Inside your coffee bag will usually be a one-way air valve, it will look a little like the one to the right, if you cut it out of course. If you are still using the coffee bag you can see it usually by taking a look inside, though also a pin-hole on the outside will tell you it’s there. Usually, these are found in higher grade gourmet types of coffee, though are becoming more common place for supermarket brands too.
This “thing” is your air-valve, it allows air out of the bag but does not allow air to enter the bag. Hence it’s named the one-way air valve.
This “bit of plastic” is critical to helping your fresh coffee stay fresh for longer. Preventing oxygen and scent molecules interacting with your lovely fresh roasted coffee.
Why You Need An Air-Valve
The process of roasting green coffee produces carbon dioxide, as a by-product. This is released consistently as oxygen then interacts with the coffee beans.
If the beans are then ground the amount of carbon dioxide produced increases in a short period of time. The one-way air valve is added to fresh roast and ground coffee bags to allow the carbon dioxide to easily escape and not allow in more oxygen – thus slowing the rate of reaction, which slows the release of carbon dioxide and increases the life span of your lovely coffee.
Pretty neat stuff.
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How Does a Coffee Bag Air Valve Work?
Inside the plastic container, you can see above are the 3 components of this type of air valve. The air inlet (which you can see above with its paper filter), the plastic sealer (in the middle) and the outlet (which has a hole corresponding to the outer pin hole).
This is how the 3 pieces are constructed within the bag and main container.
As you can see it’s a fairly simple device which allows carbon dioxide to escape by “lifting” the sealer to allow flow, but when air comes from outside of the bag the sealer is closed onto the Inlet which prevents oxygen from entering the bag.
Below is a diagram showing how the sealer lifts to allow air flow from inside the bag to outside.
And this final diagram shows how the air valve is designed to prevent air entering the bag by closing the seal and inlet together.
The air-valve is something that we often consider to be a “thing” on the outside of our coffee bags, we don’t often think about why it’s there (basically to stop the bag exploding and also extending the life of your coffee) nor how it works. This simple little doo-dah is your coffee’s life saver.