Skip to main content
Coffee Tips

Why Does Coffee Smell Like Tuna?

As a coffee enthusiast, the most exciting part of the coffee world is enjoying the warm and relaxing rich aroma of coffee. It creates a friendly environment and one that is diverse. Plus, the smell wakes you up and gets you in a good mood to get through your daily activities. However, imagine opening up your bag of coffee expecting the usual pleasant aroma, only to smell fish, specifically tuna. Or walking into your favorite coffee shop only to get a whiff of a fishy smell.


girl holding a bad smelling coffee cup


Ideally, the words fish and coffee shouldn’t be associated with each other. Furthermore, the fishy aroma is enough to damage most people’s relationship with coffee. If this has ever happened to you, you’re in the right place. This article answers the question “why does coffee smell like tuna” and explains everything you need to know about coffee and the fishy smell.

The good news is that the fishy smell of coffee is pretty normal. The smell is a result of chemical reactions that occur during the roasting process. You’ll find that dark roasted coffee beans are more susceptible to the fishy smell as a result of long exposure to heat. Read on for more details.


Why Does Your Coffee Smell Fishy?

The fishy smell of your coffee doesn’t mean that there is something wrong with it. As mentioned earlier, the fishy smell results from the chemical reactions that occur during the roasting process. Dark roasted coffee beans are susceptible to the fishy smell since their roasting process is longer thus more heat exposure.

Apart from the roasting process, there are some other factors to look out for if your coffee smell like tuna. They include:

  • Immature coffee beans
  • Improper Storage of coffee
  • Unclean coffee equipment
  • Coffee Beans’ hygroscopic nature

Despite the factor that has caused the fishy smell of your coffee, there’s no need for alarm. The smell is normal and shouldn’t raise concerns. However, if you notice the presence of molds or rancid beans, throw out the coffee beans. Let’s discuss these factors in detail.


Immature Coffee Beans

The maturity of your coffee beans can affect the taste and smell of your coffee. Additionally, it’s hard to tell if the beans have matured after they are roasted and have taken the brown hues. You’ll only realize your coffee beans are immature if you buy unroasted coffee beans or until you taste your brewed coffee. Immature coffee beans are a result of:

  • Growing coffee beans in a less ideal environment
  • Harvesting unripe coffee fruits
  • Lack of fertilizer
  • Drought
  • Coffee trees being affected by rust diseases


Improper Storage of coffee

Depending on how you store your coffee beans, the taste and smell of your coffee may be affected. For example, exposure of your coffee beans to heat and moisture may cause oxidation, which results in stale and fishy-smelling coffee. Additionally, if your roaster doesn’t practice good coffee storing habits between the roasting and bagging process you may end up with oxidized and fishy-smelling coffee.

To store your coffee, use an airtight container or a vacuum container. Store your coffee in a cool and dark place away from moisture, heat, and air to avoid chances of oxidation. Additionally, don’t store your coffee in the refrigerator since it absorbs the odors around – could be odors of tuna, onions, fish, etc. Also, you can store your coffee in small batches to maintain freshness. Ensure you use your coffee within a week after opening the airtight container.


Unclean Coffee Equipment

One way to ensure that the taste and smell of your coffee are at their best is to clean your equipment before brewing your coffee. This is because the coffee oils and other organic or inorganic materials in your coffee often build up on the equipment leading to the rancid, fishy smell. This is especially common if you use a reusable coffee filter. Therefore, clean your coffee equipment – including your coffee grinder before brewing coffee. We’ll discuss more on cleaning your coffee equipment. Read on.


Coffee Beans Hygroscopic Nature

Coffee beans and coffee grounds are hygroscopic meaning that they absorb moisture and odors when left in the open. Usually, coffee beans undergo the drying and roasting processes which dehydrate the coffee beans, leaving them in the need to reabsorb moisture. Therefore, when exposed to moisture and odors from the surrounding environment they absorb them quickly, something that may affect the taste and smell of your coffee. For example, coffee will smell like tuna if the beans absorbed the tuna smell from the surrounding environment. This explains why coffee beans are used as air fresheners and deodorants.


A Cleaning Guide for Your Coffee Equipment

As mentioned earlier, one way to ensure that the smell and taste of your coffee are at their best is by cleaning the coffee equipment. To do this you’ll need to:

  • Remove the removable parts of your brewing equipment.
  • Thoroughly wash the parts with soap and water.
  • Run equal amounts of vinegar and water through your brewing equipment two times.
  • Then run water through the brewing equipment to rinse off the vinegar.

This cleaning should be done at least monthly. For daily cleaning, rinse off the coffee carafe, reusable filter, and water reservoir. Additionally, to clean your coffee grinder, run a quarter of a cup of uncooked rice through the grinder, then unplug it and use a damp cloth to wipe it. Otherwise, stale coffee grounds on your grinder may contribute to the fishy smell and bad taste of your coffee.



The fishy smell of your coffee is normal and shouldn’t bother you. It is a result of chemical reactions that take place during the roasting process. If you can tolerate the smell, you can buy the coffee brands you love and enjoy your coffee. However, if you’re sensitive to the smell, you can opt for lighter coffee roasts that aren’t susceptible to the smell.

Additionally, ensure that your brewing and grinding equipment are clean before using them, and store your coffee beans or coffee grounds properly to avoid oxidation. Most importantly, get rid of your coffee if you notice molds or rancid coffee.