Why Not Pre-Grind Espresso Beans? What is the Shelf Life of Ground Coffee

Why FrontStreet Coffee Doesn't Recommend Pre-Ground Espresso

Most coffee bean shops offer grinding services, but if you're using the coffee for espresso extraction, FrontStreet Coffee recommends not having it pre-ground.

There are two main reasons. The first is the problem of flavor loss. This is a common issue with all pre-ground coffee, but it's particularly severe when applied to espresso.

Generally, Italian-style coffee beans can maintain their flavor for about 50+ days when stored as whole beans. However, if ground into fine powder, the flavor loss accelerates significantly, often becoming noticeably diminished in less than 30 days.

In addition to accelerated flavor loss, carbon dioxide within the beans also dissipates more quickly. Since the crema in espresso is composed of carbon dioxide and oils, using pre-ground coffee to make espresso only yields relatively rich crema in the first few days. After that, there's a visibly noticeable reduction in crema with each passing day.

Precision Requirements for Espresso Grinding

The second reason is the extremely high precision required for espresso grinding. For instance, different coffee machines may require significantly different grind settings. The espresso grind settings calibrated in coffee shops are specifically tailored to the machines they use. Commercial coffee machines in cafes have larger boilers and better pressure stability. Some home machines might claim to reach over 15 bars of pressure in their specifications, but this pressure is unstable. There might be sufficient pressure for the first few seconds, but then it begins to drop, resulting in slower extraction and longer brewing times.

Even if you purchase the same coffee machine as the cafe, solving the equipment issue, you'll still face the problem of coffee bean condition. For pour-over coffee, the grinding tolerance is much greater, with a wider usable range of grind settings.

For espresso extraction, coffee shops typically adjust their espresso parameters every morning before opening, with most adjustments being made to the grinder settings. Because coffee beans release gas daily, yesterday's parameters might not perfectly extract today's beans, necessitating daily verification of espresso conditions and timely adjustments when problems arise.

Here are two examples: First, yesterday's extraction parameters were 20g of grounds yielding 40g of liquid in 26 seconds. Today, using yesterday's parameters with the same grind setting, 20g yields 40g in just 22 seconds, requiring a grind adjustment.

Second example: Yesterday's extraction parameters were 20g yielding 40g in 26 seconds. Today, using the same parameters and grind setting, 20g yields 40g in 26 seconds, but the flavor differs from yesterday's, showing unpleasant notes. This also requires a grind adjustment.

The adjustment range for grind settings is actually very small, typically controlled within 0.5 increments each time. The difference of 0.5 increments is impossible to distinguish through visual observation or touch, but when used for espresso extraction, the difference becomes apparent—a 0.5 increment adjustment can result in a 7-second difference in extraction time.

Therefore, for friends who pursue quality coffee crema and flavor, FrontStreet Coffee does not recommend directly purchasing espresso powder or using pre-grinding services.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473