Why Do Coffee Bags Have Vents?

Why Do Coffee Bags Have Vents?

Is there anything more disappointing than eagerly expecting that first cup of morning joe only to have it taste old or yuck, even stale?

Have you ever stopped to think about how coffee bean packaging keeps all that flavor locked in tight?

It’s amazing, really.

After all, most of the coffee we drink is harvested from remote locations the world over and has a long, long journey from far-flung fields to the bottom of your favorite mug.

Coffee manufacturers go to great lengths to ensure that the first sip has that just roasted, fresh coffee bean flavor we expect.

And that’s exactly what the vent (or small pin-sized) hole is for on your bag of coffee beans.

The Vent Keeps Oxygen Out While Keeping Flavor In

It all comes to simple physics.

Coffee bags have vents to allow carbon dioxide (CO2) that is trapped inside of the bag to slowly release (a process known as degassing) while keeping oxygen (O2) from infiltrating the bag and turning the coffee stale.

Coffee releases carbon dioxide, which is a by-product of the roasting process and at least some of it is necessary to keep the rich flavor intact. However, too much of it can cause an excess buildup in the bag and possibly cause it to burst open. Conversely, cutting a large hole in the bag would allow oxygen to enter and, as mentioned earlier, quickly make the beans go stale.

The solution?

A one-way valve/pin-sized hole that allows carbon dioxide to escape while preventing oxygen from entering.

It’s also sometimes called an “aroma hole” or “smelling hole” since you can give the bag a little squeeze and catch a whiff of the heavenly scent coming from inside. It’s a great way to tell if you’ll like the beans before you purchase.

Why Is Carbon Dioxide Important for a Good Cup of Coffee?

A sizeable portion of the carbon dioxide is released within twenty-four hours of the roasting process. It is estimated that this can be as high as 40% and can continue on for a few days afterward.

However, in order to brew a flavorful cup, coffee manufacturers need to ensure that some of the carbon dioxide remains so that it prevents a chemical reaction known as oxidation. A common example of oxidation you might be familiar with is the rusting of iron metal.

While exposing fresh roasted coffee to oxygen won’t turn them orange, it will cause the coffee to go stale quickly and stale coffee is bad, bad, bad coffee.

How Do Coffee Vents Work?

You’re probably wondering how the valve can release carbon dioxide while keeping oxygen from penetrating the bag at the same time. 

It’s all thanks to an ingenious one way exhaust system that limits the penetration of oxygen to less than one percent.

The pressure from within the bag forces the carbon dioxide out through a thin layer of flexible plastic but can collapse before any oxygen may enter, allowing for a virtually impenetrable seal.

Prior to this innovation, vacuum sealing (which is still used) was the most popular method for keeping some carbon dioxide within the bag. However, once the vacuum pressure is lost, oxygen quickly takes over. By implementing the coffee vent, manufacturers have been able to greatly extend the shelf life of coffee.

What Releases Carbon Dioxide Faster – Whole Beans or Ground Coffee?

According to a study from the Journal of Agricultural and Food Sciences, it was discovered that roast and/or ground coffee had a shorter (faster) degassing period than whole beans and also released less carbon dioxide in total.

In fact, the mere act of grinding the beans released up to three quarters of the trapped carbon dioxide in under 90 seconds!

Not surprisingly, the study’s authors concluded that the destruction of the beans during grinding was responsible for the rapid release of carbon dioxide. It was also discovered that the finer the grind, the greater the rate of carbon dioxide release.

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