My coffee machine smells bad

It’s not uncommon for a coffee machine to develop a bad smell, considering that we use these appliances daily, and they use water, coffee, and even milk. Therefore, coffee machines become ideal wet environments for the growth of spoilage bacteria, which ultimately cause unpleasant odours.

It’s clear that the bad smell from a coffee machine is due to poor maintenance and cleaning or a small oversight that can result in these unpleasant odours. But each coffee machine is different, and not all smells will have the same origin.

To determine where the odour is coming from, we need to consider the type of coffee machine you’re using and the type of odour it emits. Although this may seem complicated, don’t worry; I’ll explain it below.

Identifying different coffee machines’ bad odours

Bad smells in coffee machines can have different causes, so that these smells can be different.

Odour produced by coffee and lime residues

Coffee residue can build up in your machine over time, particularly in areas where the coffee directly contacts the machine, such as the brew unit, coffee grounds container and the carafe.

Water residue can also be a factor, particularly if your water source has a high mineral content. Over time, minerals in the water can accumulate in your coffee machine, leading to the formation of limescale.

❓ The odours produced by coffee and lime residues in a coffee maker are often described as stale, musty, or earthy. The coffee residue can have a rancid, sour, or rotting wood smell, while the lime residue can give off an earthy or muddy odour.

Odour from milk and other food residues

The spoilage of foods, such as milk, can cause decomposition odours. Although the coffee machine needs a milk reservoir for this to occur, a splash of milk or any other food can seep inside the machine and generate bad smells due to humidity and temperature.

❓ The odour of decomposing milk can be quite unpleasant and strong. It is often described as sour, rancid, or rotten. The smell may also have a hint of ammonia or a cheesy aroma.

Odour from burnt internal components

Another odour to be aware of is the smell of burning. This smell can be very dangerous, as it may indicate an electrical fault in the coffee machine. If you notice this smell, the best thing to do is to unplug the coffee maker immediately and disassemble it to find out where it came from or take it to a service centre to check it.

❓ The odour of burnt electrical and electronic components can vary depending on the materials involved, but it is often described as acrid, sharp, or metallic. It may also smell burnt or smoky, with hints of plastic or rubber.

Metallic odour due to metal decomposition and scaling

Finally, there are rusty metal smells that often appear in Moka pots. This smell can be produced by the oxidation of the metal when it comes into contact with water.

The metallic odour from metal decomposition and scaling can be described as a sharp, pungent, or sour smell reminiscent of rust or corrosion. It may have a metallic or chemical character, with a hint of sulfur or ammonia.

The type of coffee machine can affect the presence of bad odours

More complex coffee machines, such as superautomatic coffee machines, have more built-in parts and are more prone to accumulate dirt and generate bad odours over time. On the other hand, simpler coffee machines, such as Moka pots, tend to be less prone to odours, although they are not odour-free either.

Superautomatic coffee machines

In my experience, this type of coffee maker often emits unpleasant odours due to the accumulation of coffee and limescale residues.

Because it has many compartments and performs many operations automatically, it’s normal for the coffee residue to end up deposited in some corner for a long time, where high temperatures and humidity can cause bad odours.

I recommend that you thoroughly remove all movable parts and perform deep cleaning with this type of coffee maker, as coffee residues are likely causing the bad odour. If you also perform a descaling, even better.

Coffee pod and espresso Machines

Both coffee pods and espresso machines are user-friendly, although espresso machines require slightly more maintenance. However, both machines can encounter similar odour issues.

Both machines often have milk nearby to prepare cappuccinos or lattes, with the espresso machines typically equipped with a steam wand.

It’s crucial to check for areas where milk may have splashed into the machine, as this is one of the most frequent odour causes. If the coffee machine has a steam wand or milk tank, cleaning it thoroughly after each use is advisable.

Moka pots

As we have discussed earlier, the metallic odor of moka pots is distinct and develops after prolonged contact with water with metal.

To eliminate this odor, immerse the coffee pot in a solution of equal parts water and white vinegar for around 30 minutes. Afterward, scrub the pot thoroughly in the solution until it restores its original appearance.

You can then simulate the preparation of a coffee by using the water and vinegar mixture in the reservoir.

Thorough cleaning of the coffee machine

To thoroughly clean your coffee machine and eliminate odors, it is crucial to focus on external components (with the exception of superautomatic machines). Most waste that can cause unpleasant odors is usually found in the drip tray and areas close to the extraction spout, depending on the coffee machine type.

For instance, you may encounter an unpleasant odour if you own a coffee pod machine. In this machine, coffee residue accumulates in the area just below the nozzle where the coffee is dispensed.

Although most of the coffee goes directly into the cup, some small droplets get stuck to the inside walls or plastic of the machine. Over time, these droplets can accumulate and create significant coffee residue.

I recommend adopting a proactive approach and practising regular light cleaning after every use instead of waiting for the machine to show calcification symptoms or bad odors. This involves wiping the machine’s exterior with a damp cloth and periodically cleaning the drip tray in the dishwasher.

The importance of the water tank

Do not forget to clean the water tank of your coffee machine regularly. Water often contains sediments (especially in certain cities), which can lead to unpleasant odors in the machine over time.

We tend to overlook the accumulation of residue at the bottom of the water tank or glass jug of filter coffee machines. I recommend washing the tank periodically in the dishwasher to avoid any potential for bad odours.

By taking these steps, you can prevent accumulated sediments and unpleasant odors from developing in your coffee machine.

Descale your coffee machine to eliminate bad smells

To eliminate bad smells from your coffee machine, decalcification can be an effective solution. This process involves removing lime and other organic residues that may be encrusted in the machine and can be done regularly to improve its operation.

Some coffee machine brands offer special descalers when the machine smells bad. However, you can use a universal descaler or white vinegar to clean your coffee machine.