My coffee smells like tuna fish

My friend Paul writes:

Here’s a question that hopefully won’t tax your superior barista knowledge banks too greatly. A co-worker of mine once mentioned that occasionally brewing coffee smells like tuna fish to him. I thought that was odd until I noticed it too. Now it doesn’t happen all the time, but sometimes when I smell brewing coffee there is a distinct odor of tuna. I’ve done a google search and found other people who have had this experience, but I’ve found no satisfactory explanation.

My guess is that somehow it’s related to the chemical trimethylamine, which is what gives fish a “fishy” odor. The chemical has an extremely low odor threshold, so it can be detected by scent even in very low concentrations. But what could be producing the trimethylamine? Do you have any idea what could be causing this?

I have no idea, actually. I checked my copy of Illy and Viani’s Espresso Coffee, a collection of scientific papers about coffee, and couldn’t find anything on it. A table reviewing odor compounds found in ground coffee doesn’t include trimethylamine. The compound with the closest description is probably methanethiol, which leaves a “putrid, cabbage like” sense impression.

Another possibility is that the coffee with that smell was stored improperly and picked up off flavors from something else. Any other ideas?

[Cross-posted at STC.]


50 thoughts on “My coffee smells like tuna fish”

  1. Not to cast any aspersions on the quality of coffee your friend drinks but fish like odours are often the result of the oils turning rancid. Certainly a possibility if the coffee is old or the brewing equipment badly cleaned.

  2. Although trimethylamine is one compound that gives fish a “fishy” odor, it is by no means the only one. Trimethylamine is also found in all fish (as far as I know) not just tuna, and the aroma of canned tuna is very different from the aroma of, for instance, fresh tuna sashimi, let alone the aroma of a completely different fish such as salmon, or catfish. I suspect that coffee and fish do have a good many aroma compounds in common, though perhaps not usually in very high concentrations. Canned tuna may specifically gain some compounds that fresh fish does not have, and perhaps some of these are present in coffee.

    Either way, it’s an interesting concept for a flavor pairing. Maybe I’ll try a fish and coffee meal some time.

  3. I bought some of the Starbucks Bold Coffee and it has that “fishy” smell…I keep th beans in the freezer and it’s only been 2 weeks! Ther is only ice and fruit in there…so it couldn’t have picked up any wierd flavors from there. And I thought toring the beans in the freezer was the best was to keep them…?

  4. Hazelyn,

    The smells might have come from the refrigerator, or perhaps you just got a bad bag of coffee. In any case, taking coffee in and out of the freezer can damage the beans. Your best bet for coffee storage is to keep it at room temperature in a sealed container and use it within a couple weeks of roasting. Unless you have some reason to store coffee long term, there’s no need to freeze it.

  5. Regarding the coffee smells like fish comments, I too found a bag of coffee smelling a bit like fish (it was dark roast organic). I searched and came across this blog. I also found a coffee company called Trager Brothers Coffee which sells coffee online. One of their products called Dark Roast Sumatra is listed with the comment “PS if it smells like fish when you grind it, then you got the good stuff.” I could not find any other references to fish and coffee that had any logical answers.

  6. I think espresso smells like tuna. There is a building on campus at Boise State University that has a coffee/espresso stand on the ground floor and it smells like tuna every time I walk into the building. I don’t think everyone notices the smell in the same way. When we brew regular coffee at work, I smell coffee; but when we brew espresso, I smell tuna. Another co-worker smells it too.

  7. It is not the same “fishy” smell of fish going bad or fresh fish. It is definitely a smell from canned tuna and many types of coffee. It is strongest during brewing and is not related to how clean the coffee maker is. I have experienced this all my life and never understood why.

    1. i picked up a bag of d&d coffee original and within one month it lost its signiture aroma,and exeptional taste,i also put it in a plastic container with a lid on it.i f#$&ing cant beleive it my last bag too .my only belief is maybe someone switched it with el cheapo crap that went rancid or date was wrong on the package.

  8. I smell like fish sometimes, but that’s usually when I don’t shower for a week or two. My coffee smells like roses though. Sometimes I wish I could trade places with my coffee beans so I would smell good for once.


    Amines present in coffee – DM, EM, E, P, IB, SRT (pg 38,165)
    DM – Dimethylamine – ammonia odor
    EM – Ethylmethylamine – ethylmethylamine : — C2H6— NC + 2 H2 = C2H6— N— CH3. …. It has a strong ammoniacal and fishy odor. It is very soluble in water …… the active constituents of coffee, tea, and chocolate on the one hand
    E – Ethylamine – ammonia odor
    P – Propylamine – 1 : either of two flammable isomeric liquid bases C3H7NH2 of ammoniacal fishy odor ; especially : the normal amine CH3CH2CH2NH2
    IB – Isobutylamine – A clear colorless liquid with a fishlike odor
    SRT – Serotonin

  10. I also recently bought a bag of starbucks french roast and seattle best french roast……both of them were dark roast…….I bought them on sale and was wondering why they too smelled of fish. However, I think that I will go back to Maxwell House premium roast…..

  11. I bought a bag of Starbucks one Christmas at Wal-Mart and threw it out because it smelled so strongly of fish. A gentleman in the coffee business told me that the smell is caused by the glue used to seal the package. I just opened a small packet of Donut Shop Coffee and immediately noticed the same obnoxious odor. Disgusting.

  12. The patrons and baristas at the cafe that I’m writing in from, just had this discussion. From my perspective of a chem student, it seems that the grinding process generates a source of amines, from which we pick up the characteristic fishy odors. Whether the amines are the result of:

    -methylamine degradation from alkaloids (caffeine??)
    -or maybe that the amino acids (that build the proteins still found in the cofee) are being freed from their previous structures

    is up for debate.

    The fishy smell has become nostalgic and characteristic of a good cup to come! Till then, happy drinkings!

  13. @Juan: doi:10.1016/j.foodchem.2004.03.056

    I also found this article from the journal, Food Chemistry. It helps fill in the gaps.

  14. Came across this blog after searching “my coffee smells like fish”. I have a fishy bag of Seattle’s Best. Smells fishy, tastes delicious.

  15. Yep, my Seattle’s Best Coffee #5 (purple bag now, “Bold, Dark, Intense”), smells like fish when scooping it out and into filter. It stinks up my cabinet like fish too. I don’t put it into the freezer beacuse I go through it so quickly. It is delicious though! It’s not “coffee gone bad”, it is good stuff! It reminds me of latte strength.

  16. My wife and I were trying to figure out the smell and were sure that we were doing something wrong. The strongest smell is during brewing (Starbucks Verona). Is this the sign of really good coffee?

    Apparently we are not the only crazy ones who smell fish! The coffee tastes great and is fresh. Also, the coffee maker is clean. So I guess it’s just how it is.

    Enjoy life!

  17. Glad to find this information! My Seattle’s Best coffee has a distinct smell of chemicals and–yes–fish! At first I thought it was just one bag but then the next smelled the same (and it’s a different variety: 4 instead of 3). The coffee still tastes okay but I’m not keen on paying for it if it smells this way. In fairness, only the grounds smell this way before brewing. So the coffee in your cup seems relatively unaffected.

  18. Same. Seattles Best(starbucks generic brand) smells like fish. It’s a brand new bag that I got from the store, I love the smell of brand new coffee, opened it up, took a big wiff, and YUCK. Will never buy it again.

  19. I wonder if the smell is not in the coffee or packaging but in my nose. I am the only one in my household who smells the canned tuna odor.

  20. Just a thought….
    I too have noticed a fishy smell when I open the Starbucks bags at work (the company I work for treats us to Starbucks brand) . Perhaps I am a little paranoid but, I have heard that when GMOs (genetically modified organisms are used in certain food processing, because they often use fish genes, foods that have nothing to do with fish will often have a hint of fishyness in their scents.
    Does anyone else know anything about this?

  21. I definitely smell that fish smell, but others I’ve talked to in the same room with the smell do not. As a chemist, I think it’s an amine thing. Sixto, you have heard wrong.

  22. I’m pretty sure this phenomenon has to do with the variable volatility of the different aromatic components which make up coffee’s aroma. In my experience it only smells like tuna from across the room. Up close, it smells like coffee. This is because most odors are a highly complex mixture of different compounds, some of which “travel” further than others through the air. I assume the fishy compound in coffee is a more volatile one than the others. I’ve also noticed that fresh ripe strawberries smell rotten from a certain distance as well.

  23. Unbelievable, I’m not alone. I began buying Starbucks Pike Place Roast (the standard blend) here in Dresden, Germany, and both I and my colleague can smell the faint tuna. I’m talking whole beans here so it must be either a volatile that’s leeching from dried beans.

    1. Same here. Last week i got a bag of Starbucks Breakfast Blend ground coffee. i keep it in the pantry. during the brewing process it smells like tuna fish. but a cup of it only smells slightly like tuna. and it doesnt taste bad at all. it tastes pretty good.

  24. I worked as a barista in a third wave coffee shop for a while and have found a common thread between fishy coffees: Oceania. (The coffees at our shop were all natural organic, so I can vouch for the absence of GMOs in the crop). I only noticed the “canned tuna” smell in the coffees from the Pacific Islands. My theory, and this has not been tested, is that there is a chemical in the soil, consistent across the islands, that grows into the plants and sets itself in the coffee bean. This chemical may come from the waste of disposed fish parts (a major part of the islanders’ diet) when these fish parts are used in compost and fertilizer for the coffee farms.

    Any thoughts or substance?

  25. Oh man, good to know that I am not the only one who has experienced this phenomena. First I thought I affiliated tuna with coffee because of some life experience, and my brain had made a connection between the two. Then I thought I might have some super cool/weird sensory disorder like synethesia. Turns out, you guys have had the same experience. I’d be curious to hear a legitimate & in-depth explanation behind this issue.

  26. I just was enjoying a Starbucks brand pre-bottled ice coffee when I noticed it smelled unmistakenly like fish. A google search later and I’m here. So chaulk one more up for coffee taking up the smell of fish somehow. Now I can only hope that this realization doesnt ruin my perception of coffee. Hopefully this is a fluke and I won’t notice it in future coffee endeavors.

  27. I also notice that coffee smells like canned tuna. As others have said, it’s more noticeable from a distance where you can’t smell the strong coffee smell, but get a whiff of just a slight bit of odor. This is fresh coffee and nothing is wrong with it afaik.

    I also notice that urine sometimes smells like cheerios (or cheerios smell like urine). A slight oat-y smell.

    Maybe I just have a nose more sensitive to certain scents.

    1. I think its the fertilizer they use to grow the coffee. I read that fish makes a great nutrients for a growing plant

  28. I had the experience twice when the guys a Starbucks openen the big grinder cap. Actually it smelled like fish and a bit like garbage. And the beans look kind of wet. Considering the great “saucy” acid of the Starbucks flavour I would consider that being the foundation. Maybe it’s some kind of fermentation that emulates the one of that “best” coffee (kopi luwak) which is digested by monkeys before being collected, can’t say. My main problem with it is that i really don’t like thuna. Nor garbage.

    You might ask the Starbucks Barista to open the cap for you. maybe they also have the theory behind it. or at least a nice “selling” story.

  29. I’m not a coffee drinker but I eat a lot of canned tuna. I’ve noticed this for years. Just now at work someone brewed a pot of coffee (I have no idea what type) and, across the room, I’m smelling tuna, which is what brought me to this site. I’m so glad I am not alone in experiencing the phenomenon!

  30. Pingback: Slight skunk smell
  31. It’s true, it has nothing to do with your coffee maker/brewing system as far as I can tell.

    I was a barista at a popular coffee chain for about a year, and without fail, it was ONLY the French Roast (and sometimes, the Italian Roast) that had this “fishy” odor. These beans were fresh out of the bag, right after opening, that smelled fishy before grinding them.

    I’m assuming it has to do with the oils and caffeine as stated above, or the amino acids in the oils of the beans, especially the richer, darker bold roasts.

  32. Melissa confirms what I read on a different website tonight. The darker roasts have had some of their caffeine “corrupted” into another compound which smells fishy. I’ve been roasting my own Peruvian organic green beans at home for about 4 weeks now. I shall go back to slow rather than fast roasting – but not too gently because “under” roasted coffee is really bitter.

  33. Its got zero to do with rancidity. It doesn’t smell rotten or bad, it just smells like tuna. Its with instant coffee as well when brewing. There’s just something similar about their smells. Sometimes its more obvious than others.

  34. I have often noticed the same thing in our office when my boss makes espresso from his Espresso machine. Others surprisingly have said the same thing “I smell tuna” or “Who’s eating tuna?”

    There are many smells that to me seem to mimic other smells. This may be weird but I also notice that freshly popped popcorn can smell like a wet baby diaper. lol.

  35. I think the fishy smell is due to the rich fertilizer they use to grow the coffee. Im pretty sure it’s the plant food the company uses.

  36. We strictly use Dunkin Donuts original, whole bean coffee; have been for over 10 years. Excellent flavor with Capresso grind & brew made us loyal coffee shop bean drinkers. However, within the last 4 months started to smell a strong fishy odor. Cleaned the brewer fastidiously, especially the hot plate and blamed the odor on different cleansers. The smell not only comes from the brewer and the counter but is also in the coffee itself. Can I blame our never-ending head colds on this chemical event? Why has this just started all at once? Has Congress allowed something to change? Lots of questions…and refuse to accept no answer! Help.

  37. I have not bought Seattle’s Best in a while but it was on sale. I remembered I did not like it last time, but thought I’d give it a try. I remembered a distinct funk smell and burnt taste. I remembered it tasted like someone shoved coffee grounds into my mouth. I bought a pre-ground bag. It stinks like either urine or ammonia, but I don’t think fishy. The taste is positively awful, rot gut. And I mean it. It is not fit for consumption. I actually got some other coffee and cut the Seattle’s Best with it. I won’t dare try Seattle’s Best again! Gross.

    1. I agree..thats exactly how all the coffee has been smelling ! bought 4 bags saturday ..different brands..McDonalds was least smelly,least bitter…….and I have never been a fan of McDonalds coffee from the restaurant

  38. Interesting thread. Look to the Brazilian beans – almost certainly a component in all the blends mentioned here. Can smell awful…but taste great, even straight out of the roaster. Not a freshness/rancidity issue, possibly roast height (we tend to roast Brazils slightly darker than some here, but nothing like Starbucks dark). Perhaps an agronomist with experience of Brazilian farming practices and fertiliser usage could throw some light on whether there is anything in the soil that may create this characteristic.

  39. I’m going with Frank about the amines present in coffee. We live close to the Berres Brothers Coffee Roasters factory (fantastic place) and get that tuna aroma occasionally. We are by no means coffee connoisseurs so we stick with our little Keurig but we’ve gotten that same fishy aroma out of many different K Cups and coffees. Blame it on the Ethylmethylamine

  40. Glad I found you people. I have been following that unpleasant coffee smell for a while.
    Very interesting thing because first thing about coffee I think is a great smell.
    When i realized that coffee has another smell, have started to follow it.
    First time I discovered it after drinking espresso, when tried to drink some more from my almost dried cup. After more testing realized that smell is present only when used without milk or cream.
    Next I found it in the instant coffee jar. The smell appeared in a jar much later, perhaps a week after opening,, later becoming stronger. It is also present in a cup too, while it is full and warm as well as after it. Then I bought a different brand from a different producer. The same thing repeatedly happened.

  41. it is the concentration of certain chemicals that may cause the impression of smelling something else . a high concentration of mercaptan from coffee may seem like skunk musk on steroids and a low concentration mercaptan in skunk musk may smell like roasting coffee . also olfactory hallucinations may happen when one smell triggers a memory in the brain . olfactory hallucinations may also be caused by nerve damage .

  42. O thank you, Ev 12/15 comment). I have always noticed
    the slight skunk smell when I brewed generic or store
    brand coffee. It’s always cheaper. BUT last week, there
    were 2-3 Keurig names on sale; however, this time, the
    slight skunk odor again. I’ll keep checking this blog to
    see if anything surprising comes up!

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