Why do we add salt when we're cooking rice? I know one reason is related to the boiling point of water but someone said it is also related to "Osmosis". What is the relation between adding salt and osmosis. How does it help cooking rice?
In osmosis, normally, water will move toward the side of membrane with higher concentration of salt, and this can happen with or without heat (though much faster with higher temp. because of the fast motion of molecules).
So my guesses are:
1. This can prevent over-bloating of the rice due to over-absorption of water, and perhaps prevent grain damage.
2. Since osmosis squeezes out water from lower to higher concentration, it might be able to 'squeeze' out the flavor molecules of the rice better, which might come along as water passes out..(but this might only happen if you don't put the salt at start, but wait until the rice bloats a bit, cause after all, what can you squeeze out of a dry grain with no water?)
3. Another effect (due to increased boiling point) is that water evaporates at a slower rate than without salt.
These are just guesses, I'm not sure I'm 100% correct.
The amount of salt used for cooking is not nearly enough to have a physical effect on the process. The boiling point elevation is less than 1 degree and any osmosis effect will be small (especially when compared to the brine used in pickling). The purpose of adding salt is for flavor.