Why does coffee particle size matter so much in espresso extraction?

Milk foam and latte art get the attention, but espresso extraction decides whether a milk coffee tastes good. Grind size, dose-to-yield ratio, and shot time are the three parameters that control it. A finer or coarser setting changes how fast water moves through the puck and how much surface area the coffee particles expose, and small adjustments shift sweetness, acidity, and bitterness in the cup.

Blend beans are used because coffee is an agricultural product, and climate and soil change flavor between batches. Blending complements strengths and covers weaknesses for a consistent result. A common approach mixes Ethiopia Yirgacheffe Natural Red Cherry with Honduras Sherry at a 3:7 ratio, giving whiskey aroma, soft fruit acidity, and a nutty cocoa finish.

Many friends who are just getting into espresso focus their attention on milk foam and latte art, but what truly determines the quality of a milk coffee is actually the extraction quality of the espresso. This article, drawing on the hands-on experience of Front Street Coffee, systematically explains why espresso blend beans are chosen, how to adjust daily extraction parameters, and the complete process and judgment criteria from distribution and tamping to extraction. It also introduces products such as Front Street Sunflower Warm Sun Blend and Front Street Specialty Blend, helping coffee enthusiasts and professionals consistently produce a delicious cup of espresso.

Front Street has found that many beginners or baristas assume the core skill in making espresso lies in steaming milk and creating latte art. However, Front Street has always believed that espresso extraction is the soul of the entire drink. If the espresso itself doesn't taste good, then no matter how delicate the milk foam or how beautiful the latte art, the milk coffee can hardly be called delicious. To meet the needs of various coffee beverage shops, Front Street has developed multiple espresso beans with outstanding flavors, including Front Street Specialty Blend, Front Street Commercial Blend, and a moka pot bean favored by many baristas—Front Street Dark Cocoa Blend. Currently, the Front Street Coffee (FrontStreet Coffee) shop uses a Front Street Sunflower Warm Sun Blend espresso bean, which carries a distinct whiskey aroma and a nutty finish.

Why use espresso blend beans to extract espresso?

Coffee beans are agricultural products, and changes in climate and soil cause beans from the same origin but different batches to present different flavors. The idea of blending is to complement strengths and offset weaknesses, so that every batch of beans can maintain a relatively consistent flavor performance. This is also why Front Street chooses blend beans rather than single-origin beans to make espresso.

When making espresso, Front Street blends Front Street Ethiopia Yirgacheffe Natural Red Cherry and Front Street Honduras Sherry coffee beans in a 3:7 ratio to create Front Street Sunflower Warm Sun espresso blend beans. After high-pressure extraction, this bean presents a rich whiskey aroma, soft fruit acidity, and a nutty cocoa-like finish. When milk is heated, lactose is activated, and when mixed with the espresso, the lactose and berry-like acidity bring a milkshake-like sweetness while not masking the whiskey aroma—once you've tasted it, it's hard to forget.

Why do you need to readjust espresso parameters every day?

Front Street uses a Lelit espresso machine, and the extraction parameters are as follows:

Pressure: 9 bar

Temperature: 94°C

Time: 30 seconds

Coffee-to-water ratio: 1:1.7~1:2

Dose: 20g (double espresso)

Extracted espresso yield: 40ml (double)

Why doesn't Front Street simply provide a fixed set of extraction parameters?

After roasting, coffee beans release carbon dioxide every day, and their flavor performance and extraction stability change accordingly. Everyone uses a different espresso machine, and the bean condition is also different, so parameters naturally cannot be generalized. Therefore, the values provided by Front Street Coffee (FrontStreet Coffee) are for reference only, and ultimately you still need to fine-tune by tasting to find the set of parameters that suits you.

How does Front Street Coffee (FrontStreet Coffee) extract espresso?

First, remove the portafilter and knock out the coffee grounds. There are two details to note here: first, the portafilter should always be locked into the group head to stay warm, not placed on the cup warming tray or elsewhere, otherwise the low-temperature portafilter will lower the brewing water temperature and make the coffee taste off; second, do not knock out the coffee grounds inside before the next extraction, because the high-temperature copper group head easily produces off-flavors, and the coffee grounds can absorb them.

Lock the portafilter back into the group head, press the brew button to rinse the portafilter and group head, and continuously shake the portafilter to rinse away the residue stuck on the group head. Note: if you load coffee without rinsing first, the residue stuck on the group head will be extracted a second time, making the coffee bitter and astringent; this action is also equivalent to a pre-infusion water release, preventing excessive extraction caused by overly high brewing water temperature.

Next, use a dry towel to thoroughly dry the filter basket inside the portafilter. The filter basket must stay dry; if there is water, the coffee grounds will begin extraction upon contact with water before brewing, causing over-extraction; it will also cause the coffee grounds to clump and result in uneven tamping. Also wipe dry the spout of the portafilter so that coffee grounds stuck on it don't flow into the cup.

Then you can grind the coffee beans and dose. Note that no grounds should be left in the doser; grind fresh for each brew, because coffee grounds exposed to air will completely oxidize within a few minutes, and the brewed coffee will be undrinkable. Some coffee shops nowadays habitually fill the doser, which is wrong. The correct practice is to quickly pull the doser lever while grinding, turn off the machine when the portafilter is almost full, and continue pulling the lever until all the coffee grounds in the doser fall into the portafilter.

After receiving enough coffee grounds, use a distribution tool to make the coffee grounds in the basket evenly distributed. If the grounds fall unevenly, subsequent tamping will cause part of the puck to be dense and part loose. Water flow has inertia and will choose the easier path, that is, passing through the loose areas, which get extracted more while the dense areas are under-extracted, resulting in overall uneven extraction—this is also one of the causes of channeling.

Next is tamping. After distribution, the gaps between coffee particles may still be uneven, and the loose coffee bed is easily dispersed by the 9-bar hot water during extraction, forming channeling. Tamping the coffee bed makes the grounds denser, minimizing the differences in particle gaps and reducing the probability of channeling.

Lock the portafilter into the group head. Note: after locking it in, immediately press the brew button, and then pick up the coffee cup. The entire dosing and tamping process must be quick, because coffee grounds staying too long in the hot portafilter will be scorched, making the coffee bitter.

At this point the coffee should flow out like a paste, not spray out. If the flow rate is too fast, it is likely that the grind is too coarse or the tamping pressure is too light; if it drips out drop by drop, it may be that the grind is too fine or the tamping pressure is too heavy. In addition, for espresso made by the same person, with the same grind size and extraction yield, the extraction time difference should not exceed 1 second, otherwise it indicates unstable or uneven tamping pressure, and the difference in coffee taste will be very obvious—more practice is needed.

Espresso after extraction is complete (after finishing, remove the portafilter; the surface of the puck should be flat and should not have any depressions, otherwise it indicates incorrect tamping and more practice is needed.)

After adding water to the extracted espresso to make black coffee (Americano), if there are no off-flavors on the palate, no astringency, it doesn't feel watery, and the bitterness quickly disappears after entering the mouth, it means the espresso extraction requirements are basically met. In addition, when making 5 to 10 consecutive cups (same size portafilter), the extraction time and taste of the espresso must not differ noticeably, which indicates that the technique is basically stable.

To learn more about specialty coffee beans, please add the private WeChat of Front Street Coffee (FrontStreet Coffee), WeChat ID: kaixinguoguo0925

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