Group (10) for measuring the quantity of carbon dioxide dissolved in a liquid contained in a closed container (11) made of a material optically transparent at least at one portion of a head space (13) of the same (11), the measuring group (10) comprising at least one inspection area (20,20′) suitable for housing at least one container (11), at said at least one inspection area (20,20′) at least one laser spectroscopy device (16) being provided for measuring the partial pressure of the carbon dioxide present in the head space (13) of a container (11) placed in said at least one inspection area (20,20′), characterized in that means for mixing (12) the content of said container (11) are in addition provided at said at least one inspection area (20,20′).