For a long time, I believed this advice:
Don't refrigerate your fish sauce. Whatever can happen to this brew
has already happened; it's not going to go bad. You can pass your
half-empty bottle down as a family heirloom, and your grandchildren
will enjoy the same golden liquid that you have on your shelf today.
And then one day I noticed what was clearly white mold growing in the bottle; so much for sharing it with my grandchildren. For reference, this was one of those standard big one-liter bottles from an Asian grocery, and I use the stuff maybe every couple of weeks.
So is it generally OK to keep fish sauce at room temperature, and how do I know it's gone bad? The sniff test obviously isn't of much use. I get the feeling that fish sauce gets darker as it ages, but that's hard to measure.
Best Answer
That advice isn't "wrong" and millions of people keep keep fish sauce in a cabinet for decades. Regarding safety, it's generally OK to store fish sauce at room temperature for years, but that isn't recommended by government worrywarts for best quality. Still Tasty. Pathogens run in fear faced with this stuff, but it can (rarely) develop "offness".
It is conservative to even bring up this article from Slate:
So, grudgingly, I say throw this batch out 'cause it's fuzzy. But don't lose any sleep over it.
Next time buy a bottle that you're likely to use within a couple of years and keep it in the fridge after opening.