The proper storage of green coffee is essential for maintaining freshness and quality. When green coffee is exposed to too much humidity, heat, or light, beans can become stale and age much more quickly, take on defects, or in some cases, become mouldy.
When we talk about age in this context, we mean the natural, irreversible process which causes coffee quality to diminish.
At the same time, however, we’re also seeing more and more “aged” coffees appear on the market. For instance, barrel-ageing is becoming more prominent across the industry.
As developments like these start to gather speed, it’s important to ask questions about their popularity and how we make distinctions. To learn more, I spoke to two coffee professionals. Read on to find out what they had to say.
You may also like our article on how ageing cold brew affects flavour.
Understanding how green coffee changes over time
Generally speaking, coffee’s freshness dictates how many of the flavours and aromas we can taste in a given cup. This means that fresher coffee is generally more vibrant and complex.
However, it’s important to note that green coffee stays fresh for much longer than roasted coffee. Most specialty roasters consider green coffee to be fresh for six to 12 months after it is harvested and processed.
Roasted coffee, meanwhile, loses freshness over a matter of days and weeks. This is because roasted beans are more volatile and less stable than green coffee, as the roasting process traps gases inside the beans. These gases (mainly carbon dioxide) help the roasted coffee stay fresh, but will gradually begin to diffuse out of the beans within days of the roast.
As coffee beans age, they begin to lose freshness – especially roasted coffee, as it is a much more unstable product. When this happens, the volatile compounds degrade to cause undesirable characteristics, such as flat or stale flavours.
Dr. Gerson Silva Giomo is the Specialty Coffee Head Researcher at the Agronomic Institute of Campinas in Brazil.
“Unlike the ageing process used to make wine, the ageing of coffee is more associated with a loss in quality, rather than an increase,” he tells me.
He explains that as coffee beans age, the presence of water-insoluble compounds like lignin increases, which encourages further degradation.
“In the ageing process, flavour and aroma compounds are degraded by oxidation, and the intensity of ageing varies according to different environmental conditions,” he says. “This generates additional flavours that did not exist before [when the coffee was fresher].”
As roasted coffee gets older, more of the insoluble compounds, such as cellulose and hemicellulose, combine with the oxidised lipids and pass through cell membranes. This creates new flavours in the coffee which are undesirable, causing it to taste flat, musty, and even rancid.
Old green coffee, meanwhile, can taste baggy, papery, and woody. Furthermore, acidity diminishes over time, meaning that coffee is more likely to taste flat as it gets older.
Gerson also explains that for green coffee, appearance and colour can be used as a rough indicator of age. As green beans darken or take on brown or black colours, we can determine that they are older; conversely, fresher green coffee tends to be a green-grey colour.
How to identify old coffee
Gerson says that the flavours of old green coffee are usually distinctive and recognisable.
“In general, older or past crop coffee has less sweetness, less acidity, and less body than fresher coffee,” he explains. “Additionally, it can taste like jute bags, cardboard, or dry wood, depending on how old the coffee is and how it was stored.”
Prior to roasting, older green beans will increase more in size compared to fresher coffee. Furthermore, they will also be less dense than fresher coffee, which should be taken into account when roasting them.
Gerson also notes that roasted coffee becomes shinier over time, as more and more of the oils unlocked by roasting migrate to the surface.
How does coffee age?
Although old coffee – whether green or roasted – is likely to have lost its flavours and aromas, there are a number of distinctions between the two.
Fresh green coffee is generally defined as being from the current harvest season – though this depends somewhat on the country it is grown in.
Past crop coffee refers to coffee that is left over from the previous harvest, and is therefore older than coffee from current harvests. However, it’s important to note that past crop coffee can still be high-quality and have desirable attributes.
As roasted coffee gets older, it loses its freshness quickly. Most specialty roasters recommend brewing roasted coffee no later than a month past its roast date to experience the coffee’s full spectrum of flavours and aromas.
But what about “resting” coffee?
Once roasted, coffee requires a short rest period to release some of the carbon dioxide which is created during the roasting process. This is known as “degassing”.
Coffee can be considered too “fresh” if it is brewed too quickly after roasting, as the higher volumes of carbon dioxide can block the extraction of certain desirable volatile flavour and aroma compounds. As such, it must be left to degas.
When we talk about coffee ageing, we generally associate this with undesirable qualities. However, there are a number of processing techniques which rely on ageing to change or enhance flavours and aromas.
Many of these processing techniques have been used for centuries in countries like India and Sumatra. One of the most prominent examples is Monsoon Malabar, which exposes the harvested coffee to monsoon rain and winds along the coast of Malabar for between three and four months.
Typically, this process results in more earthy and spicy flavours, with a much heavier body.
Trevor Jermasek is the Operations Manager and green coffee buyer for Water Avenue Coffee in Portland, Oregon.
He emphasises how it’s important to be aware of these cultural differences around the term “aged coffee”, as it doesn’t always indicate a lower quality.
For the most part, however, roasted coffee beans cannot be intentionally aged, like with processing techniques or barrel-ageing. This is because roasted coffee is much more unstable than green coffee, and the coffee’s flavours have already been developed considerable during the process of roasting.
Ageing coffee for processing
Some of the most well-known coffee processing methods which involve intentional ageing are used in Java, Indonesia, and the Malabar region of India. One of the best-known examples of this is Monsoon Malabar processing.
As part of this processing method, the beans are exposed to monsoon rains and wind, and are continuously rotated in driers to release the moisture. After the ageing process is complete, they are sorted and graded before being rested again.
Although the ageing process usually lasts for a few months, some regions can age coffee for years at a time – this is particularly prominent in Sumatra. Gerson tells me this results in a much thicker mouthfeel with almost no acidity.
Each country often has its own denomination of origin (or geographical indication) for its respective aged coffees, which means they are defined by the region they are produced in. Ultimately, this means the flavours cannot be truly replicated in any other part of the world.
However, for many of these coffees, even though they are aged, they are generally still delivered in the same crop year. Because green coffee is non-volatile and considered stable, and it ages more slowly, it is only considered past crop when a new crop year comes around.
This means that green coffee aged for several months can still comparatively be considered “fresh”.
Exploring barrel-aged coffee
More recently, we have seen another trend gathering speed: the practice of barrel-ageing coffee.
This involves placing green coffee inside of barrels which have been used to manufacture beverages such as whiskey, wine, rum, and other alcoholic drinks.
Trevor tells me that Water Avenue Coffee produces wine barrel-aged coffee.
“When we barrel-age coffee at the roastery, we place fresh green coffee beans in freshly emptied barrels which have been used to make wine,” he says.
As green coffee is highly susceptible to a number of environmental conditions, the wood of the barrel will influence the flavours in the coffee,
“In our barrel-ageing process, we intentionally manipulate the flavour of the beans,” he explains. “The coffee will absorb the intense aromas and residual wine moisture from inside the barrel.”
Naturally, this leads to more fruity and “funky” flavours once the coffee is roasted and brewed.
“The process results in coffee with a unique wine-like character that mimics the intense fruit-forward flavours experienced with natural processed coffee”, Trevor says. “We often get tasting notes like dark chocolate, cherry, port, oak, strawberry jam, or fig.
“To some extent, barrel-aged coffee is like high-end flavoured coffee,” he tells me. “It’s important to source distinct, high-quality coffees that can become the foundation for completely new and unique flavours that can only come from the ageing process.”
Trevor explains that the total length of time it takes to age the coffee depends on how much moisture is contained in the wood of the barrel. Generally speaking, the coffee will be roasted anywhere from two weeks to one month after ageing is complete.
“More and more roasters are experimenting with ageing coffee processes in a lot of different ways,” he concludes.
Although we might associate freshness with quality, aged and old coffee are not the same.
Ageing is an important part of exploring new flavours and mouthfeels in coffee, and does not always imply a coffee of lower quality. Old coffee, however, is more than likely to have lost the majority of its flavours and aromas – resulting in a dull, flat cup profile.
When it comes to ageing coffee, the more that is understood about the process, the more we can appreciate these coffees. While the flavours may not be for everyone, it can be a new experience for some consumers.
Enjoyed this? Then read our article on Café L’Ambre, where coffee is aged for 23 years.
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