2 bags of coffee

Coffee bean packaging – Science of proper coffee storage

Have you ever noticed how you can smell your coffee beans, right through its packaging? Even when it’s packed in a sturdy plastic/aluminium bag? You can almost tell what type of coffee is in there! But if you put your nose against a vacuum pack of ground coffee you barely smell any coffee. Just smelling wouldn’t tell you what’s in there.

How come this smell of coffee beans manages to get out of the pack? Shouldn’t that bag be tightly closed to keep your coffee fresh?

Turns out, it isn’t completely closed though. Have you ever looked really closely at your pack of beans though? Even though it’s barely noticeable, you will notice a little valve within the bag! That valve is very important and is a big reason of why you smell your coffee so well. Some true coffee bean science is used to explain what’s going on.

coffee bag
See that circle in the white plastic within the green circle? That’s the valve we’re looking for.

Coffee bean packaging

As with most food, you pack coffee beans for various reasons. The most obvious reason is that packaging is a convenient way to transport your beans. It ensures that beans don’t get lost along the way and that it doesn’t get dusty or dirty during transport and while sittig on shelves.

But, the packaging can also play a very important role in keeping these (ground) beans nice and fresh!

Remember how coffee beans are roasted to deliver their characteristic flavours? During this roasting process the beans develop a lot of flavours thanks to a lot of chemical reactions producing these delicious molecules. Their colour changes from greenish into the brown bean we’re used to seeing. Those roasted flavours aren’t necessarily fixed to the coffee bean permanently though. Over time the flavour molecules will leave the beans if exposed to air. As a result, beans may become stale over time. This is where packaging comes in!

Packaging depends on our usage

Of course, you can package coffee beans in simple paper bags. And where this may work perfectly fine for beans you’ll be using within a few weeks, it’s not great for beans that you need to keep fresh for weeks or months at a time. As a result, which packaging you’ll choose or see being used for beans and ground coffee depends on the duration of the storage, whether it needs to undergo harsh transport conditions and what freshness and quality requirements you have!

non-decafeinted green coffee beans, not roasted
Unroasted coffee beans, notice the green colour

Requirements of coffee bean packaging

For a pack to be suitable for coffee beans, there are a few considerations to take into account: keeping the flavour in, letting the gas out and keeping the oxygen out.

Keeping flavour in

First of all, the packaging needs to be able to keep those fresh roasted flavours within the packaging. This means that you will need to use a packaging material that won’t allow easy permeation of these molecules through the packaging.

Typically, metal cans can be used for this, or laminated packaging materials. These laminated films are made up of several layers of material, generally at least some sort of plastic with a thin metal layer. Even though these materials have great shelf life properties, their main disadvantage is that most are almost impossible to recycle. It is not possible to easily separate those layers again.

Paper bags are not good at keeping flavours in. Instead, gas molecules can freely move in and out of a package.

Letting gas out

Coffee has a quite special internal structure. As with any plant cell, the cells within the coffee bean have a strong outer wall and a bag of water, a vacuole, within that cell. During roasting you’re essentially drying out the coffee bean. However, the coffee bean doesn’t collapse, instead, the cell walls hold the structure in place, while the water within is evaporating. As a result, a roasted coffee bean is quite porous.

plant cell, quick description

This porous structure can hold onto gases quite well during roasting. However, over time a lot of these gases will escape. The major gas here is carbon dioxide (CO2). In the first few hours after roasting coffee beans release very large volumes of carbon dioxide. This release of gas is very important for coffee roasters & packers to understand. If you would pack a freshly roasted coffee bean right after roasting in a bag that is impermeable to carbon dioxide it might well blow up and break. The pressure can become really high if that gas can’t escape!

The darker the roast and the faster the roast, generally the more gas will escape. This dependence on various process parameters makes it important for manufacturers to think about their packing process, because different coffee beans or different roast will likely need different treatments.

There are roughly three ways that manufacturers cope with these escaping gases:

  1. They leave the beans to degas so the majority of those gases have left the coffee beans. The exact duration for this can vary from a few hours to a few days. The majority of gases will escape in the first few days, with quantities flattening out over time.
  2. Pack the beans in a pack that can resist some pressure. Some degassing is likely still necessary, but when using a pack that can withstand some pressure you need to degas for a shorter amount of time.
  3. Pack the beans in a pack that lets the gas out easily. However, that generally also means that your flavour molecules will disappear easily. This is best for shorter shelf lifes.
  4. Pack the beans in a pack that lets gases out, but doesn’t let anything else come in! This last option is especially helpful to prevent the next mechanism of staleness: the presence of oxygen!
Here’s what happens if the valve isn’t working well. The bag on the right side was completely closed, causing it to blow up by excess gas within. The bag on the left had a functioning air valve through which the gases could flow to the outside.

Oxygen

Oxygen is a common enemy for a lot of products. Oxygen is known to participate in oxidation reaction . In the case of fats, these, oxidation reactions are the cause for rancid fats. Coffee contain some fat as well which can go stale. But it also contains a lot of flavour molecules that can all react with oxygen. Generally, the reactions deteriorate the quality of the coffee.

By creating a pack in which oxygen cannot enter, the shelf life and quality of the coffee beans will stay good longer.

Other

There are several more factors that influence coffee bean packaging. Moisture should be kept away from coffee as well and lower temperatures are better for preservation than higher) not going as low as a fridge or freezer though. Read the article by SCA mentioned below for more details.

Types of coffee bean packaging

Knowing this (and your use case scenario) you can start looking at suitable packaging. This approach by the way isn’t unique to coffee. You can do it for any food or drink. Step 1: determine how your product needs to be protected. Second, determine how and when your product will be used.

Within the coffee bean world, there are the following most common types of packaging:

  1. Airtight packaging (e.g. a plastic bag)
  2. Paper bag
  3. Airtight pack, with a one-way valve (allowing gases to escape).

So which pack is best? There is no one best method, but there are best methods for several most common use cases!

Buy it and use it – Paper

If you buy or make coffee that will be used within as little as a few weeks or days, there is no need to try and use special packaging to prolong shelf life. Instead, if you buy the coffee shortly after roasting, a paper bag will serve you just fine. The beans can degas without any issues and not enough time passes for the flavours to get lost or the oxygen to do its work in oxidatio.

Optimal freshness – Airtight + one-way valve

If you need to store your coffee beans for a longer period of time, a pack with a one-way vale is the way to go. This pack allows you to pack the beans quite quickly after you’ve roasted them. That way, you’re able to keep a lot of that flavour within and protect them from oxygen.

A major disadvantage is the recyclability of these packages, which is noticeably worse than that of just a paper bag.

If you don’t want to or can’t use the one-way valve but want a longer shelf life than the paper bag, a ‘regular’ closed bag is fine. However, you have to wait longer to pack these beans. You have to make sure that all that carbon dioxide has had a chance to escape.

Ground coffee beans considerations

Ground coffee deteriorates in a very similar way as coffee beans do. However, they have one major difference. By grinding up the coffee beans, those intricate pores and structures within the coffee bean are broken down. Instead, all the internals are exposed to the air. As a result, all that built up carbon dioxide (CO2) can escape easily. Instead of waiting days for the degassing to occur, for ground coffee beans it’s a matter of hours or a day.

This exposed inside does have the disadvantage that is it more prone to spoilage. The flavours can escape more easily as well and oxygen can enter the powder without any issues. This is why ground coffee generally needs some more protection.

Vacuum packs

A common packaging solution for ground coffee is to pack it under vacuum. The absence of any air helps delay most reactions and it keeps all the flavours within!

Metal cans

Another common option (depending on where you live) is to find ground coffee stored in metal cans. These provide some sturdiness and again aren’t very well penetrable for any gases.

coffee bean packages glass jar and plastic bag
Once a coffee bean pack has been opened it is best to store them airtight, for example in a glass jar.

Opening & then storing the beans

Then comes the dilemma, you’ve bought your beans, opened the pack and probably won’t use all the beans at once, what to do?

It is just about always best to not buy too much coffee in one go, it is hard to keep the quality high. Generally speaking it is best to store the coffee in an airtight container to prevent oxygen from coming in, as well as moisture and light. There is one exception. If your coffee beans have been roasted recently, they might still release carbon dioxide gases. If so, do not fully close the packaging to allow air to escape, close after a couple of days.

Sources (& some inspiration)

Inspirationfeed, 30 Stimulating & Creative Coffee Packaging Designs, July-12, 2019, link ; for design inspiration!

Ohl, Danielle, Are One-Way Valves Right for Your Coffee Packaging Process?, Viking Masek, April-15, 2018, link

Roasting House, What kind of packaging is best for freshly roasted coffee?, 2015, link ; a nice experiment between packaging types, but they only tested a shelf life of 7 days

Sage, Emma, What is the Shelf Life of Roasted Coffee? A Literature Review on Coffee Staling, SCA (Specialty coffee assocation), Feb-15, 2012, link

Samo Smrke, Marco Wellinger, Tomonori Suzuki, Franz Balsiger, Sebastian E. W. Opitz, and Chahan Yeretzian, Time-Resolved Gravimetric Method To Assess Degassing of Roasted Coffee, J. Agric. Food Chem.2018, 66, 5293−5300, link

Niya Wang, Physicochemical Changes of Coffee Beans During Roasting, Guelph University Thesis, link

2 comments

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  • Nice.
    What I would like to know is how many days does it take after roasting of beans to safely pack them in vacuum pack

    • Hi Amar,

      Great question! I must admit that I’m not a coffee roaster myself and there is very little published on this.
      That said, you can vacuum pack ground beans immediately after grinding (in fact, that’s what you should do, as soon as the coffee has been ground into powder it will start losing flavour).
      You should only grind the beans once they’re cooled down completely. Grinding warm beans will give issues with both grinding as well as packaging afterwards. As far as I know, there is no specific wait to hold on to before grinding apart from the initial cooling.

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