When you are planning to customize coffee bags, you will definitely think of optional-addons, such as a zipper and one way degassing valve. As we all know, the function of a zipper is to reseal to ensure the freshness of coffee beans, so why do coffee bags have a valve? 

The construct of degassing valve: 

First of all, the core design logic of the coffee bag degassing valve is one-way conduction, that is, only the gas in the bag is allowed to be degassed, while blocking the outer air from entering. Secondly, most common coffee bag degassing valves are flexible diaphragm one-way valves, which are mainly composed of four key parts:

Filter Mesh: Prevents coffee grounds from clogging the 5 degassing holes.

Valve Body: The circular base is fixed on the surface of the coffee bag, with 5 degassing holes in the center, which is the channel for gas to enter and exit. It is made of food-grade plastic and is sealed with the bag body to avoid air leakage.

Flexible Diaphragm: A thin sheet structure covering the degassing holes of the valve body, with its edge tightly fitting the valve body to form an initial sealing state. The elasticity of the diaphragm is the key to one-way conduction - When it is subjected to the pressure of the gas in the bag, it will be pushed, forming a gap between it and the valve body, opening the degassing channel; after the pressure disappears, the external gas will exert pressure on the diaphragm and block the degassing holes.

Cover: The cover has grooves around it to allow air to pass through, and the four corners can be inserted into the valve body, which can not only prevent the diaphragm from being contaminated by external debris, but also guide the degassing gas to diffuse smoothly into the air, while preventing external dust from entering the valve through the degassing holes. 

How does a one way valve work?

1. Let carbon dioxide out

After roasting, whole coffee beans will continue to release carbon dioxide (CO₂) over several days or even weeks . As the gas accumulates in the bag, the air pressure in the bag gradually increases. When the air pressure reaches a certain threshold (usually 0.1-0.3bar, the specific value varies depending on the valve type), the thrust of the gas on the flexible diaphragm will overcome the pressure of the external air pressure, so that the edge of the diaphragm is separated from the valve body, forming a tiny gap. At this time, the carbon dioxide in the bag passes through the gap between the diaphragm and the valve body, and then degassed from the bag through the 5 air holes of the valve cover. As the carbon dioxide is degassed, the air pressure in the bag drops. When the pressure is lower than the threshold, the diaphragm will fits tightly with the valve body again. There is no gap between the flexible diaphragm, thus closing the degassing channel. 

2. Prevent oxygen and moisture from entering

When the air pressure inside the bag is equal to the outside air pressure, the flexible diaphragm always maintains a close fit with the valve body. If the outside air tries to enter the bag at this time, it will exert inward pressure on the diaphragm, which will make the diaphragm fit tightly with the valve body. Even if there is a slight fluctuation (such as shake during transportation, changes in ambient air pressure), the diaphragm can ensure the closing state, thereby completely blocking oxygen, water vapor and other outside gases from entering the bag, preventing the coffee from deteriorating due to oxidation or moisture. 

Disadvantages of coffee bag without degassing valve:

1. The buildup of carbon dioxide produced by the coffee beans will cause the bag to inflate like a balloon and eventually burst.

2. Carbon dioxide accumulation affects the flavor of coffee and odor. 

3. It is not conducive to maintaining the freshness shortens the shelf life. 

Situations where a valve is unnecessary: 

1. Ground coffee powder: Typically, ground coffee (pre-ground coffee) has already finished degassing by the time it gets sealed.

2. Nitrogen flushing: Some large-scale commercial operations (such as coffee canning) remove all oxygen and flush the container with inert nitrogen before sealing.

So, the importance of one way degassing valve has two main point, that is let CO2 out and prevent oxygen and moisture from entering. To ensure your whole coffee beans are still fresh when they reach your customers, contact us to ask a small tiny one-way degassing valve on your custom coffee bag!