In modern method of processing, the term milling encompasses cleaning, drying, dehusking, aspirating of husk, separating paddy and brown rice, polishing to remove bran and grading rice and broken by rice polisher. A modern rice mill consists of a paddy pre-cleaning system which sieves and aspirators, efficient paddy separators, improved rice whiteners, graders and auxiliary equipment such as elevators, conveyors, automatic weighing machine. Parboiling is a pre-milling most-heat treatment given to raw paddy in order to improve its milling quality, nutritive value, cooking quality and storability. Equipments for parboiling and drying have been installed in some modern rice mills. If parboiling operation is used then, there is an overall increase in total rice recovery of about 6 % over huller mills and 10–20 % reduced percentage of broken (Houston 1972). If different sets of machines are used then all the by-products viz.; husk, bran and broken are obtained in a useable form and this rice milling system may be energy intensive.
Rice processing machines produced in developed countries are mostly unaffordable by rural farmers, hence there was need to develop cost effective/efficient machines produced from available local materials desirable in food industry that meets the need of the rural farmers. This study was to evaluate the performance of a developed rice dehusking/destoning machine at Federal University of Agriculture, Abeokuta, Nigeria. Minitab 16 was used for analysis of variance of two main factors to obtain its optimum operational parameters.
The key function of paddy separator is to remove paddy from rice. If rice contaminated with paddy, the consumer can get a negative impression that the rice is not clean. After the separation, brown rice is sent along the conveyor chain and down to the bucket elevator which shifts rice to a container above a polisher. When the polishing step begins, rice can be released to the machine immediately.
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