How to use a green coffee moisture metre

Janice Kanniah
August 18, 2022
How to use a green coffee moisture metre

While roasting coffee can create major changes in the beans, it is by no means the sole determiner of quality. 

The way green coffee is grown and developed is just as important. Additionally, a 2022 study revealed a coffee’s production and processing also affects its overall quality.

This includes factors such as the growing altitude, temperature, humidity levels and exposure to sunlight. More so, the type of nutrients and level of moisture the coffee is exposed to will make a difference in quality. 

For optimal coffee quality, producers aim to keep coffee moisture levels high, as it can help produce better acidity and cup quality. The ideal level is between 10.5% and 11.5%, and this can be impacted by how green coffee is stored and shipped to its roasting destination.

All roasters want to work with green coffee while it is at its best. Therefore, they can benefit from monitoring these levels, and a green coffee moisture metre is one of the most effective tools to do so. 

To learn more about how to use a green coffee moisture metre, I spoke with 2021 German Brewers Cup Champion, Nicole Battefeld Montgomery.

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An image of a roaster holding a green coffee bean in an article on how to use a green coffee moisture metre

Why are green coffee moisture levels important?

Green coffee moisture levels are important, as they can affect the way the beans react during the roasting process and help develop different flavours. 

“The main problem is when the moisture content is too low,” says Nicole, who is also a roaster and SCA trainer. “This may cause the beans to break during the roast and get baked or burned easily. Overall, the taste of dry coffee can be grassy, woody, and stale.”

A range of factors can affect green coffee, which in turn can impact the coffee’s moisture levels. 

For instance, extreme temperatures can create condensation on the inside of the green coffee’s storage bags. This increases humidity and moisture, which can dampen the coffee’s aromas and flavours. 

However, if the air is too dry, it may cause the beans to lose moisture. That said, too much moisture may lead to mould, mildew, or fermentation. 

Naturally, the quality of green coffee will degrade over time. While time itself may not directly cause this degradation, it can help roasters measure how much the other factors impact the coffee.

The general time frame for green coffee to be considered fresh is between 6 to 12 months. Failure to determine the moisture levels of green coffee can make a roaster’s job more challenging. 

“Roast behaviours will be different,” Nicole explains. “Additionally, roast profiles won’t be able to be reproduced, which can lead to inaccurate taste profiles.”

An image of green coffee drying on raised sun beds in an article on How to use a green coffee moisture metre

What are green coffee moisture metres & why are they used? 

Nicole believes roasters, green bean buyers, and exporters can all benefit from using green coffee moisture metres. 

“It can help them measure the moisture content in green beans and roast beans,” she says. “This way, you can adjust the drying phase of your roast.”

Ultimately, this can affect how much of a coffee’s sweetness, acidity, and viscosity comes through after roasting. As less moisture is present, the coffee will lose it quicker during roasting, which will impact the roast length and temperature.

The average modern green coffee moisture metre tends to have a range of benefits, including advanced calibration, multiple grain scales, and battery operation. 

Roasters can use these metres to document a coffee’s moisture levels over time, and pinpoint any issues that may be changing it, such as its roast environment or storage. 

Using a green coffee moisture metre can help reduce product loss. Additionally, it can generate predictable metrics roasters can use as indicators for specific roast profiles or coffees. 

More so, it can create a more accurate production schedule that predicts when a coffee will reach optimal moisture levels. 

A coffee metre could show that the coffee’s storage area needs a dehumidifier, or requires a temperature-controlled storage space.

It may also mean the roaster needs to experiment with a higher roast temperature to remove excess moisture. Depending on the roasting machine used, the bean’s density, volume, and other external factors.

An image of green coffee beans in a traditional jute sack in an article on How to use a green coffee moisture metre

Tips for maintaining optimal coffee moisture levels

Storing green coffee in a cool, dark, and dry environment is one of the most effective ways to maintain optimal moisture levels. 

That said, it is also a good idea for roasters to invest in the right type of packaging. Several studies have found the best indicator of a coffee’s longevity is its packaging – especially when it is hermetically sealed and excess air is removed.

Roasters who store their coffee in traditional jute or paper bags may struggle to stabilise its moisture levels. Research shows green coffee stored in permeable bags can exhibit chemical differences as early as 3 to 6 months into storage.

While this change may only be noticeable to experienced cup tasters, it is irreversible and indicates degradation has begun.

Investing in sustainable packaging that comprises multiple barrier layers can help prevent this. Choosing better quality green coffee packaging can also give roasters more storage freedom, as the coffee will be less vulnerable to external elements.

Additionally, it can free roasters from having to maintain a climate-controlled storage environment. This helps lower electricity consumption, making the business more environmentally sustainable in the long run.

An image of a coffee roaster holding a multilayer unbleached kraft paper coffee bag in an article on How to use a green coffee moisture metre

Upgrading green coffee packaging is a wise investment. It can make the roasting process more predictable, allowing roasters to experiment with different roasting styles and coffees. 

MTPak Coffee can provide specialty coffee roasters with branded and fully customisable green coffee packaging in a range of sizes, as well as in small batches.

Additionally, we can help package your roast coffee, as well as design and digitally print coffee bags that showcase your company’s personality.

We offer a range of high-quality, recyclable, compostable and biodegradable packaging solutions. Our line of coffee bags are made from renewable resources such as kraft paper and rice paper.

We offer a 40-hour turnaround and 24-hour shipping time, as well as low minimum order quantities (MOQs) no matter what packaging size or material used.

For more information on sustainable coffee packaging, contact our team.

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