Abstract: The invention relates to a straw comprising a tube (11) and a gas-permeable and liquid-tight stopper (12), said stopper (12) being arranged in the tube (11), close to an end (16). The invention is characterised in that the stopper (12) comprises an indicator component (20) having a first pre-determined colour in the absence of previous contact with said substance (21) and a second pre-determined colour, of a different shade from that of the first colour, once it has been in contact with said substance (21). The assembly comprises the straw (10) and a device (26) for controlling the filling of the straw.

Abstract: The container straw comprises a tube (11) and a stopper (12) that is permeable to gasses and impermeable to liquids, which stopper (12) is arranged in the tube (11) near one end (16), characterized in that it comprises an indicator component (20) configured to emit, at least when the container straw (10) is full, light the spectrum of which contains at least one spike having a peak of predetermined wavelength. The assembly comprises the container straw (10) and a container straw recognition device (26).