Process and apparatus for the control and the adjustment of a press during a juice extraction operating having at least one pressure increase sequence and measuring and comparing to a predetermined value the rate or the amount of liquid extracted before, during or after the pressing, or the partially pressed materials to be pressed remaining in the press after the pressing, and then using the resulting value of the difference of the rates or the amounts of extracted liquid and the value of the expected rates or amounts or the amount of materials to be pressed remaining in the press, if applicable, partially pressed, to begin, continue, interrupt, modify or complete the process of extracting the juice. The process is at least partially programmed.