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post-harvest technology of rice terminologies
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) Page | For more Information contact: Visit Rice Knowledge Management Portal http://www.rkmp.co.in Rice Knowledge Management Portal (RKMP) Directorate of Rice Research, Rajendranagar, Hyderabad 500030 Email: naiprkmp@gmail.com, pdrice@drricar.org, shaiknmeera@gmail.com Ph: 91-40-24591218, 295 Fax: 91-40-24591217 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 Page | For more Information contact: Visit Rice Knowledge Management Portal http://www.rkmp.co.in Rice Knowledge Management Portal (RKMP) Directorate of Rice Research, Rajendranagar, Hyderabad 500030 Email: naiprkmp@gmail.com, pdrice@drricar.org, shaiknmeera@gmail.com Ph: 91-40-24591218, 295 Fax: 91-40-24591217 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 Page | For more Information contact: Visit Rice Knowledge Management Portal http://www.rkmp.co.in Rice Knowledge Management Portal (RKMP) Directorate of Rice Research, Rajendranagar, Hyderabad 500030 Email: naiprkmp@gmail.com, pdrice@drricar.org, shaiknmeera@gmail.com Ph: 91-40-24591218, 295 Fax: 91-40-24591217 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 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 Page | For more Information contact: Visit Rice Knowledge Management Portal http://www.rkmp.co.in Rice Knowledge Management Portal (RKMP) Directorate of Rice Research, Rajendranagar, Hyderabad 500030 Email: naiprkmp@gmail.com, pdrice@drricar.org, shaiknmeera@gmail.com Ph: 91-40-24591218, 295 Fax: 91-40-24591217 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 Page | For more Information contact: Visit Rice Knowledge Management Portal http://www.rkmp.co.in Rice Knowledge Management Portal (RKMP) Directorate of Rice Research, Rajendranagar, Hyderabad 500030 Email: naiprkmp@gmail.com, pdrice@drricar.org, shaiknmeera@gmail.com Ph: 91-40-24591218, 295 Fax: 91-40-24591217 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 hp motor The cost of machine is Rs 20,000 and cost of cleaning comes to Rs 5/100 kg Page | For more Information contact: Visit Rice Knowledge Management Portal http://www.rkmp.co.in Rice Knowledge Management Portal (RKMP) Directorate of Rice Research, Rajendranagar, Hyderabad 500030 Email: naiprkmp@gmail.com, pdrice@drricar.org, shaiknmeera@gmail.com Ph: 91-40-24591218, 295 Fax: 91-40-24591217 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 250300 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 to tonnes per hour capacity batteries of to 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 Page | For more Information contact: Visit Rice Knowledge Management Portal http://www.rkmp.co.in Rice Knowledge Management Portal (RKMP) Directorate of Rice Research, Rajendranagar, Hyderabad 500030 Email: naiprkmp@gmail.com, pdrice@drricar.org, shaiknmeera@gmail.com Ph: 91-40-24591218, 295 Fax: 91-40-24591217 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 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 Page | For more Information contact: Visit Rice Knowledge Management Portal http://www.rkmp.co.in Rice Knowledge Management Portal (RKMP) Directorate of Rice Research, Rajendranagar, Hyderabad 500030 Email: naiprkmp@gmail.com, pdrice@drricar.org, shaiknmeera@gmail.com Ph: 91-40-24591218, 295 Fax: 91-40-24591217 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 6668% 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 MT/ hr; operating for single shift / day of hr Page | For more Information contact: Visit Rice Knowledge Management Portal http://www.rkmp.co.in Rice Knowledge Management Portal (RKMP) Directorate of Rice Research, Rajendranagar, Hyderabad 500030 Email: naiprkmp@gmail.com, pdrice@drricar.org, shaiknmeera@gmail.com Ph: 91-40-24591218, 295 Fax: 91-40-24591217 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 Raw paddy godown Cleaning unit Drier and necessary supporting structures such as, boiler /blower system etc., Milling section, Finished product stores, Machine rooms, Auxiliary structures such as office watch and ward etc 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' Cleaning Shed - Similar to the raw paddy godown 25' x 32' 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' Finished product or Milled rice storage shed 30' x 35' Machine shed - with masonry structure with ACC sheet roofing on lean truss 40' x25' 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 Page | 10 For more Information contact: Visit Rice Knowledge Management Portal http://www.rkmp.co.in Rice Knowledge Management Portal (RKMP) Directorate of Rice Research, Rajendranagar, Hyderabad 500030 Email: naiprkmp@gmail.com, pdrice@drricar.org, shaiknmeera@gmail.com Ph: 91-40-24591218, 295 Fax: 91-40-24591217 ... 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. .. 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... 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