Roasting coffee to reveal a rich and desirable aroma takes time, effort, and a whole lot of trial and error. However, once you get there, you need to make sure that consumers will be able to enjoy it at home or in cafés, no matter how long it takes to reach them.
Here’s where packaging comes into play. By using the right materials and features, you can preserve your coffee’s aroma long enough for consumers to experience the same tasting notes that you list on the bag.
To understand more about aroma and how packaging protects it, we spoke with Yu Yuki, Sales Manager at MTPak Coffee. Here’s what we found.
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What Is Aroma & Why Does It Fade?
Aroma is what we smell when roasted coffee beans release their volatile flavour compounds, and is generally used to describe the smell of brewed coffee (the equivalent term for dry coffee is “fragrance”).
However, while the word “aroma” is often associated with smell alone, often much of what we can taste in a coffee when we drink it is its aroma.
This is because the human tongue can only pinpoint a number of basic sensory tastes (bitterness, sweetness, and mouthfeel, for example). Therefore, many of coffee’s more complex flavour notes are actually derived from your sense of smell.
The flavour compounds we can identify in coffee aroma are actually created from aroma precursors during the roasting process, and particularly during the Maillard reaction. When this occurs, there is a huge release of aromatic compounds; some of them are pleasant, others not so much.
A coffee’s aroma and how much it has faded is often used as an indicator of freshness. Simply put: the more aromatic compounds in the bean, the fresher it is, and (usually) the better it tastes. The release of volatile components in coffee occurs naturally, but certain environmental factors can speed up the process, causing the aroma to fade more quickly.
Methanethiol is also used as one of the indicators of freshness. Methanethiol is a pungent chemical on its own right, but surprisingly, in coffee, it serves as a flavour compound that actually hides undesirable odours.
In his book, A Question of Freshness, Paul Songer says: “When ground coffee is set in open air, reduction of methanethiol can be perceived within one day and 70% is gone within three weeks.”
Exposure to oxygen, or oxidation, is one of the most common reasons that aroma fades in coffee. In the Specialty Coffee Association Podcast, Samo Smrke from the Zurich University of Applied Sciences said: “When I talk about chemical freshness, I’m talking about coffee aroma because coffee aroma is basically chemicals that are present in the coffee beans. So, the loss of chemical freshness means loss of aroma, oxidation of aroma, or the change of aroma.”
According to Smrke’s research, higher temperatures also speed up the process of oxidation in packaged coffee. This accelerates the loss of some of coffee’s more sensitive volatile compounds, such as methanethiol or butane‐2,3‐dione (often associated with butter, caramel, fruit, and other sweet tasting notes).
Furthermore, while it’s best to store coffee beans in a cool, dry place, they should not be frozen. When defrosted, condensation will lead to moisture in the beans, reducing their quality and dissolving some of their volatile compounds. A few degrees below room temperature is best.
How Does Packaging Help Preserve Coffee Aroma?
In 1895, Thomas Royal manufactured the first multi-layered paper coffee bag. Yu tells me that having multiple layers is a key part of effective packaging. “One layer is rarely enough to protect the aroma of roasted coffee beans,” she explains. “To protect against moisture, oxygen, sunlight, heat, and other factors, you need different materials.”
In his study, Smrke tested the effectiveness of aluminium as the inner layer in coffee packaging. He discovered that this was the most effective oxygen barrier when compared to plastic, paper, and other, more porous alternatives. Aluminium also provides protection against moisture.
However, mass-produced aluminium packaging layers can be expensive. As such, they are often replaced with metallised films (polymer films coated with a thin layer of aluminium).
Yu adds that both researchers and packaging manufacturers are also looking for more sustainable options that can be easily biodegraded or reintroduced into the supply chain. She tells me that this year, MTPak Coffee launched fully recyclable, multi-layer packaging that preserves the aroma of roasted coffee.
This packaging, she tells me, only has two distinct layers. She explains that using fewer layers reduces the packaging’s environmental impact and ultimately minimises its carbon footprint during manufacturing.
Sealing Your Coffee Bag
After you’ve chosen the right packaging, the next step is filling and sealing your bags. If coffee packaging is improperly sealed, it will lead to oxidation, and consequently unhappy consumers.
Yu explains that once a roaster has chosen their bag, there are several options on the market. “There are hand/foot sealers and automatic sealers, direct heat sealers, impulse sealers, vacuum sealers, and more,” she says.
Investing in sealing equipment can be expensive, so Yu recommends making a choice based on the volume of your roastery, your desired speed and efficiency, and the shape and opening type you use for your packaging. “A typical hand impulse sealer might be difficult to use with multi-layered side-gusseted bags, for instance.”
To ensure freshness as well as accessibility, most consumers opt for resealable coffee packaging. Yu tells me that the reusable seal options on the market include ziplocks, velcro zippers, tin ties, or tear notches. Again, the best choice may depend on the structure and size of your coffee bag, along with your personal preference.
Degassing & Coffee Aroma
The one-way degassing valve is a fairly new concept. It was invented in the 1960s by Goglio, a company based in Milan, Italy. Degassing is where gases (namely CO2) are released from roasted coffee beans. While CO2 in roasted coffee stops it from tasting flat and stale when brewed, too much will have a negative effect on extraction.
Degassing valves can be placed on almost any coffee bag structure with a heated application process that doesn’t compromise the seal on your existing packaging. Degassing valves are usually made of five parts: a cap, an elastic disc, a viscous layer, a polyethylene plate, and a paper filter.
While coffee is generally degassed for a few days after roasting, this process continues for a while afterwards. When CO2 builds up inside your packaging and puts pressure on the degassing valve, it releases it without compromising the integrity of your packaged coffee or allowing oxygen inside. This keeps more aromatic compounds in the coffee, stopping the complex flavours from fading as quickly.
“The degassing valve can be applied at any moment,” Yu says. “Roasters can order packaging with valves, or apply them on pre-made bags with manual applicators. This second option might be more convenient for smaller roasteries, whose coffee is often consumed in a shorter time span.”
Modified Atmosphere Packaging: What Is It?
Using modified atmosphere packaging (MAP) is a way of extending the shelf life of food or beverage products by controlling the balance of gases within sealed packaging.
In coffee, MAP removes or replaces the oxygen within packaging to reduce the risk of oxidation and ultimately preserve more of the coffee’s volatile aroma compounds.
Using MAP generally involves vacuum-sealing the product before “replacing” the natural composition of gases within.
Vacuum-sealed packaging was invented in the early 20th century. However, while vacuum-sealing alone does preserve the volatile flavour compounds in coffee and prevent oxygen from reaching the beans, it is not a perfect solution. Coffee will still degas within the vacuum-sealed pouch, which can potentially lead to ruptures as the packaging expands.
One of the most popular MAP techniques is nitrogen flushing, which “flushes” away oxygen by replacing it with nitrogen.
This method reduces the chances of oxidation, preserving aromatic volatile compounds and keeping them sealed inside the bag. Unlike oxygen, nitrogen will not affect the flavours or aromas of roasted coffee. Outside of coffee, nitrogen flushing is also commonly used to package and preserve potato chips.
Yu tells me that even smaller roasteries can use this method by buying nitrogen gas canisters. She also advises roasters who use MAP to purchase a gas analyser, as this will allow them to track and monitor the levels of oxygen inside their packaging.
Aroma is an essential part of coffee flavour. It is directly linked to the taste and freshness of roasted coffee.
However, protecting your coffee’s aroma against external factors including oxidation, moisture build-up, and temperature can be difficult. Complex and delicate flavour profiles are what specialty coffee consumers look for. Preserving them is one of the key functions of good coffee packaging.
So, by knowing how aromatic compounds are created and what can cause them to disappear, roasters can make more informed decisions about their packaging. Effective coffee pouches will help you to deliver the aromas you experience in your roastery to home brewers and baristas alike.
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