I don't know about you, but some people I know will freak out if I lift up the lid on a pot of cooking rice to stir or check its done-ness. They say "you should never ever ever lift the lid". It is like a commandment. Sure I can see that some steam will be released, and temperature lowered. But is it such a problem to lift the lid once or twice when cooking rice? Are there some consequences that I am overlooking?
I am going to assume you are cooking the rice on a pot rather than in rice cooker. If you are cooking it in the rice cooker, you wouldn't need to lift the lid to check for done-ness. However if you are cooking in a rice cooker, the lid should not be immediately lifted off after it says it is done cooking. You need to let it sit for about 5-10 minutes so the steam can continue to cook.
If you are cooking in a pot, the main reason why you do not want to lift the lid is because you want a even cooking temperature throughout. Typically when you cook rice(once again I am going to assume just plain white rice), you start the water/rice mixture by boiling it on high until it comes to a boil. I do recommend stirring it at this point. But not after covering. Then you set it to very low and cover and let it simmer for about 15-20 minute or more depending on quantity. By doing this, you can evenly cook the rice throughout so that the rice isn't too overcooked on the bottom. If you continue to lift the lid, the temperature would drop, and the top would be less cooked than the bottom. So you would need to cook it longer for the top to be cooked while the bottom is being overcooked.
In addition, the steam that is escaping is the water that you put into the rice. thus when you lift the lid, the water is escaping and will result in the rice being dryer than optimal. If you want to add more water, this will slow the cooking process on top of it already being slowed by losing temperature when you lift the lid. This will result in slower cooked rice.
The effects are negligible, assuming you are not lifting the lid for more than a few seconds. There is a lot of liquid water in the system, so heat loss will be barely measurable. Same goes for the amount of water exiting the system in the form of steam.
Opening it once or twice shouldn't be a problem, as long as you do it fairly quickly. I've had to do that before when cooking rice on the stove simply because it was foaming up too much due to the starch. That being said, I haven't had to check rice for doneness before. Jay's instructions for cooking rice are the same instructions I've used and it cooks the rice just fine. Lifting it too much will result in rice as Jay noted, but once or twice, very briefly, shouldn't be a big deal.
Ok, here we go....my mom was a total tyrant when it came to cooking rice properly. Yes, she is Japanese. Yes, from Japan. And yes, I'm one of those people who freak out when people lift the lid when it's cooking.
Here is how it was explained to me. I have subsequently tested the theory and found hard, empirical evidence on why lifting the lid is BAD.
I agree with Jay on all his points. But here is the main reason for not lifting the lid:
If the rice is still hard in the middle of the grain, lifting the lid will cause the temperature to drop. Once this happens, by the time the temperature rises back to equilibrium, you will have OVERCOOKED the outside of the individual grains, which will become mushy. Conversely, if you lift the lid and cook the rice for the normal amount of time, the center of the grain will be hard and UNDERCOOKED.
All you have to do is cook rice and try it both ways to see the difference. A significant amount of steam does escape if you check it and it does affect the resultant consistency of the rice, which affects the taste and enjoyment of it. If you don't care about that, hey, go nuts, but if you want it to turn out better/right, cook it at the specified time without lifting the lid, it's not rocket science.