Humectant (HA) and water activity

Hi

  I seen articles advocating reducing water activity using humectants like glycols or sodium pca. One of the best humectant is HA . Will HA significanty reduce water activity ? (since its water retaining ability is very high)

Comments

  • PharmaPharma Member, Pharmacist
    Gelling is not equal to reducing water activity ;) .
    Ethanol works well too but I wouldn't call it a humectant.
  • I am not taking about gelling . The water activity is reduced by humectants and yes HA has good water binding property (along with NA PCA that is known to reduce water activity)

     
  • Cdsgames said:
    I am not taking about gelling . The water activity is reduced by humectants and yes HA has good water binding property (along with NA PCA that is known to reduce water activity)

     
    You did not understand his response.  He was kindly saying....HA does not bind water as you are thinking it does....it gells it....Not the same!
  • Are we talking about hydroxyl groups ?
  • PharmaPharma Member, Pharmacist
    No, at least I'm not.
    Take for example salt (NaCl), it is a poor humectant but greatly reduces water activity. Same goes for sugar (which would contain hydroxyl groups but this is irrelevant).
    Deliquescent substances (mostly salts) bind water very well but they are rather poor humectants, hence their frequent use as desiccants. Humectancy is only partially correlated with water binding or water affinity. A humectant also needs to let the water go under physiological conditions. This has nothing in common with water activity. Sure, substances which do not alter water affinity will not be suitable as humectants simply because they do not interact with water (= water is the only common denominator).
  • OK got it , thx you very much .
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