Learn pre-infusion on the Bezzera Matrix MN with the video below.
What is Preinfusion?
Pre-infusion is what allows a small amount of water through first, before beginning the shot. It allows this water to saturate the coffee and get the grounds equally wet. This can make the coffee extract more smoothly. Water will always take the path of least resistance. By letting the water saturate the grinds before brewing at 9 bars of pressure, this can help prevent channeling.
Pre-infusion on the E61 Brew Group