A humectant's a hygroscopic substance. It's often a molecule with several hydrophilic groups, most often hydroxyl groups, but amines and carboxyl groups, sometimes esterified, can be encountered as well; the affinity to form hydrogen bonds with molecules of water's crucial here. Since hygroscopic substances absorb water from the air, they're frequently used in desiccation. When used as a food additive, the humectant has the effect of keeping the foodstuff moist. Humectants are sometimes used as… (More on Humectant)