Rice absorbs water when cooking thanks to the starch present in its grains. When rice is heated, the starch gelatinizes and retains water, giving rice its soft and tender texture.
A grain of rice is primarily composed of starch, a large molecule made up of numerous sugars linked together. This starch is found in cells surrounded by walls rich in dietary fiber, particularly cellulose. These fibers act as a sort of framework protecting the interior of the grain. There are also some proteins that will affect the final texture after cooking, as well as a small amount of lipids (in other words, fat), concentrated mainly in the outer shell and the germ of the grain. Finally, various vitamins and a few minerals are also hidden there, but in modest amounts compared to the starch, which truly reigns supreme.
Rice mainly contains starch, a carbohydrate that can swell in the presence of water. When you put your rice in hot water, the starch begins to absorb and trap the water, much like a sponge would. More specifically, starch consists of two types of molecules: amylose and amylopectin. As these molecules are heated, they unwind, allowing water to penetrate easily. As a result, the grain becomes tender and fluffy as the water distributes inside. That's why during cooking, rice visibly expands, changes texture, and becomes soft to the bite.
Temperature plays a key role for the starch molecules present in the grain. When heated, these molecules gain energy and begin to vibrate. This breaks the weak bonds that hold them together, allowing water molecules to easily insert themselves between them. Around 60-70°C, starch begins to gelatinize, swelling and opening up to water. As the heat increases to boiling, this phenomenon intensifies, creating a fluffy and digestible mass in the end. Without reaching these high temperatures, forget tender rice: your grains would remain hard as small pebbles, as the starch molecules would hardly move.
When you submerge raw rice in hot water, a lot of things happen on a microscopic scale. The most important is what is called osmosis. Basically, water naturally moves from an area where there is a lot to an area where there is less. And indeed, inside the grain of rice, the water concentration is lower than outside. As a result, water slowly crosses the cell wall to balance the water concentration inside and outside the grain. This osmotic phenomenon causes the rice to swell, softens its texture, and directly contributes to the cooking you observe in your pot. As cooking progresses, the balance establishes itself, and your grain is perfectly hydrated.
When the grain of rice absorbs water, the first thing we notice is its swelling. Basically, the rice acts a bit like a "sponge," and its volume can actually double or triple. This water absorption softens and gradually detaches the starch molecules inside, making the grain more soft and tender to the bite. The microscopic cracks already present in the dry grain widen, sometimes leading to visible cracks to the naked eye. The result is cooked rice that becomes more airy, sticky, or fluffy depending on the varieties and the amount of water absorbed.
A grain of rice can absorb up to three times its initial volume of water during cooking, which is why your pot can easily overflow!
Adding a pinch of salt to the water when cooking rice slightly raises its boiling point, speeds up the softening of the grains, and enhances their final taste.
Basmati rice releases less starch than other varieties, which is why it is less sticky after cooking, making it ideal for pairing with your saucy dishes.
The starch present in rice is also used to make paper, vegetable glues, and even eco-friendly bioplastics!
If your rice remains hard after long cooking, it is likely due to an initial lack of liquid or insufficient temperature. Make sure the water proportions are correct (usually about two parts water to one part rice) and maintain a gentle, constant simmer during cooking.
Yes, adding salt to the water slightly alters the osmotic exchanges, but this impact remains minor. The main benefit of salt is to enhance the flavor. The grain continues to absorb water primarily due to the starch and the cooking temperature.
Round or short-grain rice contains proportionally more amylopectin starch, promoting increased water absorption and a stickier texture. In contrast, long-grain rice absorbs less water, resulting in more distinct grains after cooking.
Yes, it is recommended to rinse the rice before cooking to remove the excess starch from the surface of the grains. This results in lighter, less sticky rice and promotes more uniform water absorption during cooking.
Absolutely! You can definitely replace water with broth, milk, or even plant-based milk to cook the rice. The grain absorbs the liquid in the same way, while adding more flavor to your dish.
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