When paddy is brought into the mill it can contain foreign material such as straw, weed, seeds, soil and other foreign material. If these are not removed prior to hulling the efficiency of the huller and milling recovery are greatly reduced.

The first separation is done by scalping or removing the objects that are larger than the grain.

The second separation retains the grains but allows broken grains, small stones and other foreign objects like weed seeds to pass through.

A simple pre-cleaner used in rice mills usually contain an oscillating double screen bed with an aspirator. The air aspirator sucks out dust and the light empty grains. Air dampers are provided and have to be adjusted to prevent the good grain from being sucked out.

This process removes foreign materials that are of the same size as the rice grains, introduced into the rice during harvest or handling. This is done by using a gravity separator known as a de-stoning machine. As the stones or other dense particles are heavier than the rice grains, the forced air flow through the machine causes the rice grains to float on a cushion of air just above the screen. This then enables the screen to carry the denser stones up the screens where they get discharged through the chutes. This thus ensures the removal of all stones from the rice grains.

Traditionally, husking or de-husking was done using mortars and pestles, but in today's modern times, it is done by passing the grains between two abrasive surfaces that are moving at different speeds.

The steel huller removes the husks and whitens the husk in one pass. Paddy is fed into the machine and is passed through a revolving steel shaft and a cylindrical-shaped mesh screen.

This machine has two steel discs, which have an emery coating. Resistance between the emery surfaces on the discs removes the husk leaving the brown rice kernel. Brown rice and husks are then deployed across the circumference over the revolving disc and then find their way out through an outlet. Huller efficiency in this machine is around 85 to 90%.

After separating the husk and paddy, the husk is removed by suction (aspirated) and then transported to a storage dump outside the milling plant.

The output that is received from the huller is a mixture of paddy rice, brown rice, husk, bran and broken paddy. Lighter material like husk and brand are aspirated by the huller. The remainder is sent into the paddy separator where the unhulled paddy rice is separated from the brown rice.

White rice is produced from brown rice by removing the bran layer and the germ. The process used to whiten brown rice can be classified as 1) abrasive and 2) Friction.

1) Abrasive:

In this process the grain is whitened by the abrasive action of the rice kernel passing through a moving abrasive surface and stationery screen.

2) Friction:

Grain kernels in this method are forced against each other and a metal screen by a steel-ribbed cylinder rotating inside a metal-plated cylinder. This frictional force removes the bran layer from the grain, whitening the rice in the process.

Rice is then passed through polishing machines that are connected in a series. 'Mist' polishing sometimes forms the last process of polishing, wherein a fine mist of water with the dust retained on the whitened rice helps to improve the luster of the rice without reducing the yield.

The rice is then accurately weighed and then labeled suitably. The modern mechanical weighing system allows for a very accurate and speedy weighing process.

Parboiled rice or converted rice is rice that has been partially boiled in the husk. The 3 steps in parboiling are soaking, steaming and drying. These steps make rice easier to process by hand, boosting its nutritional profile, while changing its texture. Parboiling drives nutrients, especially thiamin from the bran to the endosperm, hence parboiled rice is almost similar in nutritional value to brown rice.