Choosing the correct water-to-rice ratio for a rice cooker can be tricky, especially for novices or those that want to cook different kinds of rice. Generally, the amount of water a cook uses depends on the type of rice he or she wishes to make. Those making sticky rice, rice that naturally clumps together, don’t need as much water as those making ordinary white rice. Hard-shelled rice varieties — such as basmati, brown, and wild — often require two or three times the water white rice needs. Sometimes determining the proper water-to-rice ratio requires a little experimentation, but starting out with a reasonable estimate usually helps.
Rice cookers are often touted as a foolproof method for cooking rice. It is true that these little machines are purposely designed to cook rice at the perfect temperature, let off just the right amount of steam, and turn off automatically when the rice is finished cooking. Most even come with instructions, though these instructions generally do not cover all the different kinds of rice. This is where the cook’s intuition and a little basic knowledge about rice may come in quite handy.
For sushi rice, also called glutinous rice or Thai sweet rice, the cook usually needs about .75 parts water for every 1 part of rice. Choosing a water-to-rice ratio in which the amount of water is less than the amount of rice ensures that the rice cooks through and sticks together, instead of becoming fluffy and soft. Rice that absorbs too much water will slide against itself and is unsuitable for making sushi, rice balls, or most other recipes calling for sticky rice.
Those that want light, fluffy, tender rice — for either a risotto or rice pilaf — should typically try a 1:1 water-to-rice ratio, meaning 1 part water for every 1 part of rice. This generally works well with long grain white rice and jasmine-scented rice. If the rice turns out too sticky for the cook’s taste, adding an extra .75 part of water for every 1 part of rice should alleviate the problem. This takes the water-to-rice ratio up to 1.75 parts water to 1 part rice.
Brown, wild, and basmati rice are a bit different from their light-colored cousins. Not only do they typically require more water, they also require a soaking time. Many cooks pre-soak all kinds of rice, but only whole grain rice truly needs it. This softens the hard outer shell of the rice and encourages the rice to steam into soft, tender, fluffy grains. Soaking may be done in a bowl or directly in the rice cooker for up to 2 hours prior to cooking.
Both soak water and cooking water ratios for these harder rice grains are usually the same. Generally, about 4 parts water for every 1 part of whole grain rice works best. More water means a longer cooking time, which is usually necessary for hard rice. Cooks may also use the soak water as the cooking water, as this usually prevents flavors from being lost.