paddy husker had high husking energy efficiency compared to impeller husker for randomly husked short grain rice and for all the three varieties of rice husked as single grain. Optimal husked ratio in terms of husking energy efficiency was also found to be optimal in terms of system cracked ratio and system broken ratio for all the three varieties of rice.
Performance analysis of experimental impeller and rubber roll huskers was carried out using three different varieties of rice namely; Akitakomachi (short grain), Delta (long grain) and L201 (long grain). Impeller husker speed was varied from 1400 to 3300 rev/min and rubber roll husker clearance was varied from 0.4 to 2.4 mm. In rubber roll husker, rough rice was husked randomly and as single grain vertically and horizontally. For both huskers, variation of husked ratio with specific husking energy was well expressed by the Weibull's distribution function. Husking energy efficiency, system cracked ratio and system broken ratio curves were well expressed by the empirical equations. The three performance parameters were used to optimize the husking performance of the two huskers for the three varieties of rice.
When the husk and bran layer is removed in one process and the white rice is directly produced from the paddy, it is called one step milling process. The husk and the bran layer is removed separately and the brown rice is produced as an intermediate product, it is called two step milling process. The rice is passed through a number of different operations and machines from paddy to white rice is called multistage milling process.
Irrespective of the scale of rice processing, paddy rice must be harvested at full maturity and timed carefully. Delay during harvest leading to alternating wet and dry period is responsible for the development of stress in the kernel, which in turn results in high levels of grain shattering during milling further down the processing line. Grain shattering during milling can additionally become a real problem if grains become overheated during the rice polisher, whether it remains too long in the hot sun or inside a mechanical dryer.