May 12, 2023

How long do nitrogen-flushed coffee capsules stay fresh?

As easy as they are to use, coffee capsules are difficult to manufacture. To make them, we roast coffee, grind it to the perfect size using a state-of-the-art roller mill, pack the perfectly ground coffee into a capsule shell, then seal the capsule with filter paper. After this, however, there is then the matter of ensuring it stays fresh.

At Metropolis, we flush our coffee capsules with nitrogen as part of the sealing process. Many other brands across the food and beverage industry do this, for all kinds of products. But how long do nitrogen-flushed coffee capsules last? And is nitrogen flushing the best option to get the longest shelf life for your coffee pods?

Whether you already offer coffee capsules or want to enter the capsule market, read on to learn more about nitrogen-flushed coffee capsules.

A coffee roaster checks on the progress of roasted coffee beans.

Why is coffee freshness important?

Roasted coffee can be considered fresh when its original flavor and aroma characteristics are unimpaired. While green coffee is a stable, non-volatile food product, roasted coffee is “volatile”. This means that exposure to certain factors can cause it to lose these characteristics pretty quickly.

There are several factors that affect the freshness of roasted coffee, including oxygen, heat, light, and moisture. Exposure to these factors can cause the more delicate and subtle flavor notes and aromas in coffee to flatten. This in turn causes the coffee to become stale.

However, of these four factors, oxygen is arguably the most prominent. Put simply: if you leave roasted coffee out for long enough, the flavor compounds start to degrade. After long enough, the coffee will taste flat and stale, with its more unique and vibrant flavors gone.

While this is a concern for roasted coffee beans, it becomes a much bigger problem once you grind your coffee. When you grind coffee, its surface area increases a lot. This in turn means the oxidation process speeds up. This is why many baristas swear by grinding fresh coffee for every shot of espresso or batch of drip coffee.

Light and heat can also alter flavor over a long enough timeframe, although the effects aren't as severe as with oxygen. Exposure to moisture, meanwhile, can lead to the growth of mold, which is why good storage is so important.

Metropolis Coffee packaging in use inside a coffee roastery.

How do we measure freshness?

While taste is the simplest way to figure out whether or not coffee is stale, there are also other methods.

The Zurich University of Applied Sciences is a great source for all kinds of coffee science. But in 2017, they conducted a study into coffee freshness.

During the study, Professor Chahan Yeretzian identified two markers for coffee freshness. These were the presence of aroma compounds (a chemical marker of freshness) and CO2 levels (a physical marker).

As soon as you roast your coffee, it starts releasing CO2. We call this "degassing". Most of the gas is released within the first couple of days, which is why coffee roasters "rest" batches. If you don't do that, you end up with a bitter, astringent taste in your coffee.

However, you can also use CO2 levels to pinpoint how old coffee is. In turn, this allows us to determine how fresh it is.

For the second metric, however, Yeretzian’s study looked at the evolution of the aroma profile of coffee. Using this, his team created a “freshness index”. Long story short: using this freshness index, he determined that both packaging and storage temperature have a significant impact on freshness.

The shells of coffee capsules that will be nitrogen-flushed for maximum freshness.

Freshness in coffee capsules

As we mentioned earlier, increasing a coffee’s surface area effectively exposes it to more oxygen. In turn, this means it gets less fresh more quickly once it's ground. The finer you grind, the more of a problem this becomes. Finer grind sizes increase surface area even more and therefore pose more of a “risk” to freshness.

When you grind coffee to fill a capsule, the grind size must be incredibly fine for it to properly extract in the machine. This means freshness is even more of a challenge to control for capsules!

Technically, coffee capsules can have a shelf life of anywhere from 6 to 24 months. This depends on the quality of the seal and how well-protected the coffee is against oxygen. However, how they taste is another question entirely.

Generally, if you buy coffee capsules that have been properly sealed and flushed free of oxygen, they have a much longer shelf life and taste better for longer.

Nitrogen-flushed coffee capsules, for instance, maintain the freshness and quality of the coffee inside for far longer than would otherwise be possible.

A Metropolis Coffee roaster holds six nitrogen-flushed coffee capsules in their hand.

What are nitrogen-flushed coffee capsules?

Nitrogen flushing uses nitrogen gas to remove oxygen from packaging. Many food and beverage businesses use it for coffee capsules as well as a range of other products.

Nitrogen is used as it is heavier than oxygen, meaning it sinks and pushes oxygen out as a result. This helps to extend a product’s shelf life.

However, as well as increasing shelf life, nitrogen flushing also slows down the release of CO2, keeping coffee fresher for longer. Studies have shown that the shelf life of nitrogen-flushed coffee is, on average, double that of coffee that has not been flushed.

Nitrogen-flushed coffee in a bag should be brewed within seven to ten days once you open the bag. Fortunately, for nitrogen-flushed coffee capsules, this isn't an issue, as the coffee remains sealed in the shell until the moment it’s extracted.

Nitrogen-flushed coffee capsules are a perfect way to offer customers fresh, high-quality coffee while also maximizing convenience. At Metropolis, we fill, seal, and nitrogen-flush our espresso capsules using a state-of-the-art Italian filling and sealing system. This means we can guarantee a 12 to 24 month shelf life for any Metropolis coffee capsules.

At the same time, our capsules are also commercially compostable, making them a perfect option for businesses looking to offer coffee capsules and keep waste down -- without the need to buy the equipment themselves.

Interested in learning more? Check out our wholesale co-packing and private-label espresso capsule solutions today.

Certified compostable facilities may not exist in your area. To find a composter near you, visit or on all packaging and marketing materials.

Metropolis Coffee is not affiliated with, endorsed, or sponsored by Nespresso. Nespresso is a registered trademark of Société des Produits Nestlé.