Coffee capsules first took the world by storm in the mid-2000s thanks to brands like Nespresso and Keurig. Since then, pod consumption has shown no signs of slowing down, with the global market expected to be worth some US $29.2 billion by 2025.
However, while convenience is a priority consumers who drink coffee pods, freshness is nowhere near as high on the agenda. At a glance, you can see that capsules typically have shelf lives of six to 12 months – but this doesn’t give you any information about when the coffee was roasted and when the capsule was sealed.
So, should coffee drinkers be thinking about freshness when buying pods? To answer this question and learn more, I spoke to three coffee professionals who work with pods. Read on to find out what they said.
You may also like our article on a brief history of coffee pods
What is coffee freshness?
Coffee is deemed to be “fresh” when its flavour is unimpaired, with qualities showcasing the terroir and climate the coffee was grown in – at least to some degree. Any loss of flavour or aroma indicates that the coffee is ageing.
The main variables that cause coffee to stale are moisture, oxygen, temperature, and time. But is it possible to quantify freshness and how it degrades?
Chahan Yeretzian is a Professor of Analytical Chemistry, Bioanalytical Chemistry, and Diagnostics at the Zurich University of Applied Sciences (ZHAW). He is also the CEO of the Swiss Coffee Alliance and was on the Specialty Coffee Association‘s Board of Directors from 2015 to 2018.
Chahan has written extensively on coffee freshness, including a study entitled Protecting the Flavours—Freshness as a Key to Quality.
He explains that the focus of this study was to develop objective approaches for measuring freshness. Chahan and his team introduced two markers for freshness: one based on aroma compounds (“chemical markers”) and one on degassing (“physical markers”).
“Freshness can be represented as the ratio between two specific coffee aroma compounds,” he says. “Some are very abundant in freshly roasted coffee and degrade rapidly during storage. Others do not exist in fresh coffee; they are generated and appear as coffee loses its freshness. So, some decrease while others increase.
“By taking the ratio of such compounds, one obtains a ratio that changes as the coffee loses its freshness.”
Chahan explains that he and his research group identified several of these freshness markers which were related to the some of the compounds responsible for coffee aroma.
“The physical marker that we identified is the amount of [carbon dioxide] (CO2) in the coffee,” Chahan says. “If you have no CO2, it cannot be fresh coffee.”
When coffee is roasted, CO2 is produced and remains in the coffee beans. Around 1% of the total weight of freshly roasted coffee is CO2. However, over time, CO2 is released from the beans. This process is known as degassing.
The less CO2 a coffee contains, the more it has degassed since roasting, and the older it is. This is why we relate the amount of CO2 left in coffee to its freshness.
While quantifying freshness might be important to understand coffee at a scientific level, Kent says that it can be subjective.
“Freshness [is] anything above a set threshold that achieves the desired flavour and sensory experience that consumers look for,” he tells me. “For some roasters, that may be a high threshold that coffees only stay above for a few weeks. For others, that threshold may allow for months of freshness.”
So how does the process of manufacturing coffee capsules affect freshness?
Kent says: “Freshness in capsules is all about the right equipment and proper timing. Roasters have to have excellent planning to avoid long waiting times during roasting, grinding, and degassing.”
Manufacturing capsules: How do they keep the coffee fresh?
Joseph Fisher is the Head of Roastery Production & Video at April Coffee Roasters in Copenhagen.
“The grinding process, degassing, and subsequent packing must be controlled very carefully during production,” Joseph says. “It is within these steps that the greatest loss of aromatic compounds can occur.”
Once ground, coffee loses around 60 to 70% of its retained CO2, indicating an almost immediate loss of freshness.
“Ground coffee is susceptible to oxidation,” Chahan says. “It must be ground in the optimal environment. You have to know how long to degas [for] and [when to package it].”
Degassing is a critical aspect of manufacturing capsules, as the capsules must be hermetically sealed once the coffee is added.
There is a “sweet spot” for manufacturers to find: making sure the coffee has released enough CO2 so that the capsules swell without rupturing, but not enough that the coffee tastes stale or flat. It’s fairly common for capsules to swell slightly because of degassing, but they should not burst.
Kent says: “Capsule manufacturers’ degassing silos often use nitrogen to preserve the freshness, and the degassing time is controlled optimised for ideal freshness.
“In addition, during capsule production, the percentage of oxygen inside the capsules should always be [below] 1%.”
Minimising the presence of oxygen inside the sealed capsules helps to slow down the staling process and keeps the “vulnerable” ground coffee fresher for longer.
However, the types of materials used to make capsules will also have an affect on freshness.
“The biggest barrier to freshness in capsules remains the material which they are packed within,” Joseph notes.
Chahan tells me that he has carried out comprehensive research into the relationship between freshness and capsule packaging material. One of his studies compared different materials at a range of thicknesses.
The body and cover of the capsules were both taken into account as variables. The capsules were stored at room temperature for 46 weeks, and retention and loss of freshness were measured through two volatile compounds found in coffee.
The best results (with highest retention of the compounds in question) were found when both the body and cover of the capsule were made of aluminium.
“Aluminium has the best barrier properties,” Chahan tells me. “Glass and aluminium are definitely better than all [other] composites, [but] glass is not practical.
“Aluminum is practical and strong physically, which means [it] can support high [pressures]. You can also pack [aluminium capsules with] gas without deforming the capsule.”
There are many factors that make capsule extraction different from espresso and filter, including extraction time and dose.
Joseph says: “It’s typical for a coffee capsule to contain approximately 5.5g of ground coffee, which means that your grind must be optimised to ensure that each capsule extracts perfectly.
“Contact time is often relatively short and the flow rate can be quick, therefore it is common that the grind size for capsules is comparable to that of traditional espresso.”
Grinding for capsules is carried out using specialised equipment that is rarely found in cafés, as the machines are more suited for use in capsule production facilities.
“[Companies] generally roast a little darker to have a more critical range of grinding [for] stable extraction, which can only be done with a roller mill,” Chahan says. “You will not be able to achieve the same share of fines [with] flat or conical burrs.
“[First] you break [the beans]. [Secondly], you [break to a smaller size] [and lastly], you reach the grind distribution you want. You achieve a smaller share [of] fines while still grinding fine.”
Kent tells me that VOILA uses a similar technique. “In addition to the roller mill, we use a compactor to improve the coffee density and particle shape,” he says. “From there, we adjust the particle size to suit the target flow and extraction rate.”
Despite the smaller doses in pods (which is between a quarter and a third of the amount used for a single espresso shot) the perfectly uniform grind size and specialised extraction method allows each coffee particle to retain more of the original flavours and aromas of the coffee.
The coffee is degassed, ground, and hermetically sealed in a nitrogen-rich, low-oxygen environment. This allows manufacturers to maximise freshness and retain more of the volatiles present in the coffee.
How can roasters keep capsules fresher?
To ensure coffee freshness when selling capsules, roasters and retailers should adhere to a number of optimal grinding and packaging procedures. But what else can they do to keep the coffee within fresher for longer?
Capsules are known for their long shelf lives, despite containing preground coffee.
“It started with 12 months [shelf life] and it was then extended to [up to] 18 months, depending on the [company’s] distribution systems,” Chahan tells me.
“However, we studied the true shelf lives of capsules [for] up to a year. You can justify one year, even longer, but most capsules last up to six months. Sometimes, it’s not credible to extend shelf life depending on the packaging and [processing] before packaging.”
Broadly speaking, large capsule manufacturers like Nespresso generally label their pods with a shelf life of six to nine months. While whole bean coffee should be consumed within two to three months of roasting, the unique process of capsule manufacture (from degassing to grinding and packing) means they remain fresher for longer.
Kent says consumers and retailers should still think of capsules as having the potential to be fresh and delicious.
“Customers have a tendency to think of capsules a little bit like canned food, but that isn’t really the case. Roasters should be indicating a best before date, just like they do with bags of whole bean coffee.
“Even though the timeline is longer, showcasing these dates only helps ensure the best experience for customers,” he says.
Material freshness & sustainability
As stated above, aluminium is largely recognised as the best capsule material.
However, capsule manufacture (and use) is a hotly-debated sustainability issue. Research indicates that over 400 Nespresso capsules are consumed every second across the world. This creates a substantial amount of waste.
To tackle this issue, capsule manufacturers and retailers are investing in compostable and recyclable materials to create a more circular economy for pod packaging. But different materials affect freshness in a variety of ways.
Kent says: “Aluminium capsules provide [ideal] barrier properties against oxygen and water vapour. This means the shelf life (in terms of organoleptic properties) is much longer than compostable capsules.
“In contrast, compostable capsules have limited barrier properties, and the shelf life in terms of organoleptic properties starts to degrade around five to six months after production. This is what we use for our best before date, giving consumers the best experience.”
Joseph explains that sourcing suitable compostable materials was difficult when April started to manufacture coffee pods.
“At the time, there was no compostable material available which could ensure that the ground coffee remained fresh.
“The alternative was to pack each capsule separately in a sealed pouch, which contradicted the use of compostable materials in the first place.”
However, he notes that modern standards for sustainable packaging are improving, and freshness is far more attainable.
“Technology has now advanced to the point where we can be confident that each capsule will remain fresh and will brew consistently each time,” Joseph concludes.
Freshness may not be the biggest priority for many capsule consumers, but it’s an integral part of enjoying coffee.
To enhance your experience when buying pods, pay close attention to expiration dates and packaging materials. Try to purchase capsules from high quality roasters and retailers where possible, even if it does come at a premium – the extra cost is likely to be worth it.
Enjoyed this? Then read our article on how to store roasted coffee & prolong its freshness.
Photo credits: Joseph Fisher, VOILA.LABS
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