The science of cooking rice...

[hzrt8w]

In another online forum, people are describing a way of cooking rice without any measurement. It said: no matter how much rice you want to cook, just pour the rice in, and pour in enough water to cover the top of the rice and then some. Put your index finger straight down, with the finger tip just touching the rice. The water level should be filled up to the first knuckle of your finger. Your rice would come out nicely, no matter how much rice you cook.

I have been thinking of the implication of this instruction, and have always been wondering why it would work. I am a student of science. This method does not seem very scientific for me. For any kind of chemical process:

If I use 1 cup of X and mix it with 1 cup of Y to produce Z, then

If I use 2 cups of X, I should mix it with 2 cups of Y.

The above mentioned method seems to entirely violate the laws of physics/chemistry. It said I can use this method on a 4-person rice cooker or on a 500-person cooker like those in the kitchen onboard an aircraft carrier.

Is there a scientific explanation on why it would work? My attempted theory: that water would "fill in the space between rice grains"? So no matter how many rice grains you have, the water would fill in the space between the grains so the ratio is more or less constant?

[sheetz]

Maybe the amount of water needed to cook the rice is simply the amount necessary to barely cover the rice. The half inch or so of water above this level is to account for evaporation. I've noticed that the longer it takes the rice to cook the more water is needed. For example, glutinous rice cooks faster than regular long grain rice and needs a little less water, whereas brown rice takes a lot longer and requires significantly more water.

[Hiroyuki]

Funny, my mother used to say the same thing about the water level. So, it's universal, regardless of the rice type (long or short grain)?

I think (without any confirmation) that it's a good rule of thumb, but is only workable under certain conditions (the shape of the pot, the amount of rice, etc.).

[Shalmanese]

When you cook rice, some portion of the water is absorbed into the rice grains which is proportional to the amount of rice being cooked and some portion is evaporated off which is proportional to the time the rice takes to cook. If we call the quantity of rice R and the water absorbed per unit quantity ratio p and the amount evaporated e, then the total quantity of water W is pR + e.

The one knuckle heuristic is only very rough and ready and works well for medium quantities of rice. Scaling it too far up or down will result in sub-optimal rice.

Whats most likely the factor is that rice is simply pretty tolerant to the amount of water you put in. If you put in slightly too little water, the residual steam and heat will still cook the rice. If you put in too much, the rice will not deteriorate significantly with overcooking while the excess moisture boils off. If you're cooking it in a rice cooker, it's even more tolerant.

[Ben Hong]

Calculate you must not. Just do, Luke. Use the force.

[srhcb]

When you cook rice, some portion of the water is absorbed into the rice grains which is proportional to the amount of rice being cooked and some portion is evaporated off which is proportional to the time the rice takes to cook. If we call the quantity of rice R and the water absorbed per unit quantity ratio p and the amount evaporated e, then the total quantity of water W is pR + e.

Whats most likely the factor is that rice is simply pretty tolerant to the amount of water you put in. If you put in slightly too little water, the residual steam and heat will still cook the rice. If you put in too much, the rice will not deteriorate significantly with overcooking while the excess moisture boils off. If you're cooking it in a rice cooker, it's even more tolerant.

←

This makes sense.

I include an additional step. After most of the water appears to be absorbed I let the rice sit off the heat with a clean kitchen towel between the pan and lid for 10-15 minutes. I reason that if there's a little extra water it gets absorbed by either the rice or towel, and if there was too little, (assuming it didn't start to burn), the residual steaming effect will equalize the moisture between the grains.

SB (at least, this works for me)

Edited November 27, 2006 by srhcb (log)

[Majra]

My brother uses Ming Tsai's "Mt Fuji" method for cooking rice, explained as: "Flatten the rice with a palm and without removing your hand, add water until it touches the middle and highest knuckle of your hand." It does work, but I just use the lines on my rice cooker to measure the water.

[SuzySushi]

I don't know why the "rule of thumb" (or knuckle) method works, just that it does! This is how I learned to cook rice in a saucepan from my Asian friends.

It seems to work no matter what the size of the saucepan, as long as the amount of rice is proportionate to the size of the pan -- e.g., I wouldn't try to cook just 1 cup of raw rice in a 5-quart Dutch oven.

Maybe as Sheetz suggested, the water level above the rice is meant to account for evaporation as the pan comes to a boil. I know that another Asian method of cooking rice, besides covering the pot at the outset, is to bring the rice and water to a boil uncovered and cook until the water above the rice evaporates and pinholes appear on the surface, then cover, turn the heat to the lowest setting, and steam until the rice is fully cooked.

[edited for spelling]

Edited November 27, 2006 by SuzySushi (log)

[rjwong]

I know that this rule of thumb works when I'm cooking long-grain rice.

MIND YOU, isn't it different when cooking long-grain and short-grain rice together for a recipe of Naw Mai Fun (Chinese Sticky Rice)? One needs more water for long-grain rice and less water for short-grain. And depending on your long/short grain rice proportions, isn't it just a matter of "hit-and-miss"?

[Domestic Goddess]

Most of Filipinos also use the one knuckle rule. Any pot, any amount of rice, you use the one knuckle rule. Wash the rice in the pot, 3 times. Fill the water in the pot until it reaches the first knuckle of the thumb when you stick it into the water (the thumb tip should touch the rice level under the water).

Set the heat on high and put the pot on the stove. When the rice starts to boil, take the lid off the pot and put it askew on top of the pot (to let some of the steam out). Turn down the heat on the lowest setting and let the rice simmer until the water has evaporated completely. Put the lid on securely on the pot and let simmer one minute more. Turn off the heat and let the pot sit for 5-10 minutes to "fully" cook it.

[jo-mel]

Calculate you must not. Just do, Luke. Use the force.

←

LOLOL! I love it! Our no-nonsense Ben at his best!

I have a little note I wrote aeons ago, about water to rice ratios.

Long grain:

1 cup rice to two cups water

1 cup water for each added cup of rice

Medium or short grain:

1 cup rice to 1 1/2 cups water

1 cup water for each added cup of rice

As for me, when I do measured it out, (very rarely) it seems to end up with

the finger knuckle of water above the rice level.

So that is what I usually do. I also follow the 'crater' directions and really don't time it.

That's one great thing about rice cookers. You don't have to think about timing.

My big question is how to keep the serving spoon from having rice stick to it. Grease it? I usually use medium grain rice and I know it is a stickyish rice , but it sticks to the spoon like glue.

[SuzySushi]

My big question is how to keep the serving spoon from having rice stick to it. Grease it? I usually use medium grain rice and I know it is a stickyish rice , but it sticks to the spoon like glue.

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Have you tried one of those nonstick Japanese rice paddles? They're made of white plastic with little nubbles. Not elegant, but they do the job!

[hzrt8w]

My big question is how to keep the serving spoon from having rice stick to it. Grease it? I usually use medium grain rice and I know it is a stickyish rice , but it sticks to the spoon like glue.

←

The ancient, utilitarian Chinese method is to have a small bowl set aside next to the rice pot/cooker. Fill the bowl with water. After scooping rice, immerse the rice scoop/spoon/paddle in the bowl of water for the next person to use.

[sanrensho]

Have you tried one of those nonstick Japanese rice paddles? They're made of white plastic with little nubbles. Not elegant, but they do the job!

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I second the plastic paddles with nibs. And they have the added advantage of not needing to be washed before using.

[Dejah]

The bowl of water method suggested by Ah Leung works for me. I usually have a pot of soup on the stove as well, so I dip the scoop into the soup instead of water. Tastier.

[jo-mel]

Thanks for the great ideas about the spoon and the rice. Never thought of dipping it! Makes sense.

And-- SusySushi -- I will look for that plastic paddle the next time I'm in an Asian store -- like 3 days from now. I've always picked up the wooden paddles, but the nibbly one is now on my list. Thanks!

[Domestic Goddess]

Be careful when you dip the paddle in soup and then use it to scoop the rice. The leftover rice should be refrigerated immediately since the soup contamination on the rice in the pot would hasten spoiling. Esecially in humid countries like mine - Philippines.