HOME > Chowhound > General Topics >


Fish: ammonia-like flavor?

  • a

Hello - I had fish tacos (for those folks in LA, at Bread & Porridge on Wilshire in Santa Monica) and in one of the tacos, the fish had an odd ammonia-like aroma. This has happened to me once before at a casual fish restaurant that's basically on the beach and fairly popular so I assumed there was good turnover on the fish (Reel Inn on PCH in Malibu). After eating the fish, on both occasions, I didn't get sick, but I'd like to know why the fish tasted this way. Are there any Chowhounds out there who might know why this happens, and also what is it?

Thanks very much for any information - I'm quite puzzled.


  1. Click to Upload a photo (10 MB limit)
  1. I don't know what sort of chemical reaction causes this unpleasantness, but I've always thought of it as a sign that the seafood in question has gone past it's prime. This is common with shrimp, I know. I've noted this before buying "fresh" seafood. When buying fish I always smell it first. If the fishmonger won't allow me to smell it, I don't buy it. pat

    1. s
      Suzanne Fass in NYC

      It means the fish is BAD, as in rotted. If you get anything like that again, take the offending item back, tell them you are afraid it may kill you -- it may or may not -- and never go to that place again.

      1. Yes, it was starting to spoil. The reason you didn't get sick is because spoilage bacteria are not necessarily pathogenic, whereas pathogenic bacteria alone might not give any bad taste to the food, even though you could get very sick later.

        My daughter and I had some really bad uni once, and if spoilage could kill, we'd both be dead. As it was, we didn't even get sick.

        1. Yes, the fish is bad. I once ate a piece of fish with the ammonia-like smell. I had a horrible reaction. My throat closed up and my face puffed up. I had to be taken to the ER. I have no fish allergies whatsoever.

          1. Yikes! Now that I know, I'm so grateful they were only two bad meals and not anything worse! Thank you so much for responding so quickly. Angie5

            1. As everyone else is saying, the fish was bad. For some reason i've noticed this ammonia aroma most often in fish that has cartilage, like Skate and Shark. Would these have been Shark tacos by any chance?

              8 Replies
              1. re: Mistermike
                Gabriel Solis

                Funny you should mention this. I was reading in _Cooking with Pomiane_ today and ran across the following as a reason for the tradition of serving skate with black butter:

                "In fact, skate should be kept for a time before being cooked, and the fishermen say that it is very tough when fresh from the sea. ...For one reason or another, the grown-up skate always has to wait to be cooked and very often it gives off a smell of ammonia in consequence. The same thing applies to other members of the same family such as dog fish.... So skate often smells of ammonia and chemists know that ammonia forms, together with acrolein, an insoluble and odorless compound. Acrolein is fromed by the action of fat at a high temperature.

                If, therefore, we sprinkle cooked skate with black butter which has been darkened by the action of heat, we add enough acrolein to annihilate any possible smell of ammonia."

                I don't know if his science is correct (elsewhere in the book it generally is), but it seems plausible (though not really an answer to why skate with black butter--I mean, it merely provides an answer to why skate with some kind of hot, fatty preparation...). In any case, I do so love this book, and thought the passage was oddly appropriate to the conversation. Oh, the other thing is it suggests that, indeed, the fish was a bit past its prime, and that, indeed, the bacterium that causes this ammoniac odor/flavor, is harmeless when it dies.



                1. re: Gabriel Solis

                  The fish wasn't bad. Like the last post said, cartilaginous fish (skate, shark, etc.) for whatever reason process uric acid differently in their bodies. When they are killed, you need to give the fish a day or two to allow the ammonia smell to dissipate. Freshness, in this case, is not everything...

                  1. re: chefsmartypants

                    I'd like to say that the rotten skate that I had (the $1,000 ER visit) was old (somebody told me). There was an ammonia smell coming from that fish. So while a skate may have an ammonia smell after it's freshly killed, the smell could also be the result of it being past its prime.

                    1. re: Jennifer J
                      Gabriel Solis

                      Actually, the point of the passage from Pomiane is that skate develops an ammoniac smell as it ages, rather than right away, but at the same time becomes more tender, and thus, needs a sauce like burre noir to neutralize the offending odor. I'll admit to not knowing much about skate myself, though. Just clarifying what Pomiane has to say on the topic.


                      1. re: Gabriel Solis

                        Gotta disagree here. If fish smells like ammonia, it's bad. Brining it in some icy brine may help, but the fish is just plain bad. Oh, I know there's more than a few Englishmen who'll disagree with me here, but lets remember that they hang game birds by their feet until the carcass falls to the ground.

                        I love skate, I prepare and eat it with some frequency, and I won't buy it if it smells like ammonia. All fish has been dead for a few hours before you buy it, and that's under the best circumstance. There's no need for a fish to go through an extended period of aging for it to be tender. The freshest skate will turn out beautifully, the ammonia-smelling ones will always smell like ammonia.

                        1. re: Greg Spence

                          Not sure whether this adds anything, but I've noticed that skate is the most likely to have the ammonia smell - implying that there's something 'different' about skate (and possibly shark, based on above comments).
                          So how old should skate be to be at its 'best'?

                    2. re: chefsmartypants

                      Chefsmartypants has the closest answer I think. I'm willing to bet that that fish taco was indead shark, and they do have a very high uric acid content due to I think, an absence of an organ that filters the blood like a kidney. I live in the middle of the ocean around a lot of old fishermen. I've had some really great shark hash, and some really bad shark hash - the bad having a bouquet similar to a 2 week old diaper. These old sea dogs tell me that a shark must be hung and bled immediately after it's caught so that the uratic acid doesn't permeate the meat. Makes sense to me.

                  2. re: Mistermike

                    I'm not sure what kind of fish was in my tacos, but I'm fairly certain it wasn't shark as the flesh was very white, light, and flaked easily. It seemed like snapper or something like that. Angie5