What starch granules actually do
Raw rice is packed with tightly wound starch granules. When those granules hit hot water, they absorb moisture and swell — eventually the structure breaks down and the starch sets into a soft, cooked texture. That process is gelatinization.
According to Harold McGee in On Food and Cooking, the gelatinization temperature varies meaningfully by starch type: potato starch begins to swell at 58–65°C (136–149°F), wheat starch at 58–64°C (136–147°F), and rice starch at 68–78°C (154–172°F) — the highest of common cooking starches. That higher threshold is why rice needs more water and heat than wheat-based foods to cook through. Fully gelatinised starch can absorb 10–30 times its own weight in water, which is why the water ratio in rice cooking is so consequential.
Below the gelatinization threshold, the granules don’t absorb enough water. Above it, they over-absorb and burst, releasing free starch into the water — which makes rice gummy.
Why rinsing matters
The surface of dry rice is coated with loose starch dust — fragments broken off during milling and handling. That surface starch dissolves instantly when it hits water, well before the gelatinization temperature is reached. The result: starchy cooking water that makes the rice clump.
Rinsing removes that surface starch before cooking. The water you rinse with should run clear before you put the rice in the pot. Two or three rinses usually get there.
The ratio changes in a pressure cooker
On a stovetop, rice is cooked in more water than it needs because evaporation takes a significant portion of it. The typical 1:2 ratio (one cup rice to two cups water) accounts for what boils off.
A pressure cooker is sealed. No steam escapes. So the ratio drops — closer to 1:1.25 or 1:1.3 by volume. All the water goes into the rice, not into the air. Using a stovetop ratio in a pressure cooker gives you mushy, waterlogged rice.
Why 3 minutes works
Three minutes at high pressure sounds too short. But inside the pressure cooker, water boils at around 120°C rather than 100°C. Gelatinization happens faster at higher temperatures, and the 10-minute natural release that follows keeps the rice cooking gently in the residual heat without adding more water.
Skipping the natural release — going straight to manual pressure release — stops the cooking abruptly. Some grains end up undercooked in the center. The rest period is part of the cooking time.
