What is Pre-infusion?
- idavisonbkk
- Jan 30
- 2 min read
What is Pre-infusion? The secret to a perfect espresso
If you’ve ever wondered why some espresso tastes smooth and well-balanced while others taste flat or overly bitter, one key factor behind a great shot is the pre-infusion system — an important feature in professional espresso machines.
What is Pre-infusion?
Pre-infusion is the step where hot water is gently applied at low pressure for a short time before full high-pressure extraction begins.
In simple terms, it prepares the tightly packed coffee grounds in the portafilter by evenly wetting them before the real extraction starts.
Normally, espresso is extracted at around 9 bars of pressure. During pre-infusion, however, the pressure is much lower (about 2–4 bars), or sometimes just gentle water flow by gravity. This stage lasts only a few seconds before the machine ramps up to full pressure.
Why is Pre-infusion important?
Pre-infusion does more than just add water — it directly affects espresso quality in several ways:
1. Even saturation of coffee grounds
Ground coffee inside the puck can have uneven density and trapped air pockets. Low-pressure water helps saturate the grounds evenly and releases trapped carbon dioxide, allowing the puck to expand and become more uniform.
2. Reduces “Channeling”
Channeling happens when water finds weak spots in the coffee puck and flows through those paths too quickly, leaving other areas under-extracted. This causes uneven flavor — bitterness from over-extracted spots and sourness from under-extracted ones.Pre-infusion helps reduce channeling, resulting in smoother and more even extraction.
3. Unlocks complex flavors
Gentle pre-wetting allows coffee compounds to dissolve more easily when full pressure begins. The result is a more balanced, rounded flavor — not just sharp bitterness or acidity — allowing the bean’s true character to shine.
How does Pre-infusion work in espresso machines?
Lever Machines
Baristas control pressure manually. They gently press the lever to allow low-pressure water flow first, then press fully to create high pressure.
Pump-driven Machines
Many modern espresso machines include built-in pre-infusion. This may be programmed automatically or achieved by allowing a brief slow water flow before the pump reaches full pressure.
In summary
Pre-infusion may seem like a small step, but it makes a big difference in espresso quality. It leads to smoother, more balanced, and more flavorful shots.If you’re choosing an espresso machine, having a pre-infusion feature is an important factor worth considering.
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