Mold In Cold Brew Coffee: Stop It With These 10 Top Tips

So, you’ve brewed your cold brew coffee, then come back to it after a few days and now you find a patch of mold growing all over it. This is a frustrating experience for anyone, especially after the length of time it takes to make. So, now you’d like to know how to stop it from going moldy again

To prevent cold-brew coffee from becoming moldy, store the ground beans in an airtight container with a humidity level lower than 60%. Ensure all equipment is cleaned and dried after each use. Refrigerate and use within 1 week of brewing for the best flavor; don’t steep for more than 24 hours.

In this article, I answer everything you need to know about mold in cold brew coffee, so keep reading!

moldy cold brew coffee

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How to prevent cold brew coffee from going moldy

To prevent mold growth in cold brew coffee, we need to do everything we can during the brewing and storage stages to make it as difficult as possible for mold to grow by taking away what it needs to liveOpens in a new tab..

With this in mind, follow these simple steps to prevent mold growth in your old brew coffee:

  1. Thoroughly clean your cold brew maker with warm water and detergent before making up a new batch.
  2. Check the coffee beans for any signs or symptoms of mold growth. Discard the pack if you find mold growing on the grounds.
  3. Always use beans that have been stored in an air-tight container and away from sources of moisture.
  4. Use a freshly cleaned, air-tight container to brew your coffee.
  5. Brew away from sources of heat such as radiators or stoves.
  6. If storing, place in the fridge, and keep for no longer than 1 week.
  7. Clean all equipment used, and make sure it is thoroughly dry before storing away.
  8. Grind right before brewing to ensure maximum flavor and preserve freshness.
  9. Use filtered water for brewing to avoid introducing impurities which could assist mold growth.
  10. Inspect any seals on the brewing equipment for signs of growth before using.

Why does cold brew coffee get moldy?

The process used to create cold brew coffee takes far longer than making a cup of instant or filtered coffee. In fact, creating a single brew can take anywhere from 24-48 hours. If this is done at room temperature, mold has more than enough time to settle and begin to grow.

Mold only needs a few things in order to thrive, these are:

  • Nutrients
  • Moisture
  • An ambient temperature betweenOpens in a new tab. 71.6 to 95 degrees Fahrenheit

As you can see, a batch of cold brew coffee provides all these things, as the coffee grounds provide the nutrients, the liquid used provides the moisture and if brewed at room temperature (which is betweenOpens in a new tab. 70-75 degrees in most American homes), it also has the perfect climate.

Is there mold in cold brew coffee?

You may have heard of coffee beans naturally having mold in them, and you may be wondering if your pack of cold brew coffee also has mold in it. The good news is that cold brew coffee is no more likely to contain mold than any other food product as long as it is stored and processed correctly.

Of course, as coffee beans are a natural product, there is the possibility that somewhere along the transportation or harvesting process, mold may have developed. There is again little need for concern though, as the high temperaturesOpens in a new tab. used during the roasting process will kill any mold or bacteria that was growing without spoiling the taste or texture of the brew.

As long as proper brewing techniques are followed, the beverage is stored correctly in a refrigerator and the French press or any other brewing components you use have been cleaned properly, you have little reason to be concerned.

How to tell if your cold brew has gone moldy

One of the first signs that your cold brew has gone moldy is small patches of a white, black or blue, powdery substance on the surface of either the liquid or the coffee grounds (if using a cold brew coffee maker with a built-in bean grinder).

If you cannot see any mold, you may be able to smell it, as it has a characteristically “mustyOpens in a new tab.” odor that may remind you of an old basement or attic.

Finally, if you cannot see or smell mold, you may well be able to taste it. Should you be unfortunate enough to take a sip of moldy coffee, it may taste a great deal more “earthy” than usual. The coffee itself will also often taste bland and a little sour.

How long does it take for cold brew coffee to grow mold?

If the circumstances are just right, mold can grow exceptionally fast. If for example, you had set your coffee on the side to brew, mold could begin to grow within 24-48 hoursOpens in a new tab.. This is why it is important to make sure you take proper preventative measures (more on this later), to ensure your coffee isn’t ruined before you’ve had a chance to drink it.

A few major factors that affect the speed at which mold grows on cold brew coffee, are light, moisture, and temperature.


Sunlight and UV light of any kind have anti-bacterial and anti-fungal propertiesOpens in a new tab. due to their ability to disrupt the organisms’ DNAOpens in a new tab., and cell structure, reducing its ability to reproduce and spread. Direct sunlight will drastically reduce the speed at which fungi can grow, however, it will not prevent it completely. Dark areas of the home are more prone to mold growth for the reasons mentioned above. It is therefore best to ensure that if you are storing cold brew coffee in a cupboard or pantry, you ensure there is little to no moisture in the container as the dark conditions are ideal for growth.

Unfortunately, exposing coffee beans to direct sunlight can cause oxidizationOpens in a new tab., which can negatively impact the flavor profile, increase the rate of rancidity, and cause a loss of aroma, so keeping the beans in a transparent container on a shelf is not advised.


As previously stated, mold begins to grow at its most rapid rate when there is an ambient humidity of 60%Opens in a new tab. or above, with levels between 70 to 80 percentOpens in a new tab. being where mold grows at its fastest. Ensuring you store your coffee an in airtight container with as little moisture as possible reduces the potential for growth.

If possible, store the coffee beans in an area that has a lower humidity than the kitchen, as along with bathrooms, these tend to be the most humid rooms in a property. For example, you could store the beans in a pantry away from where the majority of cooking is being done.


The ambient temperature of your home can play a big part in the speed at which fungi can grow on your coffee, as mold grows at its fastest rate in temperatures between 77°F (25°C) to 86°F (30°C) degreesOpens in a new tab.. The most common setting for thermostats across the United States is between 70°F (21°C) and 75°F (23.9°C)Opens in a new tab., which makes for a very comfortable temperature for mold to spread.

It is for these reasons that it is so important to reduce the humidity and moisture the beans are exposed to, as there is very little else you can do about either the temperature or amount of light the beans are exposed to without either damaging the taste of the coffee or becoming uncomfortable in your home.

What types of mold grow on cold brew coffee?

The most likely strains of mold you will find growing on or in your cold brew coffee, are either AspergillusOpens in a new tab. or penicilliumOpens in a new tab.. These are commonly known as white mold (penicillium) or black mold (Aspergillus).

These strains are often seen with a powdery, velvety, or sometimes slimy texture. However, it is very difficult to tell which strain of mold you are dealing with by simply looking at it, as there are thousands of possible variations, some of which can be toxic, and others quite harmless.

Can you get sick from drinking moldy cold brew coffee?

It is possible that if cold brew coffee that contains mold is drunk, it could be potentially hazardous to your health.

Some mold strains produce mycotoxinsOpens in a new tab. when they feel threatened as a defense mechanism. In some susceptible individuals, even small quantities of these toxins can cause very serious health complications.

In those less at risk, either ingesting or inhaling mold or its spores in small quantities is generally unlikely to cause any great harm. However, if inhaled or ingested in larger quantities or over longer periods of time, they can become troublesome, and may lead to any (or all) of the following symptomsOpens in a new tab.:

  • Vomiting
  • Nausea
  • Diarrhea
  • Gastrointestinal discomfort

How to clean moldy cold brew coffee-making equipment

In the previous section, I briefly explained how to clean the equipment you may be using to brew your own cold-brew coffee.

However, in some cases, there may be mold that has been growing for some time and become established. If this is the case, your equipment need not be thrown away. It is salvageable but will require a deeper cleaning before being used again.

In order to clean established mold from cold brew coffee makers, use the following steps:

  1. Disassemble your cold brew coffee maker.
  2. Create a solution of one part vinegar to two parts water and pour it into a spray bottle.
  3. Liberally spray the vinegar solution over each part of the coffee maker and leave it to sit for ten minutes.
  4. Using warm water and detergent, use a soft-bristled brush to scrub each component, paying careful attention to any lips or seams.
  5. If required, use a toothbrush to clean out any residual mold left in the filter and repeat the process.
  6. Make sure that each component of completely dry before reassembling.

*If your cold brew coffee maker has any electrical components, such as a built-in grinder, read the manual that came with it to use the manufacturer’s recommendation for cleaning this part of the machinery.


Cold brew coffee is just as likely to grow mold as any other food item, which can cause Illness. If the preventative measures mentioned in this article are used, you may never have to deal with mold, but if you do, do not be concerned, your cold brew-making kit may still be salvageable with a simple deep-clean.

Over to you

I hope this article has given you some guidance on how to stop your cold brew coffee from becoming moldy and has given you some good tips on how to stop it from happening in the future. Now I’d like to turn things over to you though. Have you ever drunk a moldy cold brew? Do you have any other experiences or tips you think would be useful to add? If so, I’d love to hear about them in the comments below. If you leave a message, I’ll get back to you ASAP.

Chris Walker

Chris Walker has struggled for several years with mold after buying his own property. After finding the solutions to several issues around his home, he decided to create this site in order to answer as many questions about mold and mildew as possible to help others dealing with the same problems.

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