Moldy Cold Brew Coffee: How To Stop It Happening

Cold brew coffee has grown in popularity massively over the past few years. It has low acidity levels, with a rich and smooth taste that just can’t be found in filter, instant, or espresso coffees.

However, cold brew coffee uses no heat (as the name would imply), and it also does not use pressure, which means it takes considerably longer to brew than your average cup. The time it takes gives mold a chance to settle and begin to grow, so, how can you tell if your cold brew is growing mold, is it dangerous, and can you prevent it?

In this article, I answer these questions and more, so keep reading!

If brewed and kept at room temperature, coffee can begin to grow mold within 24-48 hours. After brewing, If kept in a refrigerator, you can expect it to last for two weeks if kept in an airtight container. The two most common mold strains found in cold-brew coffee are aspergillus and penicillium.

moldy cold brew coffee

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Can cold brew coffee get moldy?

Absolutely, cold brew coffee can begin to grow mold in the same way that many other foodstuffs can.

The process used to create the coffee takes far longer than making a cup of instant or filter 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 between 60-80 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 between 65-75 degrees in most American homes), it also has the perfect climate.

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 “musty” 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 hours. 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.

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 aspergillus or penicillium. 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 mycotoxins 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 symptoms:

  • Vomiting
  • Nausea
  • Headaches
  • Brain fog
  • Gastrointestinal discomfort

How to prevent cold brew coffee from going moldy

The usual method to prevent mold from growing is to starve it of what it needs, which is mostly nutrients and moisture. Seeing as we are dealing with cold brew coffee, there is nothing we can do to take away either the moisture it wants or the nutrients it needs.

Instead, we need to do everything we can during the brewing process to make it as difficult as possible for mold to grow.

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 any of the beans.
  3. Use a freshly cleaned, air-tight container to brew your coffee.
  4. Brew away from sources of heat such as radiators or stoves.
  5. If storing, place in the fridge, and keep for no longer than 1 week.
  6. Clean all equipment used, and make sure it is thoroughly dry before storing away.

How to clean 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, and using a soft-bristled brush, scrub each component, paying careful attention to any lips of seams.
  5. 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.


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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