What one way degassing valve contributes on the quality of coffee

16 Jul 2019

Usually, the one-way degassing valve needs to satisfy the basic need perfectly in order to provide a better environment to keep the bean. The working principle of this one-way degassing valve is to make the released carbon dioxide sink, which allowing lighter oxygen and nitrogen to be squeezed out of the bag or jar.

- “What if I put the coffee bean in a glass jar without any space for carbon dioxide to emit or air to come inside? Does it affect the quality?”

- “Well, I would say a YES. Because our coffee beans are all freshly roasted every week and the carbon dioxide from the roasted coffee bean will emit continuously.”

This conversation above happened in a coffee shop between a customer and the owner and we believed that customer who noticed on the one-way degassing valve would usually have some similar questions. You may find it different on the smell of coffee bean compared with the first day you used it and the tenth day, that results from the effect of emission of carbon dioxide and fresh air comes from outside the container. So, how do you reduce the effect on your drinking experience? Milk may be your coffee partner at that time if you usually just drink Espresso, Americano or Long Black. Or actually, you should listen to what every coffee bean seller would suggest you finish your coffee bean as soon as possible in order to have better taste since some coffee beans are better without the milk.

In fact, there is a process called ‘resting’ for coffee beans after roasting, which is a process of emitting carbon dioxide and stopping fresh air from outside. The flavour of coffee bean may have some slightly changes during the process and it also has a peak time when the coffee bean has the best taste. You will never know when the best time is until you find out the taste becomes a bit worse on the other day.

As we mentioned before, once you started your exploring journey in coffee, there is always something new to learn about: from the origin of coffee and its appropriate roasting process, to the exaction method of the coffee. Coffee resting can be seen as an important but an easily ignored point to know more about. Usually, when coffee roaster finishes the roasting process, he will leave coffee beans in a big jar or bag for them to cool down. After he receives the order from consumer, he will start to put coffee beans into package bag with one-way degassing valve, then the coffee bean will be delivered to the consumer. One of the most important elements in ‘resting’ is the time, from the moment that the coffee bean is roasted, this process has started. If consumer doesn`t have the coffee bean the next day after roasted, the coffee bean may have finished its ‘resting’ process. Therefore, the general suggestion is to finish the coffee bean as soon as possible. If you see the coffee package starts to swell and expand, it means that you should enjoy the coffee bean even more faster. Besides, sometimes you may find that oil is leaking from the coffee bean, it is also a signal for you to finish them quickly!

We all know that different kinds of coffee beans are suitable with different kinds of roasting method and even exaction method, it is the same when it comes to the ‘resting’ process. First of all, the quantity of emission of carbon dioxide from light roasting, medium roasting and dark roasting are not the same since the water content contains in the coffee bean will be vary. Usually, the carbon dioxide emitted from dark roasting coffee bean will be the most, and the followed by medium and light roasting. In addition, the quantity of carbon dioxide is an element for coffee barista to judge whether the coffee bean is fresh. For instance, in the hand craft coffee, when you observe that coffee bean is ‘breathing’ once you add the hot water to steam, it means that the coffee bean is still fresh; in the espresso coffee, the coffee bean is fresh if you find that there are some crema on the top of coffee, or you can observe the colour, dark red and crimson are much better than golden yellow.

So, what is the real reason that the change of carbon dioxide emission would influence the taste of coffee? After the roasting process, the flavour of the particular coffee bean is nearly fixed but will still have slightly change due to contact with air and carbon dioxide. When we use the coffee grinder, more carbon dioxide will come out, and when we brew the coffee with water, that carbon dioxide prevents the contact between coffee powder and water. But as carbon dioxide emissions continue for longer, the amount of carbon dioxide that prevents that contact will decrease correspondingly, making the coffee powder and water interact more strongly in order to better extract the taste of the coffee.

Lastly, we provide a suggested ‘resting’ time for different kinds of coffee beans:

- Super light roasting: 14 days

- Light roasting: 10 days

- Medium roasting: 7 days

- Medium and dark roasting: 4-5 days

- Espresso coffee bean: 21 days (café speed up the process by increasing the area of coffee beans in contact with the air)

Although coffee resting is an important step on making a better taste of coffee, it is also an experience needs to be accumulated. You cannot know the perfect duration time for each coffee bean needed for resting until you buy it, try it, and distinguish the flavour carefully. Don’t forget to enjoy yourself during this journey rather than sticking on such rules though! We hope you find this article useful and enjoy reading it, and we would love to become your pal on this coffee journey, or we say it, an adventure!

Tag: one way valve

Originally published 16 Jul 2019, updated 16 Jul 2019.