What is the correct way to seal hermetic coffee bags?

Esther Gibbs
April 1, 2024
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Preserving the freshness and quality of coffee throughout the supply chain is critical to the industry’s success. That starts with packaging and storing green coffee correctly, which is where hermetic coffee bags come into play. 

Coffee producers work tirelessly to ensure their crops are grown with care. For arabica coffee, this labour of love can take up to three years of cultivation before the tree bears fruit. Even if coffees are produced to the highest standards and achieve high cup scores, without properly hermetic coffee bags, the quality of the crop will degrade. 

The incorrect storage of green coffee can damage the beans during transit, leading to a lower cup score or defective flavours in the brew. 

To find out more about hermetic coffee bags and the factors surrounding green coffee storage, I spoke to Javier Gutiérrez Abril from Caribbean Goods, an importer specialising in coffee from Guatemala. 

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The importance of airtight green coffee packaging

Javier believes that “true transformation happens when people unite” and works to do this by reducing the barriers of access to the market between producers and coffee roasters in the UK. Born in Guatemala, Javier has witnessed the country’s corruption and violence and understands the challenging economic situation for many in the region. 

Through Caribbean Goods, Javier seeks to be a force for change, empowering farmers, reshaping markets, and transforming the future of the industry. He explains why it is so important for coffee cherries to be well protected and transported correctly from the start of the journey.  

When coffee cherries are picked by hand, they are usually placed in 100-lb bags. “If some of the cherries have any type of fungus, they contaminate the others, which can affect the flavour,” Javier says. “Once they’re picked, the cherries must be processed as soon as possible to avoid fermentation inside the bag.”

After processing, Javier explains the cherries are then milled and left to rest in storage rooms.  This is where the coffee, still in parchment, is packaged in the same 100-lb plastic bags that were used to transport the cherries. “These ‘rooms’ vary from mega warehouses to rooms made with clay. It’s important that these rooms are well guarded, as they’re susceptible to break-ins,” Javier adds. “They tend to be ventilated, as temperature is critical here. During summer, the warehouse can heat up too much and compromise the taste of the coffee. So, farmers tend to leave windows or install air vents.”  

Javier notes the importance of storing coffee beans in protective packaging. As coffee beans are porous, they’re at risk of taking on flavours from their surroundings. “I’ve met farmers who store the coffee next to old tractors or oil-fuelled machines, and as expected from time to time, you find a strong, oily taste on the cup. I believe it is cross-contamination.” 

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What is the correct way to seal hermetic coffee bags?

After dry milling, the coffee is stored in GrainPro bags or vacuum-sealed plastic bags. GrainPro bags, or hermetic coffee bags, work as a barrier to protect the coffee from oxygen, moisture, and pests. 

Hermetic green coffee bags are specialised storage and packaging solutions that seal in freshness and maintain the sensory attributes of the coffee. Multiple layers of high-barrier packaging mean these airtight bags extend shelf life while preserving natural oils and flavours for more decadent, nuanced products. 

Commonly, hermetic coffee bags are made from high-strength polyethylene (PE). They are specifically designed to keep products fresh without the help of pesticides or insecticides. Beyond this, hermetic coffee bags maintain water activity while protecting the coffee from moisture and oxygen. This, in turn, prevents any microbial activity that would lead to mould and fungus in the beans. It also protects from any moisture migration between green coffee and the atmosphere which would lead to quality degradation or a ‘past crop’ taste

Javier also highlighted that correct storage and shipping conditions are crucial for green coffee quality. “Coffee is like a sponge. Green coffee will absorb any flavours that surround it. Once, I wanted to ship a pallet of cacao in the same container as green coffee, and the guy at the dry mill was furious! They carefully check what enters the dry mill to avoid compromising the coffee flavour.”  

Options for sealing hermetic coffee bags include resealable zippers, twist ties, or zip ties. The bags can also be vacuum-sealed to extend the freshness of a coffee. 

“While I could transport everything in vacuumed sealed bags, it would cost a lot in packaging,” he explains. “Vacuum-sealed options are great but very expensive. I use 30kg burlap bags instead of 69kg, but I will need more than double the bags to fill a container. This means that we need to pay for double the bags. Vacuum-sealed options tend to be around 25 cents extra per lb.” 

For more expensive, higher quality, or rare coffees, it is well worth the cost in order to maximise freshness and quality control. For example, many competition coffees are vacuum-sealed in small resealable bags. Commercial grade coffees, on the other hand, sometimes come in the burlap sack without additional protection, as the quality is lower. This also helps to keep transport costs low. 

For the majority of specialty coffees, the extra cost of vacuum sealing is unnecessary and may -not be financially feasible. A high-quality hermetic bag that is sealed to remove any oxygen and that acts as a barrier to protect the coffee from moisture, paired with correct storage conditions, is ample to keep coffee its optimum flavour. 

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What to consider when investing in green coffee bags?

For those receiving coffee, it is important to visually inspect that the coffee has been packaged correctly, according to the contract. Beyond this, they must identify any possible damage to the packaging that could affect flavour. Coffee roasters and importers are advised to cup a sample for large contracts to ensure that there are no defective flavours. Additionally, they should check the colour, moisture, and density of the beans. If there is damage or an unexpected result from the tests, businesses must contact the importer to address the situation. 

At MTPak Coffee, we offer a range of green coffee packaging solutions specifically designed to protect your coffee and preserve flavour while reducing your business’s carbon footprint. Our range of hermetic green coffee packaging is made using high-strength PE and boasts superior water and air properties. More so, they can keep your products fresh without the help of pesticides or insecticides for over a year.

For more information, contact our team

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