Home Cosmetic Science Talk Formulating Preservation Need for High Glycol Product?

  • Preservation Need for High Glycol Product?

    Posted by evchem2 on November 8, 2024 at 9:59 am

    I’m working on a hot-pour gelled product that contains 70% glycols (50% propylene glycol, 17% Dipropylene glycol). Packaging is a twist-up stick type like many common deodorants. The pH is ~4.5 (measured as a 50% mix with deionized water). I tested water activity and got a reading of 0.94, which seems a bit higher than I expected considering the glycol content but I haven’t had a chance to test a_w before now. I read that this should inhibit growth of many bacteria but I assume I still need something for yeast and mold and any hardy bacteria. I’m debating inclusion of some sodium benzoate, pentylene glycol, and/or methylheptylglycerin. The challenge is the product is being positioned as “microbiome friendly” - I need to ensure sufficient preservation but I’ve been encouraged to avoid ‘strong antimicrobials’ which could disrupt the beneficial bacteria balance. Any suggestions on preservative inclusions?

    Adamnfineman replied 2 weeks, 3 days ago 3 Members · 10 Replies
  • 10 Replies
  • PhilGeis

    Member
    November 8, 2024 at 10:25 am

    0.94 - about at the edge of Gram negative inhibition, not enough for other bacteria and fungi.

    not picking on you - but how “microbiome friendly”?

    • evchem2

      Member
      November 8, 2024 at 11:01 am

      The info I got is a specific ingredient was plated with certain topical resident microbes in vitro and showed some vague positive results (promotion of some ‘beneficial’ bacteria, reduction of some others associated with malodor). Now I’m being asked to develop a formulation for further testing to show if the claim can be substantiated for a full product.

      Do my selected preservatives (benzoate, methylheptylglycerin, pentlyene glycol) seem adequate to cover whatever may still grow?

  • PhilGeis

    Member
    November 8, 2024 at 2:34 pm

    what’s pH?

    • evchem2

      Member
      November 11, 2024 at 7:18 am

      it’s ~4.5, I dilute it 50% with DI water to get a reading since the product is a solid gel otherwise

      • PhilGeis

        Member
        November 11, 2024 at 10:10 am

        4.5 is the dilurted product - not the product itself.

        How much water is in the product itself?

        • evchem2

          Member
          November 11, 2024 at 1:26 pm

          ~27% water

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