I do a lot of Thai cooking at home and I frequently use fish sauce (nam pla/nuoc mam) to flavor curries and noodle/rice dishes. Recently I made a fried rice with a dash of nuoc mam, and when I tasted it, it made me kinda nauseous/queasy. This was the first time this has happened, so I thought it was kinda unusual.
I've had this large bottle of Vietnamese fish sauce for a few months sitting out on my counter, not refrigerated. Now, I realize the way they make this stuff in Thailand and Vietnam is that they take the little anchovies/shimps and put them in big jars with salt and let them ferment for months upon months outside in the heat in the open air before they bottle it. So its -already- got a wicked aroma and funky taste. I mean, its already "bad", right?
Is it possible for this stuff to go rancid? Or maybe I used too much?