Preinfusion systems

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Let’s take a look at the main systems and evaluate their differences.
Lever system.
Typical of lever machines, this system enables the barista to manually modulate the pre-infusion time at every brewing. When the barista pulls down on the lever, hot water enters the group from the boiler, immersing the coffee. The longer the barista keeps the lever down, the longer the pre-infusion phase will be. A true professional waits until the first drops of coffee come out of the spout before pulling up on the lever (this means that water has permeated all of the coffee in the group). For effective pre-infusion, water pressure should not exceed two bars when it enters the group. (A note of clarification: In normal lever machines, water entering the group comes from the boiler, at pressure equal to between one bar and 1.2 bars, and at 120-130°C. This is the same water source used for steaming. But in the case of the Athena Leva by Victoria Arduino, heat exchangers are used (even as it is a lever machine), so water temperature can be controlled and adjusted to optimize the quality of the brewed coffee. Because of this feature, to get the best pre-infusion we advise the use of a suitable pressure reducer upstream from the machine to reduce the water’s plumbed-in pressure, which usually is four to six bars. Due to its advanced technology, coffees brewed on an Athena Leva are particularly creamy and not burned (as can be the case when using water at high temperatures).
Pump delay system
Delayed pump activation can be programmed with this system, rather than the pump engaging as soon as the group’s sinusoidal valve opens. When the operator presses the button to begin brewing, the machine opens the group’s sinusoidal valve, letting water flow into the portafilter; at the end of the delay, water pressure from the pump is activated. To be effective, this system requires the use of a pressure reducer up stream from the machine, as the pre-infusion pressure is equal to that of the plumbing system. In addition, it is effective only in one-group machines, or where each group is equipped with its own pump.
Double opening electronic system
When the operator starts the brewing process,the machine activates the pump and the opening of the sinusoidal valve on the group at the same time; the valve remains open for several seconds (in some cases, the amount of time can be adjusted) and then closes briefly before opening again. This is an economical system, as it does not require any additional equipment. However, this system usually does not perform as well as others because, in the first phase, water enters at high pressure, resulting in a less effective and more jarring permeation. The water will tend to disrupt the tamped coffee, creating breaks that prevent a complete infusion. In addition, opening the sinusoidal valve twice for each brewing cuts its life cycle in half.
Flow reduction system
A calibrated gigleur (normally within a range from 0.4 to 1 mm) is used here to reduce water flow, slowing down the increase in the pressure curve. This system does not guarantee a true pre-infusion (at low pressure), but simply a softer trend on the pressure curve. This system also depends on a cavity or void space between the group’s sinusoidal valve and the coffee bed, without which it is minimally effective.
Pre-infusion chamber system
Consists of the presence of an expansion chamber downstream from the group’s sinusoidal valve, reducing water pressure in the panel for the time required to fill it. In fact, upon entering this cavity, the water loses pressure while falling on the coffee’s surface and permeating it. The expansion chamber’s dimensions take into account both the desired pre-infusion time and the group’s download capacity; excessive dimensions would hinder the complete emptying of the cavity at the end of the cycle, leaving the coffee grounds excessively wet. A variation of this system features a spring with a piston inside the chamber that helps to empty the chamber at the end of the brewing cycle. .

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SIS System
Nuova Simonelli recently introduced the SIS system, which enables a softer increase in the water pressure curve and has a nine-second pre-infusion time. The same results achieved by experts on lever machines are re-created with this system: The first drops of espresso come out of the spout while still in the pre-infusion phase. With the SIS system, superior brewing quality is possible, as well as compensation for possible tamping mistakes made by the operator..