Rice has a special problem with regard to loss of nutrients, i.e. minerals and vitamins, during cooking since its normal nutrient content is low.
Certain amount of minerals and vitamins are lost even during preliminary washing before cooking. Hence washing with a large quantity of water and repeated washing must be avoided. Washing may remove as much as 40% of the thiamine and nicotinic acid. Rice must be washed, if washing is necessary, with minimum amount of water.
Boiling rice in excess water and discarding the gruel (kanjee) also results in loss of some amount of minerals and vitamins. However, loss due to discarding of kanjee is not as much as during washing. Cook in just sufficient amount of water so that all the water is absorbed and no kanjee is discarded. Pressure cooking would be the best option. However, if rice is parboiled and that rice is used, loss of vitamin and minerals due to washing and discarding of kanjee is much less. Parboiling diffuses nutrients into the grain and a protective gelatinised starch coating is formed on the grain preventing leaching.