Post-Harvest Technology in Rice.pdf

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Rice Knowledge Management Portal (RKMP)

Directorate of Rice Research,

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Post-Harvest Technology of Rice

Rice terminologies

Dr.R.T Patil

Director

Central Institute of Post Harvest Engineering and Technology

PO: PAU Campus, Ludhiana-141 004 (Punjab)

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Rough rice or paddy: Defined as rice in the husk after threshing.

Stalk paddy: Defined as unthreshed in the husk, harvested with part of the stalk.

Husked rice/brown rice: Rice from which the husk only has been removed retaining still the bran

layers and most of the germs. Such rice is sometimes reflected to as bran rice even though there

are variations having red or white bran coats.

Milled rice: Rice from which husk, germs, bran layers have been substantially removed by lower

machinery, also known as polished rice and if milled to high degree it is called as white rice.

Under milled rice: Rice from which the husk germs and bran layers have been partially removed

by power machinery and is also known as unpolished rice.

Hand produced rice: Rice from which the husk, germ and bran layers have been partially removed,

without the use of power machinery, also known as “home produced” or “hand milled rice”.

Parboiled rice: Rice, which has been specially processed by steaming or soaking in water, heating

usually by steam and drying. Parboiled paddy can be milled to various degrees or home produced

in the same way as ordinary paddy. It is called as parboiled milled or parboiled hand pounded.

Raw milled: The paddy, which is milled not after giving heat treatment, such as parboiling.

Coated rice: Defined as rice milled to a high degree and then coated with glucose on “Talcum”.

Whole grain: Refers to husked, milled or hand produced rice which does not contain any broken

grains smaller than 3/4 of the size of the whole kernel.

Broken rice: Husked, milled or hand produced rice consisting of broken grains of less than 3/4th

size of the whole grain but not less than 1/4th.

Fragmented rice: Small brokens upto 1/4th size of the whole grain.

Husk: The by-product from the milling of rice consisting of the outermost covering of the rice

kernels.

Bran: A by-product from the milling of rice consisting of the outer layer of the kernels with part of

germ.

Rice polishing: Now defined as the by-product from milling rice, consisting of the inner bran layer

of the kernel with part of the germ and a small percentage of the stoney interior also known as

rice meal or rice flour elsewhere.

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Glutinous rice: A type of rice, which after cooking has a peculiar stickyness regardless of how it is

cooked.

Scented rice: A type of rice, which contains aroma and gives scented smell on cooking.

Rice flour: Ground polished rice which is mainly starch with very little gluten. Used in the same

way as corn flour and for noodles, sweets and short pastry.

Quick cooking rice: Rice that had been completely cooked then dehydrated.

Head rice yield: Head rice yield is the weight percentage of rough rice that remains as whole rice

(three-fourths kernel or greater) after complete milling.

Milling yield/Total yield: Milling yield is the weight percentage of rough rice that remains as

milled rice; i.e., the sum of head rice and "brokens."

Rice bran oil: It is the oil extracted from the germ and bran of rice.

Puffed rice: It is a type of puffed grain made from rice; usually made by heating rice kernels under

high pressure in the presence of steam, though the method of manufacture varies widely.

Popped rice: Raw rice is traditionally popped by heating rough rice at higher temperatures about

240°C for up to 45 seconds. The hull contributes to pressure retention before popping. aGood

popping varieties have a tight hull and a significant clearance between hull and brown rice and

when freshly harvested are free of grain fissures.

Rice flakes: The production of rice flakes begins with parboiling of rice which helps to soften the

grain and prepare it for processing. Once the rice is tender, the cooked grains are rolled and

flattened. After the mixture is the desired thickness, the flattened rice is allowed to dry

completely. The dried flakes are run through another rolling process to create simple flakes.

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Introduction

Rice is the staple food for 65% of the population in India. It is the largest consumed calorie

source among the food grains. With a per capita availability of 73.8 kg it meets 31% of the total

calorie requirement of the population. India is the second largest producer of rice in the world

next to China. In India paddy occupies the first place both in area and production. Indian Basmati

Rice has been a favorite among international rice buyers. Following liberalization of international

trade after World Trade Agreement, Indian rice will become highly competitive and has been

identified as one of the major commodities for export. This provides us with ample opportunity for

development of rice based value-added products for earning more foreign exchange. Apart from

rice milling, processing of rice bran for oil extraction is also an important agro processing activity

for value addition, income and employment generation.

It has been reported that about 9 percent of paddy is lost due to use of old and outdated

methods of drying and milling, improper and unscientific methods of storage, transport and

handling. It has been estimated that total post harvest losses of paddy at producers’ level was

about 2.71 percent of total production. To minimise post harvest losses, precautions should be

taken to follow proper post harvest practises. They include timely harvest at optimum moisture

percentage (20 percent to 22 percent), use of proper method of harvesting; avoid excessive

drying, fast drying and rewetting of grains. Ensure drying of wet grain after harvest, preferably

within 24 hours to avoid heat accumulation, uniform drying to avoid hot and wet spots and

mechanical damage due to handling. The losses in threshing and winnowing can be avoided using

better mechanical methods. Proper sanitation during drying, milling and after milling to avoid

contamination of grains and protect from insects, rodents and birds and use of proper technique

of processing i.e. cleaning, parboiling and milling helps in reduction in post harvest losses. To avoid

storage losses maintaining optimum moisture content i.e. 12 percent for longer period and 14

percent for shorter storage period is essential.

Harvesting at proper maturity

Paddy crop should be harvested, when the grains become hard and contain about 20-22

percent moisture. Harvesting before maturity means a low milling recovery and also a higher

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proportion of immature seeds, high percentage of broken rice, poor grain quality and more

chances of disease attack during storage of grain. Delay in harvesting results in grain shattering

and cracking of rice in the husk and expose the crop to insects, rodents, birds and pests attack, as

well as lodging. Harvesting during wet weather conditions should be avoided and done by

adopting proper method. The water from paddy field should be drained about a week or 10 days

before the expected harvesting, which helps in employing mechanical harvesters. Avoid pest

infestation prior to harvesting. Harvested material should be protected from rain and excessive

dew by covering, avoid direct sun drying, which leads to an increase in breakage of the grains

during milling. For combine harvesting, moisture percentage should be 18 per cent, or lower.

When paddy is harvested by hand it gets a chance to get dried before threshing. In the case of

combine harvesting, a sizeable percentage of green kernels are threshed along with mature

kernels. It paddy is harvested with a combine harvester and kept in gunny bags, rotting of seed will

invariably start. Therefore, it is very necessary that the paddy harvested with combine harvesters

must be dried until moisture percentage comes down to 13 per cent, or lower. Similarly, the

paddy harvested by hand should also be dried to 13 per cent or below moisture content. At the

time of storing the moisture in the seed grain should never exceed 13 per cent and there should

be no green kernels. Use tarpaulin or pukka (cemented) floor for drying

Threshing of Paddy

Align all the panicles in one line to get proper threshing. If the threshing is delayed, keep

the harvested paddy stalk bundles in a dry and shady place, which facilitates the air circulation and

prevents excessive heating. Thresh the paddy in the field itself. Transport the grain in bags, which

minimises the grain losses. Avoid too much post harvest handling of paddy to minimise the grain

losses. Pack the paddy in sound B-Twill jute bags totally free from any contamination.

Simple pedal operated threshers are also used to thresh the paddy in the field. One person

operates the thresher with foot pedal and one or two persons feed the bales from behind for

threshing. These threshers are also motorised with Single phase 1HP electric motor for threshing

of Paddy. The machine is run and one or two persons feed the bales from behind for threshing.

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Mechanical Paddy threshers consist of worm type threshing cylinder, oscillating box,

winnowing and cleaning attachment, feeding chute etc. These threshers can be operated both

with motor and diesel engine tractors. During threshing the paddy crop's straw is separated from

grain by worm type cylinder. The straw is thrown out from the machine with the help of blower.

Other impurities like dust/dirt are thrown out through other outlet. Extra blowers provided

cleaning the grains of left-over impurities. The capacity of these machines varies from 300 kg/h to

1500 kg/h.

Cleaning of Paddy

The hand operated and power operated winnowing fans are commercially available. The

paddy threshed by manual beating or by pedal operated paddy thresher is cleaned by using these

fans. These winnowing fans consist of frame either made up of wood, angle iron, welded steel or

combination of the two along with driving mechanisms namely, sprocket and chain, belt and

pulleys and single or double reduction gears.

A hand operated paddy winnower was developed by Central Rice Research Institute,

Cuttack. Two women workers are required for the operation of this winnower, one for cranking

the blower and other for feeding the threshed material and collection of grain. The average output

was found to be 242 kg grain/h and winnowing efficiency was found to be 88.36%. The equipment

developed was found to be suitable for operation by women workers as the heart rate, work pulse

value and energy expenditure rate are within the acceptable limits.

Motorised paddy winnowing machine was developed at TNAU Coimbtore. It consists of a

feed hopper to hold the grain for cleaning. It discharges the grain over a scalper and removes

bigger size impurities. A blower provided at the bottom, passes air against the grain falling

through the scalper which separates the straw, chaff and other impurities. The dust, chaff and

straw are collected separately and cleaned paddy is taken out through another outlet near the

bottom of the unit. The capacity of the machine is 500-750 kg/h and operated with 1 hp motor.

The cost of machine is Rs. 20,000 and cost of cleaning comes to Rs 5/100 kg.

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Milling of Paddy

Rice milling is the oldest and the largest agro processing industry of the country. At present

it has a turn over of more than 25,500/- crore per annum. It processes about 85 million tonnes of

paddy per year and provides staple food grain and other valuable products required by over 60%

of the population. Paddy grain is milled either in raw condition or after par-boiling, mostly by

single hullers of which over 82,000 are registered in the country. Apart from it there are also a

large number of unregistered single hulling units in the country. A good number (60 %) of these

are also linked with par-boiling units and sun -drying yards. Most of the tiny hullers of about 250-

300 kg/hr capacities are employed for custom milling of paddy. Apart from it double hulling units

number over 2,600 units, under runner disc shellers cum cone polishers numbering 5,000 units

and rubber roll shellers cum friction polishers numbering over 10,000 units are also present in the

country. Further over the years there has been a steady growth of modern rice mills in the

country.

Basic Milling machines

Traditional huller

It is a relatively small unit with a throughout capacity of 100 to 150 kg per hour operated

by oil or steam engine or an electric motor. In small villages single hullers are used while in bigger

mills of 1 to 2 tonnes per hour capacity batteries of 3 to 4 hullers are used. Most of the other

operations, excepting milling proper, are done invariably. The huller does the job of the husk

removal and bran removal simultaneously. The working element of this machine is made of cast

iron, which bears very heavily on rice grains thereby breaking them to pieces which are liable to be

lost alongwith husk. The hullers even though cheaper in cost are wastage and have high labour

requirement.

Centrifugal shellers

In this machine the grains are subjected to centrifugal force by means of a rotating

impeller. Significant characteristics of these centrifugal shellers are: Their high capacity and simple

constitutional features as there is only one moving part i.e. an impeller. Its casing is lined with

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rubber. The paddy is fed to the centre of the rotor from where it is thrown towards the casing

with great force where it is shelled. This machine has a very good potential, as there is a possibility

of combining several units and obtain a compact multistage mill to affect complete shelling.

Another advantage, in case of this type of machine is that heating of grains does not take place as

there is no grinding action involved. Polishing of brown rice obtained is done by a separate

polisher. The centrifugal shellers are available which have the built-in winnower to remove the

husk.

Disc sheller

In this type the two operations of dehusking and whitening were intended to be carried

out separately in separate machines. The disc sheller mills may be called unit mills as all the

operations involved in milling, cleaning, dehusking paddy separation, polishing and grinding are

done mechanically and by separate machines. The basic machine i.e. under runner disc sheller

consists of two discs with their inner faces lined with emery bottom one rotating and the other

stationary. The paddy passes in between the two discs and gets shelled or dehusked. Therefore

the breaking is less and the white rice yield is also more of the order of 66-68 percent with 10 to

15 percent brokens. There are adjustments provided on the dehusker so that the clearance

between the discs could be adjusted for most of the variety of paddy. It gives a marked increase (2

to 4 percent) in rice output over conventional huller in almost all milling condition.

Rubber Roll Sheller

The greatest advantage of rubber roller over cast iron cylinder or the emery roller is that

due to their compressible nature the grain handled gently during the process of dehulling. The

functional coefficient between paddy grain surface and rubber is lower than that of paddy and

steel. This facilities easy dehulling. The two rubber rollers rotate in opposite direction at

differential speed to take off the aspiration. Since all the paddy is not dehusked paddy must be

separated. This is accomplished by a paddy separator. The brown rice (rice with bran coating on) is

then fed to rice whitener where the bran is removed.The rubber roller mill gives better quality rice

and bran which fetch more price in the market.

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Composite Rice Mill

The basic rice milling processes consists of Pre Cleaning to remove all impurities and

unfilled grains from paddy, De-stoning for Separating small stones from paddy, Husking to

removing husk from paddy, Aspiration to separate the husk from brown rice/ unhusked paddy,

Paddy Separation which separates the unhusked paddy from brown rice, Whitening to removing

all or part of the bran layer and germ from brown rice, Polishing to improve the appearance of

milled rice by removing the remaining bran particles and by polishing the exterior of the milled

kernel, Length Grading to separate small and large brokens from head rice, Blending is for mixing

head rice with predetermined amount of brokens, as required by the customer.

The recovery of whole grains in a traditional rice mill using steel hullers for dehusking is

around 52-54%. There is excessive loss in the form of coarse and fine brokens. Further loss of large

portion of endosperm layers during the dehusking operation further accentuates the problem.

Against it, the recovery percent of whole grains in modern rice mills using rubber roll shellers for

dehusking operation is around 62-64%. The whole grain recovery percent further increases to 66-

68% in case of milling of parboiled paddy. Thus it can be seen that there is an overall improvement

of recovery of whole grains by about 10-14% if one uses rubber roll shellers for rice milling

operations. The recovery of various components from these improved rice mills are milled head

rice: 62-68%, rice bran: 4-5%, rice husk: 25%, and germ wastages: 2%-8%

It has been observed that dehusking using rubber roll shellers reduces the risk of breaking the

grain because husk is pulled off almost at once and pressure is applied by means of resilient

surfaces across the width of the grain, where kernels, generally are much more uniform than they

are by length. Moreover, the process does not remove the internal epidermis of the husk. Thus

the deshelled grains with their silver skin envelope are protected against scratches and keep

longer and better while the silver skin and the germ increases the quantity of bran which is

produced while whitening. The improved rice mills have a better husk and rice bran aspiration

system. The same prevents mixing of fine brokens with rice bran. Therefore the quality of rice

bran obtained is better.

Generally 2.00 to 2.50 acre of land is required for establishing an improved rice milling unit

having an installed processing capacity of 2 MT/ hr; operating for single shift / day of 8 hr

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duration; 300 days per annum; i.e. 4800 MT /annum. The land should be with proper elevation.

Low lying areas should be avoided. Else proper land filling, compaction and consolidation should

be done. Drainage and linkages with road and other communication should also be ensured. The

layout of the rice milling plant should be done in a manner that helps in smooth operation of

various unit operations in tandem to bring about optimal capacity utilization and economizing

power consumption. The tentative cost of land and land development charges for the model

project has been considered at Rs. 5.00 Lakh ( Rs. 3.75 Lakh being the cost of the land @ Rs. 1.50

Lakh per acre for 2.50 acre and the remaining Rs. 1.25 Lakh being the cost for site development

such as construction of boundary wall, internal roads and drainage system etc.) The various

construction requirement of an improved rice milling unit are 1. Raw paddy godown 2. Cleaning

unit 3. Drier and necessary supporting structures such as, boiler /blower system etc., 4. Milling

section, 5. Finished product stores, 6. Machine rooms, 7. Auxiliary structures such as office watch

and ward etc.

1. Raw paddy godown- RCC framed superstructure with 10'' thick brick walls, IPS flooring with

damp proof treatment with 1.62 kg DPC /sq.m of floor area and base of the side walls, roofing

consisting of ACC sheets affixed with J hooks, bolts and other accessories to steel truss made of

MS angle of desired section 80' x 35'

2. Cleaning Shed - Similar to the raw paddy godown 25' x 32'

3. Milling shed -RCC framed superstructure with brick walls, IPS flooring and roofing consisting of

ACC sheets affixed with J Hooks and nuts to steel trusses made of MS angle of desired section and

strength bearing capacity. 80' x 35'

4. Finished product or Milled rice storage shed 30' x 35'

5. Machine shed - with masonry structure with ACC sheet roofing on lean truss 40' x25'

6. Auxiliary structures; a Office unit 10' x 15' , Labor quarters 30 ' x 15', Machine Room for auxiliary

machines like blowers/ generator set etc. 40' x 15', Bore well and water connections, e Sanitary

and plumbing

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Parboiling of Paddy

Parboiling of paddy is a hydrothermal process in which the starch granules within the rice

grain are gelatinized by the application of steam and hot water. This helps in higher percentage of

recovery of head rice. Parboiling rice drives nutrients, especially thiamine, from the bran into the

grain, so that parboiled white rice is 80% nutritionally similar to brown rice. It reduces breakage in

milling, improves storage life and helps in the preservation of protein and vitamins in the rice. The

starches in parboiled rice become gelatinized, making it harder and glassier than other rice. In

conventional methods, parboiling is carried out by hot water soaking and subsequent steaming.

Under the prevailing global energy crisis, any parboiling method which saves energy is a welcome

feature. Energy can be saved in the parboiling process by skipping any one of the three distinct

unit operations namely, soaking, steaming and drying or by combining any two operations at a

time. Direct steaming of freshly harvested high moisture paddy improves the head rice recovery

but with inferior quality. Parboiling of the soaked paddy could be carried out with less energy

input by applying the dry heat instead of moist heat (steam) which takes care of both

gelatinization and subsequent drying. One of the possible methods for energy saving for parboiling

of paddy is the continuous dry-heat parboiling. The dry-heat parboiling has the unique feature of

parboiling and drying of paddy, simultaneously. The heat requirement for parboiling of paddy is

the same irrespective of method employed to achieve it, however the efficiency of the system is

governed by thermal efficiency of the heating source, heat transfer between source and the

subject, heat loss by conduction, convection and radiation, and sensible heat of the system.

Drying of parboiled paddy

Sundrying of parboiled paddy

Most of paddy parboiled in the traditional mills is sun dried on a drying floor. The drying

floor is normally cemented floor consisting of layer of brick bats with cement plaster on it. The

parboiled paddy is spread on the floor 10 to 30 mm thick layer by labour with the help of a plank

then it is continuously stirred by a spiked plank or by feet. After four hours of drying in sun, paddy

is heaped and covered by mats for tempering for a period of 2 to 3 hours. Then the paddy is

spread again for 2 hours in the sun to dry it to desirable moisture content. Therefore, drying of

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parboiled paddy from 30 percent to 13 percent moisture content takes about 6 hours during

summer and relatively long period about 8 to 10 hours during winter.

Mechanical drying of paddy

It is the process utilising mechanical means for drying grain by ventilating natural air or

heated air through the grains mass to accomplish removal of moisture from it. In other words

mechanical drying of paddy refers to removal of moisture from wet paddy by unheated and/or

heated forced air at a predetermined rate of flow, air temperature and air relative humidity. Rate

of moisture removal could be regulated. It is observed that if paddy is harvested at about 24

percent moisture and dried mechanically in stages by 3 or 4 passes of heated air the milling losses

are minimum. Heated air convection type dryers are commonly used for drying paddy. Types of

commonly used dryers are Bag dryers, Bin or batch dryers, Continuous flow dryers and Rotary

drum dryers

Bag Dryers:

This type of dryer is suitable for drying smaller quantity of grains. It requires large number

of unskilled labour for handling the bags. The dryer consists of a large floor area in the building

with the opening over which the grain bags are placed. The openings are covered with a

perforated material to support the bags and allow air movement through the bags. The air is

blown in the holes by a burner and air blower assembly. In this type dryer, air is heated up to 45°C

and is blown in the dryer at the rate of 4 cubic meters per minute per bag of 45 kg of dried grains.

The bag should be turned once during operation for exposing both sides to heated air.

Batch Dryer:

The dryer consists of a bin or a container to hold grain with an air blower and a burner for

providing hot air. The bin or the container is fitted with a perforated bottom in case of most of the

bin or batch dryers. However godown or a room in a building with a perforated floor may also be

used. The godown or room is equipped with air dust system for air distribution throughout the

room. A fan with heater unit is then connected to the duct system to supply the required air to dry

the grains. In all batch type dryers the depth of grain is limited due to high power requirement to

force air through deeper grain mass.

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Continuous flow dryers:

Continuous flow dryers are of two types (I) mixing and (ii) non-mixing type. Both types of

dryers are used for commercial drying of paddy and hence high drying capacities. Grain is usually

fed in the top and flows through the dryer by gravity. Rate of discharge is mechanically regulated

at the bottom. Drying is accomplished by forcing heated air through the grain as it flows

downwards. In non-mixing columnar dryer the paddy descends between two parallel screens set

15 to 20 cms apart while heated air is blown through the screens. No appreciable mixing occurs

and effect is similar to drying in static bed with a depth equal to distance between the screens.

Mixing type are of many designs, two of the most popular being baffle design and Louisiana State

University design. In a baffle dryer paddy flows downward in zig-zag path through the baffles while

heated air is forced through the grains. The Louisiana State University dryer consists of a bin in

which layers of inverted shape air channels are installed. Alternating layers are air inlet and air

exhaust channels. Each layer is offset so that the top of each inverted channel split in the stream

of paddy coming on it. Paddy flows between channels taking a zig-zag path as it descends. Drying

air passes from air inlet the air exhaust channels thus removing moisture from the paddy.

Rotating Drum dryer:

This consists of a large drum 1 to 2 meter in diameter and 3 to 6 meters in length placed on

a slight inclination and the drum rotates about its axis. The inside of the drum is equipped with the

helical straight edge ribs to provide the mixing and the forward movement of the paddy during

drying operation. The hot air blown at the lower end of the drum and the paddy flows counter

current to direction of air flow. These types of dryers are normally used for drying parboiled

paddy.

Modern Paddy Dryers

The new developed mechanical dryers reduced the moisture of parboiled paddy from 36%-

12% in a continuous operation within a few minutes. This offers several advantages over the

conventional dryer in terms of lower utility consumption, reduction in breakage, no color

variation, single pass drying, increase in equipment life and minimal maintenance. It is supplied

with steam heater, hot air blower and exhaust fan with dust collection system. The continuous

steaming and drying system consists of Continuous steaming vessel with feed and discharge

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control, Pre-Dryer (Static Fluid Bed) and Vibrating Fluid Bed Dryer. The cleaned and steamed

paddy is soaked in the soaking tank at required temperatures for a desired duration. After removal

of water from the soaking tank, the soaked paddy is passed through continuous steaming vessel

for proper gelatinization to ensure minimum breakage of grain. The steaming vessel is provided

with controlled feed and discharge mechanism to optimize gelatinization. This steamed paddy at

36% inlet moisture is continuously fed into a Static Fluid Bed Dryer at a uniform feed rate where

the surface moisture is instantly removed. There after the paddy at 32% moisture is fed into first

vibrating fluid bed dryer, where the paddy is kept in suspended stage and the moisture is reduced

to 22%. This paddy at 22% moisture is fed into second fluid bed dryer where the moisture is

reduced to 16% and is then fed into third fluid bed dryer where the moisture is further reduced to

12-14%. However, in case of Basmati Rice, the moisture is reduced to 22% using the static and

first Vibro Fluid Bed Dryer and further drying is carried out in LSU dryer upto 12%.

Mini Parboiling Unit

Improved parboiling technique of hot water soaking and atmospheric steaming (CFTRI) and

pressure parboiling (RPEC) has been developed. The Cuttack centre has developed a mini

parboiling unit for on farm/domestic parboiling of paddy. Traditionally soaking and steaming are

done separately with parboiling unit. Both the operations can be done without any further

handling in the same unit. A hot soaking for 3-5 hours in 75°C water and steaming and subsequent

sun drying results in about 2 percent more head rice than achieved traditionally. The capacity is 75

kg per batch with output of 150 kg per day.

Toxins in Rice

Aflatoxin: -Aflatoxins are the type of mycotoxins, which are derived from the fungi, which

affect human health. Aflatoxins are produced by Aspergillus flavus, Aspergillus ochraceus and

Aspergillus parasiticus. Contamination of Aflatoxins occurs at any stage from field to storage,

whenever environmental conditions are conducive for fungi. The fungie are generally regarded as

storage fungi, which grow under conditions of relatively high moisture/humidity. It causes severe

liver damage and both liver and intestinal cancer in humans. Generally, milled rice contains low

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levels of Aflatoxins, but parboiled rice and paddy harvested in rainy season contains high Aflatoxin

levels. Storage insects like rice weevil, lesser grain borer, khapra beetle, etc also encourage

Aflatoxins in paddy/rice. According to PFA Rules, 1955, the Aflatoxins in rice should not be more

than 30 microgram / kilogram.

Prevention and Control of Aflatoxins: The paddy/rice should the stored at safe moisture level.

Prevent the growth of fungi by drying of grains. Use proper and scientific storage method. Prevent

insect infestation by adopting chemical treatment to avoid fungus contamination. Separate the

infected grains.

Packaging

Good packaging provides not only convenient handling in transportation and storage but

also attracts consumers to pay more. Packaging is essential to avoid spoilage and to prolong the

quality. Packaging of paddy/rice is also important for long-term storage to fulfil the demand of old

rice in the market, particularly in case of Basmati and non-parboiled rice. Paddy/rice, if kept in

open, quality may be adversely affected. Packaging is closely related to labelling and branding. In

present scenario, branding and labelling of rice has significant impact on consumer preference.

More care is required in packaging of rice meant for export. This is because of demonstrative

effect and the requirements of consumers in different countries; exporters have now started using

transparent, colourful and attractive packaging. For good packaging, the packages must protect

rice very well and should be long lasting, look clean, convenient to handle and carry out from the

store easily.

The graded rice should be packed in new, clean, sound and dry jute bags, cloth bags,

polywoven bags, polyethylene, polypropylene, high molecular high density polyethylene paper

packages or in other food grade plastic/packaging materials. The packages shall be free from

insect infestation, fungus contamination, deleterious substances and undesirable or obnoxious

smell. Each package shall be securely closed and suitably sealed. The rice shall be packed in

quantities as specified under the provisions of the Standards of Weights and Measures (Packaged

Commodities) Rules, 1977 as amended from time to time. Suitable number of consumer packs

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containing graded material of the same lot may be packed in master container. The packaging

materials used in packaging of paddy/rice are Jute bags, HDPE / PP bags, Polythene impregnated

jute bags, Poly pouches and Cloth bags. Usually, the cost of a HDPE bags may be around 50-60

percent of the cost of jute bags. In paddy/rice, usually B-Twill jute bags are used. The initial cost of

packaging varies according to the type of material used for making bags. Rice is stored in HDPE

bags for six months, whereas in jute bags, for 3 months. Thus, the economics of packaging

depends not only on the type of packaging material but also the duration for which the paddy/rice

is likely to be stored.

Transportation

Paddy is transported usually in bulk from field to the market, while rice is transported both

in bulk and bags. The following means of transportation are used at different stages of marketing.

There are different modes of transport used in paddy/rice transportation. Road and rail transport

are normally used for internal markets, whereas, for export markets, the mode of transport is by

Sea.

Road transport is the most predominant mode of transport used in the movement of

paddy/rice. Road transport is used in right from the producing fields to the ultimate consumer.

The initial movement of paddy/rice is done on village roads, which are generally non tarred

(Kachha), and mostly tracks wind through the fields. Over the years, road transport has expanded

phenomenally, due to the development of roads in rural areas, as well as by the increase of

numbers and efficiency of different types of vehicles i.e. trucks and tractors etc. The following

means of road transport are employed in different parts of the country to transport paddy/rice.

Railway is one of the most important means of transportation of paddy/rice. Railway is

cheaper than road transport and more suLa transport of paddy/rice depends on distance, quantity

etc. Railway transportation requires more handling cost, as it requires loading and unloading

charges and local transportation cost. However, losses are more in case of transport by railways.

For safe and scientific storage of paddy/rice, the storage should be easily accessible. The

land of the site should be protected from moisture, excessive heat, insects, rodents, and bad

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weather conditions. In godowns, sufficient space should be provided between two stacks for

proper aeration. The structure should be clean, free from left-over grains, cracks, holes and

crevices in the structure and should be fumigated before storage. Before storage, paddy/rice

grains should be properly dried and cleaned to avoid quality deterioration. It is advisable to always

use new and dry gunny bags. If old bags are to be used disinfect them by boiling in 1 percent

Malathion solution for 3-4. Minutes and dry them properly. Separate storage of should be

maintained for new and old stock. Bags of should be kept on wooden crates or bamboo mats

along with a cover of polythene sheet to avoid absorption of moisture from the floor. Proper

aeration should be provided in clean weather condition and avoided in rainly aseason.

Improved storage structures

1. Improved bins

Different organisations developed and designed improved storage structures for scientific

storage of foodgrains, which are moisture resistant and rodent-proof. These are Pusa Kothi, Nanda

bins, PKV bins, PAU bins, Hapur Kothi and Chittore stone bins etc

2. Brick-build godowns

These are made by brick-walls with cemented flooring for storing paddy/rice in bulk and

bags.

3. Cement plastered bamboo bin

This bin developed by Post Harvest Technology Centre, Kharagpur, in which bamboo strips

are used to form the skeleton of the bin and cement-sand mortar (1:2.5 ratio) is plastered on

outer and inner surface of the bin.

4. CAP (Cover and plinth) storage

It is an economical way of storage on a large scale. The plinth is made by cement concrete

and bags are staked on open and covered by polythene cover.

5. Silos

Silos are used for storage of foodgrains. These are made from concrete, bricks and metallic

materials with loading and unloading equipment.

Utilisation Pattern

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Staple food: Rice is a staple food and used by many ways as under. Rice is used as a staple food by

more than 60 percent of World population. Cooking of rice is a most popular way of eating. There

are many ways of domestic use like khichadi, pulav, kheer, zeerarice, iddli, dosa etc.

Starch: Rice starch is used in making ice-cream, custard powder, puddings, gel, distillation of

potable alcohol, etc.

Rice bran: It is used in confectionery products like bread, snacks, cookies and biscuits. The

defatted bran is also used as cattle feed, organic fertilizer (compost), medicinal purpose and in

wax making.

Rice bran oil: Rice bran oil is used as edible oil, in soap and fatty acids manufacturing. It is also

used in cosmetics, synthetic fibers, plasticisers, detergents and emulsifiers. At present, about 6

lakhs tonnes of rice bran oil is produced from 35 lakhs tonnes rice bran per annum in the country.

It is nutritionally superior and provides better protection to heart,

Flaked rice: It is made from parboiled rice and used in many preparations.

Puffed rice: It is made from paddy and used as whole for eating.

Parched rice: It is made from parboiled rice and is easily digestible. In India, about 4-5 percent of

total supplies of rice is used as parched rice.

Rice husk: It is used as a fuel, in board and paper manufacturing, packing and building materials

and as an insulator. It is also used for compost making and chemical derivatives.

Rice broken: It is used for making food item like breakfast cereals, baby foods, rice flour, noodles,

rice cakes, Idli and dosa etc. and also used as poultry feed.

Rice straw: Mainly used as animal feed, fuel, mushroom bed, for mulching in horticultural crops

and in preparation of paper and compost.

Paddy as a seed: The paddy is used as seed. The proportion utilized for seed purpose varies from 2

to 6 percent of total production.

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Innovation in Rice Processing

Soft drying for high moisture paddy

Soft drying of paddy is a quite new concept in which moisture transfer takes place from

raw paddy to dry dusk utilizing dry husk’s hygroscopic character without heat stress under normal

temperature (Fig. 1). The running cost of soft drying is low because no heat is required, only

aeration is done using high capacity blowers. The storage tanks with mixing arrangements can be

used for drying. The process provides higher head yield due to no heat stress to grain as in sun

drying or mechanical drying. There is no cracking of grain due to drying. It is energy saving

technique because of no heavy mixing of paddy during drying. The drying of moistened paddy is

relatively simple as there is no quality concern. In the process, dry husks are likely to absorb

moisture from raw paddy moisture. Gradually, moisture contents of higher and lower get

balanced.

Bio polishing

Mechanical milling results in lower head rice yield with loss of major nutrients. To minimize

the loss incurred during mechanical milling and to resolve the problems associated with brown

rice, a novel alternative polishing method has been attempted to bio-polish the rice with some

selected multi-enzymes having the catalytic properties to degrade the bran layer of rice. The

enzymes are the selective biocatalysts, which are very specific to their targeted reactants. Thus

through such processes the amount of by-product yield is minimum. These enzymes can be

produced in large quantities through biotechnological route where different types of bioreactors

can be used. Depending upon the nature of fermentation process, the reactor systems can be

selected.

Such bio-polishing has been carried out on germinated brown rice to get softer, nutritious

brown rice with the added benefits of germinated rice. The bio-polished rice has been found to be

superior in every aspect when compared to milled rice. The salient features of bio-polishing are no

loss in head rice yield, nutrient rich than milled rice, fibre content more than milled rice, with

benefits of germinated brown rice, softer with less cooking time than brown rice, enzyme treated

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rice has been found to have better shelf-life as compared to the non-treated rice, enzymatically

treated rice possessed higher antioxidant potential, free amino acids, crude fibre and phenolics as

compared to the non-treated rice. There are many benefits of bio-polishing, such as mechanical

damage to rice kernel can be avoided, parboiling process can be skipped, nutrient loss or weight

loss can be avoided, selective bio-polishing has helped to retain the mineral with minor losses in

Magnesium, Iron and Zinc, while Calcium content increased by 10%, enzymatic treatment

exhibited more positive effect on water uptake ratio and volume expansion ratio, less cooking

time, and easier for digestion (www.tech2transfer.com/pdf/enzymatic_polishing.pdf).

Calorific and nutrient content of brown and milled rice and losses during milling

Parameters Enzyme treated rice Milled rice

Protein (%) 7.68±0.312 7.28±0.294

Ash content (%) 0.97±0.09 0.26±0.18

Crude oil (% of bran) 16 ± 0.98 -

Free amino acid (mg equivalent

of leucine /g of rice)

1.5 ± 0.093 1.1 ± 0.082

Crude fibre (%) 5.6 -

Total phenolic content µg

equivalents of gallic acid

154 34

Calcium mg/100g of rice 2.92 0.91

Magnesium mg/100g of rice 14.75 13.59

Iron mg/100g of rice 1.92 1.36

Zinc mg/100g of rice 0.65 0.44

Thiamine mg/100g of rice 0.073 ± 0.012 0.032 ± 0.009

Pyridoxine mg/100g of rice 0.726 ± 0.025 0.072 ± 0.011

Niacin mg/100g of rice 0.834 ± 0.058 0.364 ± 0.028

Riboflavin mg/100g of rice 0.042 ± 0.01 -

Optimum cooking time (min) 28 ± 2 18 ± 2

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Volume expansion ratio 3.22 4.00

Water uptake ratio 2.8 3.6

Grain elongation ratio 1.49 1.69

Hardness of cooked rice 59.7 ±1.68 56.0 ±1.52

Cost Rs 100-110/kg* Rs 55-60/kg

*Calculation done based on the laboratory data and reagents used

Process for quick cooking brown rice

Consumption of brown rice is extremely valuable to health. The bran fraction accounts for

5-8% of the brown rice weight and is the most nutritious part of the seed. The problem is that

brown rice takes a long time to cook (40-45 min.), due to the slow rate of hydration. This long

cooking time produces sticky soft texture on the surface, unlike white rice. Consequently, the

consumption of brown rice has been significantly limited in some of the countries. A novel process

for increasing the rate of hydration of brown rice without loss of the nutritious and beneficial

portions of the seeds has been discovered. In this process, rice is bombarded with rice flour

sufficient to create microperforations in the water-resistant outer coat of the seed. These micro-

perforations in the treated rice significantly increase the rate of hydration, and hence, decrease

cooking time to about 20 minutes (Guraya et al. 2003).

Curing of high moisture paddy

The process of accelerated ageing in freshly harvested paddy is called curing. Generally,

newly harvested fresh rice cooks to pasty mass, whereas when the process of ageing is applied,

the stickiness reduces and the cooking quality improves. The curing of high moisture paddy yields

partially parboiled rice and compares better in nutrition than raw rice. It is also better in colour

and texture than the parboiled rice. The research work was reported with variety White Ponni and

it was observed that open steaming of paddy for 30 min duration is sufficient enough for curing.

Beyond this level, parboiling effect was imparted in the treated rice. In a study, the varieties Asd

36 and IR 50 were harvested at different moisture levels and the quality parameters, viz., milling

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and cooking characteristics after curing were reported to be better for ASD-36

(http://mofpi.nic.in/annualreport/reports/pprc9798/report.htm).

In both the varieties, the maximum shelling and milling breakage were observed in treated

samples of 12-13% moisture range. Hence, inspite of higher bulk swelling volume and better

colour of this moisture range samples, the one at 15-16% moisture range were found to be

suitable for curing treatment. Among the different open steaming, viz., 5, 10, 15, 20, 25, and 30

min, the treatment of 20 min open steaming showed better performance in all moisture ranges

studied (http://mofpi.nic.in/annualreport/reports/pprc9899/report.htm).

Rice based products

Rice-based healthy French fries:

Rice is also hypoallergenic, nutritious and easily digested, and it stores well. The fries from

broken and immature/thin rice kernels were developed, which has been reported to fetch a lower

price than regular whole rice. The new product made from rice flour mixtures is quite similar to

the potato fries in texture, cooking and other properties. In tests, the rice fries generally absorbed

25-50 per cent less fat from oil during cooking than potato fries. The possibility is being explored

to use of rice fry as a "functional food," since it can be fortified with vitamins, minerals, protein

and other nutrients (Kadan, et al., 2001-I & II and

www.foodnavigator.com/news/ng.asp?id=41123-rice-based-healthy).

High power rice flour:

Rice contains abundant starch and high quality protein and are commonly used in food and

beverage industries. Generally, rice contains 6-10 per cent (w/w) protein and 70-80 per cent (w/w)

starch. Separation of protein and starch allows for the processing of high-protein rice flour and

starch hydrolysates into different products. To simplify the production process and improve the

cost effectiveness and efficiency of starch bioprocessing, the scientists expressed a

thermotolerant and bi-functional starch hydrolase, amylopullulanase (APU), in transgenic rice

seeds. Transgenic rice seeds were heated at high temperatures. Starch in transgenic seeds was

hydrolyzed rapidly at these temperatures, and the concentration of soluble sugars increased

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significantly with incubation time. The researchers found a correlation between APU activities and

the starch-to-sugars conversion rates. The more APU present in seeds, the faster the rate of starch

hydrolysis to sugars. Scientists generated novel APU-transgenic rice seeds. It is reported that the

unique feature of heat-activated rapid autodrolysis of starch in these seeds could not only

eliminate the need for the addition of commercial enzymes, but also improve the efficiency of

starch bioprocessing. According to the researchers, these seeds can be processed to

simultaneously produce high-protein rice flour and sugar syrups for human consumption. In

addition, it is claimed that a similar approach could be applied to other cereals, such as maize,

which might offer even less production cost than rice

(http://www.foodnavigator.com/news/ng.asp?id=41123-rice-based-healthy).

Rice bars:

Snack bars using rice include granola, breakfast, and energy bars. Snack bars target the

health conscious consumer and are often enriched. A breakfast bar contains milk infused into the

grains composing the bar to give one the taste of a bowl of cereal. Crisped rice is used in granola,

breakfast, and energy bars. High-pressure extrusion processing is generally used for the

manufacture of crisped rice for these snack bars

(www.irri.org/publications/wrrc/wrrcPDF/session9-06.pdf).

Rice desert:

Desserts with rice emerged in the late 1990s with waxy rice serving as a fat replacer in ice

cream. The addition of 1.5% waxy rice starch improves the creamy mouthfeel and overall texture,

allowing the product to mimic premium (higher fat) ice cream. The excellent freeze-thaw stability

of waxy rice starch helps reduce iciness during storage (Bakal 1994, Wilkinson and Champagne

2004). Crisped rice provides texture to a number of chocolate dessert products.

Rice dairy products:

Rice has also found new applications in dairy alternatives and electrolyte-replacement

drinks. Rice offers a lactosefree, hypoallergenic alternative to cow and soy milk products. In soy

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milk, rice flour and syrup can be used to help mask beany flavors and keep insoluble proteins

suspended in solution (Burrington 2002). In electrolyte-replacement drinks, the long-chain

carbohydrates and proteins of rice enhance the absorption of fluid and electrolyte salts into the

body’s cells (Greenough 1998).

Half products for microwave puffing of expanded food product:

Third-generation snack products or pellets, sometimes referred to as semi- or half-

products, are not new to the snack-food industry. In fact, they have been very popular in many

regions of the world. Extrusion systems for the production of multidimensional third-generation

snacks are efficient, economical to run and result in a product with built-in marketing flexibility

due to long shelf-life and high bulk density prior to frying or puffing. In its product aspect, half

products or pellets especially useful in the at-home preparation of a puffed finished food product.

The finished puffed food products include both R-T-E cereal embodiments and snack food

embodiments.

The half products are fabricated from gelatinized farinaceous cereal dough essentially

comprising rice flour, wheat flour, wheat starch, sugar(s), fatty triglyceride, salt, and moisture. The

half pellets desirably weigh about 0.05 to 3.5g each. The pellets further essentially include a sugar

coating. The pellets are further essentially characterized by being puffable to at least three times

their original size, and as being case hardened. The dough is further essentially characterized as

being high shear dough. For producing microwavable half products, the processing steps are (i)

forming a preliminary mixture comprising a starch-containing material, comprising rice flour,

wheat starch and/or wheat flour, oil, sugar(s), salt and added water adequate to bring the total

moisture content of the mixture from about 16% to about 35% by weight; (ii) gelatinizing the

starch content of the mixture to form a dough by subjecting the mixture to high shear agitation

while heating to prepare a highly worked dough; (iii) extruding the resulting dough through a

shaped die and cutting to provide formed dough pieces; (iv) drying the formed dough pieces to

form half products having a moisture content approximately in the range of 9.5% to 17% by

weight under conditions which result in at least some case hardening; and (v) sugar coating the

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half products to provide a sugar coated half product having a weight ratio of sugar coating to half

product ranging from about 0.02 to 0.08:1 (www.freepatentsonline.com/5102679.html).

Vitamin-enriching rice extrusion process

Vitamins and minerals tend to be lost during the whitening and polishing of rice, but a new

extrusion mechanism transforms rice broken into vitamin-enriched rice pellets. The resulting rice

pellets can be customized in terms of colour, shape, size, and the composition of their component

substances and their cooking characteristics can also be tailor-made. Depending on the specific

process applied, the extruded product may serve as instant rice pellets, as quick-cooking rice

pellets, or as a product for admixture to natural rice.

In this process, the rice broken obtained during whitening, which up to now were usually sold as a

low-grade animal feed, are finely ground and transformed by cooking extrusion into rice-like

grains, a vitamin mix is added to the rice in the form of a powder or sprayed directly onto the rice,

the new process integrates the vital substances in the extruded rice grains themselves. This

conserves most of the sensitive vitamins during storage, washing and even cooking, and results in

more efficient rice processing.

It is possible to enrich the rice pellets with various micronutrients such as vitamin A and the

vitamins of the B complex in addition to minerals and trace elements. But in addition, proteins,

essential amino acids, fatty acids, and antioxidants plus probiotic and prebiotic ingredients can

also be added (http://www.foodproductiondaily.com/news/ng.asp? id=55229-buhler-develops-

vitamin).

Processing Rice Bran

Bran is the hard outer layer of grain and consists of combined aleurone and pericarp. Along

with germ, it is an integral part of whole grains, and is often produced as a by-product of milling in

the production of refined grains. When bran is removed from grains, the latter lose a portion of

their nutritional value. Bran is present in and may be milled from any cereal grain, including rice,

corn (maize), wheat, oats, barley and millet. Bran should not be confused with chaff, which is

coarser scaly material surrounding the grain, but not forming part of the grain itself.

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Bran is particularly rich in dietary fiber and omegas and contains significant quantities of

starch, protein, vitamins and dietary minerals. It contains various antioxidants that impart

beneficial effects on human health. A major rice bran fraction contains 12%-13% oil and highly

unsaponifiable components (4.3%).[citation needed] This fraction contains tocotrienols (a form of

vitamin E), gamma-oryzanol and beta-sitosterol; all these constituents may contribute to the

lowering of the plasma levels of the various parameters of the lipid profile. Rice bran also contains

a high level of dietary fibres (beta-glucan, pectin and gum). In addition, it also contains ferulic acid,

which is also a component of the structure of non-lignified cell walls. However, some research

suggests that there are levels of inorganic arsenic (a toxin and carcinogen) present in rice bran.

One study found the levels to be 20% higher than in drinking water.[1] Other types of bran

(derived from wheat, oat or barley) contain less arsenic than rice bran, but not necessarily the

same health benefits.

The high oil content of bran makes it subject to rancidification, one of the reasons that it is

often separated from the grain before storage or further processing. The bran itself can be heat-

treated to increase its longevity.

Uses of bran

Bran is often used to enrich breads (notably muffins) and breakfast cereals, especially for

the benefit of those wishing to increase their intake of dietary fiber. Bran may also be used for

pickling (nukazuke) as in the tsukemono of Japan. Rice bran finds particularly many uses in Japan,

where it is known as nuka. Besides using it for pickling, Japanese people also add it to the water

when boiling bamboo shoots and use it for dish washing. In Kitakyushu City, it is called Jinda and

used for stewing fish, such as sardine. Rice bran and rice bran oil are widely used in Japan as a

natural beauty treatment. The high levels of oleic acids make it particularly well absorbed by

human skin, and it contains over 100 known vitamins, minerals and antioxidants including gamma

oryzanol which is believed to impact pigment development. Bran oil may be also extracted for use

by itself for industrial purposes (such as in the paint industry), or as a cooking oil, such as rice bran

oil.

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Bran for pets and livestock

Bran is widely used as a major component in foods for cows, buffaloes, goats, rabbits,

guinea pigs, etc. Rice bran is sometimes fed to horses for its nutritional value, particularly as a

plant-based fat supplement. It is considered an excellent way to put weight onto a thin horse,

without the problems associated with overfeeding grain. Rice bran is also included in some foods

for aging dogs. A rice bran extruder apparatus maintains a continuous flow of bran with

appropriate heating to stabilize the bran to prevent information of free fat acid and rancid oil. A

supply hopper includes a rotating paddle to stir the bulk bran for continuous gravity feed of the

bran into a feed conveyor mounted immediately beneath the hopper. The feed conveyor is

aligned with the bran extruder to supply bran to the inlet opening. The extruder includes a flighted

rotor and terminates in a conical discharge nozzle. Extrusion of the bran results in heating of the

bran to stabilize the lipase, destroy bacteria and produce stable bran providing oil and an edible

end product. The flighted rotor has closely spaced flighting and at least 12 agitator elements

secured between the flights for at least the last four flights to establish a continuous movement of

the powdery rice bran through the extruder and positively prevents blow back of the bran. The

extruder is directly connected to a universal voltage and frequency motor which operates at 885

RPM and produces 75 horsepower with widely differing A.C. voltages and/or frequencies. A

slipping clutch is provided in the direct drive connection to prevent damage if the extruder is

overloaded.

Bran for oil extraction

A modification of the process of oil extraction from rice bran is proposed, introducing one

or two enzymatic reactions previous to solvent extraction. Although a total aqueous enzymatic

extraction process did not result in reasonable oil extraction yields, an interesting alternative

result from enzymatic reactions previous to solvent extraction or pressing. A thermal treatment of

rice bran is first applied to deactivate lipase, but also to gelatinize starch previous to reaction with

α-amylase. This is followed by a saccharifying step with glucoamylase to produce glucose (28

g/100 g of rice bran treated), while the residual paste, 66.7% of the original bran, may be

subjected to a proteolytic process for protein extraction or directly treated with the solvent to

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obtain bran oil. Finally, under the defined extraction conditions using hexane, yields of oil are 5%

higher when rice bran has been previously treated with α-amylase.

Rice bran for Nutraceuticals

Historically, preserving rice bran for general consumption was not feasible. With traditional

milling methods, an enzyme called lipase rendered the bran and germ rancid in a matter of hours.

This system of rice bran processing had no shelf life and, therefore, little commercial value. An

enzyme called Lipase, which exists naturally in the bran layer, comes in contact with the bran’s oil

and begins rapid degradation of the bran within seconds after removing the bran from the rice

kernel. Delicately deactivating the destructive effects of Lipase activity, while maintaining 100% of

the nutrition in rice bran can only be accomplished by means of our all natural, non-chemical

process.

Processing take place immediately after raw rice bran is removed during the milling

process and enzymes that cause rancidity neutralized. It results in highly nutritious rice bran with a

one-year shelf life. The stabilized rice bran is available in granular, fine or extra fine grinds.

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Stabilized rice bran can further be reprocessed into different modified product derivatives such

dextrinized bran, nutrient-dense soluble fiber fraction of SRB and insoluble fiber fraction.

Value-added processing with respect to rice milling has traditionally treated the rice bran

layer as a homogenous material that contains significant concentrations of high-value components

of interest for pharmaceutical and nutraceutical applications. Investigators have shown that high-

value components in the rice bran layer vary from differences in kernel-thickness, bran fraction,

rice variety, and environmental conditions during the growing season. The studies were conducted

to quantify the amount of rice bran removed at pre-selected milling times and to correlate the

amount of rice bran removed at each milling time with the concentration of vitamin E, gamma-

oryzanol, rice bran saccharide, and protein. The rice bran fractionation is a useful method to

obtain targeted, nutrient-rich bran samples for value-added processing. Results showed that the

highest oryzanol and protein concentrations were found in the outer portion of the rice bran layer,

while the highest rice bran saccharide concentration was found in the inner portion of the bran

layer. Vitamin E concentration showed no significant difference across the bran layer within a

variety, though the highest magnitude of concentration occurs within the first 10 seconds of

milling. To extract the higher concentration of oryzanol and protein only the outer portion of the

bran layer requires processing, while to extract the higher concentration of rice bran saccharide,

only the inner portion of the bran layer requires processing. Rice bran, which is originally a by-

product of rice processing that is usually discarded or used for animal feed, has emerged in recent

years as a functional ingredient for use in foods and dietary supplements. It is considered to be a

rich source of vitamins, minerals, antioxidants and fiber.

Processing of Rice Husk

Rice milling industry generates a lot of rice husk during milling of paddy which comes from

the fields. This rice husk is mostly used as a fuel in the boilers for processing of paddy. Rice husk is

also used as a fuel for power generation. Rice husk ash (RHA) is about 25% by weight of rice husk

when burnt in boilers. During milling of paddy about 78 % of weight is received as rice, broken rice

and bran. Rest 22 % of the weight of paddy is received as husk . This husk is used as fuel in the rice

mills to generate steam for the parboiling process. This husk contains about 75 % organic volatile

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matter and the balance 25 % of the weight of this husk is converted into ash (RHA). This RHA in

turn contains around 85 % - 90 %amorphous silica. So for every 1000 kgs of paddy milled, about

220 kgs (22 %) of husk is produced, and when this husk is burnt in the boilers, about 55 kgs (25 %)

of RHA is generated.

Application of Rice Husk Ash

RHA is a carbon neutral green product and a good super-pozzolan. This super-pozzolan can

be used in a big way to make special concrete mixes. There is a growing demand for fine

amorphous silica in the production of special cement and concrete mixes, high performance

concrete, high strength, low permeability concrete, for use in bridges, marine environments,

nuclear power plants etc. Other uses of rice husk ash are for green concrete, refractory, ceramic

glaze, insulator, roofing shingles, waterproofing chemicals, oil spill absorbent, specialty paints,

flame retardants, carrier for pesticides, insecticides and bio fertilizers etc etc.

Processing of Paddy Straw

Fresh rice straw has high energy content, but its use as feed for ruminants is limited by the

high levels of lignin and silica in the straw. These make it difficult for livestock to digest. By

processing the rice straw, its quality and digestibility can be improved. Processing can also

increase the protein content of rice straw. The rice straw can be processed by applying urea

(ammoniation) even at small or medium-sized farms. This technology can be used to provide

animal feed in the dry season or as a feed supplement.

Fiberboard

By incorporating rice straw with wood chips fibreboards were made. Medium-density

fiberboard were successfully produced from a 50/50 mixture of rice straw and hardwood chips.

Paper and Dissolving-Grade Pulps

Pulp is used in making paper and cellulose products that have many industrial uses. Rice

straw can be used as a source of pulp for making commercial grade paper and also for high grade

artistic paper.

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Gasification for Energy

Gasification is the thermo-chemical process required to convert rice straw to a gas type of

fuel that could replace natural gas and diesel. The straw is processed through a hammer mill

before entering the fuel-feed system. The system can convert 500 to 1,000 pounds of rice straw

per hour to hot raw producer gas that captures 60 to 65 percent of the energy in the raw fuel.

Conversion to Sugar Syrup and Yeast Protein

Sugar syrup and yeast protein were produced from rice straw in the laboratory by the

Department of Environmental Toxicology at UC Davis. The most successful procedure produced 25

grams of sugar from 100 grams of rice straw. The sugar was used to produce food grade yeast. The

yeast single-cell protein was comparable to other protein sources when the yeast was fed to mice

at 50 percent of the total protein source. A lower nutritional value was obtained when the yeast

single cell protein was fed as the sole protein source. The technical feasibility for converting rice

straw to sugar and single-cell protein has been proven though its commercial feasibility needs to

be confirmed.

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References

Nutritive value of Indian Foods, Gopalan, C., et.al. Indian Council of Medical Research Publication,

1971.

Principle & Practices of Post Harvest Technology, Pandey, P.H. (1998).

Agricultural Marketing in India, Acharya, S. S. and Agarwal, N. L. (1999).

Handling and Storage of Foodgrains, S.V. Pingale (1976).

Post Harvest Technology of Cereals, Pulses and Oil seeds, Chakruverty A.(1988).

Marketable Surplus and Post Harvest Losses of Paddy in India-2002, Directorate of Marketing &

Inspection, Nagpur.

Alam A, Wani Shafiq A, Parray GA. 2007. Current status and future prospects of aromatic rice

cultivation in Kashmir. Rice India, 17(2):22-26.

Bakal A. 1994. The lowdown on formulating low fat. Prep Foods, 163: 75-78.

Burrington KJ. 2002. More than just milk. Food Prod. Design, 12: 37-64.

Greenough WB. III. 1998. Oral hydration therapy: something new, something old, Infec. Dis. Clin.

Pract. 7: 97-100.

Guraya, H.S., James Jr, C., Champagne, E.T. 2003. Novel rice processing technologies: an

environmentally friendly way. Temperate Rice Conference Proceedings. CD-ROM.

http://mofpi.nic.in/annualreport/reports/pprc9899/report.htm

Kadan RS, Bryant RJ and Boykin DL. 2001-I. Effects of processing conditions on qualities of rice

fries. Journal of Food Science, 66(4): 610-613.

Kadan RS, Bryant RJ and Boykin DL. 2001-II. Rice fry texture as affected by gum application and

mechanical perforation. Journal of Food Science, 66(8): 1084-1088.

Swaminathan MS. 2008. Science and shaping the future of rice. Rice India, 18(1): 65-72.

Wilkinson HC, Champagne ET. 2004. Value-added rice products. In: Champagne ET, editor, Rice

Chemistry and technology. 3rdedition. St. Paul, Minn. (USA): American Association of Cereal

Chemists. P 473-493.

www.freepatentsonline.com/5102679.html

www.foodproductdesign.com/articles/0601de.html

www.foodnavigator.com/news/ng.asp?id=41123-rice-based-healthy

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www.ficciagroindia.com/general/agriculture-statistics

www.n-sharyo.co.jp/business/plant_e/sds.htm

www.irri.org/publications/wrrc/wrrcPDF/session9-06.pdf

www.tech2transfer.com/pdf/enzymatic_polishing.pdf

^ "Inorganic Arsenic in Rice Bran and Its Products Are an Order of Magnitude Higher than in Bulk

Grain - Environmental Science & Technology (ACS Publications)". Pubs.acs.org. 2008-08-21.

http://pubs.acs.org/cgi-bin/abstract.cgi/esthag/asap/abs/es801238p.html.

^ "Superfood rice bran contains arsenic - environment - 22 August 2008 - New Scientist".

Environment.newscientist.com. http://environment.newscientist.com/channel/earth/dn14592-

superfood-rice-bran-contains-arsenic.html?feedId=online-news_rss20.

Singh S P and L P Gite 2007. Ergonomical Evaluation of a Hand Operated Paddy Winnower by

Women Workers Journal of Agricultural Engineering Vol. 44(4): October-December, 2007.

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UTILIZATION OF BY-PRODUCTS OF RICE MILLING INDUSTRIES

The economics of rice milling industries is largely dependent on the useful commercial

utilization of its by-products. Husk, Bran and Broken Rice are the by-products of the rice milling

industries. These by-products can be used in better and profitable manner both for industrial and

feed purposes. The methods for the effective utilization of these-by-products are discussed

below:-

Rice-Husk

Rice husk constitutes the largest by-product of rice milling and one fifth of the paddy by

weight consists of rice husk. Rice husk has a considerable fuel value for a variety of possible

industrial uses. Hence, the major use of husk at the moment is as boiler fuel, wherever parboiling

is practiced. Rice husk is tough because of its silica-cellulose content. The silica content in husk is

the highest among plant offal. It contains 15 to 18 percent silica, therefore, it is a potent source of

silica for the manufacture of silicates or in glass manufacture. Also pulverized husk is available

wherever paddy is parboiled and it is mixed with other mill fractions as cattle feed. Pulverized

husk has a low feed value and it has low protein content. It contains more than 30% crude fibre. If

nitrogen content in pulverized husk is increased by blending with other nitrogen rich feeds and

fibre content is brought down to around 10 per cent, pulverized husk can be used as cattle feed on

large scale.

Rice-Bran

Rice bran is the most valuable by-product of the rice milling industry. It is obtained from

the outer layers of the brown rice during milling. Rice bran consists of pericarp, aleurone layer,

germ and a part of endosperm. Rice bran obtained during milling amounts to 4 to 9 per cent of the

weight of paddy milled. True bran amounts to 4 to 5 per cent only and rest is polishing of inner

bran layers and portion of the starchy endosperm.

Rice bran can be classified into three groups -

Full fatted raw bran (i.e. raw bran) obtained from milling of raw paddy

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Full fatted parboiled bran (i.e., parboiled bran) obtained from milling of parboiled paddy

De-fatted/De-Oiled bran obtained after extraction of oil from either raw or parboiled bran.

Rice bran can be utilized in various ways. It is a potential source of vegetable oil. Refined oil

can be a supplementary source of edible oil. Raw rice bran contains 12-18% oil, whereas parboiled

bran contains 20-28% oil. The de-oiled bran contains about 1 to 3 percent oil only. Rice bran also

contains high fat and protein. It also contains vitamins, minerals and many other useful chemicals.

Because of its nutritional value, it is being used as feed for poultry and livestock. Defatted/de-oiled

bran contains higher percentage of protein (17-20%) vitamins (A and E) and minerals than full

fatted bran obtained from raw and parboiled paddy. In fact, full fatted bran is an excellent

ingredient for both food and feed.

Crude bran oil contains high free fatty acids (FFA) and is used for manufacture of soap and

fatty acids. Crude oil of high FFA is refined and produced of low FFA content (about 5%) for edible

purpose. Tocoferol and waxes of high melting points are the by-products of the bran oil refining

industry, which are suitable for various industrial uses.

Various uses of rice bran, bran oil and its different constituents are discussed below:-

Edible Oil Grade

Bran oil contains low linolenic acid and high tocoferol; hence, it has distinct advantage over

other vegetable oils. Edible oil can be produced by refining and suitable hydrogenation of bran oil.

There is immense potential to increase edible rice bran oil in India. In fact, there is a vast gap

between the potential and actual production of rice bran oil in India. The paddy production in

India and possible availability of rice bran production and extraction of bran oil production are

given below:-

Paddy production during 2000-01 = 126.67 million tonnes

Estimated Bran production @ 7.5% of Paddy = 9.50 million tonnes

Estimated oil production @15% of bran produce =14.25 lakh tonnes

Present production of bran oil = 5.00 lakh tonnes

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Scope to increase bran oil production (14.22-5.00) =9.25 Lakh tonnes

There is a gap of 9.22 lakh tonnes between actual production and production potential of

rice bran oil in India. This gap is mainly due to the poor milling machinery being used by millers in

the country. In fact, poor rice milling machinery produce poor quality rice bran which can not be

used for oil extraction economically as its oil contents is very low. If financial & technical supports

are provided to the rice bran oil producers in the country, the total production of rice bran oil can

be increased as estimated above. Presently, Japan is the major producer of rice bran oil. If proper

efforts are made with Japan authority for technology transfer, this will help in improving the

production potential of rice bran oil in India. During the year 1991-2000 the rice bran oil

production has shown increasing trends in the country. Edible rice bran oil in India has not become

very popular among the consumers. Therefore, a consumer awareness campaigns is required to

be initiated at various level. If rice bran oil is popularized as alternative healthy edible oils, country

can reduce the edible oil imports and it could become potential substitute for import oils. This will

also help the country to save the foreign exchange.

Rice bran oil is more economical than the other traditional cooking oils because while

cooking it absorbs 20-25% less oil as compared to other traditional cooking oils. Besides, at the

time of frying there is no much degradation of oil. The rice bran oil possesses the same frying

properties as ground nut oil. Rice bran oil fries the food faster and after frying it becomes more

golden brown colour resulting in lighter testing food. Food cooked in rice bran oil increases it

flavour and palatability.

Industrial Grade Crude-Oil

(a) Soap Manufacture

Rice bran oil contains high free fatty acid (FFA) hence, highly suitable for manufacture of

soft soap and liquid soap. Other kinds of metallic soap such as aluminium, barium and calcium

soaps are also manufactured from rice bran oil and they find market as components of lubricants.

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(b) Free Fatty Acid Manufacture

By hydrolysis technique of the triglycerides of fatty acids into fatty acids and glycerol, fatty

acids and glycerol are obtained. The uses of hydrogenation in combination with fractional

distillation pure stearic and oleic acids are obtained.

Protective Coatings

From rice bran oil resin based paints, enamels, varnishes etc. are prepared.

Plasticisers

Fatty acids and fatty oil based plasticisers are used in the plastic and rubber industries.

Tocoferol

Crude rice bran oil contains 2% - 4% tocoferol and it has nutritional and antacid effect.

Edible oil contains about 1% - 2% tocoferol rest is lost during deodorizing process.

Rice Bran Wax

Rice bran wax is used for coatings of candy, fruits and vegetables as it prevents moisture

loss and shrinkage. It is also used as component for manufacture of carbon paper base, stencils,

candles etc.

Use of De-Oiled Bran and Bran

Feed

De-oiled/ defatted rice bran, which is a rich source of protein (17 to 20 per cent) and

vitamins (vitamins A & E) is used as a cattle and poultry feed. De-oiled bran is more suitable for

feed than raw bran due to higher nutritional value, higher digestibility and better keeping quality.

Food

In preparation of bakery products such as bread, cake, biscuits etc. de-oiled/defatted bran

can be used as an ingredient. In baking flour, fine powder of de-oiled bran can be added up to

20%.

Fertilizer

De-oiled/ defatted bran contains plant nutrition i.e., N.P.K. and it can be used as fertilizer.

Raw bran is not suitable for use of fertilizer because it contains high fat and wax, which are

harmful for plants and roots.

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Medicinal Use

Rice bran contains valuable Vitamin-B complexes, amino acids, phosphoric acid compound

etc. and can be used in pharmaceutical industry. Protein can also be easily extracted from rice

bran.

Broken Rice

Broken rice is another by-product of rice milling industry. From the nutritional point of

view, broken rice is as good as whole rice itself. Broken rice has low economic value as compared

to whole rice. Generally, broken rice is of poor quality due to admixture with grit, stones and clay

particles. Therefore, broken rice is used either as a part of animal feed or partially in the diet of

poor people. If the quality of broken rice is improved by cleaning the paddy properly before

milling, it can be utilized and marketed straightway for preparation of Idli, Dosa and other such

preparation in which rice flour or wet-ground rice paste is needed.

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