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Front Street Coffee has noticed that many friends have fallen in love with espresso with golden crema and hope to make it at home. Compared with pour-over, espresso is made using steam pressure, with hot water passing through coffee grounds to brew a small amount of coffee liquid with a rich texture and strong flavor. Although it looks simple to operate, changes in parameter details will affect the quality of the brewed coffee, so every step needs to be carefully controlled and every parameter needs to be considered.
Before espresso appeared, coffee was brewed by immersion, which not only required finely grinding coffee beans but also slow extraction, requiring a long wait. In order to speed up the brewing process, Italians thought of using steam pressure to force high-temperature, high-pressure water through the coffee puck to accelerate the original drip extraction rate. With continuous improvement and updates, the common semi-automatic and fully automatic espresso machines we see today were developed.
Common commercial espresso machines can provide more than nine bars of stable atmospheric pressure and hot water above 90 degrees Celsius. The high pressure forces hot water to quickly pass through finely ground coffee, extracting coffee liquid with rich crema, intense aroma, and a heavy mouthfeel. In order to extract an ideal shot of espresso, the barista's job is to master the various parameters that affect coffee flavor and then adjust them to the optimal extraction range.
There are many factors affecting the flavor from a coffee bean to a cup of coffee liquid, including grind size, coffee machine boiler pressure, water temperature, distribution and tamping force, dose, extraction time, beverage weight, and many other factors and details. Usually, the machine's pressure and water temperature are set and not easily changed. Distribution and tamping force are controlled according to the barista's habits. The four major factors used in daily extraction adjustment are dose, time, yield, and grind size.
The coarseness and uniformity of the grind are the most important factors affecting flow rate changes between each cup of espresso. A difference of just 1 gram in dose can cause the total flow time for extracting the same amount of espresso to differ by several seconds. When coffee particle size is uneven, the denser areas after tamping create greater resistance to water flow, making the extraction distribution uneven. Grinding directly affects the flow rate, time, and flavor changes of the coffee liquid.
The ratio of dose to extracted liquid weight is what we often call the brew ratio, and it is a relatively intuitive extraction parameter. The dose depends on the capacity of the basket model in the portafilter and is divided into double and single types. For example, the coffee machine at Front Street Coffee stores uses a double dose of 20 grams of coffee powder, and adjustments are made up or down from this parameter base (accurate to 0.1 grams). Since the brew ratio is not fixed, the coffee yield should be determined by the coffee's flavor performance.
In the past, baristas did not have precise weights and would directly observe changes in the color of the crema to determine the yield. At the beginning of extraction, it appears dark brown and relatively rich; over time, the color gradually turns golden, then light yellow. Generally, when the crema turns pale, it means extraction should end. Today's espresso extraction standards are more rigorous, with more stable data summarized, and the brew ratio also tends toward a fixed reference value of 1:2. For example, Front Street Coffee stores use 20 grams of coffee powder to extract 40 grams of liquid.
Extraction time is affected by the interaction of the above key factors. Generally, espresso extraction time is between 25 and 30 seconds. When the brew ratio is determined, the shorter the extraction time, the fewer coffee substances are dissolved; the longer the extraction time, the more coffee substances are dissolved. With the same brew ratio, if you want to change the extraction time, you can only do so by adjusting the coffee grind size and dose.
Once we understand the relationships among the various influencing factors, we can make adjustments based on the state of the coffee liquid and the feeling after tasting. The expression of coffee flavor depends on the espresso beans we use. Here, the self-roasted "Front Street Sunflower Warm Sun Blend" is used, made from sun-dried Yirgacheffe Red Cherry coffee beans and Honduras Sherry coffee beans. An ideal espresso will present whiskey aroma, vanilla, cream, and berry acidity.
For friends who like mellow coffee, Front Street Classic Espresso Blend is recommended. This is a recipe composed of three origins: Brazil, Indonesia, and Vietnam. It uses a dark roast, which can highlight the mellow aroma of the coffee to the greatest extent. The extracted espresso not only has rich and dense golden crema, but also offers aromas of dark chocolate, caramel, butter, and roasted almonds on the palate, with very rich layers. It can be purchased at the Front Street Taobao store or the Front Street Tmall flagship store.
For example, the extraction parameters for Front Street's first espresso were: 19.8 grams of coffee powder, 40 grams of coffee liquid, and 26 seconds, with a relatively fast flow rate. The coffee tasted thin, with neither the wine aroma nor the fruit aroma obvious, and a lingering astringency in the finish, which may have been due to under-extraction and too much extraction in the later stage. Front Street Coffee would increase the dose and reduce the yield to make the coffee flavor more concentrated. When the coffee has no astringency and the wine aroma becomes stronger, it means the adjustment direction is correct.
If the flow rate is still too fast and the aroma is not enough, it may be insufficient extraction, so you need to make the grind finer and extend the extraction time. If the flow rate is slow and the taste is strongly bitter or sharply sour, it is very likely over-extraction, and you need to reduce the extraction yield. This can be done by reducing the dose and making the grind coarser so that the yield is greater within the same extraction time.
Front Street Coffee believes that as long as we sort out the relationships among extraction parameters, adjusting a delicious espresso is not difficult. But we need to be clear that most home espresso machines are not as stable in function as commercial machines and produce very few cups, which also tests our grasp of the parameters. Front Street Coffee suggests recording the parameters and flavor performance of daily extractions that taste good, and comparing and summarizing more, which will help improve our adjustment efficiency.
The above content is compiled by CoffeeHunters, a coffee news website.
