Why is coffee freshness important?

In recent years, freshness has started to become more and more of a priority for coffee drinkers around the world. The phrase “freshly roasted” is commonly used by roasters and coffee shops to market their beans.

Roasted coffee is considered to be fresh when you can taste its original, unimpaired characteristics and qualities. Over time, it gradually loses its flavours and aromas, eventually becoming flat, bland, and stale. All the nuances and complexities in its flavour profile will fade away over time.

So, what can you do to prevent this? Can you keep your coffee fresh for longer? And what should you look for when buying a bag of beans? Read on to find out.

What to expect once coffee is roasted

When coffee is roasted, it goes through a series of irreversible chemical and physical changes.

Among other things, volatile soluble flavour compounds develop – these are what give you those delicious flavours in the cup.

However, continued exposure to oxygen will cause the soluble compounds in roasted coffee to degrade. There’s no way to completely stop this – with each day that passes, your beans will become less vibrant, and start to lose their more complex and delicate flavours.

During the roast, the moisture in green coffee evaporates, and gases start to form inside the bean. At around 392°F or 200°C, the pressure caused by the formation of these gases and the growing amount of water vapour causes the bean to rupture, with an audible cracking sound – known among roasters as “first crack”.

Once roasted, the beans start to release these gases in a process known as degassing. It’s actually beneficial to let coffee degas for a few days after roasting. If you don’t, these escaping gases can cause bubbles to form when you brew coffee, and negatively affect extraction.

One of the most important gases that forms during the roasting process is carbon dioxide. It plays a key role in extraction, determines how much crema forms when your coffee is brewed, and even affects the overall sensory profile in your cup. It is also commonly regarded as an indicator of freshness.

Ultimately, you want your coffee to degas enough to be able to extract it properly, but not so much that it starts to lose flavour. There is a “sweet spot”, a few days after roasting, where the flavours and aromas in your coffee are as noticeable as they will ever be.

Which factors affect freshness?

While you can’t completely stop the soluble flavours in coffee from degrading over time, you can slow down the process.

There are a number of factors that affect coffee freshness once it has been roasted. These include:

  ● Moisture
  ● Odours
  ● Light
  ● Heat
  ● Surface area
  ● Oxygen 

Oxygen is arguably the most important factor. It effectively “attacks” the soluble flavour compounds in your coffee, causing them to degrade. This process is called oxidation – it’s the same thing that causes some metals to rust.

Oxidation is also why it’s important to grind coffee fresh and in small quantities, rather than all at once. When you grind coffee, you increase its overall surface area, which speeds up the process of oxidation. While coffee beans retain their flavour for a few weeks after roasting, ground coffee starts to lose its flavour in just a matter of minutes.

Coffee beans are also highly absorbent, which means that moisture and odours are another threat to the delicate flavour of your coffee. Storing an unsealed bag of coffee beans in the refrigerator, for instance, can cause them to take on nearby odours. These will then be present in the cup when brewed.Exposure to moisture can even cause mould to develop.

Light is another key factor. Direct light can alter the flavour of roasted coffee, which is why it is generally sold in bags that are opaque, rather than translucent or transparent. The same is true for heat – if coffee beans are left in a warm place for an extended period of time, they will lose their complexity.

Keeping your coffee fresh

Despite all the things which can cause your coffee to turn stale and lose its flavour, there are a few things you can do to maximize the freshness of your beans.

When storing coffee at home, make sure to keep it in a cool, dry, dark place – inside a cupboard and away from any appliances is always a good start. Use airtight packaging if you can and using vacuum seal would be most ideal. Some roasters will supply opaque resealable packaging which is suitable, but if not, you can always empty your coffee beans into another container – as long as it’s airtight.

Buy your coffee regularly, and buy in small quantities. Stockpiling coffee might seem cost-effective, but if you don’t use it quickly enough, you’ll end up with stale beans. Aim to buy whole bean coffee and grind fresh, rather than buying pre-ground coffee. Look for degassing valves on coffee bags. This is standard for most speciality coffee roasters. Degassing valves are one-way vents that allow roasted coffee to degas without letting oxygen in.

Only grind as much as you need when you brew coffee, to make sure you don’t have pre-ground coffee left over.

Pay attention to the roast date on the packaging. Coffee is best around four or five days after roasting, and should be consumed within thirty days. To make sure you get coffee as fresh as it can be, buy from a local roastery, or choose priority delivery when buying online.

There are many factors to keep in mind when storing coffee at home. Extended exposure to oxygen, heat, light, moisture – any one of these can affect the delicate flavour of your beans.

However, there’s no better defence than knowing what to expect and how to store coffee at home. With this knowledge, you’ll be in the best possible position to make sure you drink fresh, delicious coffee every single day.