR-122 were procured from Krishi Vigyan Kendra
Farms, SBS Nagar and were evaluated in Department of
Processing & Food Engineering, PAU, Ludhiana. Samples
were cleaned of any foreign material prior to analysis for
properties and milling characteristics.
D= Diameter of pile, cm
The bulk density values of paddy were determined using the
following relation (Mohsenin 1980).
𝐵𝑢𝑙𝑘 𝐷𝑒𝑛𝑠𝑖𝑡𝑦
𝑔
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑝𝑎𝑑𝑑𝑦 𝑔𝑟𝑎𝑖𝑛𝑠 (𝑔)
=
𝑐𝑐
(4)
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑡𝑕𝑒 𝑐𝑜𝑛𝑡𝑎𝑖𝑛𝑒𝑟 (𝑐𝑐 )
The true density values of paddy were determined using the
following relation (Mohsenin 1980).
𝑇𝑟𝑢𝑒 𝐷𝑒𝑛𝑠𝑖𝑡𝑦
𝑔
𝑐𝑐
=
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑝𝑎𝑑𝑑𝑦 𝑔𝑟𝑎𝑖𝑛𝑠 (𝑔)
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑡𝑜𝑙𝑢𝑒𝑛𝑒 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑑 (𝑐𝑐 )
(5)
The porosity (%) values were determined using the following
relation (Mohsenin 1980).
𝑃𝑜𝑟𝑜𝑠𝑖𝑡𝑦 % =
𝑇𝑟𝑢𝑒 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 −𝐵𝑢𝑙𝑘 𝐷𝑒𝑛𝑠𝑖𝑡𝑦
𝑇𝑟𝑢𝑒 𝐷𝑒𝑛𝑠𝑖𝑡𝑦
𝑥 100
(6)
Milling Characteristics
The cleaned paddy samples were milled in laboratory
scale dehuller (Make: Satake, Japan) and polisher (Make:
Satake, Japan) available in laboratory of Department of
Processing & Food Engineering, PAU, Ludhiana. Following
parameters were evaluated during the study for different
varieties of paddy.
Husk content (%) was computed using the equation
Physical properties
𝐻𝑢𝑠𝑘 𝐶𝑜𝑛𝑡𝑒𝑛𝑡 % =
Physical properties determined includes characteristic
diameter (cm), sphericity from the physical dimensions of
paddy grains.
𝐶𝑕𝑎𝑟𝑎𝑐𝑡𝑒𝑟𝑖𝑠𝑡𝑖𝑐 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 𝐷𝑎𝑣𝑔; 𝑐𝑚 =
3
𝑎𝑏𝑐
(1)
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑕𝑢𝑠𝑘 (𝑔)
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 𝑢𝑠𝑒𝑑 (𝑔)
𝑥 100
(7)
Bran content was computed using the equation
𝐵𝑟𝑎𝑛 𝐶𝑜𝑛𝑡𝑒𝑛𝑡 % =
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑟𝑖𝑐𝑒 𝑏𝑟𝑎𝑛 (𝑔)
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑏𝑟𝑜𝑤𝑛 𝑟𝑖𝑐𝑒 (𝑔)
𝑥 100
(8)
𝑆𝑝𝑕𝑒𝑟𝑖𝑐𝑖𝑡𝑦 =
𝐷𝑎𝑣𝑔
𝑎
(2)
Total yield was computed using the equation
𝑇𝑜𝑡𝑎𝑙 𝑌𝑖𝑒𝑙𝑑 % =
When the bulk materials are poured onto a horizontal
surface, a conical pile will form. The internal angle between
the surface of the pile and the horizontal surface is known as
the angle of repose. Angle of repose was determined using a
method described by Mohsenin (1980).
𝜃 = tan−1
2𝐻
𝑥 100
(9)
Head yield was computed using the equation
𝐻𝑒𝑎𝑑 𝑌𝑖𝑒𝑙𝑑 % =
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑕𝑒𝑎𝑑 𝑟𝑖𝑐𝑒 (𝑔)
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 𝑢𝑠𝑒𝑑 (𝑔)
𝑥 100
(10)
(3)
𝐷
Brokens (%) was computed using the equation
𝐵𝑟𝑜𝑘𝑒𝑛𝑠 % =
Where,
H = Height of pile, cm
Page | 60
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑤𝑕𝑖𝑡𝑒 𝑟𝑖𝑐𝑒 (𝑔)
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 𝑢𝑠𝑒𝑑 (𝑔)
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑏𝑟𝑜𝑘𝑒𝑛𝑠 (𝑔)
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 𝑢𝑠𝑒𝑑 (𝑔)
𝑥 100
(11)
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Milling degree was computed based on the amount of bran
removed from the brown rice. It is calculated using the
equation
𝑀𝑖𝑙𝑙𝑖𝑛𝑔 𝐷𝑒𝑔𝑟𝑒𝑒 % =
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑚𝑖𝑙𝑙𝑒𝑑 𝑟𝑖𝑐𝑒 (𝑔)
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑏𝑟𝑜𝑤𝑛 𝑟𝑖𝑐𝑒 (𝑔)
𝑥 100
(12)
Milling recovery is computed using the following equation
𝑀𝑖𝑙𝑙𝑖𝑛𝑔 𝑅𝑒𝑐𝑜𝑣𝑒𝑟𝑦 % =
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑚𝑖𝑙𝑙𝑒𝑑 𝑟𝑖𝑐𝑒 (𝑔)
𝑊𝑒𝑖𝑔 𝑕𝑡 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 𝑢𝑠𝑒𝑑 (𝑔)
𝑥100
(13)
Statistical Analysis
The data was subjected to ANOVA using Statgraphics Plus for
Windows Version 3 (Statistical Graphics Corp.) to analyze
whether there was a significant difference in varieties on the
basis of studied parameters. The method currently used to
discriminate among the means was Fisher's least significant
difference (LSD) procedure.
III. RESULTS AND DISCUSSION
Physical Properties
Average values of physical properties along with standard
deviations for different varieties of paddy are presented in
Table 1. The physical dimensions viz. length, breadth and
thickness of the grain samples are shown in Fig. 1. Maximum
length was found to be 0.97cm for PR-114 closely followed by
0.96 for PR-121. Maximum breadth was found to be 0.39 for
PR-121 closely followed by 0.38 for PR-122 and PR-118.
Maximum thickness was found to be 0.25 for PR-121 and PR118 closely followed by 0.24 for PR-114 and 0.23 for PR-122.
Table-1: Average values (± S.D) of physical
properties of different paddy varieties
Page | 61
Maximum characteristic diameter Davg was observed
to be 0.456cm for PR-121 followed by 0.445cm for PR-118,
0.437 for PR-114 & 0.431 for PR-122. Since the P-value
observed during statistical analysis was less than 0.05, there
was a statistically significant difference between the mean
characteristic diameter (Davg) from one variety to another at
the 95.0% confidence level. Variety PR-121 followed by PR118, all the mean differences between different varieties are
significantly different (5% level) except between varieties PR114 & PR-118 and PR-114 & PR-122. Maximum value of
sphericity was found out to be 0.484 for PR-118 followed by
0.475 for PR-121, 0.472 for PR-122 and 0.449 for PR-114.
Since the P-value of the F-test is less than 0.05, there is a
statistically significant difference between the mean sphericity
from one level of variety to another at the 95.0% confidence
level. Paired comparison shows statistically significant
differences between means of different varieties except
between varieties PR-121 and PR-122. Maximum value of
angle of repose was found out to be 44.8o for PR-122
followed by 38.8o for PR-114, 35.1o for PR-121 and 33.1o for
PR-118. Since the P-value is less than 0.05, variety has a
statistically significant effect on angle of repose at the 95.0%
confidence level. Paired comparison showed a significant
difference in means of all varieties. Maximum value of bulk
density was found out to be 0.608 g/cc for PR-121 closely
followed by 0.606 g/cc for PR-118, 0.559 g/cc for PR-114 and
0.570 g/cc for PR-122. Since the P-value of the F-test is less
than 0.05, there is a statistically significant difference between
the mean bulk density from one level of variety to another at
the 95.0% confidence level. Paired comparisons showed a
significant difference in means of all varieties. Maximum
value of true density was found out to be 1.239 g/cc for PR118 followed by 1.168 g/cc for PR-122, 1.159 g/cc for PR-121
and 1.039 g/cc for PR-114. Since the P-value of the F-test is
less than 0.05, there is a statistically significant difference
between the mean true density from one level of variety to
another at the 95.0% confidence level. Paired comparisons
showed a significant difference at 5 % level of significance in
mean values of true density for all varieties except varieties
PR-121 & PR-122. Maximum value of porosity was found out
to be 51.182 for PR-122 followed by 50.789 for PR-118,
47.547 for PR-121 and 42.390 for PR-114. Since the P-value
of the F-test is less than 0.05, there is a statistically significant
difference between the mean porosity from one level of
variety to another at the 95.0% confidence level. Paired
comparisons showed a significant difference at 5 % level of
significance in mean values of porosity for all varieties except
varieties PR-118 and PR-122.
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Page | 62
100
P R -1 2 1
P R -1 1 4
80
P R -1 1 8
60
P R -1 2 2
40
20
ry
ee
ve
gr
ns
M
il
M
li
il
li
ng
ng
re
co
de
ke
B
d
ea
H
ro
yi
yi
el
el
d
d
0
t
Maximum value of husk content (%) was found to be
22.73 for PR-114 followed by 22.16 for PR-118.
Comparatively less value was observed for PR-122(19.58) and
PR-121(19.68). Husk content of PR-121 and PR-122 was
significantly lower than that of PR-114 and PR-118 varieties
whereas the mean difference in husk content of PR-121 and
PR-122 was non-significant. Since one P-value is less than
0.05, variety has a statistically significant effect on husk
content at the 95.0% confidence level. All differences in
means were significantly different except between varieties
PR-121 & PR-122. Maximum value of bran content (%) was
found to be 5.63 for PR-122 followed by 5.60 for PR-114.
Comparatively less value was observed for PR-118(4.13) and
PR-121(4.39). Non-significant difference in bran content was
observed for all comparisons except that bran content was
en
Table-2: Average values (± S.D) of milling characteristics for
different varieties of paddy
al
Average values of milling characteristics along with
standard deviations for different varieties of paddy are
presented in Table 2 and the variation in these properties is
illustrated in Fig. 2.
ot
Milling Characteristics
T
Fig. 1: Physical dimensions of paddy samples
t
S iz e p a ra m e te rs
nt
D a v g S p h e ric ity
en
c
co
b
nt
a
n
0 .0
ra
0 .5
co
P R -1 2 2
B
P R -1 1 8
1 .0
k
D im e n s io n , c m
P R -1 1 4
V a lu e , %
P R -1 2 1
significantly higher in PR-114 than in PR-121 and PR-118.
All differences in means were significantly different except
between varieties PR-121 & PR-118 and PR-114 & PR-122.
Maximum value of total yield (%) was found out to be 76.32
for PR-122 followed by 75.50 for PR-121. Total yield was
lowest for PR-114 (71.73). Since one P-value is less than 0.05,
variety has a statistically significant effect on bran content at
the 95.0% confidence level. Maximum value of head yield
(%) was found out to be 64.86 for PR-121 followed by 63.96
for PR-122. Head yield was lowest for PR-114 (59.15). Since
the P-value of the F-test is less than 0.05, there is a statistically
significant difference between the mean head yield from one
level of variety to another at the 95.0% confidence level. All
differences in means except between varieties PR-118 and PR122 were statistically significant. Maximum brokens (%)
were found out to be 12.33 for PR-114 while minimum
brokens were found out to be 10.18 for PR-118. Since the Pvalue of the F-test is less than 0.05, there is a statistically
significant difference between the mean brokens from one
level of variety to another at the 95.0% confidence level. All
differences in means were significantly different at 5% level
of significance. Maximum milling degree (%) was found out
to be 95.03 for PR-122 followed by 94.83 for PR-118.
Minimum milling degree was for PR-114 (93.23). Since the Pvalue of the F-test is less than 0.05, there is a statistically
significant difference between the mean milling degree from
one level of variety to another at the 95.0% confidence level.
The differences in mean values were non-significant except
between varieties PR-121 & PR-114 and varieties PR-114 &
PR-118. Maximum milling recovery (%) was found out to be
76.31% for PR-122 followed by 75.50% for PR-121. Lowest
milling recovery was for PR-114 (71.72). Since the P-value is
less than 0.05, variety has significant effect on mean Milling
recovery at the 95.0% confidence level. All differences in
means were statistically significant at 5 % level of significance
except between varieties PR-122 and PR-121.
us
1 .5
H
IJSART - Volume 1
M illin g p a r a m e te r s
Fig. 2. Average values of milling characteristics for
different varieties
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Issue 4 –APRIL 2015
IV. CONCLUSION
Maximum characteristic diameter (0.456cm) and
bulk density (0.608 g/cc) was observed for PR-121 while
maximum angle of repose (44.8o) and porosity (51.182) was
observed for PR-122. Husk content of PR-122 is minimum
(19.58%) but comparable to PR-121 (19.68%) with non
significant difference in means. Head yield is maximum for
PR-121 (64.86%) & brokens (10.25%) are also less which are
comparable to PR-118 (10.18%, minimum). Milling degree
(94.38%) and milling recovery (75.50%) of PR-121 and
milling degree (95.03%) and milling recovery (76.31%) PR122 are comparable with non significant differences in means.
It can be concluded that for milling purpose variety PR-121
can be considered as best closely followed by PR-122 amongst
the varieties investigated.
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