Manufacturing Process of Rice
The processing of rice is very well standardized. First of all, paddy is cleaned to remove unwanted matters like mud, stones, chaff etc. This cleaned lot is then fed to de-husker with the help of rubber roller where husk is separated. The brown rice is then taken to huller where polishing is done by mild friction created within the polishing chamber. The resulting polished rice and bran are separated and collected. Recovery of edible rice is around 80%. By-products constitute about 15% whereas balance 59% is waste and process loss. Be1ow is the detailed process flow:
The paddy contains foreign materials such as straw, weed seeds, soil and other inert materials as well. The pre-cleaners separate three groups of materials: â The first separation is done by scalping or removing the objects that are larger than the grain. Either a flat oscillating screen or a rotary drum screen that allows the grain to pass through but retains straw is used for tbis purpose. The second separation retains the grains but allows broken grains, small stones and weed seeds to pass through. In the third one, Aspirator is installed to remove the dust and light empty grains.
In this process, small stones left in previous step are separated from paddy. Rice deâstoring machine is made up of two sets of carriage each comprising of three screens. The first in each working deck serves to separate the stones slightly bigger than the grain; the second screen serves to separate the stones smaller in size than the grains while the third screen serves to convey the stones down to the stone chutes.
Paddy in its raw form cannot be consumed by human beings. It needs to be suitably processed for obtaining fice. Rice milling is the process which helps in removal of all impurities and foreign materials from paddy grains to produce polished rice. Rice forms the basic primary processed product obtained from paddy and this is further processed for obtaining various secondary and tertiary products.
Level of Processing of Rice In food grains especially paddy, the major processing is being done in the secondary processing. Primary processing only consists of sorting, cleaning, primary de hushing etc. It is the secondary processing which has all the milling, polishing and other steps which converts raw paddy into rice. Though there has been technological advancement like use of sortex machines but tertiary processing is still tool in Bihar for rice.
Parboilinz Par boiling is one of the critical processes, which determine the quality and taste of par boiled rice. Precise control of the temperature pressure, time and water requirement of par boiling is essential for getting a superior par boiled rice. The cleaned paddy from the godown is fed to the boiling tank and it is open steamed and then soaked for nearly five hours. After five hours, saturated steam from the boiler is supplied to this tank and parboiled in two/three hours. Here the temperature and pressure of the steam supplied is precisely controlled so that the heat input never exceed the pre - determined level, which is fixed, based on the nature of the paddy, else paddy may be over- boiled and the quality of parboiled rice will be affected. The total time for parboiling will be approximately 7 - 8 hrs.
Drying The head yield is especially sensitive to the mode of drying and is usually used to assess the overall effectiveness of the drying process. The head yield may increase if drying is proper in order for the internal moisture gradients in the kernels, and the different moisture contents between the individual kernels, to equilibrate. Otherwise, undesirable odours develop, which negatively affect marketability of the produce.
The de-moisturisation (drying) process has to be controlled because if the level of de-moisturisation exceeds the prescribed level, the percentage of broken rice will increase and the taste of the rice will get affected adversely. If the paddy is not de-moisturized to the required level, the shelf life of the final product is reduced. After drying, the dried paddy is stored in silos specifically made for this purpose.
Milling The cleaned paddy is conveyed to the paddy husker for de-husking by vertical elevators. The husk is removed without affecting the shape of the rice. By using the paddy husker the percentage of broken rice is minimized during the process. The mixture of rice and husk is conveyed to variable stroke paddy separator where husk is sucked out by husk aspirator. Rice grains are collected and fed to the elevator for whitening and polishing. Around 5% to 7% of the paddy also get separated and discharged at a third point and is sent back to the de-husker for further de-husking. After this, the rice is whitened and polished using whitener & polisher.
Sorting & Packaging Rice needs to be properly sorted to attract a premium price. It needs to be devoid of discoloured kernels and any other foreign materials to attract buyers. A colour SORTEX machine is the latest technology available for sorting rice from other foreign materials. The microprocessor controlled sortex machine is capable of sorting discoloured kernels, peck defects and foreign material from rice. A bulk packaging machine shall also be installed to pack rice in different packing size.