What Impact Does Coffee Grind Size Have? What Does Espresso Grinding Service Mean? Can Coffee Ground Too Fine Still Be Used?

To reduce consumer costs in equipment and operation, most coffee bean sellers offer "pre-grinding" services. However, if you want to use pre-grinding services for coffee beans intended for espresso, FrontStreet Coffee does not recommend this!

Why Espresso Demands Higher Grinding Precision

Because compared to pour-over coffee, espresso making requires higher precision in coffee grinding.

Why does espresso making have higher requirements for grinding? It's quite simple because espresso extraction must bring out the substances hidden within the coffee grounds (in appropriate amounts) using limited water and extremely short time. This makes its grinding requirements extremely precise, as only then can a delicious espresso with high concentration and good extraction rate be extracted in a short time.

Equipment Variations and Extraction Differences

However, different people use different coffee machines, and the requirements for grind size will vary accordingly. The grind size chosen by commercial grinders is based on their own commercial coffee machines. Commercial coffee machines have multiple or large boilers, and their pressure performance is very stable. Most friends primarily use home machines, and some home machines cannot maintain very stable pressure performance, which causes significant differences in extraction and cannot guarantee that delicious espresso can be extracted using the same parameters.

The Challenge of Coffee Bean Degassing

Even with the same coffee machine, the state of coffee beans will change due to continuous degassing. This leads to completely different coffee flavors extracted using the same parameters at different times. Yesterday's parameters applied today may not necessarily produce delicious coffee because espresso extraction has an extremely small margin for error. This is why coffee shops need to adjust espresso extraction every morning to ensure they can provide customers with consistently delicious espresso coffee.

The Critical Role of Grind Adjustment

The most common problem during the adjustment process is significant differences in extraction time. For example, yesterday 20g of coffee grounds might extract 40ml of liquid in 30 seconds, but today the same amount of grounds might take 40 seconds or 22 seconds. In such situations, the primary adjustment target is the grind size, in other words, the coarseness of the coffee grounds. If we purchase pre-ground espresso powder, we cannot make many changes because it's already ground, making it difficult to extract a delicious, high-concentration coffee. This is the main reason FrontStreet Coffee does not recommend pre-grinding for espresso.

The Impact of Gas Loss on Flavor and Crema

In addition, there's the issue of gas loss. The flavor compounds in coffee are volatile (aroma, not taste), and they continuously diminish over time, just like carbon dioxide. If stored in bean form, flavor loss occurs very slowly and can last for about 50 days. However, if we grind them into powder, most of the flavor is lost during grinding, and due to the increased surface area, the remaining aroma will completely evaporate in a short time, taking less than 30 days to fully dissipate. And then there's carbon dioxide! For pour-over coffee, we use blooming to release carbon dioxide to prevent it from hindering extraction. But for espresso, carbon dioxide is an important component of crema. If carbon dioxide is lacking, the crema content will also be relatively reduced. Therefore, when making espresso with pre-ground coffee powder, there's only relatively rich crema in the first few days, followed by a visibly noticeable decrease in crema every day.

Final Recommendations

So, for friends who have requirements for coffee flavor and crema, FrontStreet Coffee recommends directly purchasing a coffee grinder. If you just want to satisfy your cravings without too many requirements, then pre-ground coffee is sufficient~~

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Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473