Do coffee bags need a vent valve?

Preserving the freshness of roasted coffee is a top concern of coffee roasters. An integral tool in achieving this goal is the exhaust valve.

Patented in 1960, the degassing valve is a one-way degassing valve that allows the beans to gradually release gases such as carbon dioxide (CO2) without contact with oxygen.

While they may look like simple plastic spouts, vent valves are extremely valuable products that allow roasted coffee beans to be transported over greater distances without being affected.

However, adding them to reusable coffee bean packaging can be problematic. As a result, some roasters may opt for bags without vent valves if their coffee is consumed shortly after roasting.

Why use an exhaust valve?

When coffee is roasted, it undergoes drastic physical changes as it increases in volume by up to 80%.

Additionally, the roasting process releases gases in coffee beans, approximately 78% of which consists of carbon dioxide (CO2).

The degassing process continues as the coffee is packaged, ground and consumed. For example, 26% and 59% of the carbon dioxide in coffee is released after coarse, medium and fine grinding respectively.

While the presence of carbon dioxide is often a sign of freshness, it can negatively affect the flavor and aroma of your coffee. For example, coffee beans that have not had enough time to vent may develop air bubbles during the brewing process, resulting in an uneven extraction.

Venting needs to be carefully controlled, as too much can spoil the coffee. However, too little degassing can affect the coffee's ability to extract properly and create crema.

Over time, through trial and error, roasters have found many ways to manage the venting process.

Past solutions have included degassing the beans before packaging or using rigid packaging that can withstand the pressure of carbon dioxide buildup. Also, they experimented with vacuum sealing the coffee in the package.

However, each method has its disadvantages. For example, waiting too long for coffee to vent can oxidize the beans. Alternatively, hard packaging is expensive and unsuitable for shipping.

The vacuum-sealing method removes excess aroma volatiles from the coffee, which negatively affects its organoleptic properties.

The breakthrough came in the 1960s when Italian packaging manufacturer Goglio introduced the vent valve.

Little changed until today, the vent valve consists of a rubber diaphragm sealed inside an injection molded valve. Its inner layer contains a liquid layer that maintains the surface tension of the valve body.

When the pressure differential reaches surface tension, the liquid moves away and moves the diaphragm. This allows gas to escape while preventing oxygen from entering the package.