One of my friends said "rasam" should not be boiled at high temperatures but he hasn't given any reason for that statement.
Is it true? If so, could you give me the reason?
Yea, you should not. The principle behind Rasam is the same as the principle behind the soup. You want the liquid to be infused with the optimum flavour from the masala, tomatoes, pepper etc. Beyond that it begins to lose its characteristic taste. Even rasam that has been heated repeatedly, tastes much worse than one that has been heated just once. If you make Rasam with whole peppers like in my place, the spiciness become unbearable if you boil it too much.
The reason is rasam is a liquid thing with necessary ingredients added to it which doesn't need to actually be 'cooked' But we need to boil so as to remove the raw flavor of tamarind or tomato used in it. So if the rasam just starts boiling its enough heat to remove the raw smell and incorporate all the essential flavors to the rasam. It 'need not ' be heated beyond that as a matter of fact.
never boil rasam. it becomes bland, just heat it till the fragrance comes out and it is about to simmer. if you dont believe, why not go ahead and boil at high temperature and drink it yourself. :)