Brewing unit with optimized holding structure and method for operating such brewing unit

The invention relates to a brewing unit (01), preferably a pre-dispensing coffee unit, for a beverage preparation device, in particular for a base-part coffee machine, comprising a support (04) and a brewing chamber (11) having at least two brewing chamber halves (02, 03) and a movable holding structure (08), according to the invention, at least two brewing chamber halves (02, 03) are configured to move relative to each other in a first direction (05), and a movable retaining structure (08) is provided in such a way as to contact/support a solid substrate part, such that the retaining structure (08) is movable between positions between the brewing chamber halves (02, 03) and above the brewing chamber halves (02, 03) according to the relative arrangement of the brewing chamber halves (02, 03). The invention is characterized in that the retaining structure (08) is connected to the support (04) via a control device (12) such that the retaining structure (08) is arranged between the brewing chamber halves (02, 03