Description

Objective of commercial milling

A commercial rice miller will have following objectives:

• produce edible rice that appeals to the customer- i.e. rice that is sufficiently milled and free of husks, stones, and other non-grain materials
• maximize the total milled rice recovery out of paddy minimize grain breakage

Terminology

To understand the different objectives of rice milling, please review the following terminology.

Back to top

Rough rice

Also called paddy rice. Rice as it comes from the field. Rice kernels are still encased in their inedible, protective hull.

Back to top

Brown rice, husked rice or cargo rice

the least processed form of rice. It has the outer hull removed, but still retains the bran layers that give it a characteristic tan color and nut-like flavor. Brown rice is edible but chewier texture than white rice. Cooking time of brown rice is longer than milled rice

Back to top

Milled rice

Also called white rice, or rice after milling which includes removing all or part of the bran and germ from the rough rice.

Back to top

Milling recovery

total milled rice obtained out of paddy; expressed as weight percentage of milled rice (including brokens) obtained from a sample of paddy. The maximum milling recovery is 69-70% depending on rice variety, but because of grain imperfections and the presence of unfilled grains, commercial millers are happy when they achieve 65% milling recovery. Some village type rice mills have 55% or lower milling recovery.

Back to top

Milling degree

a measure of the amount of bran removed from the brown rice

Back to top

Head rice

milled rice with length greater or equal to three quarters of the average length of the whole kernel. It is often expressed on a % paddy or rough rice basis (on 14% Moisture content basis).

Back to top

Head rice recovery

weight percentage of head rice (excluding brokens) obtained from a sample of paddy. Under controlled conditions head rice recovery can be as high as 84% of the total milled rice or 58% of the paddy weight. Commercial rice mills turn out 55% head rice on average, whereas head rice recovery of village type rice mills is in the order of 30%.

Back to top

Whole

a milled rice grain without any broken parts

Back to top

Broken kernel

or brokens. Depending on the rice mill this can be only one fraction or it can contain several fractions of different size:

• Large broken kernel: 50-75% of the whole kernel size
• Medium broken kernel: 25-50% of the whole kernel size
• Small broken kernel: less than 25% of the kernel size, can not pass through a sieve with 1.4mm diameter holes
• Chips: fragments of a kernel which pass through a sieve with 1.4mm diameter holes

Back to top

Impurities

materials in the rice that are not part of the milled rice kernel. May include stones, husk, chaff, weed seeds, etc.