A well-known example of a beverage maker which is adapted to make a beverage on the basis of interaction between a beverage extract and an extracting fluid is an espresso appliance. In general, such an appliance is used for making espresso by forcing hot water to flow through a quantity of ground coffee beans.
The espresso appliance has a so-called brewing chamber where the actual espresso-making process takes place during operation of the appliance. In particular, the brewing chamber is openable in order to allow the introduction of fresh quantities of ground coffee beans and the removal of used quantities of ground coffee beans, and closeable in order to allow a process during which a necessary pressure is built up inside the brewing chamber.
The quality of espresso is determined by various factors. The formation of a so-called crema layer is a good indicator of an espresso-making process with correct parameters. A crema layer is a thin layer of foam on top of the espresso fluid.
It is possible to create an artificial crema layer if so desired in certain situations. To this end, means like a check valve or a restrictor are applied downstream of a position in the brewing chamber where the beverage extract can be located, i.e. at an outlet side of the chamber. The valve or restriction has a function in raising the pressure prevailing inside the brewing chamber during the espresso-making process, and in creating a jet of freshly made espresso against the inside of an outlet tube, as a result of which foam is created.
A disadvantage of applying a valve or restriction as mentioned in the foregoing is that more water stays behind in the brewing chamber once an espresso-making process is finished. This is bothersome to a user of the espresso appliance, especially in cases where the ground coffee beans come in coffee pods, because wet pods are difficult to remove from the brewing chamber.