Can an american coffee machine split espresso extraction after a stop?

Stopping espresso before the target yield and restarting does not work well. In testing with 20g of Warm Sun blend extracting 40ml at a 1:2 ratio, the normal shot finished in about 30 seconds. The split shot stopped at half volume after 20 seconds, rested two seconds, then pushed the remaining 20ml in just four seconds, very pale in color.

The restart flows fast because the puck structure changes under pressure, so the second phase underextracts. The result can loosely be called a ristretto, but other espresso-based drinks rarely use one as a base. On an american coffee machine, it is simpler to know how to make coffee with a machine and pull a fresh shot for a balanced americano or latte.

If you accidentally press the stop button during espresso extraction before reaching the target yield, can you simply press it again to continue extracting? This article compares three espressos through actual testing—normal extraction, mid-extraction stop, and stop near the final stage—to analyze the effects of segmented extraction on the color, flavor, and concentration of the coffee liquid. Front Street Coffee uses the Warm Sun blend, testing with 20g of grounds extracting 40ml, at a coffee-to-liquid ratio of 1:2, revealing how the puck structure changes under pressurized extraction, causing the second extraction to flow too fast and underextract, and provides operational advice.

This approach can theoretically be considered a ristretto, but as Front Street says, aside from flat white, other espresso-based coffees typically don't use ristretto as a base. So, when this situation occurs, if you want a latte or americano with suitable flavor, you still have to re-extract a shot of espresso. However, some more adventurous friends start to wonder: since it wasn't extracted enough, can we press the extraction button again, like a segmented extraction in pour-over?

Can espresso extraction be divided into multiple times? Since everyone wants to know so badly, Front Street will test it out for you! In this experiment, Front Street will extract three espressos: one normal extraction and two segmented extractions. The two segmented extractions will have different stopping points, to see how the flavor differs when stopped at different points, and whether espresso extraction can really be split into two!

The coffee beans used in this experiment are still the Warm Sun blend, since Front Street only has one espresso grinder. Then ground to 1.2 on the Galileo Q18, with a coffee-to-liquid ratio of 1:2, that is, 20g of grounds extracting 40ml of espresso. First, extract a regular espresso! Since it's extracted in one go, the extraction time is a very standard 30 seconds. The flavor profile is still Warm Sun's classic whiskey aroma, butter cookie, and a slight berry tartness.

Next is a double-extraction espresso! We stopped it when it reached half the target volume, at which point the extraction time was 20 seconds, then after a two-second interval restarted extraction, and the remaining 20ml was extracted in just 4 seconds, with a very pale coffee liquid color, total extraction time being 24 seconds. And the taste of this espresso was very thin—flavor present, but not obvious.

Finally, an espresso stopped near the final stage! Front Street stopped it when it reached two-thirds, at which point the parameters were 25 seconds, 31ml! Then after a two-second interval restarted extraction! Similarly, the remaining 10ml was extracted in just two seconds. And compared to the second cup, this espresso was not as thin, more substantial, with a fuller taste. But this can only be compared to the second cup's severely underextracted coffee; compared to the first cup, its expression is still relatively weak.

So we can understand that if you accidentally stop extraction during espresso making, even if you restart, it's hard to fully extract the remaining substances from the coffee! The reason for this situation comes from the espresso machine's unique extraction method—pressurized!

Pressurized Extraction When we press the extraction button to make espresso, the espresso machine starts operating, providing 9 bars of pressure to force the substances out of the coffee with hot water. This pressure pushes the puck downward, compacts it, thereby increasing resistance, allowing the hot water to distribute more evenly! At the same time, the moment the hot water contacts the puck, a large amount of carbon dioxide rushes out, squeezing the space and also adding obstacles to the hot water flow. Thus, in such a space, the hot water can only "humbly" seep downward slowly. But if we stop extraction midway, the originally saturated spatial structure is broken. The backflush suction of the group head will draw away all substances on the surface of the puck, and at the same time, the puck's density has changed after extraction. Thus, the factors that originally hindered the hot water flow are gone, and the hot water released upon restarting can quickly seep out directly through the opened channels in the coffee bed. The overly fast flow rate inevitably prevents the hot water from fully extracting the coffee substances, so the large amount of coffee liquid released in just a few seconds is why the color is so pale.

Moreover, such coffee liquid not only tends to produce burnt bitter flavors due to channeling, but also, because its concentration is too low, dilutes the originally well-extracted espresso. So, when we are extracting espresso, if we accidentally turn off the extraction, it's best to re-extract a shot of espresso, and not do a second extraction on the same puck. To avoid that final cup of espresso full of unstable factors ruining the ultimately wonderful coffee experience. - END -

The above content is compiled by CoffeeHunters, a coffee news website.