The Purpose, Effects, and Characteristics of Coffee Pre-infusion - Is Pre-infusion Extraction Suitable for All Espresso Coffee Beans?

For more professional coffee knowledge exchange and coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style).

Introduction

Pre-infusion refers to the process of briefly reducing pressure before the espresso machine's pressurized extraction, allowing water to slowly and evenly moisten the coffee grounds. Pre-infusion enables the coffee bed to release carbon dioxide in advance, making the subsequent pressurized extraction process more stable.

Can all espresso machines pre-infuse?

Not at all! Espresso machines without pre-infusion functions immediately enter a pressurized state the moment you lock the portafilter containing coffee grounds and press the extraction button. Once pressurized, water flow converges toward the center, performing "impact-style" extraction on the coffee bed. In contrast, espresso machines with pre-infusion functions can initially reduce pressure, allowing water to flow in evenly and gently to moisten the coffee bed before proceeding with pressurized extraction.

(Left: Low-pressure water flow injection into coffee bed/low-pressure pre-infusion | Right: High-pressure water flow injection into coffee bed/no pre-infusion)

Characteristics of Pre-infusion

Early Carbon Dioxide Release

Freshly roasted coffee beans continuously release carbon dioxide for several weeks after roasting. When coffee beans are ground into powder, carbon dioxide emission accelerates. When water contacts carbon dioxide, it forms bubbles between coffee particles, blocking contact between soluble substances and water, thereby reducing coffee extraction rate. Pre-infusion addresses this by injecting an appropriate amount of water to guide most carbon dioxide emission, reducing bubble formation during extraction and improving coffee extraction rate.

Reduced Channeling Effect

When espresso machines formally extract coffee, pressure reaches 9 bar. In this pressurized environment, water flow impact-style injection can easily cause cracks between coffee grounds. These cracks guide water to pass through quickly, resulting in extracted coffee liquid becoming thin and uneven. With pre-infusion, the coffee bed becomes more solid after moistening, better withstanding the impact force of water flow, reducing crack formation, and making the extraction process more uniform.

So is pre-infusion extraction better than direct extraction?

Not necessarily!

The pre-infusion characteristics mentioned above by FrontStreet Coffee premise that pre-infusion must be performed effectively. Effective pre-infusion means that the injected water can evenly moisten the coffee bed without excess coffee liquid dripping. If too little water is used, the coffee bed moistening will be uneven, and parts of the coffee bed not releasing carbon dioxide in advance will affect the overall extraction efficiency. If too much water is used, the coffee bed becomes paste-like, unable to withstand water flow impact and forming larger channels.

Although effective pre-infusion can improve coffee extraction rate, not all coffee beans are suitable for pre-infusion. If using light to medium roast coffee beans for espresso extraction, you can try pre-infusion. However, if using medium-dark to darker roast coffee beans for espresso extraction, you must consider whether pre-infusion, while improving extraction rate, might also increase the likelihood of coffee developing burnt flavors.

For more specialty coffee beans, please add our private WeChat: FrontStreet Coffee, WeChat ID: kaixinguoguo0925

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473