Mastering Espresso Through Pre-Brew
A Tool for Precision and Control
Pre-brew is a powerful feature that allows home baristas to achieve greater control and precision in their espresso brewing, leading to enhanced flavor profiles and extraction quality.
A Legacy of Brewing with Pressure
To understand pre-brew, you first need to know how pressure works in an espresso machine. Since the 1960s, most espresso machines have used a steady pump pressure of 9 bars. This forces hot water to be pushed through the coffee puck at a consistent rate. The puck, made of finely ground coffee, creates resistance, controlling the flow of water and ensuring proper extraction.
Nowadays, new brewing features have been introduced in an attempt to make extraction even better and ultimately to make any style of espresso possible with any coffee. Adjustments to the brewing process can subtly influence the espresso’s flow, style, and its taste. This is where we can develop techniques when using pre-brew. Pre-brew, is a unique form of pressure control with its own system and results. You can choose how you would like to use it in your espresso brewing process.
What is Pre-Brew?
Pre-brew is a feature that gently introduces water to the coffee puck using an interrupted on-off-on sequence before the main brewing process begins and pressure is introduced. Think of it as a gentle wake-up call for the coffee puck, preparing it for full extraction. Unlike adjustments to brewing pressure, pre-brew doesn’t alter the brewing pressure(it will still be set to the standard 9 bars) but adds a preliminary step that can significantly impacts the extraction process.
Pre-brew is the introduction of water and limited pressure,
Pre-brew is not changing the brewing pressure,
using an interrupted on-off-on sequence, prior to the brewing process.
but it is adding in a step to control it for a time.
Why Use Pre-Brew?
Pre-brew provides an additional layer of control in the espresso-making process. When you activate pre-brew, the water gently soaks the coffee grounds, allowing them to swell and begin the extraction process. This method lets you manipulate the pressure in a way that can be finely tuned to bring out specific flavors and textures in your espresso.
For instance, using pre-brew often requires a finer grind size, which increases the surface area of the coffee and extends the time in which the coffee and water interact. This allows for more potential extraction from the same amount of coffee, ultimately enhancing the flavor profile of the espresso.
Pre-brew gives home baristas more control over extraction. When water hits the coffee grounds, they absorb it, swell up, and start releasing flavors like sugars, acids, and caffeine. Adjusting the pressure system lets you fine-tune the process. Since pre-brew increases the speed in water moves through the coffee puck, using a finer grind helps maintain the optimal flow rate and boosts extraction.
Using pre-brew with a finer grind size can increase surface areas of the coffee, extend the immersion time, allowing for more potential extraction from the same amount of coffee.
Different Pre-Brew Systems: Original vs. Modern
Original pre-brew system
The original pre-brew system—found in the GS3 AV, Linea Minis with serial numbers starting with “LM,” and Linea Micra—uses an interrupted on-off-on sequence with a single three-way valve. In this system, water is introduced at brewing pressure during the “on” period and then exhausted into the tray during the “off” period. This process is similar to activating the paddle, turning it off, and then back on again. The goal of this pre-brewing phase is to wet the top of the espresso puck, softening the introduction of water during the brewing process. For this reason, a short “on” time is recommended with the original pre-brew system.
Modern pre-brew system
In Linea Minis with serial numbers starting with “MI,” an interrupted on-off-on sequence is employed, but this system uses two separate solenoids instead of just one. Water is introduced at brewing pressure during the “on” period and then trapped inside the brewing chamber when the bottom solenoid closes during the “off” time. This form of pre-brewing ensures full saturation of the coffee puck, resulting in higher extraction without additional pressure during the pre-brewing phase. The minimal amount of water combined with static pressure allows for full immersion, ensuring even contact between the water and coffee particles. This setup allows for extended pre-brew durations if desired.
Whenever the pressure changes, the flow rate of the espresso adjusts accordingly, allowing for precise control to maintain that optimal flow rate.
The Power of Pre-Brew
The modern pre-brew system in Linea Minis with serial numbers starting with ‘MI’ is factory-set to a 2 seconds on and 2 seconds off sequence. This timing isn’t arbitrary; it was selected after thorough testing by experts at Accademia del Caffe Espresso. They found that this method, particularly the dual-valve pre-brew, produced the best-tasting results. Advanced scientific analysis also revealed that espresso brewed with this method contained higher levels of malic acid (like in apples) and citric acid (like in oranges), confirming the sensory evaluations.
Experimenting with Pre-Brew
The beauty of pre-brew lies in its versatility. By experimenting with different settings using the La Marzocco Home App, you can tailor the pre-brew process to suit your taste preferences. Whether you prefer a short, sharp pre-brew or a longer, more immersive experience, adjusting this feature allows you to unlock new dimensions in your espresso.
