Abstract: A closure including: a reservoir (4) which in turn includes a rupturable bottom (40), the reservoir (4) being applicable to a mouth (60) of a container (6) destined to contain a first product; a cutter (5), positionable in front of the rupturable bottom (40). The closure (10) takes on at least a first and a second configuration; in the first configuration, the rupturable bottom (40) being intact and at least the reservoir (4) and the cutter (5) identifying, in combination, a first chamber (2) suitable for containing a second product; in the second configuration the rupturable bottom (40) being open such as to enable a mixing of the first and the second product. The closure (1) includes moisture absorbing apparatus (7) which in the first configuration of the capsule (1) is in contact with an inside of the first chamber (2).