Why Does Coffee Smell Like Fish? (5 Reasons Explained)

Do your coffee beans smell fishy? Does your roasted coffee have a sour or fishy taste? It's actually a pretty common problem and the good news is that most of the time the coffee isn't dangerous (unless you're using rancid beans).

The bad news is that half the enjoyment of coffee comes from its rich aroma and if your roasted coffee ends up smelling fishy it's going to ruin your brew. 

But don't worry, because in this guide we'll explain exactly why it happens and what you can do to avoid drinking coffee with a fishy aroma. 

1. Roasted Immature Green Beans  

If your coffee or freshly brewed espresso coffee smell weird then it might be because of fishy coffee beans. 

Coffee comes from plant and isn’t naturally brown or dark-colored. The fruit of the coffee plant, also known as coffee cherries, matures from green to red.

To make good coffee beans, you need to wait for the cherries to ripen and achieve a deep red color. If you don’t wait for them to mature and harvest then these under-ripe green beans will produce low-quality coffee. Roasting these immature beans will create a fish-like aroma instead of a rich and flavorful smell.  

In addition to using under-ripe coffee berries, growing a coffee plant in an unsuitable environment can also lead to having immature green coffee beans which make your coffee smell fishy.

The coffee plant should be grown in tropical climates with no frost, ample sunshine, and water. If the plant doesn’t have all three of them, it will bear low-grade fruit, resulting in beans that smell like fish.  

Unfortunately, it's almost impossible to know whether you're brewing coffee with immature coffee beans or fresh beans until after we've finished.  The only way we will know is if the coffee smells or tastes odd. That's why you should only buy beans from trusted suppliers to ensure you get the best quality you can find.  

2. Oxidation During Storage 

Have you ever bought good beans from reputable brands only to discover that the coffee smells or tastes like fish? This strange ground coffee odor and taste isn't down to the brand, it's the result of how you store them. 

Coffee beans need to be stored in a cool, dry place. This leaves the coffee oils within the beans undisturbed so they can be used for great tasting coffee.

Exposing your coffee beans to heat and moisture can cause oxidation, resulting in stale coffee beans. When your beans become stale, the taste and smell are affected. This can make them smell like fish, cat urine, or even uncooked rice!

It's important that you you practice good storage. Only use an airtight container and never refrigerate your coffee grounds or beans. Refrigerating them can make the coffee beans smell like what's in your fridge.

Sometimes, manufacturers don’t have good storage practices between roasting and bagging, which can cause some oxidation. This can impact the coffee bean quality and impact the usual pleasant aroma of the coffee and ruin the taste for coffee drinkers. Unfortunately, there isn't much you can do about this - so it's best to focus on how you store them.

3. The Hygroscopic Nature Of Coffee Beans 

To create coffee beans you need to dry out the cherries after harvesting. This is usually done in the sun. Then, the beans themselves are further dehydrated during the roasting process, which leads to the first crack in the wall of the beans.  

This dehydration process leaves the coffee beans become “thirsty” or hygroscopic. This means that they will absorb the air and aroma from the surroundings and can leave your roasting coffee beans tasting strange and with a smell like fish.  

During this process the coffee beans need to be kept in a controlled environment until the roasting process is completed. This will stop weird smells getting into the roasted coffee, and keep it fresh.

4. Improper Storage  

It's not just oxidisation which can impact your fresh coffee because dried coffee bean grinds absorb the flavors and aromas of whatever is around them. These aromas will make ground coffee or instant coffee smell weird, so you need to take precautions. 

Always store your coffee grounds, beans, and granules in airtight jars or containers instead of their original packaging. You can still use the pouch that comes with them, but only if they come in resealable packs. This is especially important for dark roasted coffee which picks up odors very easily. 

This should help prevent any unwanted chemical reactions in the coffee beans, and stop you getting cat urine or fishy smelling coffee. 

5. Unclean Equipment 

Dirty coffee equipment and dirty coffee makers are one of the most common reasons that your coffee smells fishy. 

If you don’t clean your brewing and grinding equipment regularly, oils will build up around it and can cause your cup to taste and smell weird. So, even if you are using the best Robusta or Arabica coffee beans, you will still end up with a bad cup if you have an unclean coffee maker. 

To prevent this, regularly clean your coffee makers. You can even use equal parts of vinegar and water to descale your coffee maker further and ensure that everything is squeaky clean, especially your reusable coffee filter! Dark roasted coffee tends to have more oils too, so even if you're using slightly dark beans you may need to clean it more regularly. 

If you're also grinding your own beans, make sure the coffee grinder is regularly clean to prevent stale grinds from combining with your freshly ground coffee.  

Why Does Coffee Smell Like Fish? (5 Reasons Explained)

How To Get Rid Of Fish Smell In Your Coffee? 

Unfortunately, If your coffee beans already have a fishy smell then there’s nothing much you can do. There’s really no way of getting rid of the fishy smell, especially if the processing and roasting process has caused this aroma. 

If you can’t stand the fishy smell in your coffee, the best way to deal with this is to dispose of the beans or reuse them as a deodorizer.  

However, several ways you can stop it from happening before your beans smell like fish:

  • Only buy beans from reputable manufacturers. If you notice a brand has a fishy smell then don't go back to them!
  • Store them in a proper, airtight container and ensure that heat and moisture won’t get in them and cause chemical reactions
  • As much as possible, seal the container right after getting coffee to ensure that it won’t absorb any of the aromas from the surroundings
  • Clean your coffee equipment after every use as these can make your beans smell like fish
coffee before and after

Why Does Coffee Sometimes Taste Like Fish? 

If your coffee tastes like fish, it’s natural to blame your beans. But it’s not always the beans and other factors that can affect your cup and give it that fishy smell. For instance, you might be using contaminated water. Remember, a cup of coffee is 98% water. 

Any chemicals in the water you’re using can contribute to the taste of your coffee. Make sure you only use filtered or bottled water.  

Another reason that could affect the taste of your coffee is the equipment you use. Ensure that it’s properly cleaned. Your coffee cup can also make your coffee taste like fish. If you’re using the same sponge for your plates and cups, there’s a possibility that the fish taste is transferred to your cup. 

coffee about to be tasted

Common Coffee Smells Questions 

Can coffee go bad? 

Coffee beans don't go bad like bananas or apples. However, they will lose quality over time. For brewed coffee, it will start to taste bad after 30 minutes or when the cup begins to cool down.  

How do you tell if your coffee is spoiled? 

Coffee doesn’t get spoiled. However, rancid, mildewy, or moldy smell from coffee often means that the coffee has lost its quality and should be thrown out.  

Can old coffee give you food poisoning? 

No, coffee won’t give you food poisoning because it doesn't spoil or go bad. Old coffee will only taste bad but won’t harm your body.  

What does it mean when coffee tastes sour? 

The sour taste of coffee comes from bad brewing and bad beans. Under brewed coffee will taste sour and acidic. At the same time, under-roasted beans and beans that are old and stale will produce sharp, lemony flavors.  


Conclusion

If your coffee smells like fish and you're missing that dark roast coffee smell then there's no need to panic. This happens a lot, and most of the time, it won’t affect the taste of your cup of coffee.

However, most coffee lovers can’t stand the smell so it's worth switching to a different brand or storing your beans differently to prevent them from having this fish smell again.  

Kim Fernandez

Author

Kim Fernandez
Kim offers a unique perspective on coffee culture and trends. Kim's writing is personal and experiential, providing readers with firsthand advice on the latest in coffee. Beyond her writing, Kim is an avid explorer of new coffee trends and spots, always seeking to share the most genuine advice and latest trends. True to her love for coffee, you'll often find her in a café, immersed in a book with a freshly brewed cup of joe.

My favorite drink? I'd go with... A freshly brewed cup of joe

See Our Editorial Processes

Meet Our Team

Share Feedback

Leave a Comment