A pressure release valve for a steam peeler for potatoes has a differential piston assembly including a piston (60) which is movable between an open position and a closed position under steam control, and a fixed piston element (66) which is received in a secondary cylinder (88) within the main piston for defining a chamber (76) that progressively reduces in volume as the main piston moves towards its open position. The chamber receives a cushioning fluid for decelerating the piston as it moves towards the open position.
