Refrigeration of Vitamin C Serum: Yes or no?

ETcellphoneETcellphone Member
edited March 2021 in Formulating
From what I hear, keeping your vitamin C serum in a cold, dark environment like a refrigerator is a good idea to keep it fresh and potent longer. 

Would you agree with this idea?

Why do I ask? It gets a crusty residue inside the bottle.
Here is what i have noticed: I have been keeping mine in a small dropper bottle in the fridge. When I do this, I notice that the glass on the interior of the bottle gets a patchy, crusty residue which I assume is at least part L-Ascorbic acid and tocopherol. Also, when I unscrew the dropper and lift it out of the bottle, the glass tube connected to the rubber dropper is also encrusted with some of the same residue. Is putting it in the refrigerator messing up my serum? Is it separating my ingredients? 

Also, if I were to keep taking it in and out of the fridge, do you think this daily temperature fluctuation, from cold to room temperature and then back to cold again, could hurt the actives in my serum? I only have it out of the fridge for maximum 30 minutes. 

Here is the vitamin C serum formula:
- Distilled water- 72%
- L-Ascorbic acid- 15%
- Sodium lactate- 2%
- Ferulic acid- 0.5%
-Propylene glycol- 7%
- Tocopherol- 1%
- Polysorbate 80- 1%
- Optiphen- 1%
- Xanthan Gum- 0.5% (I just tried this in my newest batch, which I haven't refrigerated yet) 


Should I keep it in my dresser from now, instead of the refrigerator? 

Also, any critiques of this formula I am happy to hear. 




Comments

  • Your main solvent is water, when water evaporated L-Ascorbic acid would recrystallize.
    Maybe try adjust you glycol.
    Also, if I were to keep taking it in and out of the fridge, do you think this daily temperature fluctuation, from cold to room temperature and then back to cold again, could hurt the actives in my serum? I only have it out of the fridge for maximum 30 minutes. 
    If it was me I would not concern much since DIY L-Ascorbic acid- 15% serum has a very short shelf life maybe 3 - 7 days.
  • Bill_TogeBill_Toge Member, Professional Chemist
    to my mind it's most likely the ferulic acid or the vitamin E; they're the least water-soluble components
    I'd suggest using a more powerful antioxidant like sodium bisulphite, combined with an excited-state quencher like benzophenone-4 to keep the amount of reactive oxygen to a minimum
    UK based cosmetic chemist with 13 years' experience at the bench. I've worked with pretty much everything apart from pressed powders, soap, solid lipstick and aerosols.
  • ETcellphoneETcellphone Member
    edited March 2021
    Pattsi said:
    Your main solvent is water, when water evaporated L-Ascorbic acid would recrystallize.
    Maybe try adjust you glycol.
    Also, if I were to keep taking it in and out of the fridge, do you think this daily temperature fluctuation, from cold to room temperature and then back to cold again, could hurt the actives in my serum? I only have it out of the fridge for maximum 30 minutes. 
    If it was me I would not concern much since DIY L-Ascorbic acid- 15% serum has a very short shelf life maybe 3 - 7 days.
    Thanks Pattsi. Do you think even a formula like the one I listed would lose its potency after 3-7 days? Would you say the same thing about the near $200 cult product Skinceuticals CE+Ferulic serum? Is there no way to stop this from happening, in your opinion? 

    Skinceuticals CE+Ferulic serum ingredients: 
    Aqua/Water/Eau, Ethoxydiglycol, Ascorbic Acid, Glycerin, Propylene Glycol, Laureth-23, Phenoxyethanol, Tocopherol, Triethanolamine, Ferulic Acid, Panthenol, Sodium Hyaluronate.
  • Bill_Toge said:
    to my mind it's most likely the ferulic acid or the vitamin E; they're the least water-soluble components
    I'd suggest using a more powerful antioxidant like sodium bisulphite, combined with an excited-state quencher like benzophenone-4 to keep the amount of reactive oxygen to a minimum
    thanks Bill. I will look into these ingredients you recommended. 
  • Skinceuticals CE+Ferulic serum - would last longer than 3-7 days as they studied and stated in their patent. But IMHO it can't be 1-2 years.

    Skinceuticals CE+Ferulic serum ingredients: 
    Aqua/Water/Eau, Ethoxydiglycol, Ascorbic Acid, Glycerin, Propylene Glycol, Laureth-23, Phenoxyethanol, Tocopherol, Triethanolamine, Ferulic Acid, Panthenol, Sodium Hyaluronate.


  • Dears

    This formula needs UV filtration 
  • Even the Skinceuticals CE Ferulic oxidizes. Maybe slower than all other LAA serums but it still does.
  • PerryPerry Administrator, Professional Chemist
    I'd say don't bother with refrigeration.

    It's unlikely you will be able to detect any differences in performance between a product that was refrigerated and one that wasn't.

    The main questions to ask yourself is how can you tell that the serum is "potent" at all? What are the measurable benefits that you have experienced?

    Does it really matter how fast it oxidizes or how "potent" it is if you can't actually notice any difference?
  • PaprikPaprik Member
    edited May 2021
    If I can add .. what's the final pH? 
    Keep it around 3.5 for best results.
    How fast does it turn pale yellow [in days]?

    I keep my serum in bathroom and am making a new one every 2 - 3 weeks. Going to fridge for it everytime would be super annoying. :D 

    Also, in my opinion, you don't have enough solubiliser. You have 1% Polysorbate 80 for 1% Tocopherol. Although, I've never worked with that material, so can't tell for sure. 
    Method is crucial, do you solubilize the Toco properly before adding into water? Does it go clear before each adding? 

    And curiosity question: Do you like it with the Xanthan Gum? I'm thickening it up with a bit of HA to get the slip. Probably depending on what grade of XG you're using, but it may feel sticky? 
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