Rice Milling Process IntroductionRice milling is the process of removing rice bran layer and Husk from the paddy to obtain edible rice.Milling is done by two methods; traditional Method (Hand Pounding Method) and Mechanical Method(Modern Method). Traditional milling rice is considered to be more nutritive as compared to mechanicalmethod.Post Harvest Operations Cleaning and Huller(Husk Paddy Drying Removal) Polisher (Bran Grader removal) 1) Paddy: Paddy or rice paddy or rough rice is the individual rice kernel in its natural form, which is not processed yet. Rice can be obtained from paddy either by hand pounding/Manual method or by Mechanical Method. Various types of rice (Brown, Sela, Steamed and Raw) can be made from paddy only; once paddy goes to huller rice type cannot be changed. Moisture content at the time of harvest in paddy is 20%-24% but needs to be dried to have 12%-14% of moisture to meet the milling specifications.Types of Basmati based on processing: Basmati Paddy Steamed Sela/ Parboiled Raw/White Brown Basmati Basmati Basmati Basmati
Brown Rice: Brown rice or Hulled rice or unmilled rice is obtained from paddy after drying, cleaning andhusking (removing husk). Head grain has a layer of bran over it; therefore it has got more nutritionalvalue over white rice.Steamed Rice: Direct steam is given to paddy to make it steamed rice. Steaming gelatinizes starch inpaddy and it obtains cooking quality and taste and there is no need to store it, to age the rice.Parboiled Rice: To make Parboiled (Partially Boiled) rice, paddy is boiled/soaked in water for 1-2 days toget moisture of 30%-35%. Paddy is soaked/boiled in water and then passed through steaming and thenit is dried either under open sky or mechanically. Parboiling reduces susceptibility to breakage and lossof essential mineral and vitamins; parboiled also contains 80% of nutrients of brown rice. Parboiled ricecontains 20%-25% bran oil.Raw Rice: When huller removes the husk/chaff paddy, the product is brown rice and further processingof brown rice through polisher gives raw rice or white rice. It has fewer nutrients as compared to Brownrice but it tastes best. 2) Cleaning and Drying: Harvested paddy grain needed to be cleaned before it is further processed. Weed seed, stones, straw and other impurities are removed from paddy by a simple pre cleaning machine which has a oscillating double screen bed before further processing. If moisture content is more than desirable content then it is dried either mechanically or under open sky. 3) Huller: Rice huller or rice husker is used to remove the rice husk/Chaff. Huller removes the husk but bran remains intact then, rice is sent to polisher for removing rice bran and for further polishing. 20%-22% husk is obtained from paddy. Husk is used as fuel, in making cardboard and to obtain Rice Husk Ash (RHA). 4) Polisher: Polisher receives rice from Husker/Huller which removes husk and polisher removes bran layer from rice. 7%-9% of bran is obtained from brown rice. Bran is further processed to extract rice bran oil and oil recovery from bran is 14%-18%. 5) Grader: When rice passes through polisher, some quantity of rice breaks, hence a grader is used to separate the broken rice from head or full length rice.Rice after grading:Rice received from grader comes in two lengths: 1) Head/Full length Rice 2) Broken RiceBroken rice can be further sub-divided in following categories: 1) Dubar (10%-12% of Broken rice) 2) Tibar (4%-5% of Broken rice) 3) Kinki (86%-83% of Broken rice)
A) Mogra B) Mini Mogra C) Tiny Mogra D) NakkuByproducts of Paddy Paddy Immature and Rice Husk Bran Damaged Rice Fully Fatty Rice Husk Ash Fully Fatty De-oiled rice Head Grain Broken Rice Parboiled (RHA) Raw Bran Bran( DRB) bran Dubar(10%- Tibar(5%-6% Kinki(85%- 12% of of broken 82% of Broken Broken Rice) Rice) Rice) Mogra Mini Mogra Tiny Mogra Nakku HuskRice Husk is the largest by product of paddy; it constitutes about 20%-22% weight of paddy. In Crop year2012 as per the FOA estimates global rice paddy production is 721 Million. 160 million tones of husk isestimated to be produced globally this year. India alone produced 150 Million tonnes of rice paddygiving around 33 million tonnes of rice husk.Rice Husk has got substantial value as fuel; it is used as fuel for burning and producing electricity andalso as a fuel for Boiler to make parboiled rice. It is also used as fodder for cattle and in manufacturingcardboards.
Rice Husk Ash (RHA) is obtained by combustion of rice husk. RHA is generally 25% of rice husk.Moreover husk contains 15%-18% silica in it; hence it can be a source for silicates for manufacturingglasses. RHA has high levels of silicon dioxide, approximately 93%.Rice husk is burnt approximately for 48 hours under uncontrolled combustion process. The burningtemperature is within the range 600 to 8500C. The ash obtained is grounded in a ball mill for 30 minutesand RHA is its appearance color is grey. RHA can either be used with cement to make mortar( greenconcrete) or it can mixed with quicklime to make a hydraulic, cement free mortar.Other uses of RHA are for refractory, ceramic glaze, insulator, roofing shingles, waterproofing chemicals,oil spill absorbent, specialty paints, flame retardants, carrier for pesticides, insecticides and bio fertilizersetc BRANRice Bran is the most important and valuable byproduct of rice milling. Rice bran is the outer layer ofbrown rice and is about 7-10% of weight of paddy. True bran amounts to 4 to 5 per cent only and rest ispolishing of inner bran layers and portion of the starchy endosperm.Rice bran has got various uses. Rice bran oil is a serious source be a source of edible oil. Raw rice brancontains 12-18% oil, whereas parboiled bran contains 22-30% oil. The de-oiled bran contains about 1 to3 percent oil only. Rice bran also contains high fat and protein. It also contains vitamins, minerals andmany other useful chemicals. Because of its nutritional value, it is being used as feed for poultry andlivestock.Uses of Rice Bran Oil and De-oiled Rice Bran (DRB):
A) Edible rice bran oil: Bran oil contains low linolenic acid and high tocoferol, hence, it has distinct advantage over other vegetable oils. 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 not 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 color resulting in lighter testing food. Food cooked in rice bran oil increases its flavor and palatability.B) Industrial Grade Bran Oil: Rice bran oil contains high free fatty acid (FFA) therefore suitable for manufacture of soft soap and liquid soap. Other kinds of metallic soap such as aluminum, barium and calcium soaps are also manufactured from rice bran oil and are used as lubricants. From rice bran oil resin based paints, enamels, varnishes, plastics etc. are also prepared. It is also used majorly in Rubber industry. Rice bran wax is used for coatings of candy, fruits and vegetables as it prevents moisture loss and shrinkage.C) Animal feed: DRB, 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. In baking flour, fine powder of de-oiled bran can be added up to 20% and it is also used in bakery products such as bread, cake, biscuits etc. DRB 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. Rice bran contains valuable Vitamin-B complexes, amino acids, phosphoric acid compound etc. and can be used in pharmaceutical industry