A degassing valve is a one-way vent that allows coffee beans to slowly release carbon dioxide (CO2), and other volatile gases without coming into contact with the air outside.
Although they may seem like little more than plastic nozzles, they play an important role in prolonging the freshness and quality of the coffee, as well as ensuring it is stored effectively.
To learn more, I spoke to Digital Projects Manager at Producer Roaster Forum, Laura Fornero, who highlighted why coffee businesses should consider including degassing valves on their coffee packaging.
What Is Degassing?
When coffee is roasted, a number of chemical reactions take place. This includes the formation of CO2 and other volatile gases inside the beans. After roasting, the built-up CO2 begins to slowly seep out, with up to 40% released within the first 24 hours.
The beans can take anywhere between two and 12 days to reach the optimum level of CO2 and consequently bring out the best possible flavour of the coffee. The time it takes depends on a few different variables, including roast profile and bean density.
However, after the coffee is packaged (whether it’s ground or beans), CO2 continues to be released. This means that if the coffee is packaged in a bag without a degassing valve, or if the valve is faulty and the gases cannot escape, the bag will balloon, and possibly rupture.
Do You Need A Degassing Valve On Your Coffee Bag?
Similar to wine, when freshly roasted coffee is exposed to oxygen for an extended period of time, it has an adverse effect on the flavour. Oxidation causes the coffee to become stale and its shelf life is significantly reduced. A degassing valve prevents oxygen from entering the bag, while at the same time allowing the right gases to escape from roasted coffee.
However, Laura tells me that if a roaster knows their coffee will be consumed before the oxygen has time to negatively affect it, a degassing valve might not be necessary.
“If the coffee is shipped in smaller pouches, a degassing valve is recommended, but it is not essential,” Laura explains. “Having said that, roasters can opt to attach one themselves if they feel it’s needed.”
The ability to attach a degassing valve on a case-by-case basis has become a popular choice among wholesale coffee roasters, who require more flexibility around when their coffee is consumed.
According to Laura, homebrewers can benefit from degassing valves too.
“High-barrier bags with quality degassing valves have become one of the best storage systems for homebrewers,” she says.
“Every time they open and close a bag, they can push any oxygen out of the package to prevent the coffee from becoming stale, which can’t be done with a regular storage jar.”
Degassing valves also have a part to play in the transportation of coffee, particularly in the specialty coffee sector. This is because roasters are often located hundreds, if not thousands, of miles away from the cafes and customers they supply. Without degassing valves, the long journey would give CO2 time to build up within the bags, which could cause them to explode.
“If a roaster is shipping their coffee over long distances, it’s a good idea to add a valve in case too much CO2 builds up before arriving at the destination,” Laura says.
“When considering whether to include a degassing valve on bags of coffee due to be transported, the most important factors are bag size, roast date, and how long they are expected to stay sealed for.”
How Does The Roast Profile Affect the Degassing Process?
Laura tells me that the time it takes for roasted coffee to release built-up gases largely depends on the roast profile. A dark roast, produced when beans are exposed to higher temperatures for longer periods, will lose gases considerably faster than a light roast.
This is because the sugars in the beans have had more time to develop, and the coffee cracks twice, rather than once, thus increasing the surface area from which CO2 can escape. This means that dark roasts reach their optimum CO2 level before the denser light roasts.
“The roast profile is also important to note if the roasted coffee beans are to stay sealed for a few days or weeks, perhaps on the shelves of a cafe or at home,” Laura says.
Small volumes of coffee that are consumed quickly or degassed in the roastery might not always require a degassing valve. However, bags of coffee that spend more time on the shelf or in transit will undoubtedly benefit from a degassing valve.