CEREAL TECHNOLOGY: RICE MILLING
Diagram
Rice with its bran, and rice without it
Brown rice
Rice with the husk removed but the bran and germ kept. Brown, nutty, chewy, rich in fiber.
↓
White rice
Rice milled and polished to remove the bran and germ. White, soft, mild, mostly starch.
Figure 1: Brown rice keeps its bran and germ, while white rice is milled and polished to remove them. Drawn in our own style from the rice discussion in Carpenter, Beriberi, White Rice, and Vitamin B, and in Goyal et al., Cereals and Cereal-Based Foods.
Introduction
Brown rice and white rice are both rice, but they differ in what milling leaves behind. Rice grows in a husk, and under the husk the grain holds bran, germ and endosperm. Brown rice is rice with the husk removed and the bran and germ kept, so it is brown, nutty and chewy, and it keeps the fiber and the B vitamins of the bran. White rice is the same grain milled and polished to strip away the bran and germ, leaving only the white starchy endosperm, so it is soft, mild and quick to cook, but it has lost most of the fiber and vitamins. Carpenter, Beriberi, White Rice, and Vitamin B, tells how chickens fed white rice lost the use of their legs, while chickens fed brown rice, where the grain still held its bran and germ, stayed healthy.
Quick comparison
Table 1: Brown Rice compared with White Rice
| Aspect | Brown Rice | White Rice |
|---|---|---|
| Parts of the grain kept | Bran, germ and endosperm | Endosperm only |
| Colour | Brown | White |
| Fiber | High, from the bran | Low, because the bran is removed |
| B vitamins | Kept, from the bran and germ | Mostly lost in milling |
| Texture when cooked | Chewy and nutty | Soft and mild |
| Cooking time | Longer, because the bran slows water entry | Shorter |
| Keeping quality | Shorter, because the bran oil turns rancid | Longer, because the oil-rich bran is gone |
| Glycemic response | Slower, because fiber slows digestion | Faster, because the starch is exposed |
| Use | Whole grain meals, where fiber and flavour matter | Everyday rice dishes, where a soft, mild rice is wanted |
| Milling | Husk removed only | Husk, bran and germ removed, then polished |
Scientific explanation
Definition
Brown rice is rice from which only the husk has been removed, so the bran and germ remain. White rice is rice that has been milled and polished to remove the husk, bran and germ, leaving only the endosperm.
Working principle
Milling starts by removing the husk, which gives brown rice. If milling goes on, the bran layers are rubbed away and the germ is removed, then the grain is polished to a white shine, which gives white rice. The bran holds most of the fiber, the B vitamins and the oil, so removing it removes those nutrients with it. The bran also slows water from entering the grain, so brown rice takes longer to cook and stays chewy, while white rice absorbs water fast and cooks soft. The oil in the bran oxidises in storage, so brown rice turns rancid sooner than white rice.
Apparatus
The books used here name no laboratory apparatus for measuring or comparing either term, so no apparatus list is given.
Measurement procedure
The books used here give no standard laboratory procedure with volumes and steps for either term, so no procedure is invented here.
Factors affecting readings
For both rices, the variety decides the starch and the texture: long grain rice cooks separate, short grain rice cooks sticky. For brown rice, the storage decides the keeping quality, because the bran oil turns rancid in warm storage. For white rice, the degree of milling decides how much bran is left: a lightly milled rice keeps more nutrients than a highly polished one.
Formulas and calculations
The books used here give no formula for either term, so no formula is given here.
Industrial applications
- Brown rice: whole grain meals and health foods, where fiber and B vitamins matter.
- Brown rice: rice dishes where a nutty flavour and a chewy texture are wanted.
- White rice: everyday rice dishes, where a soft, mild rice is wanted.
- White rice: rice flour, noodles and breakfast foods made from milled rice.
- Both: parboiled rice, where the grain is treated before milling to keep more nutrients.
Advantages and limitations
- Brown rice, advantage: it keeps the fiber, B vitamins and minerals of the bran and germ.
- Brown rice, limitation: it takes longer to cook, feels chewy, and keeps for a shorter time because the bran oil turns rancid.
- White rice, advantage: it cooks fast, feels soft and mild, and keeps for a long time.
- White rice, limitation: milling has removed most of the fiber and B vitamins.
FAQ
What is the difference between brown rice and white rice?
Brown rice keeps its bran and germ, while white rice is milled and polished to remove them, leaving only the endosperm.
Why does brown rice take longer to cook?
The bran slows water from entering the grain, so brown rice needs more time and more water.
Is brown rice healthier than white rice?
Brown rice keeps the fiber and B vitamins that milling removes from white rice.
Why does white rice keep longer?
The oil-rich bran that turns rancid has been removed, so white rice stores for longer.
What did Carpenter show about white rice?
Chickens fed white rice lost the use of their legs, while chickens fed brown rice, with its bran and germ, stayed healthy.
References and further reading
- FTN books on disk: Cereal Technology.
- Carpenter, Kenneth J. Beriberi, White Rice, and Vitamin B. University of California Press, 2000.
- Goyal, Megh R. et al. Cereals and Cereal-Based Foods. CRC Press, 2021.
