Method for the preparation of coffee

A method of preparing coffee comprising cyclically repeated steps of:

• feeding coffee beans to a coffee bean milling means;
• milling the coffee beans to a coffee powder having a selected average grain size;
• adding a selected amount of the coffee powder into a brewing chamber;
• displacing a piston into the interior of the brewing chamber and thereby reducing the internal volume of the brewing chamber containing the coffee powder until a preselected pressure is exerted on the coffee powder;
• supplying a preselected amount of hot water into the brewing chamber and forcing the hot water through the compressed coffee powder to prepare coffee;
• collecting the prepared coffee;
• measuring the length of the displacement path of the piston required to exert the preselected pressure on the coffee powder, and recording the length measurement value in a microprocessor having a memory with a length reference value stored therein and corresponding to the calculated length of the displacement path of the piston required to exert the preselected pressure on the coffee powder in the brewing chamber;
• retrieving from the microprocessor memory the length reference value stored therein;
• comparing the length measurement value and the length reference value and generating a length comparison signal;
• altering the amount of coffee powder fed into the brewing chamber during a subsequent cycle in response to the magnitude of the length comparison signal deviating from a predetermined magnitude;
• measuring the time required for the preselected amount of hot water to pass through the coffee powder in the brewing chamber and recording the time measurement value in the microprocessor having a time reference value corresponding to a calculated amount of time required for the preselected amount of hot water to pass through the coffee powder in the brewing chamber stored in the memory thereof;
• retrieving from the microprocessor memory the time reference value stored therein;
• comparing the time measurement value and the time reference value and generating a time comparison signal;
• and
• altering the degree of milling of the coffee means to thereby change the average grain size of the coffee powder fed into the brewing chamber in response to the magnitude of the time comparison signal deviating from a predetermined magnitude.