The modern rice milling machinery can be divided into two major groups: (1) rice milling machinery developed in Japan and (2) rice milling machinery developed in Europe. • The major operations performed by modern rice mills are : (1) storage; (2) cleaning; (3) husking; (4) separation; (5) whitening; and (6) grading

1. Rice

2. Figure 13Longitudinal Cross Section of Rice-3
Figure 14Longitudinal Cross Section of Rice-4
Rice production in India is an important part of the national economy. India is the world's second-largest
producer of rice, and the largest exporter of rice in the world. Production increased from 53.6 million tons in
FY 1980 to 120 million tons in FY2020-21. West Bengal is the largest producer of rice in India.
What is Rice?
Rice, just like other grains, is the edible seed of a grass. We are most familiar with rice that comes from Oryza
sativa, or Asian rice. Each grain, or seed, of rice contains:

3.  A tough outer hull – also known as the husk, the hull needs to be removed before it can be eaten. The
hull is removed in all types of rice.
 Bran – An additional layer that lies just under the hull, the bran layer is only removed in certain types
of rice varieties, such as white rice. The bran is the nutritious, whole-grain section of a rice grain and
though it is typically brownish-tan in color, it may also be red or black depending on the pigmentation
in the bran layers.
 Endosperm (also known simply as white rice) – What remains once the outer hull and bran layers are
stripped away. Though this is the most commonly consumed part of rice, it is also the least nutritious.
 Germ – Found under the hull, the germ is not a layer, but a small kernel. It is nutrient-dense and
packed full of B vitamins, minerals, proteins, and contributes to the overall color of rice. In general, the
white rice we purchase from our local supermarket or grocery store has been milled or stripped of the
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behind just the endosperm.
Forms of Rice
Brown Rice
Usually, any type of rice can come in a brown rice
version, since it’s just the same grain but with the
outer hull still intact. Rice from which only the hull
as been removed. The germ and bran surrounding
the grain makes it a whole grain, giving it a nuttier
flavor and chewier texture. When cooked, it has a
slightly chewy texture and nut-like flavor. This is a
natural source of bran. It cooks in approximately
40-45 minutes.
Parboiled Rice

4. Nutrients stay within the grain and surface starch is reduced, producing cooked rice that is somewhat more
firm in texture and very separate when cooked. It cooks perfectly in approximately 20 minutes. Parboiled rice
is processed differently. The hull is left on like brown rice, but it’s soaked and steamed. Then, it’s dried with
the hulls removed, which means that the grains have absorbed more of the nutrients than regular white rice.
The best ratio for parboiled rice is 2:1 water to rice.
Regular-milled White Rice
This rice has been completely milled and polished,
removing the bran layer. Vitamins and minerals are
added for enrichment. It takes about 15 minutes to
cook.
Types of rice
About 20 varieties of rice grown commercially in the
U.S. All can be classified as long, medium or short grain.
California grows short and medium grain varieties,
while Louisiana produces medium and long grain
varieties. Long grain rice is predominantly grown in
Arkansas, Mississippi, Missouri and Texas, with some production of medium grain varieties in each state.
There are two prominent varieties of rice plants: indica, most often long-grained and aromatic, and japonica,
short and medium grain rice. Within those two plant types, there are over 40,000 different variety of rice.
Types on the basis’s of Size
1.1.1.1 Long Grain
Long and slender, these grains are 4 to 5 times as long as they are wide. The two most popular and well-known
long-grain rice varieties are basmati and jasmine rice. When prepared properly (always thoroughly rinse your
rice in several changes of clean water), long-grain rice should cook up fluffy, tender, and the least bit clumpy.
1.1.1.2 Medium Grain
Plump, but not round. When cooked, the grains are moister and tenderer than long grain rice. The line
between medium-grain versus short-grain isn’t always clearly defined, and sometimes, medium- and short-
grain rice gets combined into the same category. Medium-grain rice are shorter than long-grain rice,
approximately two to three times longer than it is wide but less starchy than short-grain rice. Medium-grain
rice is usually fluffy and moist just after cooking, but clumps and solidifies as it cools. It creates a creamy
consistency ideal for risotto and rice pudding.Popular varieties: Italian rice including Arborio, Carnaroli, and
Vialone Nano, Calrose rice
1.1.1.3 Short Grain
Great for stir-fry recipes and puddings. Short-grain rice is round, chubby, and starchy that swell and stick
together in clumps. Mainly referred to as glutinous. Its glue-like or sticky texture, short-grain rice is best eaten
with chopsticks – or even your hands – and is often found in sweet desserts, sticky rice, and sushi. Popular
varieties: Japanese short-grain, Bomba rice, Chinese black rice, short-grain glutinous rice
Interesting Facts about Rice in India
 All rice grows as brown rice.
 The more significant part of the world consumes rice as a
staple food.
 Rice requires more development than corn and wheat.
 The Guinness World Records has a record for the biggest
bowl of rice.

5. Definitions of rice

6. The meaning of the terminology in this Rice Standards is as follows:
Rice Types:
Thai Jasmine White Rice, also called fragrant rice or "Hom Mali" rice, is recognized
worldwide as Thailand's specialty.
Thai Jasmine Rice belongs to the Indica (long-grain) category and could be divided into 3
main categories as A, B and C according to their quality; Prime Quality, Superb Quality
and Premium Quality.
Brown Rice belongs to the Indica (long-grain), similar to white rice.
The only difference between these two varieties is the milling. As a result, in brown rice,
only the husk is removed while the bran layer remains.
Because of the bran layer, brown rice contains more nutrients than white rice. In
particular, Brown rice is very high in fiber and vitamin B.
White Rice belongs to the Indica (long-grain) category. It is also known as polished rice
or fully milled rice because most of the outer layer-the husk and the bran layer-are
removed from the kernel, through the milling process.
Broken Rice, during the milling process, broken rice is separated from the white rice,
which shape remains intact. In other words, broken rice is the damaged white rice.
A grain of broken rice gives a low fiber texture and low nutrient level, while retaining its
high energy content.
Short Grain Ricebelongs to the Japonica (short-grain) category and has short, round, and
plumpy kernel. When cooked, short-grained rice is stick together, although not as much
as glutinous rice.
In Japanese and Korean cuisine, short-grained rice is primary consumed in every meal.
Parboiled Rice means non-glutinous rice that has passed through the parboiling process
and has its bran removed.
Parboiled rice are divided into 9 grades: 1) 100% Sorted 2) 100% 3) 5% Sorted
4) 5% 5) 10% Sorted 6) 10% 6) 10% 7) 15% 8) 25% 9) Broken rice
A1
Glutinous Ricealso called sticky rice or sweet rice, consists of amylose and amylopectin
starch. With a chalky white texture.
The standards for White glutinous rice are specified as follows:
White glutinous rice 10%
- Short Grain
- Long Grain

7. COMPOSITION
The chemical composition of rice is influenced to some extent by genetic and environmental factors. The
composition of Indian rice is; moisture, 10.9-13.8 proteins, 5.5-9.3; carbohydrates, 73.4-80.8; fiber, 0.2-1.0;
and mineral matter, 0.8-2.0 percent. The germ, the pericarp and the aleuronic layers, which are richer than
endosperm, in nutrients like protein, mineral and vitamins are separated from the grain during milling along
with the husk.
The major carbohydrate of rice is starch (72-75 per cent). Rice also contains some free sugars like glucose,
sucrose and dextrin. The protein content of rice is lower than that of wheat. The rice proteins are richer in
arginine compared to other cereal proteins. They are deficient in lysine and threonine. Most of the minerals
present in rice are located in the pericarp and germ. Polished rice is poor in calcium and iron.
NUTRITIVE VALUE OF RICE
Food
Energy
K.cal
Protein
g
Fat
g
Carbohydrates
g
Calcium
mg
Iron
mg
bCarotene
mcg
Thiamine
mg
Ribo-
flavin
mg
Niacin
mg
Rice, parboiled, hand
pounded
349 8.5 0.6 77.4 10 2.8 9 0.27 0.12 4.0
Rice, parboiled,
milled
346 6.4 0.4 79.0 9 1.0 - 0.21 0.05 3.8
Rice, raw, hand-pounded 346 7.5 1.0 76.7 10 3.2 2 0.21 0.16 3.9
Rice, raw, milled 345 6.8 0.5 78.2 10 0.7 0 0.06 0.06 1.9
Rice has potential in a wide range of food categories. Besides having nutritional and medicinal benefits, the by-
products of rice are equally important and beneficial. By-products from growing rice create many valuable and
worthwhile products. The unedible parts that are discarded through the milling process and the edible part
could be transformed into some products.
Chemical Composition
1.1.1.4 Carbohydrates
Starch, the major component of rice, is present in the starchy endosperm as compound granules that are 3-10
pm in size. Protein, the second major component, is present in the endosperm in the form of discrete protein
bodies that are 1-4 µm in size. The concentration of nonstarchy carbohydrates is higher in the bran and germ
fractions than in the starchy endosperm. Brown rice contains about 8% protein, 75% carbohydrates, and
small amounts of fat, fiber, and ash. After milling, the protein content of rice is about 7% and the
carbohydrate content (mainly starch) about 78%. Starch is found primarily in the endosperm; fat, fiber;
minerals, and vitamins are concentrated in the aleurone layers and in the germ.
Starch, the main carbohydrate of rice, comprises up to 90% of the rice solids. In common rice, amylose
amounts to 12-35% of the total starch; in waxy (glutinous) rice, the amylose content is much lower.
1.1.1.5 Proteins
Protein composition of milled rice is unique among cereals. The rice proteins are rich (at least 80%) in glutelins
and have a relatively good amino acid balance. Among the protein fractions, albumin has the highest lysine
content, followed by glutelin, globulin, and prolamin. The high lysine content of rice protein is primarily due to
their low prolamin content. Proteins in milled rice are generally lower in lysine than proteins in brown rice.
The proportions of albumin and globulin and the total protein are highest in the outer layers of the milled rice
kernel and decrease toward the center; proportions of glutelin have an inverse distribution. In rice, as in other
cereal grains, the proteins differ considerably in their amino acid composition and biological value. The most
notable differences are in the high concentration of lysine in albumins and of cystine in globulins, and in the
very low lysine and cystine concentrations in the prolamines. Rice protein is not ideally balanced; it is
relatively low in lysine concentration when compared with the FAO Reference Pattern; supplementation with
lysine and threonine significantly increases the biological value of rice protein.
The subaleurone region, which is rich in protein, is only several cell layers thick, lies directly beneath the
aleurone, and is removed rather easily during milling. From a nutritional standpoint, it is therefore desirable to
mill rice as lightly as possible and retain some of the protein in the subaleurone or to breed cultivars that have
either an increased, number of aleurone layers or have the protein more evenly distributed throughout the

8. endosperm. Protein content of the grain determines the protein distribution between bran polish and milled
rice. Protein distribution is more uniform throughout the grain as the grain increases in total- protein content.
Also, high-protein milled rices usually have more thiamine. The increase in protein content is related mainly to
an increase in the number of protein bodies and a slight increase in their size.
1.1.1.6 Lipids
Brown rice contains 2.4-3.95% lipids. The lipid content depends on
● The variety
● Degree of maturity
● Growth conditions
● Lipid extraction method
The lipid content of bran and polished rice is affected by the degree of milling and the milling procedure.
Polishing gradually removes the pericarp, tegmen, aleurone layer, embryo, and parts of the endosperm, but
parts of the lipid-rich germ may remain attached to the endosperm even after advanced polishing and removal
of up to 20% of the rice kernel. The major proportion of the lipid in rice is removed with the bran (containing
the germ) and the polish.
Oil in
● Bran 🡪 10.1-23.5%,
● Polish 🡪 9.1-11.5%,
● Brown rice 🡪 1.5-2.5%,
● Milled rice 🡪 0.3-0.7%
In the rice kernel, as in other cereals, lipid content is highest in the embryo and in the aleurone layer, and the
lipid is present as droplets or spherosomes. The spherosomes are submicroscopic-about 0.5 µm or less in the
coleoptile cells. Much higher quantities of lipids are present outside the aleurone granules than inside them.
The testa contains a fatty material, and a sheath of fat-staining material encloses the aleurone granules. Rice
lipids are mainly triglycerides, with smaller amounts of phospholipids, glycolipids, and waxes. The three main
fatty acids are oleic, linoleic, and palmitic. The main glycolipids are acyl sterol glycosides and sterol glycosides,
and either diglycosyldiglyceride or ceramide, monohexoside.
The distribution of lipid types is not uniform in the rice kernel. Approximate ratios of neutral and polar lipids
are 90:10 in bran, 50:50 in the starchy endosperm, and 33:67 in the starch. Thus the bran is rich mainly in
neutral lipids; the endosperm contains relatively high concentrations of polar lipids.
1.1.1.7 Minerals
There is a considerably higher concentration of ash
and of individual minerals in outer layers of the
milled rice kernel than toward the center. P, K, Mg,
Fe, and Mn are concentrated in the aleurone layer;
P, K, and Mg are particularly high in the subcellular
particles of the aleurone layer; Ca is abundant in
the pericarp. The phytin-P constitutes almost 90%
of the total bran-P and 40% of the milled rice-P.
1.1.1.8 Vitamins
Rice and its by-products contain little or no vitamin
A, ascorbic acid, or vitamin D. Thiamine, riboflavin,
niacin, pyridoxine, pantothenic acid, folic acid,
inositol, choline, and biotin are lower in milled rice
than in brown rice and substantially lower than in
rice bran, polish, or germ.
Milling of Rice
The objective of rice milling is to remove the hull,
bran, and germ with minimum breakage of the
starchy endosperm.
Rice Milling
Rice milling is carried out either at small scale or
large scale. The objective of the rice milling is to

9. remove the husk and bran with minimum possible breakage of endosperm. Paddy is generally harvested at 18-
25% moisture and then dried to 12-13% moisture either on farm or at the mill before processing. In an ideal
milling process this will result in 20% husk, 8−12% bran depending on the milling degree and 68−72% milled
rice or white rice depending on the variety.
2.3 Milling Procedure
Combine-harvested rice generally has a moisture content of about 20% (wet basis) and the grain must be dried
immediately to about 12% for storage. Rice is consumed mostly in the form of whole kernels, and accordingly
the processing of paddy is designed to give a high yield of unbroken kenel. The yield of white rice normally
varies between 66% and 70%, based on the weight of rough rice.
2.3.1 Small scale milling
In case of small-scale milling of rice, paddy is placed in a mortar and pounded with pestles either by hands or
with the feet. After some time of pounding, the rice is sifted to separate the husk. The pounding process is
repeated several times. Rice obtained by this process is called brown rice/rough rice and contain a
greaternumber of vitamins as a proportion of the pericarp, testa and aleurone layers remain on the rice grain.
Large scale milling
Schematic representation of
the rice milling process is
depicted in Fig.
1. Cleaning
Cleaning of paddy
comprises removal
of sticks, stones,
dust and other
foreign materials.
This is accomplished
by use of various
separation
methods. The paddy
is first passed over a
screen to remove
larger particles,
straws and string.
After that it is
passed through
second screen,
which is having
smaller perforations
than first screen, to
remove weed seeds
and sand. The
paddy then flows in
the form of a thin layer into a channel where an air current removes dead grains and other lighter
impurities. At the last, paddy is passed through magnetic separator to remove metal
particles.Undesired material, heavier than rough rice (but of similar size) is removed through a de-
stoner/gravity separator.
2. Hulling/Shelling
Husking or de-hulling is a process for removing the rice
hull from the rough rice. Common husking technologies.
Three different husking technologies are commonly
used: Steel husker, underrunner disk husker and rubber
roller husker. In order to separate the remaining
unhusked paddy grains from from the brown rice
fraction and feed them back into the husker a paddy
separator is used. In rubber rolls husker rollers rotating
at different speeds, in opposite directions. A horizontal
inward pressure is applied on the rubble rollers,
pneumatically. Due to the difference in the seed of

10. rotation, a shear force is generated on the surface of hull (with two sides being rubber by tow rubber
rolls) that breaks apart of the surface/hull. The roll diameter varies from 150 to 250 mm and the roller
width from 60 to 250 mm. The correct clearance is dependent on the varietal characteristics and the
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This method of hulling can achieve hulling efficiencies of 85% to 90% with minimum broken or cracked
grain. The rice with the hull removed is commonly known as brown rice/rough rice. Conventional
shellers consist of two steel plates, 4 x 5 feet in diameter, mounted horizontally.

11. 3. Separation-Rice husk and broken rice are removed from the husked material at the winnowing section
which is referred to as aspirator. In the aspirator the material is divided into a mixture of brown rice,
unhusked whole grains, and rice husk. The husked material is taken out by suction of the aspirator fan.
After passing through the rubber roll husker, the brown rice and unhusked paddy grain will move the
next step: the paddy separator.
4. Scouring/Pearling/Whitening
White rice is produced from brown rice by removing the bran layer and the germ. The bran layer is removed
from the kernel by applying friction to the grain surface either by rubbing the grains against an abrasive
surface.
i) Abrasive whitening: In this process the
grain is whitened by the abrasive action of
the rice kernel passing between a moving
abrasive surface and stationary screen.
The hard rough surface is usually stone or
a carborundum type material. The
abrasive process peels off the bran layers
from the brown rice and applies less
pressure on the grain than a friction
process and is therefore better suited for
long grain varieties. Abrasive polishers can be either vertical or horizontal in design. The vertical
cone whitener is very common in many Asian countries.
ii) Friction whitening: In the friction whitener the grain kernels are forced against each other and a
metal screen by a steel-ribbed cylinder rotating inside a metal-plated cylinder. The frictional forces
created between individual rice grains and between the grains and the metal screen surface
remove the bran layer from the grain. Friction polishers are always horizontal in design and apply
more pressure on the grain than an abrasive whitener.
In both the abrasive and friction whitener, provisions are made for a jet stream of air through the cylinder and
portholes to cool the grain, and blow off fine bran. This minimizes breakage and improves efficiency of
subsequent steps in the milling process.
5. Polishing
The surface of whitened rice is still rough and is smoothened by a humidified rice polisher. The rice
grain consisting inner layers of bran is passed through polishing machine often referred to as brush. In
this machine last bran fraction is removed. The grain is now called polished rice.
6. Rice Grading - Broken rice is removed from whole rice by passing the lot through a cylindrical indented
screen rotating at a particular speed. The broken/small grains, fit into the indents of the rotating
cylinder, are lifted by centrifugal force and gravitational pull falls the grains into a trough. Adjusting
the rotational speed and angle of trough can vary the average length of grains.
7. Packing

12. Parboiling of Rice
Parboiled rice (also called converted rice and easy-cook rice) is rice that has been partially boiled in
the husk. The three basic steps of parboiling are soaking, steaming and drying.
Parboiling is a hydrothermal treatment followed by drying before milling for the production of milled parboiled
grain. Parboiling of paddy has been known in the orient for centuries. Nearly 50 per cent of the paddy
produced in India at present is parboiled.
Parboiling is the latest pre-milling treatment which improves the quality of rice. The traditional parboiling
process in India is carried out in different way
Parboiling happens before rice is milled, that is before the inedible outer husk is removed to yield brown rice
but before brown rice is refined to make white rice.
The three main steps of parboiling are:
1. Soaking. Raw, un-husked rice, also called paddy rice, is soaked in warm water to increase the moisture
content.
a) Soaking in Cold Water Paddy soaking at low temperature (below 40°C) requires longer soaking
time which causes loss of vitamins, salts, and albumin from paddy into the water.
b) Soaking in Hot Water Soaking paddy in hot 'water eliminates all the drawbacks of cold water
soaking and reduces the time of soaking significantly.
c) Soaking under High Pneumatic Pressure Moisture content of paddy can be very rapidly increased
by increasing the pressure in the soaking tank to 0.5 to 1.0 atmospheric pressure. Under these
conditions soaking of paddy at 60-65 C temperature can be completed in 30 minutes to 45
minutes.
d) Vapour Phase Soaking Moisture content of paddy can also be' increased very rapidly by treating
paddy with steam under 0.3 to 0.5 atmosphere gauge pressure in a pressure vessel. Paddy can be
soaked in 30 minutes to 45 minutes.

13. 2. Steaming. The rice is steamed until the starch converts into a gel. The heat of this process also helps
kill bacteria and other microbes. Heat Treatment For gelatinization the paddy grain must be uniformly
heated to temperatures higher than the gelatinization temperature (GT) of paddy. The gelatinization
temperature of most paddy varieties ranges from 65 to 75 C.
Soaking in Hot Water at 90 C Soaked paddy is dumped into boiling water and temperature of
mixture is regulated at 90 C for 15-30 minutes. Soaking paddy in hot Water (90 C) under Pneumatic
Pressure Soaked paddy can be parboiled by raising the temperature of mixture to 90 C and raising the
pressure in the soaking tank to 2 atmospheres for a short period of 5 minutes.
3. Drying. The rice is slowly dried to reduce the moisture content so that it can be milled. Drying of grains
to 14% moisture content. The steamed paddy is spread out quickly at an airy place to dry. Excessive
sunshine is avoided otherwise nonuniform drying of kernel which results in breakage during milling.
Drying evaporate the moisture and this concentrates solutes in the kernel drying will also stop
microbial pathogens from developing on steamed paddy. It compresses the gelatinous amylase starch
together in a compact mass and delocalizes it from the husk making de-husking (milling) easier.
Parboiling changes the color of rice to a light yellow or amber, which differs from the pale, white color of
regular rice. Still, it’s not as dark as brown rice
Methods of parboiling and Effect of parboiling on milling quality; The method of parboiling may be classified
as follows;
1. Traditional method; by 1. Single boiling 2. Double boiling
2. Modern methods 1. CFTRI method (India) 2. Jadavpur university method (India) 3. Avorio process
(India) 4. Converted process (India) 5. Malek process (America) 6. Crist allow process (Italian) 7.
Fernandes process (Surinam) 8. Schule process (German) 9. Rice grower’s association of California
process (America)
3. Methods under investigation; 1. Brine solution method (India) 2. Kisan continuous method (India) 3.
Pressure parboiling method (India) 4. RPEC method (India) 5. Sodium chromate method (India) 6.
Parboiling with heated sand method (philipines)
2.3.2.4 Traditional methods
The technique for parboiling of rice was
developed in India to prevent losses
occurring due to breakage during hand
pounding, especially the long-grained
varieties. In this technique paddy is soaked
in excess water and later on cooked in its
husk, the objective being pre-gelatinizing
the starch.
Any hairline cracks are sealed due
to homogeneous mass of gelatinized starch
and thus prevent breakage during milling.
The paddy is then drained and dried.
Parboiling can be accomplished in variety
of ways. The general scheme is to hydrate
(steeping) paddy to 32 – 38% moisture and
partially gelatinize the starch by steam
heating at 15 lb. pressure for 10 – 20 min.
Parboiling causes certain physico-
chemical changes such as improved milling
yields (66 – 70%), increased resistance to

14. insects and firmer cooked rice texture accompanied by a darker and more yellow endosperm. Parboiling has
further advantages like: during soaking and cooking the water-soluble vitamins (niacin, riboflavin, and
thiamine) which are present in germ and pericarp gets migrated into endosperm and thus improves the
nutritional value of parboiled rice. Even proteins present on the grain surface are denatured, become
insoluble, and therefore are not removed during washing and cooking.
The traditional process consists of soaking paddy in water at room temperature for 24-48 hr. or more
steaming in kettles under atmospheric pressure and drying under sun light. In a single boiling method paddy is
soaked in ordinary water for 24-72hr. and then steamed.
In double boiling method steam is first injected in to row paddy in the steaming kettle before soaking.
Hot paddy raises the temperature of soaking water to 45-50 o
C which helps to reduce the soaking time to 24hr.
there after soaked paddy is steamed sometimes, the soaking water is heated to about 50o
C than the row
paddy is put in to it and in this case first steaming is not required.
CFTRI parboiling process (Central Food Technology Research Institute, Mysore)
CFTRI method; In this process, parboiling tanks are filled with clean water and heated to a temperature of
about 85o
C by passing steam through the coils placed inside the tank. Sometimes hot water is pumped from
other sources into parboiling tanks.
The resultant temperature of paddy water mixture in tank stays around 70o
C. After soaking paddy for
3 to 3.5 hrs water is drained out. The water discharge value is kept open in order to remove condensed water
during steaming. Soaked paddy is exposed to steam at a pressure of about kg/cm2 through the open steam
coils. Soaking and steaming of paddy are done in same.
The parboiled paddy is taken out by opening the bottom door and dried either under sun or by
mechanical drier. This is an extremely simple and effective process, although it is entirely manually controlled.
It is a batch process but can be made semi-continuous by using a number of tanks and staggering their
operation. The process has been adopted fairly widely in India, although the older processes and sun drying
have by no means disappeared.
2.3.2.5 Properties:
Milling yield is higher after parboiling and there are fewer broken grains, i.e., there is a greater percentage of
head rice. The grain structure becomes compact, translucent, and shiny. Germination is no longer possible, so
some storage problems are alleviated. The endosperm is denser, making it more resistant to insect attack, and
the grains remain firmer during cooking and are less sticky.
According to Luh and Mickus (1980), the most important changes occurring in parboiling processes are:
1 The water-soluble vitamins and mineral salts are spread throughout the grain, thus altering their
distribution and concentration among its various parts. The riboflavin and thiamin contents are four
times higher and the niacin level is eight times greater in parboiled rice than in whole rice. Thiamin is
more evenly distributed in the parboiled rice.
2 Moisture content is reduced to 10 to 11%.
3 The starch grains imbedded in a proteinaceous matrix are gelatinized and expanded until they fill up
the surrounding air spaces.
4 The protein substances are separated and sink into the compact mass of gelatinized starch, becoming
less susceptible to extraction.
5 Enzymes present in the kernel are partially or entirely inactivated.
6 Microorganisms and insect forms are either killed or greatly reduced in number.
Parboiled rice has a somewhat elastic texture, and for that reason resists breakage when it is milled. The
better head rice yields obtained from the milling of parboiled rice, as compared to raw rice, defrays to a
considerable extent the cost of parboiling so that the parboiled product generally does not sell for much more
than white rice.
Although parboiled rice is not quick cooking, it has certain advantages over raw rice. It is more resistant to
insect infestations and it does not break up as much when used in canned formulations such as soups and
puddings. When overcooked, it does not become as mushy as raw rice. Parboiled rice is darker than raw milled
rice and has a slightly different flavor, but it is widely accepted and is often preferred to white rice. in some
rice-eating areas of the world, however, attempts to introduce it have not been successful. Its color, which is
usually a light tan, is probably an adverse factor for consumers who look upon extreme whiteness as a
indication of high quality.
Advantages of parboiling of rice

15. 1. De-husking of parboiled rice is easy and the grain becomes tougher resulting in reduced losses during
milling
2. Higher yield of head rice from milling because kernel is
more resistant to breakage.
3. Milled parboiled rice has greater resistance to insects and
fungus infection.
4. The nutritive value of rice increases after parboiling
because the water dissolves the vitamins and minerals
present in the hulls and bran coat and carries them into
the endosperm.
5. The water-soluble B vitamins, thiamine, riboflavin and
niacin are higher in milled parboiled rice than in milled raw
rice.
6. Parboiled rice does not turn into a glutinous mass when
cooked.
Disadvantages of parboiling of rice
a) It has a bad smell due to prolonged soaking.
b) It has a dark colour due to heat treatment.
c) It requires prolonged cooking time and more fuel.
d) Since the oil content is more, the polisher may get choked.
e) The heat treatment may destroy antioxidants. Hence,
rancidity may develop.
f) Due to the high moisture content, mycotoxins may be formed.
g) Drying cost is added to the total processing cost, extra capital investment.
Brown Rice versus White Rice
Parboiled rice White rice Brown rice
Calories 194 205 194
Total fat 0.5 grams 0.5 grams 1.5 grams
Total carbs 41 grams 45 grams 40 grams
Fiber 1 gram 0.5 grams 2.5 grams
Protein 5 grams 4 grams 4 grams
Thiamine (vitamin B1) 10% of the RDI 3% of the RDI 23% of the RDI
Niacin (vitamin B3) 23% of the RDI 4% of the RDI 25% of the RDI
Vitamin B6 14% of the RDI 9% of the RDI 11% of the RDI
Folate (vitamin B9) 1% of the RDI 1% of the RDI 3.5% of the RDI
Vitamin E 0% of the RDI 0% of the RDI 1.8% of the RDI
Iron 2% of the RDI 2% of the RDI 5% of the RDI
Magnesium 3% of the RDI 5% of the RDI 14% of the RDI
Material Moisture Protein Lipid Fiber Ash Degree of Polishing
Brown Rice 15.5 7.4 2.3 1.0 1.3 0
Rice Bran 13.5 13.2 18.3 7.8 8.9 -----
Polished Rice 15.5 6.2 0.8 0.3 0.6 8 – 10
Composition of Rice (%)

16. Zinc 5% of the RDI 7% of the RDI 10% of the RDI
2. DEFINITION OF TERMS
For purposes of definition, the following terms shall apply:
 Paddy. Unhulled grain of Oryza Sativa, which means, grain with the glumes enclosing the kernel. It is
also known as "palay" or "rough rice" or "rice grain".
 Milled Rice. Kernels obtained after removal of hull bran.
 Sample. A small quantity taken from various portions of the lot as representative of the whole lot.
 Glutinous Rice. A special type of rice whose grains are white and opaque in appearance. It coagulates
into a sticky mass cooked.
 Broken Milled Rice. This contains a minimum of 75 percent broken kernels in the whole lot.
 Enriched Rice. Milled rice which has been treated to enhance its nutritive value by adding vitamins and
minerals.
 Germ. Small white portion which lies on the ventral side of the rice kernel from where the seed
germinates.
 Brown Rice Rice grain from which only the hull has been removed. This is also known as "dehulled
rice" "cargo rice" or "husked rice".
 Hull. Outermost cover of paddy This is also known as husk.
 Head Rice. A kernel or a piece of kernel with its length equal to or greater than 8/10th of the average
length of the unbroken kernel.
 Big Broken. Pieces of kernels smaller than 8/10th but not less than 5/10th of the average length of the
unbroken kernel.
 Medium Broken. Pieces of kernels smaller than 5/10th but not less than 2/10th of the average length
of the unbroken kernel.
 Small Broken. Pieces of kernels smaller than 2/10th of the average length of the unbroken kernel.
 Brewers. Small pieces of particles of kernels that pass through a sieve having round perforations 1.4
millimeters in diameter. This is also known as "binlid" or "chips".
 Chalky Kernels. Kernels, whole or broken one half or more of which is white like the color of a chalk
and brittle.
 Chemical Residue. Residue acquired by rice through the use of chemical as plant nutrients or as
pesticides. The residue may also be acquired any stage of growing, harvesting, distribution marketing
or processing, Residue of any approved chemical substances added to rice for human nutritional
purposes are, however, excluded.
 Contrasting Types. Kernels and pieces of kernels of varieties or types of rice other than the variety or
type designated wherein size and shape of kernels differ distinctly from characteristics of kernels of
the variety or type designated.
 Objectionable Odors. Odors which are entirely foreign to rice.
 Damaged Kernels which are distinctly damaged by insects, water, fungi, and/or any other means.
 Discoloured kernels. Kernels that have changed their original color as a result of heating and other
means.
 Foreign Matters. All matters other than rice kernel is rice polishing and paddy such as weed seeds and
other crop seeds.
 Grade. A designation indicating the quality of rice determined with reference to its acquired
characteristics specified in Table I.
 Immature Kernels. Kernels which are light green and chalky with soft texture.
 Red Streaked Kernels. Kernels, whole of broken having red streaks the total length of which is one half
of more of the length of the kernel.
 Red Kernels. Kernels, whole or broken which have 25 percent or more of their surface red.
 Brown rice, husked rice or cargo rice: The least processed form of rice. It has the outer hull removed,
but still retains the bran layers that give it a characteristic tan color and nut-like flavor. Brown rice is
edible but chewier texture than white rice. Cooking time of brown rice is longer than milled rice.
 Rough rice: Also called paddy rice. Rice as it comes from the field. Rice kernels are still encased in their
inedible, protective hull.
 Rice Standards means the minimum specifications of rice of each type and grade for domestic and
international trade.

17.  Paddy means rice that is not yet dehusked.
 Chalky kernels mean non-glutinous rice kernels that have an opaque area like chalk covering the kernels
from 50% onward.
 Damaged kernels mean kernels that are obviously damaged as can be seen by the naked eyes due to
moisture, heat, fungi, insects or other.
 Undeveloped kernels mean kernels that do not develop normally as should be, and are flat without
starch.
 Immature kernels mean rice kernels that are light green, obtained from immature paddy.
 Other seeds mean seeds of other plants than rice kernels.
 Foreign matter means other matter than rice. This includes rice husk and bran detached from rice
kernels.
 Milling degree means the degree to which the rice is milled.
 Sieve means round hole metal sieve No.7, that is 0.79mm. (0.031 inch) thick and with hole diameter of
1.75mm 0.069 inch).
 The unit "per cent" means percentage by weight except for per cent of grain classification which is
percentage by quantity.
 Milled rice: Also called white rice, or rice after milling which includes removing all or part of the bran
and germ from the rough rice.
 Milling recovery: Total milled rice obtained out of paddy; expressed as weight percentage of milled rice
(including broken) obtained from a sample of paddy. The maximum milling recovery is 69-70%
depending on rice variety, but because of grain imperfections and the presence of unfilled grains,
commercial millers are happy when they achieve 65% milling recovery. Some village type rice mills have
55% or lower milling recovery.
 Milling degree: A measure of the amount of bran removed from the brown rice’
 Head rice: Milled rice with length greater or equal to three quarters of the average length of the whole
kernel. It is often expressed on a % paddy or rough rice basis (on 14% Moisture content basis).
 Head rice recovery: Weight percentage of head rice (excluding brokens) obtained from a sample of
paddy. Under controlled conditions head rice recovery can be as high as 84% of the total milled rice or
58% of the paddy weight. Commercial rice mills turn out 55% head rice on average, whereas head rice
recovery of village type rice mills is in the order of 30%.
 Whole kernel: A milled rice grain without any broken parts
 Impurities: Materials in the rice that are not part of the milled rice kernel. May include stones, husk,
chaff, weed seeds, etc.
 Broken kernel: Also called brokens. Depending on the rice mill this can be only one fraction or it can
contain several fractions of different size:
 Large broken kernel: 50-75% of the whole kernel size
 Medium broken kernel: 25-50% of the whole kernel size
 Small broken kernel: less than 25% of the kernel size, can not pass through a sieve with 1.4mm
diameter holes
 Chips: fragments of a kernel which pass through a sieve with 1.4mm diameter holes
 Moisture Content. The water content of the rice.
● Video- RICE MILL | RICE PROCESSING https://www.youtube.com/watch?v=RIZi9XTt9Lk

18. ● Video- Rice Milling Process- Animationhttps://www.youtube.com/watch?v=TfD5Uhg3JHo
● Video- Rice Mill Plant | Rice Processing | Paddy Processing | Industry Knowledge
https://www.youtube.com/watch?v=N_oLzIn2TQ8

19. Quality characteristics of paddy:
A number of interrelated features determine the quality of paddy. These are:
1. Moisture content of paddy,
2. Purity degree,
3. Varietal purity,
4. Cracked grains,
5. Immature grains,
6. Discolored/fermented grains and damaged grains.
These characteristics are determined by the environmental weather conditions during production, crop production
practices, soil conditions, harvesting, and post harvest practices.
 Moisture content:
Moisture content has a marked influence on all aspects of paddy and rice quality and it is essential that paddy be
milled at the proper moisture content to obtain the highest head rice yield.
Paddy is at its optimum milling potential at moisture content of 14% wet weight basis.
 Degree of purity:
 Purity is related to the presence of dockage in the grain. Dockage refers to material other than paddy and
includes chaff, stones, weed seeds, soil, rice straw, stalks, etc.
 Grain dimensions:
Grain size and shape (length-width ratio) is a varietal property. Long slender grains normally have greater
breakage than short, bold grains and consequently have a lower milled rice recovery. For instance, the Japanese
designed milling equipment may be better suited to short bold japonica grains whereas Thai made equipment
will be more suitable for longer, slender grain types.
 Cracked grains:
Overexposure of mature paddy to fluctuating temperature and moisture conditions leads to development of
fissures and cracks in individual kernel. Cracks in the kernel are the most important factor contributing to rice
breakage during milling. This results in reduces milled rice recovery and head rice yields.
 Immature grains:
The amount of immature paddy grains in a sample has a major affect on head rice yield and quality. The
immature rice kernels are very slender and chalky and this results in excessive production of bran, broken grains
and brewer’s rice.
The optimal stage to harvest grain in many countries is at about 20-24% grain moisture or about 30 days
after flowering. If the harvest is too late, many grains are dry out and are cracked.
 Fermented grains
Paddy deteriorates through biochemical change in the grain, the development of off-odors and changes in
physical appearance. These types of damage are caused from water, insects, and heat exposure.
 Yellowing:
Yellowing is caused by over-exposure of paddy to wet environmental conditions before it is dried. This results in
a combination of microbiological and chemical activity that overheats the grain.
Quality characteristics of milled rice:
The quality characteristics of milled rice are classified both physically, and chemically.
Review the following terms before reading about physical and chemical characteristics of milled rice:
 Paddy or rough rice = similar term for paddy, or rice retaining its husk after threshing.
 Brown rice or husked rice = paddy from which the husk has been removed.
 Milled rice = rice after milling which includes removing all or part of the bran and germ from the husked rice.
 Head rice = milled rice with length greater or equal to three quarters of the average length of
 Large broken = milled rice with length less than three quarters but more than one quarter of the average length
of the whole kernel.
 Small broken or "brewers rice" = milled rice with length less than one quarter of the average length of the whole
kernel.
 Whole kernel = milled rice grain without any broken parts.
 Milling recovery = percentage of milled rice (including broken) obtained from a sample of paddy.
 Head rice recovery = percentage of head rice (excluding broken) obtained from a sample of paddy.
Physical characteristics:
Milling degree:
The degree of milling is a measure of the percent bran removed from the brown rice kernel. Milling degree affects milling
recovery and influences consumer acceptance. Apart from the amount of white rice recovered, milling degree influences
the color and also the cooking behavior of rice. Unmilled brown rice absorbs water poorly and does not cook as quickly as

20. milled rice. The water absorption rate improves progressively up to about 25% milling degree after which, there is very
little effect.
Head rice:
“Head rice” or head rice percentage is the weight of head grain or whole kernels in the rice lot. Head rice normally
includes broken kernels that are 75-80% of the whole kernel. High head rice yield is one of the most important criteria for
measuring milled rice quality. Broken grain has normally only half of the value of head rice. The actual head rice
percentage in a sample of milled rice will depend on both varietal characteristics (i.e. the potential head rice yield),
production factors, and harvesting, drying and milling process. In general harvesting,
Whiteness:
Whiteness is a combination of varietal physical characteristics and the degree of milling. In milling, the whitening and
polishing greatly affect the whiteness of the grain. During whitening, the silver skin and the bran layer of the brown rice is
removed. Polishing after whitening is carried out to improve the appearance of the white rice. During polishing some of
the bran particles stick to the surface of the rice which polishes and gives a shinier appearance.
Chalkiness:
If part of the milled rice kernel is opaque rather than translucent, it is often characterized as “chalky”. Chalkiness
disappears upon cooking and has no effect on taste or aroma, however it downgrades milled rice. Excessive chalkiness is
caused by interruption during the final stages of grain filling. Though chalkiness disappears upon cooking and has no
direct effect on cooking and eating qualities, excessive chalkiness downgrades the quality and reduces milling recovery.
Chemical characteristics:
Gelatinization temperature:
The time required for cooking milled rice is determined by gelatinization temperature or GT. Environmental conditions,
such as temperature during ripening, influence GT. A high ambient temperature during development results in starch
with a higher GT. GT of milled rice is evaluate by determining the Alkali spreading value. In many rice-growing countries,
there is a distinct preference for rice with intermediate gelatinization temperature.
Amylose content:
Starch makes up about 90% of the dry matter content of milled rice. Starch is a polymer of glucose and amylose is a linear
polymer of glucose. The amylose content of starches usually ranges from 15 to 35%. High amylose content rice shows
high volume expansion (not
High amylose grains cook dry, are less tender, and become hard upon cooling. In contrast, low-amylose rice cooks moist
and sticky. Intermediate amylose rice are preferred in most rice-growing areas of the world, except where low-amylose
japonicas are grown.
Based on amylose content, milled rice is classified in “amylose groups”, as follows:
waxy (1-2% amylose),
very low amylose content (2-9% amylose),
low amylose content (10-20% amylose),
intermediate amylose content (20-25% amylose) and
high amylose content (25-33% amylose).
Amylose content of milled rice is determined by using the colorimetric iodine assay index method.
Gel consistency:
Gel consistency measures the tendency of the cooked rice to harden after cooling. Within the same amylose group,
varieties with a softer gel consistency are preferred, and the cooked rice has a higher degree of tenderness. Harder gel
consistency is associated with harder cooked rice and this feature is particularly evident in high-amylose rice. Hard cooked
rice also tends to be less sticky. Gel consistency is determined by heating a small quantity of rice in a dilute alkali.