Abstract: A portable machine for carbonating liquid contained in a bottle is adapted to support the bottle (5) by the neck (81) through a bayonet connection and for a seal (64) which closes the bottle neck to be driven into engagement with the bottle neck by a piston (60) actuated by the first burst of gas supplied to the injection nozzle (66). The bottle is loaded into the machine through a front opening (6) and a cover (7) for closing the opening is interlocked with a gas supply valve (12) so that gas can only be delivered to the nozzle (66) when the cover is closed. The cover is opened and closed by rotating a knob (23) which is depressed to open the gas valve. The knob (23) is coupled to the gas valve (12) through a device (27) which prevents the valve being opened if the machine is tilted at more than a given angle to the upright position.