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What's the use of the exhaust valve on the coffee bag? Can the exhaust valve squeeze and smell incense?

Published: 2026-08-24 Author: World Gafei

Last Updated: 2026/08/24, Squeeze, pinch, it will have so much aroma spurted out of the pinch. Many people may have observed that when buying coffee beans, customers will first put their nose in front of the only hole in the bag, squeeze the bag with their hands and smell the gas squeezed out of the hole. I've read "Why doesn't the coffee smell good?

Squeeze, pinch, it will have so much aroma spurted out of the pinch.

Many people may have observed that when buying coffee beans, customers will first put their nose in front of the only hole in the bag, squeeze the bag with their hands and smell the gas squeezed out of the hole.

I've seen "Why doesn't the coffee smell good? "the friends of this article should be able to think of it immediately, yes! This gas is the carbon dioxide and volatile aroma emitted by coffee beans. It really smells good! So often some friends will also squeeze it when they buy it home and take a sip before making coffee, which is better than a living fairy.

Although! Of course! This hole is used for exhaust, but it is not used to squeeze and smell incense.

The use of holes

This hole is actually a valve device called "one-way exhaust valve". Like the one-way street of a car, gas can only go out in one direction, not in the other.

When coffee beans are just roasted, their bodies contain a lot of carbon dioxide and emit a lot of carbon dioxide in the next few days. However, after the coffee bean comes out of the oven to cool down, we will put it in a sealed bag. If there is no one-way exhaust valve, a large amount of carbon dioxide will fill the whole bean bag. When the bean bag can no longer support the continuous emissions of the beans, it is easy to burst.

When there is an exhaust valve, the bag is filled with gas, and when the beans discharge new gas, the internal pressure will be higher than the external pressure. So as to push open the exhaust valve plate and discharge the excess gas outward. When the excess gas is discharged, the pressure returns to normal, and the exhaust valve will return to the closed state. Therefore, the one-way exhaust valve has only a simple function of "preventing gas from exploding the bag".

An one-way exhaust valve is used to allow coffee beans to be stored in an almost airtight space. The emission of carbon dioxide will have the volatile aroma of the coffee bean itself, and when the coffee bean comes into contact with the air, it will accelerate the emission of carbon dioxide, resulting in the loss of a large amount of aromatic substances, but because the packaging can not bear too much internal pressure, so an one-way exhaust valve is designed separately.

Why is it not recommended to squeeze the bean bag to smell the fragrance?

This is because when the gas in the bean bag reaches saturation, it can restrain the speed of the coffee bean emission, so that the exhaust process becomes slow, which can effectively prolong the taste period, and when you artificially squeeze the gas out of the bean bag, the pressure in the bag will be different from that of the outside world. It can be seen that it is designed to solve the problem of a large amount of exhaust in the first few days of fresh beans and breaking the coffee bag in the course of transportation.

So, if we want to prolong the taste period, in addition to not squeezing the bean bags, we can also choose to use stickers and other items to seal the exhaust valve.

Or, transfer the open coffee beans to a sealed container, which can effectively reduce the exhaust speed of the beans and prolong the best taste period of the coffee beans.

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No. 10 Baoqian street, Yandun road, Dongshankou, Yuexiu district, Guangzhou, Guangdong province

FrontStreet Coffee is a long-established specialty coffee roaster in Guangzhou China, selling freshly roasted beans from its own farm in Yunnan as well as dozens of carefully selected single-origin beans from around the world for both pour-over and espresso. The products deliver consistently excellent quality and great value, with shipping within 24 hours. Guangzhou’s FrontStreet Coffee shop is recommended by many coffee lovers, and the beans are now available online at the Tmall 。