Can you nitrogen flush compostable coffee bags?

Holly Szakal
November 21, 2023
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Once coffee emerges from the roaster, it begins releasing carbon dioxide (CO2). Specialty coffee roasters must then package the product quickly and efficiently to preserve freshness. For several brands, this is where the process of nitrogen flushing coffee bags comes into play. 

Nitrogen flushing refers to a technique that replaces the oxygen in coffee packaging with nitrogen. This helps to create a cushion of gas that protects the coffee during transport and storage.

However, modern consumers expect businesses to invest in sustainable, eco-friendly packaging materials. More so, these materials should be recyclable, biodegradable, or compostable. 

Therefore, this begs the question of whether specialty coffee roasters can flush compostable coffee bags with nitrogen successfully. Or could the process damage the packaging materials? 

To learn more about nitrogen flushing and compostable coffee bags, I spoke with Alex Bitsios-Esposito, the founder of Cartwheel Coffee Roasters

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What is nitrogen flushing?

Nitrogen flushing is a form of Modified Atmosphere Packaging (MAP), which was first adopted by retailers in the general food industry in the 1970s. Since then, it has become a common practice across a diverse range of industries, providing reliable assurance for the freshness of various food products.

Initially, MAP was created for perishable food items that, once packaged, continue to release CO2 and water vapour internally while still absorbing oxygen. Examples include various meats, fresh vegetables, fruits, and even bags of crisps.

Within the coffee industry, nitrogen flushing involves filling coffee bags with ground or whole beans. These bags are then fed into a dispenser that flushes and seals them simultaneously. 

“Nitrogen flushing delays staling,” explains Alex, who is also a licensed Q grader and green coffee buyer. “Coffee that is flushed with nitrogen will taste like it is at its peak freshness for longer. This is because air has an oxidising effect on coffee, which means that it causes coffee to stale quickly.”

“Staling degrades the flavour of the coffee by changing its chemical composition,” he adds.  “New compounds are created and existing compounds are changed.” The process of staling is accelerated by a buildup of CO2, as well as exposure to moisture, heat, oxygen, and light.

These elements even impact vacuum-packed, low-oxygen coffee, with oxidation increasing according to packing density and grind size. Notably, research shows nitrogen flushing may double the shelf life of packaged coffee in certain circumstances. It may be even more effective when combined with vacuum sealing and layered packaging that contains degassing mechanisms.

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What to consider before nitrogen flushing coffee bags

Specialty coffee roasters who are considering flushing packaging with nitrogen should keep the following in mind:

Reserve nitrogen for larger orders. Nitro flushed coffee attains its optimal flavour approximately one to three weeks post-roast. Therefore, specialty coffee roasters should consider reserving nitrogen flushing primarily for packaging larger orders or those intended for extended travel.

Opt for degassing valves. One-way valves, or degassing valves, can be highly effective when packaging and storing nitrogen-flushed coffee. If a degassing valve is not used, there is a risk the coffee bag will balloon and possibly explode. Degassing valves allow carbon dioxide to exit the bag without allowing oxygen to enter. 

Aim for oxygen levels below 3%. Oxygen levels that exceed 5% can accelerate the oxidation process. In turn, this may impact the freshness and quality of freshly roasted coffee within days of packaging. Therefore, it has been recommended to maintain a residual oxygen level of no more than 3%. However, wherever possible, specialty coffee roasters should aim for even lower oxygen levels.

Attaining levels below the minimum recommendation also creates further opportunities to open doors with private-label coffee roasters. In competitive bidding scenarios, especially against larger industry rivals, consistently achieving a residual oxygen level of 2% or lower can be crucial and may determine the success of securing a lucrative contract.

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Can you nitrogen flush compostable coffee bags?

Clearly, there are several benefits to flushing packaging with nitrogen. Therefore, it’s no wonder the process is becoming more common in the specialty coffee industry, as it allows coffee roasters to maintain the freshness of their product.

“After roasting, our coffee bags are filled with beans, and these open bags of coffee are then placed into a flushing and sealing machine,” Alex explains. “A thin nozzle is inserted into the opening of the bag, and when the sealing commences, a programme of vacuuming all the air out of the bag and pumping nitrogen into the bag starts.”

“Vacuuming and pumping changes depending on the size of the bag, but the overall purpose is to remove all air from the bag. The bag is immediately sealed to prevent the protective atmosphere from escaping,” he adds.

After sealing, nitrogen flushing leaves a bag of coffee with less than 3% of its initial oxygen levels, thus extending shelf life up to double the initial time.

That said, research shows 78% of US consumers admit that making sustainable choices is important to them. This may cause coffee roasters to wonder if nitrogen flushing works on biodegradable packaging, as sustainability is now at the forefront of consumers’ buying minds.

Roasters can opt to appease sustainable buyers’ minds by choosing to invest in compostable coffee bags, which can be flushed with nitrogen. Additionally, barrier packaging films and low-density polyethene (LDPE), often used together, create a physical barrier between the food item and potential contaminants. 

At MTPak Coffee, we have a range of multilayer coffee bags that will keep out oxygen, while providing full sustainability. We offer a choice of natural, 100% compostable and recyclable packaging options, such as kraft paper and rice paper.

Additional choices include PLA and LDPE coffee bags, and all of our packaging options are fully customised using sustainable materials such as water-based inks. We also offer recyclable degassing valves that can be fitted to the bags either before or after manufacture.

Furthermore, we can help you decide on the best resealing option for your coffee bags, from pocket and loop zippers, to tear notches and zip locks. All our resealable features can be integrated into our recyclable, compostable, and biodegradable coffee bags.

If you are a micro roaster, we offer low minimum order quantities (MOQs) on a number of packaging options.

Images courtesy of Cartwheel Coffee Roasters

For more information on compostable coffee bags, contact our team

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