What is the harm of grinding coffee beans instead of powder? Does it have an effect on the extraction and brewing of espresso?

Sellers of coffee beans generally have a grinding service, including Qianjie! However, if this packet of coffee beans is used for Italian extraction, Qianjie does not recommend guests to choose the service of grinding powder!

I believe that this is easy to cause the confusion of most friends: it will "lose taste" faster, as long as I drink fast, the taste will "go" but me! Indeed, the primary reason why grinding is not recommended is that the coffee flavor will run away, and it is the one that runs very fast! But for espresso, the important thing is not only the flavor, but also the other ingredients in the coffee bean, such as carbon dioxide! After grinding the powder, Qianjie will seal the exhaust valve directly. in the article "the use of exhaust valve", we can know that its main use is to avoid the exuberant exhaust capacity of fresh coffee beans to burst the bag!

When the coffee beans are ground into powder, a large amount of carbon dioxide will be emitted quickly, then the coffee powder will lose the energy to burst the bag; at the same time, in order to avoid the continuous loss of flavor, Qianjie will seal the exhaust valve! From this we can know that it has lost more than half of its carbon dioxide since the beginning of grinding. Surprise question: what role does carbon dioxide play in Italian extraction? By the way, the first is the composition of oil, which, together with the aroma of coffee, is pressed into the insoluble oil of coffee and filtered out from the bottom to form a golden foam floating on the concentrated surface, that is, Crema (oil)! Generally speaking, if the beans used in espresso are preserved in an unground state and stored properly, the flavor and carbon dioxide can be retained for more than 50 days!

That is, in these more than 50 days, the extracted concentrated flavor and oil are more obvious and more. When ground into powder, the loss of flavor and carbon dioxide will be accelerated, and the amount of flavor and fat extracted every day will continue to decrease. Basically, in more than 30 days, the coffee flavor and oil extracted by these coffee powders are no longer rich.

The second is to slow down the speed of launching! When beans are still rich in carbon dioxide, the speed of launching will be slow. Because the intervention of carbon dioxide will greatly reduce the gap through which water can pass, it will be much slower. Once the carbon dioxide is greatly lost, not only the daily amount of oil will be reduced, but also the extraction speed of concentration will be accelerated! When it is close to a certain degree, there will be insufficient extraction.

In general, when this situation occurs, it is necessary to choose between adding powder and fine grinding. Fine grinding is obviously impossible to choose, so we can only adjust it by increasing the amount of powder! However, the addition of powder is limited, the powder bowl has a standard capacity, can exceed the capacity to a certain extent, but when more than too much, the handle is very difficult to buckle on the coffee machine! Therefore, when the thickness of coffee powder becomes fixed, it will be very difficult for us to adjust the extraction.

Therefore, if you are friends who have requirements for taste and oil, Qianjie suggests that when buying beans, it is best not to choose to grind beans for a long time. The taste difference between freshly ground and pre-ground powder will be very obvious, not to mention, we do not know whether the coffee powder ground by the merchant can be applied to our own coffee machine, there are simply too many risks.

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