How to Adjust Unstable Espresso Machine Extraction Pressure - Espresso Machine Coffee Making Tips

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The Foundation of Espresso-Based Drinks

Espresso is the foundation for making Americanos, lattes, and other espresso-based beverages. The most distinctive characteristic of espresso is its rich, golden crema on the surface. FrontStreet Coffee will explore the extraction secrets of espresso machines in this article.

How is Espresso Crema Formed?

Under normal atmospheric pressure brewing, golden coffee crema cannot form. When an espresso machine extracts espresso, the coffee grounds are ground extremely fine and extracted under high pressure of up to 9 bars. As hot water passes through the coffee puck, the carbon dioxide in the coffee grounds becomes supersaturated in water due to the high pressure. The carbon dioxide cannot escape and dissolves directly into the coffee liquid. Meanwhile, the high pressure forces the oils contained in the coffee to separate from the puck and be carried out by the hot water.

After coffee extraction is complete, when the coffee liquid flows out of the machine and atmospheric pressure returns to normal, the carbon dioxide remaining in the coffee liquid attempts to return to the air. However, the carbon dioxide encounters the oils in the coffee liquid. The oils envelop the carbon dioxide attempting to return to the air. This is how the crema layer is formed.

Therefore, we know that what creates the rich crema of espresso is the pressurized extraction method of espresso machines.

How Much Pressure is Needed for Making Espresso?

When FrontStreet Coffee makes espresso, the coffee grounds in the portafilter basket are extracted under 9 bars of pressure. The substances in the coffee grounds are rapidly dissolved under pressure, so espresso extraction time is very short. Pour-over coffee typically takes 2-3 minutes, while espresso extraction can be completed in 20-30 seconds. This extraction method also classifies espresso as "pressure-based extraction."

Espresso machines primarily rely on pumps to provide pressure, mainly divided into two types: vibration pumps and rotary pumps. Vibration pumps generate pressure through high-speed repetitive movements of a piston-like structure. The disadvantages are loud noise, short lifespan, and gradually increasing pressure, which cannot ensure stable pressure at 9 bars throughout the entire extraction process.

Rotary pumps, on the other hand, generate pressure through high-speed rotation of metal blades. Compared to vibration pumps, they have no reciprocating motion, resulting in less noise, longer lifespan, and immediate pressure delivery. Therefore, commercial coffee machines generally use rotary pumps, offering better stability for continuous cup production.

Effects of Inadequate or Excessive Pressure

Under normal circumstances, if the espresso machine's extraction pressure is less than 9 bars, extraction efficiency will decrease, and the crema will appear thin and light. When pressure exceeds 9 bars, extraction efficiency increases, which may cause the espresso to become bitter and burnt. Of course, this is based on extraction parameters where 9 bars is the standard.

Common Causes of Insufficient Extraction Pressure

If the coffee machine itself is not malfunctioning, FrontStreet Coffee believes the following reasons may occur:

1. Insufficient heating time, low boiler water temperature, inadequate steam, resulting in insufficient pressure.

2. Small boiler capacity in the coffee machine. After continuous production or large amounts of hot water usage, the boiler refills, causing insufficient pressure.

3. The coffee machine's boiler pressure setting is low from the factory, resulting in insufficient steam pressure under all conditions. You need to contact after-sales service to readjust the pressure.

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