An assembly comprising a container at least partially transparent and a portable device for controlling an alcoholic beverage stored in said container, said device including - a single light source emitting a monochromatic excitation light beam having a wavelength comprised between 350 and 650 nanometers; - a beam splitter oriented at 45° with respect to the direction of emission of the light source to reflect the excitation light beam; - a focus and collection lens; - a filtering device for filtering the fluorescence radiation captured by the focus and collection lens and transmitted by the beam splitter, so as to eliminate the wavelengths which are shorter than or equal to the wavelength of the light beam emitted by the light source; - a spectrometer module for producing a signal corresponding to the measured spectrum of the fluorescence radiation of the beverage; - a casing containing said light source, said beam splitter, said filtering device and said spectrometer module, - a positioning device, secured to said casing making it possible to orient the light beam coming from the light source in a direction substantially normal to the outer surface of the container, the positioning device including a positioning wedge forming a projection from one of the faces of said casing, said positioning wedge having a contact surface of complementary shape to the container and defining a spacing between the focus and collection lens and the container determined so that the reflected beam is focused inside the container, within the beverage to be authenticated contained in the container at a distance of an internal surface of the container of less than 1 millimeter and preferably less than 500 micrometers, the positioning device including a through opening for the passage of the light beam coming from the light source; - an analysis module for comparing the measured spectrum with a reference spectrum. - a single light source emitting a monochromatic excitation light beam having a wavelength comprised between 350 and 650 nanometers; - a beam splitter oriented at 45° with respect to the direction of emission of the light source to reflect the excitation light beam; - a focus and collection lens; - a filtering device for filtering the fluorescence radiation captured by the focus and collection lens and transmitted by the beam splitter, so as to eliminate the wavelengths which are shorter than or equal to the wavelength of the light beam emitted by the light source; - a spectrometer module for producing a signal corresponding to the measured spectrum of the fluorescence radiation of the beverage; - a casing containing said light source, said beam splitter, said filtering device and said spectrometer module, - a positioning device, secured to said casing making it possible to orient the light beam coming from the light source in a direction substantially normal to the outer surface of the container, the positioning device including a positioning wedge forming a projection from one of the faces of said casing, said positioning wedge having a contact surface of complementary shape to the container and defining a spacing between the focus and collection lens and the container determined so that the reflected beam is focused inside the container, within the beverage to be authenticated contained in the container at a distance of an internal surface of the container of less than 1 millimeter and preferably less than 500 micrometers, the positioning device including a through opening for the passage of the light beam coming from the light source; - an analysis module for comparing the measured spectrum with a reference spectrum.