Many people put rice in the water and then bring it to a boil when steaming rice. However, if you reverse the order—boiling the water first and then adding the rice—you can better preserve the vitamin B1 in the rice.
Vitamin B1 is a major nutrient in rice. It protects the nervous system, promotes gastrointestinal motility, and increases appetite. A deficiency can lead to polyneuritis, beriberi, and even symptoms such as numbness in the limbs, muscle atrophy, lower limb edema, and heart failure. Therefore, it is important to minimize the loss of vitamin B1 in your daily diet.
The tap water we normally use is disinfected with chlorine. If you use this water directly to cook rice, the chlorine in the water will significantly destroy the vitamin B1 in the rice, causing nutritional loss.
If you boil the water first and then add the rice, the chlorine in the water will have mostly evaporated, which reduces the destruction of vitamin B1. For those using electric rice cookers or pressure cookers who cannot separate the water and rice, they can use boiling water to cook the rice. Rice contains a large amount of starch, and these starch granules are not soluble in cold water. Cooking rice with boiling water allows the rice to start in hot water at a higher temperature, which is beneficial for the swelling and rupture of the starch, allowing it to turn into a paste more quickly and be more easily digested and absorbed by the body.