Pre-infusion is a process of slowing the introduction of water, at full force brewing/pump pressure, to the coffee/espresso grounds. By slowing or restricting brew pressure of the espresso machine the grounds will receive a low pressure wetting or saturation, before actual brewing under full pressure begins. With out pre-infusion, grounds would be hit at the full force of brewing pressure, which is approximately 9 bar (130 psi). A way to visualize a brewing scenario with out pre-infusion, would to liken a mound of sand being sprayed with water from a fire hydrant. The pressure from the fire hydrant would splatter the sand.
Roasters and baristas typically appreciate some form of pre-infusion. Pre-infusion will correct simple inconsistencies that can occur with the grind, dose or tamp such as air pockets or fissures created by aging burrs or unleveled tamping.
There are several ways pre-infusion can be accomplished. Control is offered in several types of machines and at different degrees.
• On/Off Control: Ability to enable or disable pre-infusion.
• Water Volume Control: Control over water used during pre-infusion.
• Time Control: Setting the time delay between grounds wetting and brewing.
• Pump Pressure Control: Ability to adjust pump pressure during grounds wetting.
The pre-infusion chamber is one way manufacturers slow brewing pressure build up. The pre-infusion chamber is an area or cavity that must fill before full brewing pressure is reached. While the chamber is filling, water escapes, softly wetting or saturating the grounds below. For machines with only a pre-infusion chamber and no programming capabilities, the time delay, on average, between grounds wetting and full brewing pressure is between 1-5 seconds.
Nuova Simonelli introduced the Soft Infusion System (SIS). By employing a larger pre-infusion chamber, Nuova Simonelli increased the saturation period and created a longer delay before full pump pressure was achieved. Increasing the length of the delay allows for a more complete saturation of the grounds, aiding in a more even extraction.
A pre-infusion chamber will not allow baristas to regulate or control water volume, pre-infusion pump pressure, length of pre-infusion or the delay between grounds wetting and full brewing pressure; all variables used in roast or coffee profiling.
Refined control over pre-infusion is recommended for those who wish to have more authority over the profiling of their coffee and product quality. Control of pre-infusion is offered in some lever and paddle machines, volumetric dosing espresso machines with digital displays and super-automatic machines. It is important to note that control of pre-infusion will vary and at different degrees depending on the espresso machine you choose.
There are many opinions regarding pre-infusion, and its influence during coffee profiling. If you are considering a new commercial espresso machine, addressing the importance of pre-infusion to you is recommended prior to selecting an espresso machine for your business.
For personal assistance regarding pre-infusion or other espresso machine features, contact Inland Espresso Solutions at 1 (855) 839-5665.