An activatable spoilage monitoring device (2) is housed in a lid for a container. The device comprises a reservoir containing a digestor fluid and a tray (62) containing a digestible material or gel and having a tactile pattern of protuberances (68) formed in a base of the tray. The two parts (4, 6) of the lid axially compress together as the lid is opened resulting in activation of the device by permitting the fluid to come into contact with the digestible material.