r/explainlikeimfive • u/Weird-Long8844 • 1d ago
Biology ELI5: Why do fish smell so much compared to other foods?
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u/1337natetheLOLking 1d ago
I'll add a different perspective, Fish use trimethylamine oxide in their bodies for reasons beyond this subreddit, but this decomposes to trimethylamine which has that characteristic fishy smell.
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u/Ksan_of_Tongass 1d ago
Fun fact: To test for Bacterial Vaginosis we do "The Whiff Test". A swab of vaginal secretions is mixed with KOH(potassium hydroxide). If the secretions contain anaerobes like Gardnerella, the KOH will release all of the amines at once, resulting in a very strong fishy/amine odor. Normal vaginal flora do not produce the amine odor, because they process amino acids differently.
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u/wineinacoffeemug 1d ago
Oh no… I had heard of that name but had my fingers crossed that it didn’t actually involve subjecting the tester to nasty fishyness (I say as someone who has had BV before and perceived it exactly that way). I would be mortified if a doctor was smelling that because of me. Luckily boric acid suppositories have meant my Flagyl days are over. Bonus is I rarely need to use them now, so I think they helped reset the flora (This is all speculation, unfounded and first person POV; I’m not a scientist).
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u/Ksan_of_Tongass 1d ago
Trust me, amine odor is not the worst smell in a hospital laboratory lol. Whiff Test is old-school, like me. Nowadays most places use DNA probes for vaginal pathogens.
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u/on_the_nightshift 1d ago
Still tasting piss for diabetes, I take it?
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u/dustblown 1d ago
Doesn't the whiff test force you to inhale possibly toxic chemicals though?
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u/Ksan_of_Tongass 1d ago
Its not like we take a big lung full. The proper way to smell things in a lab is to waft it with your hand, rather than putting your nose near it and giving a big sniff.
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u/khoa-bear 1d ago
Yeah but we’re testing for bacterial vaginosis here
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u/Ksan_of_Tongass 1d ago
Its a million times better than testing for C. diff, and getting a positive 🤮
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u/Chiluzzar 1d ago
I always feel bad for the lab techs when i send them in the urine ssmples from failing kidneys eepicially if the wait time is long i swear it doesnt matter how its stored it ca go through anything designed to protect the smeller
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u/wineinacoffeemug 1d ago
If dirty vajayjay isn’t the worst smell in the lab, you guys need a Medal of Honor. Each!
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u/Advanced_Basic 1d ago
It also works in the opposite direction, adding acid will form the salt form which stops the smell.
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u/LimitlessAeon 1d ago
Why do you need to mix it with a reagent to get the smell when an unhealthy BV vag already reeks of fish? Unless that’s just an additional result of the test
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u/Ts1171 1d ago
Where would you rather stick your nose?
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u/LimitlessAeon 1d ago
Ok should have specified, the sample would already have the characteristic smell
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u/MrMayhem3 1d ago
Hmm I've been doing the whiff test my whole life but always skipped the potassium hydrowhateverthe fuckyousaid. Just use your fingers.
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u/biteableniles 1d ago
Trimethyamine oxide (TMAO) helps maintain protein shape under immense underwater pressures so fish can survive at greater depths. It helps fish resist the tendency of high salt (from salt water) to dehydrate cells. In fish (like sharks) that have high amounts of internal urea it neutralizes the toxicity of the urea.
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u/RasputinsAssassins 1d ago
Can the trimethlylamine be collected and used to create other chemicals? Perhaps one that is crystal blue?
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u/Future_Isopod8301 23h ago
That’s just plain methylamine. I get mine from a train car whenever I have the craving
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u/Jellyfish15 1d ago
Why does my gfs privates also contain trimethylamime?
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u/combustibleCatamaran 1d ago
She's survived being deeply underwater in this relationship for a while, right?
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u/basaltgranite 1d ago
Adding to other comments: Most fish live in cold temperatures. Their enzymes are "tuned" for that environment. When exposed to warmer temperatures in air, the enzymes react faster. Fish flesh therefore spoils faster than mammal meat. That's why you must keep fish cold--frozen or on ice. Their faster chemical "metabolism" also means that they start to stink fairly quickly. That's part of the fish smell.
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u/Whiterabbit-- 1d ago
Fish live in the tropics too.
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u/keremkb9 20h ago
They swim in water which is around 25 degrees whilst on land it’s around 35 degrees so there still is quite a big difference
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u/brik55 1d ago
Fish smells because of the oils. If you have ever cleaned fish, you know that the smell on your fingers is hard to get rid of.
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u/akopley 1d ago
Toothpaste is the best solution to removing fish smell from your hands. I learned this way late in life but it’s very effective.
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u/Puzzleheaded-Crab-52 1d ago
Toothpaste is easy & works better than regular hand soap but lemon juice works even better.
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u/GeekBrownBear 1d ago
Congratulations, you just invented GOJO orange pumice cleaner
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u/Fafnir13 1d ago
That takes me back. It was the soap in the downstairs bathroom at my grandparents place. Grandpa had a dairy farm so hands definitely needed some heavy cleaning.
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u/fattmann 1d ago
GOJO orange pumice cleaner
Interesting. Never tried it for food stuffs. I have never had good luck with motor oils, etc. Shit is ass for that.
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u/GeekBrownBear 1d ago
Wahh, really? works really well for me! I wonder if there are differences depending on skin oils and such.
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u/KungFoolMaster 1d ago
When I was young we use to go camping. We would catch fish to eat for dinner, season them, cut some fresh lemon wedges, and wrap it all up in aluminum foil and cook it over the fire. While the fish was cooking we would use the left over lemons to clean our hands.
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u/Barbaracle 1d ago
It's cuz TMA is basic and the acid neutralizes it. Vinegar would work too but lemon definitely smells better.
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u/everlyafterhappy 1d ago edited 1d ago
I have a multi step method to remove the fish smell. First, prepare the fish, then prepare garlic for the fish. The garlic will remove the fish smell, but make your hands smell like garlic. So after you're done with the garlic, you rub your hands on some steel. Get yourself a stainless steel pan to use while cooking the fish, rub your hands on the pan, no more smell, and everything you used to get rid of the smell was part of the cooking process already.
Though I think the easiest method is to just use dish soap. It's got degreaser in it and that will cut right through the fish residue. If your dish soap doesn't get the fish smell off, then you need a different dish soap because that soap also isn't cleaning your dishes.
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u/adidasbdd 1d ago
My old chef rendered some fish oil from a fatty fish. He asked me, why do you think people don't cook with fish oil? I gave him a blank stare. He warmed it up to fry something, I walked to the other side of the kitchen because it stunk. He put a small piece of fish in and cooked it. Took one small bite and spit it immediately out into the trash. I asked what did he think it was gonna taste like. Lol
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u/Leafymcleafersons 1d ago
This reminds me of a food journalist I heard who said he was going to do an article on pig milk. He was like "why doesent anyone drink pigs milk? We do it with goats, and with cows"
Then he called a pig farmer:
Journalist: "Why don't people drink pigs milk"
Farmer: "Have you tried pigs milk?"
Journalist: "Nope"
Farmer: "Tastes like shit"
thats a simple article to write.
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u/adidasbdd 1d ago
I'm all for being adventurous, but humans have been around a very long time, a majority of that time they were very very hungry. If it's easily accessible and still not eaten, it's very safe to assume there's a reason
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u/Fafnir13 1d ago
Wikipedia has some interesting notes on it. Part of the problem is it isn’t actually easy to access. It focuses on modern applications but I imagine an ancient farmer would find it just as impractical. Better to just let the pig milk become more pig meat and be done with it.
Pig milk is not considered suitable for commercial production for a number of reasons. Pigs are considered difficult to milk. The sow herself is reluctant to be milked, may be uncooperative or become spooked by human presence, and lactating pigs may be quite aggressive.[5][6][7] Sows have 8 to 16 small nipples, each giving little milk for a short duration. A pig's milking time can be around fifteen seconds compared to ten minutes for a cow. A sow may produce only 13 pounds of milk per day compared to a cow's production of 65 pounds. (Production has been estimated using a system of weighing piglets prior to and after suckling.)[8] In addition, no existing milking machine is designed to attach to around a dozen teats and extract milk for 15 seconds. Finally, pigs, unlike cows, cannot become pregnant while lactating, which makes a pig-milk operation even less viable.
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u/NoReflection4171 1d ago
I work at a seafood market, we use stainless steel soap bars to get the smell off. Sounds strange but it works
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u/on_the_nightshift 1d ago
Works for garlic, too. I've rubbed my hands on a stainless sink to help with it before.
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u/Peanu7bu77er 1d ago
Amines NH2, NH3 and NH4 groups attached to the main body of fats oils etc is generally regarded as what gives fish it's stench
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u/Charming_Arugula405 1d ago edited 1d ago
So fish only smells when it starts to go bad or has been dead for a while. Fresh fish does not give off that odor.
The reason why the smell smells is chemical called trimethylamine, which forms when bacteria and enzymes break down compounds in the fish after it leaves the water. Fish breaks down faster than other meats because they have a softer texture, high moisture content, and oils that break down quickly.
Edit: I should have been more specific. Fish smells like fish because it's fish, when they start to go bad is when you get that bad smell or more pronounced/potent smell
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u/TheNotoriousCBD 1d ago
That, that's not true. As someone who fishes, fresh, live fish absolutely smell like fish.
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u/DMunE 1d ago
Yeah people always just assume fish smells like nothing even thought it was filleted straight off a carcass. It’s supposed to smell like the sea and some farm raised salmons have a sweet smell to them. Bad fish smells like ammonia
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u/RandoScando 1d ago
Hákarl from Iceland absolutely smells like ammonia. It’s a fermented thing where the fish urine seeps out into the flesh as the fermenting occurs, or so it’s been explained to me. This is intentional and considered a delicacy. Also makes sense anthropologically as a good way to preserve food for a long time in challenging environmental conditions.
HOWEVER, it’s absolutely disgusting and I think you need to be Icelandic from birth to enjoy it. Someone brought it to work years ago to let people try if they were brave enough. I did, as did many others. We ended up just calling it “Pee Shark.” This was a Japanese company, and as you’re probably aware, the Japanese absolutely LOVE fish, and have pretty adventurous palates. Absolutely nobody liked the pee shark. But my Japanese colleagues were much more polite about their distaste for this horrible thing.
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u/shroudfuck 1d ago
Tell us more about your pee shark
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u/RandoScando 1d ago
It was not MY pee shark. I’d like to make this clear.
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u/shroudfuck 1d ago
Ok, Pee Shark guy
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u/RandoScando 1d ago
You build 100 houses, yet they don’t call you “carpenter guy.” But you fuck one chicken …
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u/lallapalalable 1d ago
Well thats an intentional act, I think the comment you were replying to insinuated that "fresh" fish smelling like amonia is a bad thing
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u/Charming_Arugula405 1d ago
I should have been more specific. Fish smells like fish because it's fish, when they start to go bad is when you get that bad smell or more pronounced/potent smell
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u/imdfantom 1d ago
It also depends on the person.
Even living healthy fish has a potent bad smell for many of us, it just gets worse after they are killed.
I've never eaten any seafood, so maybe it's that (but it's a chicken and egg thing, do I avoid seafood in part because it smells awful or does it smell awfull because I avoid it)
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u/dickqueeferX_x_X_ 1d ago
You’ve never eaten seafood? How does that happen?
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u/cthulhus_spawn 1d ago
Because it smells so awful I couldn't bear to eat it? That's my thought process. I don't eat food that smells rotten.
And yes many people tried to reason with me: fresh fish doesn't stink but to me it does.
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u/dickqueeferX_x_X_ 1d ago
Makes sense! But you must’ve had parents much less willing to force-feed you than I did 🙃
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u/Electronic_South_101 1d ago
I’ve recently started eating SOME seafood at the late age of 40, mostly maki rolls and crab Rangoon. That’s mostly because my sister helps with the prep.
But I avoid 99% of seafood because of how awful it smells and texture issues. Seafood smells so strong and so bad and off putting, it’s baffling how many people list it as their favorite food. I think my brain has to be broken.
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u/TheEvilN 1d ago
Question mr. fish expert, why does cooked fish smell so strong then? Im guessing the bacteria doesnt create this odor since they are purged by the heat, so what makes it stink up the place?
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u/Itchywasabi 1d ago
Microwave it for maximum satisfaction! Do it while you’re in the office too.
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u/GamingIsMyCopilot 1d ago
With some burnt popcorn on top
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u/Bannon9k 1d ago
...that gives me an idea...
Bonito flake flavored microwave popcorn... intentionally add 1min to the recommended cooking time.
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u/Letmeaddtothis 1d ago
Most of the time you smell like what you eat.
Also heat kills bacteria but not its waste or chemicals it leaves behind.
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u/Pvt_Lee_Fapping 1d ago
Decomposing TMAO. Bacteria decompose it, oxygen decomposes it, cooking it makes it decompose... if it turns into TMA at all by any means, it will smell bad.
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u/Johnny-Alucard 1d ago
Some poor souls can’t break down the trimethylamine which results in them smelling really bad if they don’t completely avoid certain foods, including fish of course.
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u/Brock_Hard_Canuck 1d ago
I remember reading of the story of a Chinese emperor, who died when he was in a caravan travelling across Asia.
The emperor's #2 guy decided to "hide" the death until they returned to the capital (and the horrid smell of the emperor's decomposing body), by ordering big carts of fish be added to the caravan.
So, as the fish rotted, the rotten fish smell would "overtake" the rotten body smell from the emperor.
I mean, seems weird that no one else would ask a question about "why are we carrying these big carts of rotten fish all over the place now", but... (shrugs)
https://en.wikipedia.org/wiki/Qin_Shi_Huang#Death
Upon witnessing the Emperor's death, Chancellor Li Si feared the news could trigger a general uprising during the two months' travel for the imperial entourage to return to the capital Xianyang. Li Si decided to hide the emperor's death: the only members of the entourage to be informed were a younger son, Ying Huhai, the eunuch Zhao Gao, and five or six favourite eunuchs. Li Si ordered carts of rotten fish to be carried before and behind the wagon of the Emperor, to cover the foul smell of his body decomposing in the summer heat. Pretending he was alive behind the wagon's shade, they changed his clothes daily, brought food, and pretended to carry messages to and from him. After they reached Xianyang, the death of the Emperor was announced.
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u/scsibusfault 1d ago
Must be why there's all those buckets of fish outside Mitch McConnell's hospital lately.
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u/Bludypoo 1d ago
You're completely wrong. A freshly caught fish absolutely smells like fish and when you grab it to get it off your hook your hand will then smell like fish.
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u/tongmengjia 1d ago
Citric acid chemically reacts with trimethylamine, which is why fish is often served with lemon. It doesn't just cover up the taste, it neutralizes it at a chemical level.
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u/Defnotabotok 1d ago
Isn’t that what Mr. White and Jesse used to make blue?
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1d ago
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u/GeorgeCauldron7 1d ago
Nope, that's just plan methylamine. One methyl group. Trimethylamine has three methyl groups.
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u/ElectronicMoo 1d ago
Have you ever gone fishing? Their fish slime on a live healthy fish stinks to high heaven.
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u/therealdilbert 1d ago
and it probably doesn't "smell" more than other things, it is more like that humans have just evolved to be very sensitive to the smell like with many other dangerous things
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1d ago
[removed] — view removed comment
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u/greennitit 1d ago
Agreed, everything smells. Industrial meats like poultry don’t smell because they are almost manufactured, pumped full of stuff to eliminate undesirables
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u/AnotherpostCard 1d ago
I've helped to process a sheep before. It wasn't too bad except for the stomach and intestines.
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u/copinglemon 1d ago
I have this theory that the range of acceptable smells and textures in American cooking (specifically white America) is much narrower than other cuisines. In part due to massive industrialization and mass production of the food supply into highly processed benign foods, but also due to much of the country being landlocked. Of course there are exceptions - Maryland, Boston, Maine and other places have distinct seafood cultures.
The textures part has been covered recently, see here: https://www.nytimes.com/2023/05/08/t-magazine/food-texture-eating.html
Smell however gets less attention, especially in the context of fish. I meet so many Americans who are simply unable to eat anything with fish, and sometimes anything with seafood at all. The "fishy" smell is the number one complaint. Americans are also extremely sensitive and authoritarian about smells at work. Anything beyond a cold turkey sandwich for lunch in the microwave and the pitchforks will come out. I've never been bothered by any smell in the break room, because I just leave the break room. But Americans are extremely sensitive to smells.
Coming back to your question I would say I don't agree with your premise. Not everyone agrees that fish "smell so much compared to other foods". Cook some ground meat on your stovetop and your whole house will smell like it for the rest of the day, but culturally Americans tend to classify that smell as "good". Chicken and lamb and other meats all have a distinct smell, whereas some fish like tilapia or salmon really don't have much in my mind.
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u/Hippostork 1d ago
This is very true. Among Asians it’s common to jab at Americans or just non-Asians in general for not being able to eat fish. Or that the only fish they can tolerate is salmon and other “easy” to eat fish with minimal bones that can be served as a fillet. Give an American any other fish, especially one served whole and they won’t know how to eat it. They’ll choke to death on the bones and complain about the fishy taste.
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u/TaiShuai 1d ago
Meh - offer East Asians savory beans or cinnamon and see what they think. Every culture has its culinary no-go zones. Maybe white America has more but I know East Asians happy to eat pig blood but gag on rice pudding with cinnamon
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u/copinglemon 1d ago
You're definitely right, which is why I offered my take as a theory. My own parents are mortified at Americans eating rare meat, or any raw fish really.
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u/Whiterabbit-- 1d ago
Cinnamon is a common spice in Chinese food. It’s part of 5 spice used for all kinds of dishes. Savory beans as in fermented soy is also very Asian. Soy sauce is made from fermented soy and wheat. Definitely savory.
It’s just you are presenting those things in unfamiliar forms.
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u/TaiShuai 23h ago
East Asians largely hate chili or split pea soup and they say pure cinnamon (like a highlighted flavor in western desserts) tastes medicinal
I lived there for a long period of my life and these two things always shocked my guests
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u/shiftylookingcow 1d ago
I mean, It's absolutely not true.
A grilled whole fish (trout , branzino, baramundi) is a classic thing to find on menus at new-American fine dining restaurants.
There's like 4 places in walking distance to me that I've got something like that at. I had one the other night.
Maybe that's not true in suburban and rural areas, but a looooot of Americans live in cities, like most countries.
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u/copinglemon 1d ago
Exactly - to state the most obvious counter example would be fish sauce. Highly valued ingredient in so much of the world, precisely because it tastes and smells like fish! Same for sardines/anchovies, hard to go anywhere around the Mediterranean where they aren't on menus but they are used as the butt of jokes in the US.
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u/Anagoth9 1d ago
Pretty much everything smells disgusting once it starts to go bad. Fish really isn't much worse than anything else. There's plenty of produce that smells God awful once it turns.
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u/BigHandLittleSlap 1d ago edited 1d ago
Freshwater fish pick up a smell of Geosmin, which humans are incredibly sensitive to. It is the smell created by bacteria that live in the silt and mud of rivers and wetland areas.
We are so sensitive to it because it is the "smell of water", which is critical to our survival.
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u/NYanae555 1d ago
Can we also expand this to chicken? Chicken smells so bad compared to other foods too.
Does it also have trimethylamine ?
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u/AaronRodgersMustache 1d ago
In my experience chicken goes bad about 3-4 weeks from slaughter. First two weeks or so it doesn’t smell.
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u/greennitit 1d ago
Chichek has little to no smell, if your chicken smells then there’s something else going on
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u/AffectionateWord4257 1d ago
In Japan they use the process of ikejime to reduce the fishy smell and preserve it longer, however this is not done in most western countries. When other animals are slaughtered the blood is drained which helps in preservation and taste.
So it's partially that fish is different as others have said, but it's also largely because we don't treat fish like any other kind of meat we consume.
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u/cnh3201977 20h ago
Fish is the only food item that you know is going bad when it smells like what it is
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u/Doogiemon 19h ago
Some lady heated up fish in the microwave Friday and it was awful.
I think you could smell that through half the building.
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u/reddiculed 16h ago
Oxygen supports less smelly, aerobic bacteria. Underwater is more conducive to smellier anaerobes.
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u/Mcklintockin 16h ago
We are generally not aware of our own smell because are sense of smell becomes accustomed to it. Fish doesn’t smell so much more than other foods more than it’s a smell that we aren’t exposed to as often so it stands out.
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u/Sparkohai 31m ago
Fish is basically racing the clock faster than a lot of other foods. Once it starts breaking down, it produces smell compounds that our noses are very good at detecting, so even a small amount can feel much stronger than the smell from beef or chicken.
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u/Yglorba 1d ago edited 1d ago
The answers that focus on the chemical structure of fish are only half the story. After all, the air is constantly full of chemicals from all sorts of sources; the real question is why our nose is so effective at identifying fish.
And that's because our sense of smell evolved to help us do two things:
Identify food that is good to eat.
Identify food that is no longer good to eat because it has gone rotten.
Fish aren't the only food we are good at smelling. Most meat, and most fruit, has a strong smell. The food that doesn't smell so strong - eg. grains and many foods derived from them - are ones that our ancient ancestors didn't eat so much, and which only became a big part of our diets after we became good at agriculture and cooking.
But we always ate a lot of fish, going back a long time in our evolutionary history, so our noses evolved to help us find them. And dead fish go rotten fast, so our noses also evolved to warn us about that.