The invention relates to a method for dispensing viscous or pasty ingredients (12), which are packaged in an aseptic manner, from a tubular bag (1), which is closed prior to the first use, by means of a disposable pump (4) attached to the bag. The disposable pump (4) has an inlet (5) with a cutting element (6), and a nozzle (2) with a flange (3) is welded onto the tubular bag (1). The disposable pump (4) is rotated relative to the nozzle (2), and the tubular bag (1) is thereby cut open. A valve (9) is arranged in the region of the outlet opening of an outlet tube (8) of the pump, and the disposable pump (4) is operated after the initial opening process until a freely selectable volume has exited the closing valve. The disposable pump (4) is then operated in the opposite rotational direction in order to suction ingredients (12) present on or in the region of the valve (9) back into the outlet tube (8). In the process, the valve (9) reaches or remains in the closed valve state. A valve (9) is proposed for carrying out the method. The valve is arranged in the outlet tube (8) and comprises a membrane (93, 191) which is sealingly mounted in a sliding manner or can be inverted. Using the method, the ingredients (12) can be dispensed in a metered manner from a tubular bag (1), in which the ingredients are aseptically packaged, into virtually aseptic containers until the ingredients are practically completely used.