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.]
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Jacob Grier is a freelance writer, barista, mixologist, and magician in Portland, OR. He writes, eats, and drinks a lot. His articles have appeared in The Washington Post, Reason Online, The Oregonian, and other publications.
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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.
Thanks, Jim.
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.
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…?
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.
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.
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.
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.
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.
http://books.google.com/books?id=43sA1NhzCWsC&pg=SA13-PA17&lpg=SA13-PA17&dq=coffee+trimethylamine&source=bl&ots=BKQGf9ZMfE&sig=rZCTuahwKYjfXl4Ny6oI3ok7534&hl=en&ei=X6ANTIrlIsT6lwfBn5mmDg&sa=X&oi=book_result&ct=result&resnum=8&ved=0CCkQ6AEwBw#v=onepage&q=coffee%20trimethylamine&f=true
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
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…..
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.
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!
@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.
Came across this blog after searching “my coffee smells like fish”. I have a fishy bag of Seattle’s Best. Smells fishy, tastes delicious.
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.
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!
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.