Loss of rice nutrients in milling, washing and cooking
Rice is a global staple food. About 3 billion people, nearly half the world’s population depends on rice for a healthy living.
The rice grain consists of a brown rice kernel enclosed by the husk. The brown rice grain consists of bran layer, a germ and the starchy center of the grain. The most visible part of a rough rice grain is the husk. This is formed from the two leaves of the spikelet, namely the palea covering the ventral part of the seed and the lemma covering the dorsal portion. Both parts are longitudinally joined together by an interlocking fold. When the husk is removed a thin fibrous layer can be seen. This is called the pericarp. The pericarp consists of 3 layers namely epicarp, mesocarp and cross layer. Under the pericarp layer is the testa. Testa is rich in oil and protein. Under the testa layer is the bran layer. This part is removed during milling. It has high percentage of oil, protein, vitamins and minerals. When rice is fully milled the vitamins, protein, minerals and oil content are lessened. This also explains why persons who eat well milled rice are protein deficient or even malnourished. Thus it is advisable to take rice prepared with indigenous husking pedal locally known as dheki. In the process of extracting rice from paddy, the vitamins in the rice grain can be retained by parboiling before husking or milling. The embryo is located at central bottom portion of the grain, where the grain has been attached to panicle of the grain, of the rice plant. This is the living organism in the grain which develops in to a new plant.
When the husk, the pericarp,the bran and the embryo are removed in course of husking and milling, what remains is the endosperm. It mainly consists of starch with only a small concentration of protein and hardly any minerals, vitamins or oil. Because of its high percentage of carbohydrate, its energy value is high.
The milling and polishing process of white rice means most of the important vitamins and other nutrients from it are removed. In one sense, polished rice is nothing more than refined starch. However white rice is one of the easiest and quickest of food to digest and requires only about an hour to completely digest. Since white rice is low in fibre, it is very soothing to the digestive systems and easily digested. So it is great for relieving digestive system like diarrhea, dysentery and morning sickness. It is best food for infants, young children and old people.
Brown rice has several health benefits. The health benefits of brown rice are innumerable.
Brown rice is an excellent source of soluble fibre. It helps to lower the level of cholesterol on the blood. The fibre in brown rice means the digestion time of the carbohydrate is slower than white rice. This means there is a more controlled and slower release of sugar into the blood stream and thus it has a lower glycemic index compared to other grains. Brown rice is rich in vitamins and minerals and hence nutritionally more beneficial.
Brown rice contains more nutritional content than white rice because the milling process includes the removal of only the hull. This rice is an excellent source of fiber, magnesium, phosphorus, vitamin B1, vitamin B3, vitamin B6, potassium, selenium and calcium.
Nutrient loss during washing and cooking rice:
Washing rice prior to cooking is a common practice. But during washing some water soluble nutrients are leached out and removed. A significant amount of protein (2-7%); water soluble vitamins like thiamine (22-59%), riboflavin (11-26%) and niacin (20-60%); minerals like calcium (18-26%), phosphorus (20-47%), iron (18-47%), zinc (11%), magnesium (7-70%) and potassium (20-41%) are lost during washing of raw milled rice. However, this loss is relatively less in case of brown rice (husked by dheki). Even this loss is less in case of parboiled milled rice. Cooking in excess water is also responsible for loss of nutrients of white, brown, parboiled and un-parboiled rice.
Rice of local varieties, parboiled, husked with dheki, no washing before cooking, cooking with minimum water, ensure the highest nutrient and excellent diet for good health.