Introduction:During the process of making espresso, you may often encounter issues such as abnormal crema, channeling, overly sour or bitter flavors. This article delves into the reasons behind these common phenomena, offering a comprehensive diagnostic approach and adjustment suggestions—from coffee bean freshness, grind size, water temperature and pressure, to extraction techniques—to help you identify the root cause and improve the extraction quality of your espresso.
Whether in professional or amateur coffee preparation, the espresso extraction process is full of challenges. Even experienced baristas can’t always avoid unexpected issues, such as overly large crema bubbles, channeling, or flavors that are too sharp or sour. Though these details may seem minor, they directly affect the final flavor profile. This article will conduct an in-depth analysis from multiple perspectives on common problems in espresso making, including the storage and freshness assessment of coffee beans, examination of grind and extraction parameters, analysis of coffee crema (crema) condition, and observation techniques for the flow pattern, along with specific and actionable adjustment strategies.
First, let’s talk about the condition of the coffee beans. The roast date is a key indicator—beans are generally recommended for use within 21 days after roasting to ensure optimal flavor and appropriate carbon dioxide release. If the beans have been stored for more than three weeks, not only does their body noticeably decline, but it may also lead to insufficient crema or flavor loss during extraction. In addition, the speed of the extraction flow is also an important basis for judgment. When the grind is too fine, the flow slows down, which can easily lead to over-extraction, resulting in an oily mouthfeel and sharp acidity. Conversely, if the grind is too coarse and the flow is too fast, under-extraction is likely, leading to a thin taste lacking sweetness.
Observing the color changes of the coffee liquid during extraction is also a crucial part of diagnosis. A normal espresso will typically transition through three stages in color as it flows out: light brown, dark brown, and then nearly black. If you notice that it quickly turns black and stops flowing after the second stage, it may be due to the grind being too fine or the tamp being too hard, causing channeling or uneven extraction. In this case, it’s recommended to check the grind setting and ensure that the dose and tamp are both even and consistent.
Next, we focus on the state of coffee crema. Ideal crema should be fine, golden brown or hazelnut in color, and possess a certain level of persistence. If large bubbles appear and dissipate quickly, it may be because the coffee beans were recently roasted and still contain a lot of carbon dioxide. In this case, it is recommended to let the beans rest for several days to allow the gases to release naturally. However, if the coffee has absolutely no crema, or the extracted liquid is clear like water, it could mean the beans have gone bad, or poor storage conditions have severely damaged the flavor. When storing coffee beans, avoid direct sunlight, humid environments, and keep them away from heat sources and refrigerators to prevent crema oxidation or aroma loss.
Another common issue is channeling. Ideally, the extraction water should evenly penetrate the coffee puck, forming a stable flow rate and color. If the water flows from one side in a concentrated manner, creating obvious channeling, it indicates uneven puck density or tamping issues. It is recommended to use a bottomless portafilter (naked portafilter) to observe the flow so you can make immediate adjustments. To ensure even extraction, attention must be paid to precise dosing, a compact but not overly compressed puck, and uniform pressure during tamping. Avoid tapping the edges of the portafilter, which may cause cracks in the puck and allow water to pass through rapidly via the fissures.
When you notice that the color of the coffee liquid changes too quickly—for example, from light to dark—it may indicate that the flow rate is too fast, leading to under-extraction, resulting in a thin flavor, reduced sweetness, and possible earthy or overly bitter notes. In this case, besides checking the grind size, you should also confirm whether the water temperature is within the appropriate range. Generally, the ideal water temperature for espresso extraction is around 90°C to 96°C, and the boiler pressure of the coffee machine should be maintained at around 9 bar. In addition, steam pressure is usually kept at 1 to 1.5 bar, suitable for milk frothing but not affecting espresso extraction.
If you find the coffee flavor too sharp or bitter, it may be due to over-extraction caused by a long extraction time, high water temperature, or slow flow rate. It is recommended to recheck the grind size and appropriately adjust the tamp pressure and extraction time. Typically, the espresso extraction time is advised to be controlled between 25 to 30 seconds. On the other hand, if the coffee tastes too sour, it may be due to under-extraction, low water temperature, or the coffee beans not having fully degassed. It is suggested to let freshly roasted coffee beans rest for a few days before use.
In summary, to make a cup of espresso with balanced flavor, fine crema, and smooth mouthfeel, the key lies in mastering the condition of the coffee beans, precisely adjusting the grind and extraction parameters, and maintaining keen observation of the flow and crema states. Whether you’re using a multi-boiler coffee machine from Synesso, Expobar, or other brands, stable water temperature and pressure control are essential. In comparison, single-boiler machines are more prone to temperature fluctuations that affect extraction consistency. Through systematic observation and adjustment, you will gradually eliminate common problems and move closer to the goal of the perfect espresso.
The above content is compiled by CoffeeHunters, a coffee news website.
