How to store coffee beans to extend their shelf life? Check out Blue Bottle Coffee's experiment

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The coffee roaster will carefully observe the characteristics of the raw beans and ensure the quality of the samples through cupping. Then he can find the most ideal roasting method for the beans and try many methods to find out how to bring out the best flavor of the coffee.

But what if you have made so much effort, but the quality of the roasted coffee is compromised due to a poor storage system? Or you cannot sell the roasted coffee as quickly as expected, and the coffee beans have begun to age and become stale in the roasting factory?

Roasted coffee is susceptible to many factors: light, temperature, humidity, and, most importantly, oxygen. Good storage should keep the coffee fresh and maintain its flavor characteristics for as long as possible so that the drinker can enjoy the coffee at its best. Let's take a look at the traditional best storage methods and what the latest research says.

Why is storage so important?

Generally speaking, if green beans are well stored before roasting, their shelf life can reach one year. However, the best tasting period of roasted coffee beans is only a few weeks. Why?

If you randomly pick a passerby and show them some unroasted green beans, if they don’t know much about coffee, they will probably find it hard to believe that unroasted coffee has no aroma.

The roasting process develops the flavors and aromas we enjoy, whether that’s chocolate, caramel, floral, etc. But as the flavors we perceive in coffee change, their chemical composition also changes.

One of the most important transformations is the breakdown of sugars into various compounds, including carbon dioxide. This carbon dioxide, which remains in the coffee bean, is gradually released after roasting, a process called degassing.

Degassing is a good thing, especially if the coffee is going to be used to make espresso. If the coffee beans contain too much carbon dioxide during the brewing process, these gases will prevent the coffee from combining with water, thereby interfering with the extraction of the coffee.

However, as coffee loses its carbon dioxide, it also starts to become tasteless. In The World Atlas of Coffee, author James Hoffmann says that when coffee beans are left for too long, two things happen. "The first is that coffee gradually loses its aromatic substances, which give coffee its aroma and flavor, which means that the flavor of the coffee becomes less interesting." This is inevitable, but we can try to delay this aging process.

However, the second change comes from the influence of oxygen and moisture. When coffee beans come into contact with oxygen and moisture, they will age and develop new flavors, which are usually described as bland, woody, or cardboard. This part is more controllable and preventable by preventing coffee beans from coming into contact with oxygen and moisture.

In other words, roasted coffee beans are more fragile than green beans, especially under the influence of oxygen and moisture. This makes coffee storage a very important step.

Coffee cupping

Traditional way to store roasted beans

When the coffee is ready to be delivered to consumers, many roasters will pack the coffee beans in sealed, light-proof aluminum foil bags to prevent light, oxygen and humidity from affecting the quality of the roasted coffee beans. These packages are usually equipped with air valves to allow the carbon dioxide in the coffee beans to be discharged smoothly from the air valves.

Some roasters prefer to package their coffee beans in resealable packaging, such as ziplock bean bags, which allows the barista or brewer to reseal the package after use to minimize the impact of oxygen.

Some people also use unsealed bean bags, and while they are more environmentally friendly (depending on the material of the packaging) and are generally cheaper, they do not effectively block oxygen. Therefore, coffee beans stored in these bags will age faster.

In addition to proper packaging, roasters and brewers must also consider where the coffee is stored. Even opaque, resealable foil bags cannot protect against high temperatures. A cool cupboard or storage room is usually the best option.

Coffee bean jars are becoming increasingly popular for those who brew their own coffee at home. An airtight or vacuum seal will keep out oxygen and moisture, and some materials are even heat-resistant. Stainless steel is also better than plastic, not only because it is more durable, but also because the material is less porous. However, most people who brew their own coffee at home don't usually put too many beans in their bean jars, so these jars are more suitable for home use than for business use.

Before selling the coffee, roasters sometimes also store it in large commercial storage buckets, although the quality of the containers can vary. Of course, they are large and heavy, not easy to move when not needed, and are not a good replacement for the storage function of coffee bean bags.

These choices give the coffee varying degrees of protection, but one thing that remains constant is that roasted coffee quickly loses its quality, with just a few weeks needed for the beans to age.

Storing roasted coffee beans in professional sealed bags

Although roasted beans are more fragile than green beans, the elements that need to be prevented are the same: light, temperature, moisture and oxygen. Green coffee beans are usually sealed or airtight packaging to prevent moisture, oxygen and insects. Therefore, Charlie Habegger and Carly Ahlenius of Blue Bottle Coffee's green bean department, in collaboration with GrainPro, began testing the use of sealed packaging for long-term storage of green and roasted beans and observing its impact.

GrainPro is well known for its hermetic packaging for green coffee beans, as well as other agricultural products such as corn and soy, but the company’s goal is to solve a number of problems faced by producers, logisticians and roasters, from coffee tarpaulins used by producers for hygienic drying to the lining used in trucks for transportation.

Blue Bottle Coffee conducted the experiment between May and September 2018. The coffee they used was Rwandan Nyanza Kirezi from the 2017-2018 harvest. For the analysis of the roasted coffee, the beans were stored in three different ways 24 hours after roasting to give them time to off-gas. The coffees were:

Biodegradable paper bags (this is the standard storage method for Blue Bottle Coffee), and the bags are opened once a month for sampling

GrainPro 15kg ultra-sealed ziplock bags, sampled once a month

GrainPro 15kg ultra-seal ziplock bags remained sealed during the five-month trial

The quality of these coffee beans is then analyzed using the Specialty Coffee Association’s cupping procedure.

1. The cupping score of the first group of samples packed in biodegradable paper bags dropped from 86 points to 79 points in the past five months. After the first month, it dropped by three points, and then dropped by 1.75 points in the next month, until the total drop of 7 points. The flavor of the cupping at the beginning changed from sweetness, black tea, cream, and chocolate to a loose taste later, and finally to a low acidity, blandness, and empty sweetness.

2. The coffee that was stored in a super-sealed ziplock bag but opened once a month dropped from an initial score of 86 to 80.88. Its flavor changed from caramel sweetness, dried strawberries and lemon to overripe apricot and apple flavors, and finally to flat, bitter, cloying and malty cupping flavor descriptions.

3. The last one is the sample that was sealed throughout the process, and the score dropped from 86 points at the beginning to 82.88 points. At the beginning, the coffee flavor is apricot, floral, orange, and nut aftertaste with a slight vegetable aroma. At the end, its flavor is brown sugar, mild stone fruit, chocolate, and paper aftertaste.

“It was clear to our team that GrainPro preserved the best flavor of both green and roasted coffee compared to the control group,” said Carly Ahlenius, Green Bean Dispenser at Blue Bottle Coffee.

Five months is far beyond the maximum shelf life of specialty roasted coffee beans, but it is clear that changing the packaging can greatly extend the optimal tasting period of the beans. For example, sealed bags may not currently be the standard storage method for roasted coffee beans, but they do provide protection from moisture and oxygen, avoiding the development of bland, stale, woody and cardboard flavors.

So what’s the best way to store roasted beans? Just keep them away from moisture, light, heat, and oxygen. Ultra-seal bags are a great way to extend the best-tasting period and slow down the aging of specialty beans (especially for long-term storage). Solutions like these can increase flexibility for third-wave coffee roasters, especially for smaller companies that may not be able to estimate order volumes on a weekly basis.

No matter which packaging you choose, there are some things to figure out: give the coffee some time to degas, then seal the package, try not to open the bag, and keep them in a cool and dry place. In order to ensure that everyone can drink the best coffee, you can also share this method with everyone.

Translated from Perfect Daily Grind

Translated by Cheng Zhen Coffee

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