Freezing coffee - What does "ageing coffee" mean?

Why is coffee ageing important?

Let’s talk about ageing coffee.

This is a topic that is very close to my heart. It the last two years, the concept of ageing has completely changed my view on how I use, store and taste coffee. It can help us to best understand how coffee changes over time, and this aids coffee professionals in using coffee and communicating with their customers.

In 2019, I moved to Australia and started working for one of the best coffee companies in the world, Sasa Sestic’s ONA Coffee. I was excited and curious to see what I would learn during my time there and I can tell you one thing: these coffee nerds didn’t let me down. They introduced me to the concept of properly ageing roasted coffee beans in order to maximise flavour and experience.

What is ageing coffee?

You may have noticed that a lot, if not most specialty roasters label their coffees with the date of roasting. For a lot of consumers (and baristas), the idea that ‘the fresher, the better’ has dominated the way they purchase and use coffee. However, the flavour profile of a freshly roasted coffee is completely different to a coffee that is 14 days old, and understanding when your coffee is perfectly aged is key to creating the best experience possible.

During roasting, a chain of physical and chemical reactions takes place, the so-called ‘Maillard reaction’. It splits simple sugars into multisaccharide, evaporates air, increases the volume of the beans and as we explored, builds up CO2.

After coffee is roasted, it begins to simultaneously expel CO2 and become more exposed to O2 (oxygen). We want the CO2 to leave the bag, but no extra O2 to enter – hence why we have one-way valves on our bags. This build-up of CO2 can significantly affect brewing and make it much harder to get a tasty cup. The coffee has to rest and ‘de-gas’ before it becomes easier to brew and tastier to drink.

Ageing is essentially finding the point at which your coffee tastes best after roasting. Think about it like opening an old bottle of wine and decanting it, or letting it ‘breathe’ until it tastes perfect. With coffee, you ideally want to hit a balance between (a) the loss of aromatics and (b) the build-up of carbon dioxide. For most coffees, this process happens in a window of 6 to 23 days after roasting.

The coffee will ultimately reach a ‘peak’ where the expulsion of CO2 begins to drop, and the additional exposure to O2 causes the coffee to age faster, lose its aroma/flavour and become stale. If you have ever opened an old bag of coffee, you know what I am talking about.

Image: Röststätte Berlin

Does roasted coffee have an ‘expiry date’?

So yes, coffee doesn’t last forever (sad, I know). It is an organic product and like others, its flavour has an expiry date. As a roaster, I have realised that whilst much of a coffee's distinctive qualities are determined by where it's grown, its varietal and how it's processed, a lot of what we experience in the cup is an expression determined by roasting.

If you've had the opportunity to take in the smell of green (unroasted) coffee, you'll know how the aroma more closely resembles grassy, grainy and straw qualities. This aroma changes after roasting and gets very much like popcorn, sweet malt and chocolate – of course this varies depending on the coffee itself. Likewise, if you have ever smelled the difference between a freshly roasted coffee, a coffee that is 1-3 weeks old and a coffee that is several months old, then there is a distinguishable difference between the intensity and quality of aromas.

The short answer is no – you can technically use coffee beans months after roasting. However, the quality of flavour in your coffee doesn’t last forever, and understanding when it tastes best will improve your experience as a barista and consumer.

So when is coffee perfectly aged?

In the first few days after roasting, coffee flavour changes immensely. Many of the flavours listed on the bag or that the coffee is renowned for will be ‘muted’, or not reach their full potential. Over time, these flavours will become more apparent and will be of much higher quality.

It's important to consider how you'll be enjoying your coffee. For more gentle brew methods like drip or pour over, you can start using your coffees a little earlier. For high-pressure methods such as espresso, it's important to give the coffee a bit more time to rest and develop further.

So if you want to know how long you have to wait, the answer is very simple – try your coffees every day! For every coffee I get in my hands, I store it and try in incrementally over a time frame of about 5-23 days after the roasting date. This way I can determine when it was at its flavour ‘peak’, helping me

Do different processes age differently?

One of the tricky parts about coffee is that the rate of ageing differs between different process. After trying, testing and tasting coffees over the last few years, There are some guidelines I have realised.

I find that washed process coffees usually peak between 8-15 days, whilst natural processed coffee needs a few days longer and hit the sweet spot between 15-20 days. And then we have the crazy funky ‘carbonic maceration’ or ‘anaerobic fermentation’ coffees. Depending on the level of experimental processing they behave like real divas and need to de-gas and rest for up to 23 days.

How do I stop my coffee from ageing further?

My time working in Australia and experimenting with ageing blew my mind! I found it incredible that coffee ageing was not only common knowledge among the staff, but that all the coffees that were used in the venues were always served when perfectly aged.

One of the most special parts of their coffee ageing and service was the ‘Reserve Menu’. In addition to a list of house blends and different single origins on the regular menu, there was also a special menu of rare, experimental and unique coffees that had been aged and frozen.

By placing the aged coffee beans into vacuum-sealed bags or test tubes, the baristas were able to effectively stop the ageing process completely – this means that the coffee was perfectly aged and ready to use for years to come. These techniques have been gaining in popularity across the world of specialty coffee during the last three years, and have the potential to change the way we buy, store and sell coffee (more on this in my next blog post).

Photo: Röststätte Berlin

Applying ageing to the specialty coffee industry

I believe that it is absolutely essential that roasters and baristas invest in proper research and testing on ageing, and to start supplying ageing recommendations to their customers. Without informing the customers about the perfect age of your coffee, they will never be able to understand why coffee can taste so radically different from day to day.

As coffee professionals, we can avoid the frustration and guesswork that many consumers experience when experiencing different coffees. By providing information about ageing, we can help them to learn, grow and to become better with their brewing techniques and tasting. Providing ageing dates also helps to be able to set dates for storing those coffees for longer time by freezing them.

With the team at Röststätte, I have already started giving not just brew guides, temperature settings and detailed flavour guides for each coffee, but have now also added specific ageing and freezing dates for each coffee. This way, consumers can get the most out of their coffee and work not just more precise and efficient but also more sustainable.

If you have any questions about ageing, freezing or anything coffee related, please feel free to get in touch!

Happy brewing,

Nicole Battefeld-Montgomery